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WIND EFFECTS ON THE PERFORMANCE OF A
SOLARWALLO COLLECTOR
An Experimentai Study on a SolarwailB at the
Canadian Coast Guard Base in Prescott, Ontario.
LES EFFETS DE VENT SUR LA PERFORMANCE D'UN
COLLECTEUR SOLARWALLO
Une étude expérimentale sur un SolarwailB à la base
de la Garde Côtière Canadienne de Prescott, Ontario.
A Thesis Submitted
to the faculty of the Royal Military College of Canada
Robert M. Meier, CD, PEng Captain
In Partial Fulfillment of the Requirements for the Degree of
Masters of Engineering in Mechanical Engineering
June 2000
O This thesis may be used within the Department of National Defence but copyright for open publication remains property of the author.
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ROYAL MILITARY COLLEGE OF CANADA
DIVISION OF GRADUATE STUDIES AND RESEARCH
This is to certie that the thesis prepared by
CAPTAIN ROBERT M. MEIER, CD, P.ENG
entitied
WIND EFFECTS ON THE PERFORMANCE OF A SOLARWALLB COLLECTOR
An Experimentai Study on a SoIanvall@ at the Canadian Coast Guard Base in Prescott, Ontario
complies with the Royal Military College of Canada regdations and that it meets the accepted standards of the Graduate School with respect to quality
For the degree of
MASTERS OF ENGINEERING IN iMECHANICAL ENGINEERING1
n Signed by the final examining cornmittee:/
Chair,
External Examiner,
External Examiner,
1
Appmved by the Head of Department \,&h Date : UU
To the Librarian: This thesis is n o w g a r d e d *sified. 1 I
L
f i ~ u p e r v i s o r 1 Directeur de thèse principal
DEDICATION
To Angela Lucas. and my family.
ACKNOWLEDGEMENTS
1 wish to thank Dr. Brian Fleck, for his guidance and support during the research and preparation of this thesis.
I am also grateful to the following persons:
Mr. Lome Macmillan, Supervisor Facilities Services, for his help and allowing this study to be done on the Prescott Base.
Mr. Rick Renick from the Prescott Base for his interest, advice and the time he spent helping to set up and the instrumentation required for this research.
Mr Mike Gatien for constmcting a mounting bracket for the sonic anemometer. I would also like to thank him for his excellent advice on the design of the bracket.
Mrs Wendy Libbey for providing advice and instrumentation for this study.
Dr. Benaissa and Dr. Laviolette for their advice and help during this research.
Most importantly 1 wish to thank my wife, Angela, for her continued patience, support, and encouragement throughout my graduate studies, and my son Lucas for keeping me smiling.
TABLE OF CONTENTS
Page
. . LIST OF FIGURES .......................................................................................................... xi1
........................................................................................................... LIST OF TABLES xvi
. . NOMENCLATURE ....................................................................................................... xvir
ABBREVIATIONS ......................................................................................................... xix
CHAPTER 1 . BACKGROUND. LITERATURE REVIEW AND ................................................ OBJECTIVES OF THE PRESENT WORK 1
1 - 2 Background ......................................................................................................... 1 1.2 Overview of the operation of a Typical Solanvall@ ................................................ 4 1 -3 Literature Review ..................................................................................................... 7 1.4 Background and Objectives of Present Work .......................................................... 9 1.4.1 Background of Thesis Topic Selection ........................................................ 9 1.4.2 Research Objectives ................................................................................... 1 O
CHAPTER 2 . THEORY .................................................................................................. 1 1
OveralI Heat Balance for a Transpired Solar Collecter ............................ ....... 1 1 Efficiency and Effectiveness of a Transpired Solar Collector ............................... 12 Airflow around Buildings ...................................................................................... 1 3
Atmospheric Boundary Layer .................................................................... 1 3 Wind Direction and Building Geometry .................................................... 15
Turbulence ............................................................................................................. 16 Notation ...................................................................................................... 16 Scales of Turbulence Considered .......................................................... 1 7
Spectral Analysis ................................................................................................... 18
vi
. CHAPTER 3 EXPERIMENTAL APPARATUS AND METHODOLOGY .................. 22
17 Selection of Solarwail@ .................................... ... ................................................ Selection and Placement of Instruments ............................................................... 24
Sonic Anemometer ............... ...... ......................................................... - 24 Pyranometer ........................................................................ ,. .................... -27 Temperature Measurement ....................................................................... -28 Pressure Transducers ................................................................................ -30 Remote Weather Station ............................................................................ 30 . . . Data Acquisition System .... .................................................................................... 34
.................................................................. ............................. Hardware .. -34 ..................................................................................................... Software 34
Lab Calibration of Equipment ............................................................................... 35 ............................................. Calibration of Sonic and Cup Anemometers 35
Caiibration of Pressure Transducers .......................................................... 36 Cornparison of Sonic Anemometer, Weather Station, and Thermocouple Temperatures .................................................................... -36
................................ Calibration of Solanvall@ Exhaust Duct Flow Rates 37 Uncertainty ............................................................................................................. 37 Problems Encountered with Experimental Apparatus ........................................... 37
Thermocouple Readings ............................................................................ 37 Short Cycling and Flow Rate of Intake Fan 2 ............................................ 38 Sonic Anemometer ..................................................................................... 39 Electronic Ice Point .................................................................................... 30
....................................................... Weather Station Temperature Sensor -40
CHAPTER 4 . REStTLTS ................................................................................................. 42
Typical Output Examples ........................ .. ......................................................... 42 Typical Data Acquisition Outputs ............................................................. 42 Measurements from the Weather Station Cup Anemometer ..................... 47
Cakutated Results ........................ ..,.. ................................................................ .50 Air Temperature Rise vs . Total Solar Radiation ........................................ 50 Temperature Rise due to Non-Solar Radiation .......................................... 52 Efficiency and Effectiveness versus Solar Intensity .................................. 54
Statistical Analysis ................................................................................................. 57 Selection of Data Used for Statistical Analysis ....................................... 3 7 Analysis Based on Oncoming Wind Direction .................... .... ............. 60 Analysis of Sonic Anemometer Wind Data ............................................... 68
vii
CHAPTER DISCUSSION ......................................................................................... 77
Problems Encountered with the Experimental Apparaius ..................................... 77 Thennocouple Readings ........................................................................... -77 Short Cycling and Flow Rate of Intake Fan 2 ............................................ 78 Sonic Anemometer ..................................................................................... 78 Electronic Ice Point ................................................................................... -79
........................... Weather Station Temperature Sensor ....................... ... 79 ................................................................................................... Temperature Rise 80
Statisticai Analysis of Effkiency and Effectiveness versus Wind Direction ........ 82 Sonic Anemometer Wind Data .............................................................................. 84
Mean Flow of Air at the location of the Sonic Anemometer .................... -84 Fluctuating Components of Velocity and Temperature
......................................................... Measured by the Sonic Anemometer 90
......................................................................................... CHAPTER 6 . CONCLUSION 91
6.1 Experimentai Apparatus and Method ................................................................... -91 6.2 Statistical Analysis ................................................................................................. 93
CHAPTER 7 . RECOMMEND ATIONS .......................................................................... 95
7.1 Experimental Apparatus and Method .................................................................... 95 .................................................................... 7.2 Recornmendations for Further Study -97
7.3 Suggested Improvements to the Prescott Solanvail@ System ............................... 98 ........................................... 7.4 Suggested Improvements to the SolanuallC3 Design 100
REFERENCES ...................................... .. ........................................................................ 1 O 1
............................................................................................................ B I B L I O G W H Y 102
APPENDICES
Appendix A . Pamphlets from Conserval on SolarwallB Entitled. Tladding that ....................... Heats Fresh Air. " and "Heating for Industrial Buildings" 1 03
Appendix B . Site and Construction Drawings of the SolarwallsB Installed at the Canadian Coast Guard Base in Prescott. Ontario. Canada ...................... 108
Appendix C . Draft "Instructions" for Young Model 8 1000 Ultrasonic ............................................................................................. Anemometer 1 13
...................... Appendix D . LabVIEW Graphical Programs used for Data Acquisition 12 1 Appendix E . Calibration Plots of the Sonic and Cup Anemometers. and the Setra
................... Mode1 264 Pressure Transducers in the RMC Wind Tunnel 139 .............................................. Appendix F . Thermocouple Temperature Corrections 1 4 2
Appendix G . Calibration of SolaxwallC3 Outlet Ducts .................................................. 146 ....................................................................... Appendix H . Summary of Uncertainties 148
ABSTRACT
Meier, Robert M.. M. Eng. (Mech. Eng.). Royal Military College of Canada. June 2000. Wind Effects on the Performance of a Solarwall@ Collecter. Supervisor: Dr. Brian Fleck.
An experimentai study was camied out on a SoIarwall@ system to determine what
effects wind has on its performance. SolarwaII@, a type of unglazed solar transpired
collector, is a relatively new technology that reduces energy consumption and operating
costs associated with heating fiesh intake air for ventilation purposes. A Solarwall@
system is usually mounted on the south side of a building where it preheats fresh outside
air by drawing it through small perforations in its cladding material, which is heated by
solar radiation. The wall of the building on which the transpired solar collector is
mounted is usually subjected to the natural buffeting and turbulence of wind. This
three-dimensional flow of wind around a building and its effects on the performance of a
SolanvaIl@ system were examined.
An experimental set-up was put in place on a newly installed SolanvaIl@ at the
Canadian Coast Guard Base in Prescott, Ontario, Canada. Instrumentation to measure
temperatures, coIiector outlet flow rates, solar radiation, wind speed, and wind direction
was put in place and data were logged on site using a data acquisition system.
An ultrasonic anemometer was also placed in the centre of the Solanvall@ to study the
three dimensional flow close to the wall. Output data were analysed using a statistical
software package.
Statistical analyses of the data suggested that efficiency and effectiveness were both
influenced by oncoming wind direction. Eficiencies were generally higher when the
wind flowed over top of the building compared to efficiency values when wind flowed
pardlel to the wall. It is suggested that a recirculation or stagnation zone tended to
develop when the wind flowed over the building, which was more effective in keeping
heated air in front of the SolanvaIl@. It is also suggested îhat this heated air tended to be
swept away more readily when wind flow was parallel to the wall. Analysis of data fiom
the ultrasonic anemometer mounted near the wall tended to support these findings. It was
also noted that efficiency tended to decrease with increased turbulence levels. Finally,
sorne recommendations were given to improve the operation of the overall Solanwall@
system installed in Prescott.
Une étude expérimentale a été effectuée sur un système SolanvaIl@ pour déterminer
les effets du vent sur sa performance. Solarwall@ est un type de collecteur solaire sans
vitre à aspiration. Il représente relativement une nouvelle technologie permettant de
réduire la consommation d'énergie et les coûts associés au chauffage de l'air frais utilisé
pour la ventilation.
Un système SolanvaIl@ est généralement monté sur la partie sud d'un bâtiment. Ce
qui permet de préchauffer l'air ambiant frais en l'aspirant à travers des petits trous sur
son revêtement. Le mur du bâtiment sur lequel le collecteur solaire à aspiration est
monté, est généralement soumis à des osci1lations aéro-élastiques et à la turbulence du
vent. L'objectif de cette étude est d'étudier l'écoulement tridimensionnel du vent autour
du bâtiment ainsi que ses effets sur la performance d'un système Solarwall@.
Un montage expérimental a été mis en place pour étudier un système Solarwall@
nouvellement installé à la Base de Garde Côtière Canadienne de Prescott, Ontario,
Canada. Des températures, la radiation solaire, et la vitesse ainsi que la direction du vent
ont été mesurés sur place en utilisant un systkme d'acquisition de données. Un
anémomètre ultrasonique a été placé au centre du Solanvall@ pour étudier l'écoulement
tridimensionnel près du mur. L'analyse de toutes les mesures a été effectuée à l'aide de
logiciel statistique.
L'analyse statistique de mesures suggère que la direction du vent a un effet sur le
rendement et l'efficacité du système Solarwd1@. Cette efficacité est généralement
supérieure lorsque le vent s'écoule par dessus le mur comparativement au cas où le vent
s'écoule parallèlement au mur. Il est suggéré qu'une zone de recirculation ou de
stagnation tend à se développer lorsque le vent s'écoule par dessous le mur. retenant ainsi
l'air chauffé au voisinage du SolanvallB. Cependant lorsque le vent s'écoule
parallèlement au mur, il tend a balayer plus facilement l'air chauffé. Les mesures
fournies par l'anénomètre ultrasonique confirment ces observations. Il est aussi observé
que l'efficacité tend à décroître avec l'augmentation du niveau de turbulence.
Finalement, des recommandations ont été suggérées pour améliorer le fonctionnement du
système SolarwallOB a Prescott.
xii
LIST OF FIGURES
Figure Page
.......... Solarwdl@ installed on a Canadair building in Montreal, Quebec, Canada. 2
SolarwallO used on an apartment building in Windsor, Ontario ............................. 3
Crop drying of tea leaves using a solar transpired collector .................................... 4
Schematic of a typical installation of a transpired solar collecter system u) ......... 5
Temperature stratification usually occurs in buildings with high ceilings, which result in cold temperatures and drafts at floor level and hot air being
............................................................................................ exhausted at the ceiling 6
Flow patterns around a rectangula. building (7) .................................................... 14
Surface flow patterns showing flow separation and reattachment (Z) ................... 15
Orders of magnitude in space and time for diffemet pattems of motion in the atrnosphere (6J ................................................................................................. 18
..................................................... Denmark and New York State autospectra (6) -19
Gust wind velocity U +u, is separated into a wind velocity climate component U and a turbulent component u, (note that the turbulent
.................................................................... component has been normalized) (6) -20
Two newly installed Solarwalls@ at the Canadian Coast Guard Prescott Base. one on either side of the Welding Shop door. Experimentation was
........................................... carried out on the west SolanvallQ (left side of door) 22
Overhead Crane, two outlet ducts and two intake fans of the West Solarwall@ in the Prescott Welding Shop ............................................................ 23
The sonic anemometer mounted on its support bracket directly in the ................................................................................ centre of the west Solarwall@ 26
View of the Kipp and Zolen CM l O pyranometer mounted on the east Solarwall@ ........................................................................................................... 2 8
Placement of the thennocouple probes and pitot-static tubes in the outlet of Duct 1 of the west Solarwall@ ............................................................................... 29
Helicopter Hanger and Flight Office. The cup anemometer was mounted on the tower and the weather station display console was placed inside the Flight Office. Note there is a construction trailer in the foreground that is
................................................................................... not typically in this location 3 1
Temperaturehumidity sensor shown mounted on the north wall under the eaves of the Flight Office ....................................................................................... 32
Divisions of 16 possible cup anemometer wind directions. Orientation of the Solarwall@ and sonic anemometer have been included for future reference. Note that W for the sonic anemometer is positive in the up
direction. ................................................................................................................ 33
Time series plots showing five minute averages of (a) pitot static pressure in Duct 1, (b) total solar radiation, (c) ambient sonic, Duct 1, and wall temperatures. ........................................................................................................ --43
Mean wind velocities recorded every five minutes at a distance of 6 1 cm (24") from the Solarwall@ using the sonic anemometer ...................................... -46
Wind direction distribution for the March data set ................................................ 47
Weather station cup anemometer wind speed distribution based on the Beaufort Scale for the March data set .................................................................... 48
Temperature nse (temperature Duct 1 - sonic temperature) versus total solar radiation for the March data set. Lines represent Conserval data fiom figure 2 of appendix A (flow rate B is 0.01rn3/s/rn2 and C is 0.02m3/s/m') .......... 5 1
Temperature rise (temperature Duct I - ambient sonic temperature) versus ambient sonic temperature. Data fiom March data set when the intake Fan 1 was lefi in operation between 6 p.m. and 6 a.m. ........................................ 3 3
Efficiency and effectiveness versus total solar radiation seen by the Solarwall@ (March data set) ............................................................................... - 3 5
xiv
4.8 Box plots of efficiency and effectiveness for the Mach data subsets (a) solar radiation >200 w/m2, (b) solar radiation >600 w/m2. Circles represent outliers and stars represent extremes ...................................................... 59
4.9 Box plots of (a) wind speed, (b) total solar radiation, (c) ambient sonic temperature, and (d) wall temperature; plotted versus g e n e d wind direction for the March data set (solar radiation >600 w/rn2). Circles represent outliers and stars represent extremes ..................................................... -6 1
4.1 O Box plot of normalized estimated radiation losses as a function of wind direction for March data set (solar radiation >600~/m') . Data has been normalized using the largest estimated radiation loss. Circles represent outliers.. ................................................................................................................ ..63
4.1 1 Box plots of (a) eficiency, and (b) effectiveness, of the Solarwall@ as a function of wind direction for March data set (solar radiation > 6 0 0 ~ / m ~ ) . Circles represent outliers and stars represent extremes ....................................... ..65
4.12 95% error plots of (a) efficiency, and (b) effectiveness as a function of wind direction. Error bars include the range for 95% of the data ......................... 67
4.13 Efficiency versus mean veIocities (a) U, (b) V, and (c) W. March data set (solar radiation >600 w/rn2) ................................................................................... 69
4.14 Eficiency versus (a) RMS u < (b) RMS v ', (c) RMS w Marc h data set 2 solar radiation >600 W/m ) ..................................................................................... 7 1
............... 4.15 Eficiency versus RMS r : March data set (solar radiation >600w/rn2) 73
4.16 Emciency versus the mean of the products of the fluctuating components of velocity and temperature where (a) u 'r ', (b) v 't ', (c) w 't '. March data
2 ............................................................................. set (solar radiation >600 W/m ) -74
5.1 Box plot of outlet temperature of Duct 1 as a fùnction of wind direction 2 for March data set (solar radiation >600W/m ) .................................................... 8 1
5.2 Top view of the building. The x-y plane in front of the Solarwalf@ was broken down into quadrants at the location of the sonic anemometer and classified by nurnbers 1-4. ..................................................................................... 85
5.3 Velocity vector orientation in x-y plane as a function of oncoming wind direction. March data set (solar radiation 2600 w/rn2) ........................................ ..86
5.4 Possible wind flow and recirculation patterns seen in the x-y plane for different oncoming wind directions (a)202.5-225 degrees, (b)3 1 5-360 degrees, (c) 247.5-292.5 degrees, (d) 67.5,90, and 135 degrees. March
2 data set (solar radiation >600W/m ) ...................................................................... 87
5.5 Box plot of eEciency versus wind quadrant direction fiom March data set .............. (solar radiation >600w/m2). Circles are outliers and stars are extremes 89
Appendix
Figure
Sonic and cup anemometer velocities versus the velocities caiculated using a pitot-static tube and Delft water manometer ........................................................ 140
Caiibration curves for IWO Setra 264 pressure transducers. ........ ..... ............ 141
Temperature difference (temperature thermocouple 3 - sonic anemometer temperature) versus Julian day, during penods of no Solar radiation (between 6 a.m.and 6 p-m.). Julian day O represents 1 January 2000. .............................. -144
Temperature difference (temperature thermocouple 3 - sonic anemometer temperature) versus Julian day, during penods of no solar radiation (between 6 a.m.and 6 p-m.). Julian day O represents 1 January 2000. .............................. -144
Temperature difference (wall temperature - sonic anemometer temperature) versus Julian day, during periods of no solar radiation (between 2 a.m. and 4 am.). ................................................................................................................. 145
Temperature difference (wall temperature - sonic anemometer temperature) versus Julian day, during penods of no soIar radiation (between 2 a.m. and
............................................ 4 a.m.), after a temperature correction of -1 -25 OC. 145
Velocity profile of Duct 1. ................................................................................... 147
LIST OF TABLES
Table Page
4.1 Sumrnarry of Beaufort Scale (5J ........ .......... .... ...... . .... ..... .... .... . ...... .... . ... .... ..-........ 49
Appendix Table
H. 1 Surnrnary of uncertainty, accuracy, and ranges of the instruments used in the expenmental set up. .... .... .... . . ................ ......... . ..... ... ... ....... . . .... ..... ........... 1 4 9
xvii
NOMENCLATURE
collector area (m')
specific heat at constant pressure (Jkg OC)
collecter-to-ground view factor
collector-to-sky view factor
solar insolation incident on the collector (w/mZ)
Turbulence intensity in x-axis
Turbulence intensity in y-axis
Turbulence intensity in z-axis
collector convective heat loss (W)
collector radiant heat loss (W)
fiee stream ambient temperature (OC)
coilector temperature (OC)
collector outlet temperature (OC)
mean temperature measured by the sonic anemometer ( O C )
instantaneous temperature t(s) measured by the sonic anemometer (OC)
fluctuating component of temperature f(s) measured by the sonic anemometer (OC)
xviii
mean wind velocity in x-axis, or U(x, y, z), ( d s )
time dependent or instantaneous velocity in x-axis, or u(x. y, z, r), (m/s)
fluctuating component of velocity in x-axis. or u'(x, y. r, r), ( d s )
fiction velocity
mean wind velocity in y-axis, or V(x, y, z), ( d s )
time dependent or instantaneous velocity in y-axis, or v(x, y. r, r), ( d s )
fluctuating component of velocity in y-axis, or vf(x, y, z, r), (m/s)
suction velocity (mk)
velocity in duct of fan 1 (rnls)
mean wind velocity in z-mis, or W(x, y, z). ( d s )
time dependent or instantaneous velocity in z-mis, or w(x, y, z, r), ( d s )
fluctuating component of velocity in z-axis, or i (x. y, s r). ( d s )
height above surfôce
roughness length
Greek Symbols
a, collector absorptance
CC absorber surface emissivity
E heat exchange effectiveness
rl collector efficiency
P density (kg/m3)
CT Stefan -Boltzmann constant
r time (s)
xix
ABBREVIATIONS
Ambient temperature
Duct 1
Duct 2
Fan 1
Fan 2
RMC
RMS
Sonic temperature
Wall temperature
WMO
free Stream arnbient temperature (OC)
outlet duct o f Fan 1
outlet duct of Fan 2
West intake fan of West Solan;vall@
east intake fan o f west Solarwall@
Royal Military College
Root mean squared
temperature of the sonic anemometer ( O C )
temperature of the Solarwall@ cladding (OC)
World Meteorological Organization
CHAPTER 1 - BACKGROUND, LITERATURE REVIE W AND OBJECTIVES OF PRESENT WORK
Transpired solar collectors are a simple and inexpensive new technology that result
in reduced energy consumption and operating costs that are associated with fresh air
ventilation requirements. A transpired solar collector preheats fiesh outside air by
drawing it through smdl holes on a dark coloured surface that is heated by the sun's
radiation. The transpired solar collector is usually mounted on the side of a building that
receives the most sunlight (e-g. the south wall). The wall of the building on which the
transpired solar collector is mountea is usually subjected to the natural buffeting and
turbuience of the wind. Three-dimensional flow of wind around a building and its effect
on the performance of a transpired solar collector will be examined in this study.
1.1 Background
Demand for better indoor air quality is increasing the ventilation needs of many
buildings. "The ideal working environment is free of al1 pollutants and ensures an
adequate and continuous supply of oxygen. If these conditions are not met. people
become tired, sluggish and irritable, absenteeism increases, morale sinks and productivity
lags a)." More stringent requirements for a cleaner and healthier working environment
rnust be balanced by added costs not only in fuel to heat this additional fresh air but by
the additional pressure on the environment caused by this increased energy use. Greener
more environrnentally sound alternatives to fossil fuels are being pursued, and the
transpired solar collecter is definitely an option that has ment. Paybacks of initial
installation costs have been quoted as being typically around three to five years due to
reduced fuel consurnption requirements.
The most well known of the cornmercially available transpired solar collectors or
solar ventilation air heating (VAH) systems is the SolarwallQ system. "Solanvail@" is a
registered trademark of Conserval Engineering Inc. The system is ideal for industrial and
commercial size buildings that require large arnounts of fresh air for ventilation
requirements. Figure 1.1 show a picture of a Solanvail@ installation quoted as the
world's largest solar air heating system. The SolarwallQ was instailed on a Canadair
(division of Bombardier) building in Montreai, Quebec m.
Figure 1.1. Solarwall@ installed on a Canadair building in Montreal, Quebec, Canada.
Some other applications of transpired solar collectors are shown in figures 1.2 and
1.3 and include: corridor ventilation for high rise apartment buildings, preheat of
combustion air for central heating plants or industrial tùrnaces, and crop drying.
Figure 1.2. Solarwall@ used on an apartment building in Windsor, Ontario.
Figure 1.3. Crop drying of tea leaves using a solar transpired collector.
1.2 Overview of the Operation of a T~vica l Transpired Solar Collector
A transpired solar collector is a relatively simple and inexpensive design. A thin,
dark-coloured aluminurn or galvanized steel cladding perforated by tiny holes is placed
on top of a new or existing south facing wall. This second skin creates an "air space" or
plenum usually 20-30 cm (8- 12 in.) wide. A ventilation intake fan creates a relatively
uniform negative pressure in the plenum that draws air though the holes and up to the
buildings fiesh air intake. As air approaches the wall and is drawn through the tiny holes
(typically 0.8 mm) and up the plenum it absorbs the solar generated heat. See figure 1.4
for a cut away schematic of a typical Solarwail@ installation C-)
Outrlde Air n H u l e d Passing Thrargh Abwrbar
- - A+ S p c t
Cm(ileâ Sheet Pmwdcl Wind B a n d a y Layer
U L
Figure 1.4. Schematic of a typical installation of a transpired solar collector system (lJ.
According to Conservai Systems Inc., the manufacturer of Solarwall@, their
transpired solar collector system ais0 has other benefits. During the heating season when
the wall is working, the plenum of the Solamail@ acts like added insulation and recovers
heat that would be lost if the Solarwall were not present.
Another benefit is that the cladding material helps to cool in sumrner by preventing
solar radiation fiom striking the buildings main wall. "Hot air is thermally siphoned up
the wall and ventilated through holes at the top of the cladding, leaving the main wall
cool. By-pass darnpers in the surnmer allow non-heated air to be drawn directly into the
building, maintaining indoor air quality (l)."
In addition to the Solarwall@ itself, the Conserval distribution ducting system is
designed to deliver intake air kom the ceiling in order to reduce temperature stratification
between the floor and the ceiling (see figure 1.4). This is especially beneficial in
buildings with hi& ceilings, as it reduces overall heating requùements and reduces the
heat lost through the roof by conduction (see figure 1.5 below). Similarly dl air
exhausted fiom the ceiling area of the building will be at a lower temperature after
destratification,
Figure 1 S. Temperature stratification usuaily occurs in builduigs with high ceilings which results in cold temperatures and drafts at floor level and hot air being exhausted at the ceiling.
1.3 Literature Review
The basic problem of the transpired solar collector is one where suction is applied to
a heated perforated plate that is placed in a fluid flow. Boundary layer flow parallel to a
porous surface has received a great deal of study in aerodynamic applications, such as the
use of suction on airplane wings to reduce drag. "Heat transfer issues have been
addressed in conjunction with injection cooling for turbine blades and rocket
nozzles (2)". However, heat transfer with suction had not received much study until
recently.
Papers on heat transfer with suction have been published primarily in the last
decade. Exceptions prior to this were a German patent (Wieneke, 198 1) describing an
unglazed perforated roof absorber for heating ventilation air, and a fabnc absorber
described by Schultz (1988) used in Germany for crop drying (2).
In 1992 C.F. Kutscher presented his Ph.D. thesis entitled "An Investigation of
Heat Transfer for Air Flow through Low-Porosity Perforated Plates." Later
Kutscher et ai. examined the heat losses associated with unglazed transpired solar
collectors (2). The theory used to develop their model was based on parallel larninar flow
over a homogeneous suction surface (suction over a mesh-like surface). The model was
developed based on temperature and velocity boundary layer theory. In the model it was
assumed that most of the temperature rise occurred on the front of the collector plate as
the air passed over the mesh-Iike surface. The basic theory developed in their paper
indicated "that for unglazed transpired solar collectors, heat losses due to natural
convection are negligible, and those due to wind should be srnail for large collectors
operated at typical suction velocities (2)". However, they indicated that more research
was required to extend their theory to less ideal circumstances. This included research
into the effects of turbulence and three-dimensional nonparallel flow on the thermal
boundary layer.
Kutscher investigated the convective heat transfer effectiveness for low-speed air
flow through isothermai perforated plates, with and without a crosswind parallel to the
plate surface (5). The objective of this work was to provide information to allow
designers to optimize collector hole size and spacing. The experimentation was done in a
wind tunnel where the flow again was parallel to the test plates, in the region of
asymptotic boundary layer thickness with sufficient width to allow plate measurements to
be undisturbed by edge effects. Results from this experirnentation showed that the
suction flow rate, crosswind speed, hole spacing, and hole diarneter were major factors
affecting heat transfer.
Dymond and Kutscher developed a cornputer model to allow designers to easily
adjust design parameters of tmnspired solar collectors to achieve reasonable flow
uniformities and to determine eficiencies (4). The model they developed stemmed fiom
poor flow distribution noticed on some field applications of transpired solar collectors.
"Such poor distribution can cause radiative and convective heat losses at flow-starved
regions, reducing system performance (4)". The model was based on theory from
previous research where crosswind flow was parallel to the transpired solar collector.
1.4 Background and Obiectives of Present Work
1.4.1 Background of Thesis Topic Selection
As outlined in the literature review, most of the previous experimental and
theoreticai research done on transpired solar collectors was carried out under the
assurnption that the exterior airflow was paralle1 to the collector surface. This seems to
be a reasonable assumption for large wall surfaces and a starting point for initial studies.
However, as stated by Kutscher et al., more research was required to extend theory based
on the above assumption to less ideal circurnstances (2). This included research into the
effects of unsteady three-dimensional flow on a transpired solar collector. The proposa1
for this thesis sternmed in part fiom this recommendation.
When developing the proposal for this thesis, experimental testing of transpired
solar collectors using the wind tunnel at the Royal Military College (RMC) was initially
considered. Scaling factors associated with modelling a full-scale transpired solar
collector (e.g. 6 m x 10 m), with tiny perforations (typically 0.8 mm), quickly became an
issue. Generating and scaling atmospheric turbulence, for the mode1 mentioned above, in
the relatively small wind tunnel at RMC would have in itself presented a major
undertaking.
The idea of using a small transpired solar collector test section on an existing
building was then investigated. A search to find a large enough building with a southern
exposure to simulate actual atmospheric and building turbulence conditions was carried
out. The costs of properly installing a large enough test section soon became evident and
were not considered feasible with the limited resources available.
Conserval Engineering Inc. was contacted to determine if a full-scde operationai
SolawalI@ had been installed in the area. The Canadian Coast Guard Base in Prescott,
Ontario, was the closest available site. The Prescott Base has a number of fiuictions
including the maintenance of aids to navigation. In the fa11 of each year, navigation
buoys in the area are inspected repaired, repainted, or replaced as necessary. so that they
are ready for the next season. Any welding that is required to fullfil1 this function is
canied out in the welding shop situated on the base. Contaminates fiom the welding
process and negative pressures due to exhaust fans resdted in the requirement for
increased fresh make-up air in the shop. Two Solarwalls@ were installed in the late
spring of 1999, as an initiative to correct this situation. Permission was obtained fiom the
Prescott Base to instalI an expenmental set-up on one of the two newly installed
Solarwalls@.
1-42 Research Objectives
The first objective of this study was to set up an expenmental apparatus complete
with a data acquisition system at the Canadian Coast Guard Base in Prescott. The second
objective was to determine from data logged on site how wind and wind fluctuations
affected the performance of a transpired collector. The data were to be analysed using a
statistical software program. Oncoming wind direction, wind speed, solar radiation level,
arnbient temperature. and airtlow directly in front of the Solarwall@ were considered
important parameters for this study.
CHAPTER 2 - THEORY
2.1 Overall Heat Balance for a Trans~ired Solar Collecter
The overall heat balance for an ungiazed transpired collector fiom (S) is
pcPva Ac (Tou, - T h ) = 'c',a, - P r o , - Qconv (2.1)
"The lefi-hand of the equation represents the usefid energy collected Q)." The
temperature rise provided by the collector (AT) is the difference between the collector
outlet temperature (Tou,) and the free Stream ambient temperature (Tamb). The symbol vo
is the suction velocity ( d s ) over the collector surface (Ac) . The right-hand side of the
equation represents the total energy available less the heat lost through radiation (Q,J
and convection (G,). "Note that I, is the total radiation striking the absorber including
direct, diffuse, and reflected (3)". The collector absorptance is defined by a.
Equation 2.1 assumes that there is no heat transfer between the underlying block wall and
the fiesh intake air in the plenum, and that there is no heat transfer fiom the air in the
room to the fresh intake air as it flows through the distribution ducting. This assumption
is vaIid when Tou, approaches the indoor room temperature.
"Radiation loss occurs both to the sky and to the ground with the view factors
depending on the tilt of the absorber. Assuming the absorber is grey and diffuse, the
radiant heat loss" fiom (2) is
pd = E,~A,(?;.:,, - <..J,L. - ~ . J , ) (2.2)
The temperature of the ground or pavement in our case (Tg,) would generally be slightly
higher than Tomb (which would tend to decrease radition losses), and the sky temperature
(T&) would be slightly lower than TM (which would tend to increase radition losses).
Assurning that the increased radiation losses to the sky are counter-balanced by reduced
losses to the ground, equation 2.2 will be approximated for the purposes of dus snidy by
Qd = Er 0 A, (Tc:,, - TL ) (2.3)
Where the collector surface temperature is represented by T C O H .
2.2 Efficiencv and Effectiveness of a Trans~ired Solar CoIlector
in order to compare the performance of a transpired solar collector under various
wind conditions, a measure of its performance must first be defined. Eniciency is
defined as the ratio of the actual to the total potential heat transfer rate and is defined for
the purposes of this study by
For heat exchangers, the term effectiveness is typically used as a measure of
performance. Effectiveness is defined as the ratio of the actual to the maximum possible
heat transfer rate (total heat transfer rate less losses). Using the direct temperature
measurement used by Kutsher 0, the effectiveness is sirnply
According to Kutcher (3J this method has good accuracy at high effectiveness because
temperature differences are hi& so the impact of uncertainties in measurements is low.
Note that effectiveness values range fiom O to 1.
2.3 Airfiow around Buildings
In order to examine the effects of wind on a wall mounted transpired solar collector,
one must have a basic understanding of the flow patterns around buildings. Flow patterns
and surface pressures around buildings depend on a number of factors including;
atmospheric boundary layer profile, building geometry, wind direction, and turbulence
intensity. These factors will now be looked at in tum.
2.3.1 Atrnospheric Boundary Layer
"Wind, or the motion of air with respect to the surface of the earth, is fundamentally
caused by variable solar heating of the earth's atmosphere. It is initiated. in a more
immediate sense. by differences in pressure between two points of equal elevation (5)".
The earth's surface exerts a shear force on wind, retarding its motion. This creates what
is referred to as the atmosphenc boundary layer. The height of the atmosphenc boundary
layer normally ranges fiom a few hundred meters to several kilometers, and is inherently
turbulent. Its mean velocity profile depends on a number of factors including; wind
intensity, roughness of terrain, and angle of latitude. The mean velocity profile of the
atmosphenc boundary layer increases with height above the ground and is well described
by the log law @,fi). The velocity profile takes the f o m
where U(z) is the mean wind speed, u. is the fiction velocity, z is the height above the
surface, z,, is the roughness length, and K is von Kamih's constant (K z 0.4).
The mean velocity profile shape and its turbulence intensity strongly influence flow
patterns and surface pressures. The upwind mean velocity profile shown in figure 2.1,
results in a higher stagnation pressure on the upper part of the wall, which leads to a
downwash and recirculation on the lower one-half to two-thirds of the building (7).
Figure 2.1. Flow patterns around a rectangular building 0.
2.3 -2 Wind Direction and Building Geometq
Wind direction and building geometry have major effects on airfiow around buildings.
Flow separate at sharp edges and generate recirculating flows. Recirculating flows
usually occur on downwind walls and roof surfaces as seen in figures 2.1 and 2.2. If the
building is suficiently long, the flow will reattach to the building (see figure 2.2), whicfi
can result in two separate flow directions on a given surface. Note that, '-the downwind
wall of a building faces a region of low average velocity and high turbulence. Velocities
near the wall are typically one-quarter of those at the corresponding upwind wall
location (7)".
Figure 2.2. Surface flow patterns showing flow separation and reattachment (7).
2.4 Turbulence
2.4.1 Notation
Wind can be treated mathematically by decomposing it into a mean and fluctuating
component. The concept of mean and fluctuating components of velociîy are based on
Reynolds averaging. A Cartesian coordinate system is generally used with the
meteorological convention being; the x-axis in the direction of the mean wind velocity,
the y-axis horizontal, and the z-axis vertical (positive upward). The mean velocities
dong the x, y, and -. axes will be represented by U(x, y, z), V(x, y, z), and W(x, y, r )
respectiveiy. or simply as U, V, W. The time dependant or instantaneous velocities will
be represented by u(x, y, z, T), v(x , y, z, r), and w(x, y, z, r), or just u, v, W. The average
velocity U(x, y, r ) can be subtracted fiom the instantaneous velocity u(x, y, z, r) to obtain
the fluctuating component of the velocity uf(x, y, r, r) or just u', thus
The root mean squares (RMS) of the fluctuating components of the velocity vector are
sometimes used as measures of turbulence. More comrnonly, the non-dimensional
parameter of turbulence intensity is used. For exarnple, the turbulence intensity in the
x-direction, represented by I,, is found by dividing the RMS of the velocity fluctuation by
the mean velocity in the x-direction
similarly, I, and are the turbulence intensities in the y and z directions respectively.
2.4.2 Scales of Turbulence Considered
Wind is, by nature, unsteady and turbulent. Figure 2.3 shows the orders of magnitude
and ranges of different patterns of motion in the atmosphere. They range from
"turbulence, (vortices of air in the range of a few meters with a characteristic lifetime of
some minutes), to local weather systems and large planetary waves, which may
circumvent the entire globe and have a Lifetime of several days (6)". These phenomena,
shown on figure 2.3, are referred to as microscaie, convective scale and macroscaie 0.
Work in this thesis will be carried out mainly in the microscale and convectice scale.
Microscal e Convecüve d e Macroscale I I 1 1 t 1 1 I I w
0.01 0.10 1 IO IO* 103 104 105 106 10' Geographical dimension, m
Figure 2.3. Orders of magnitude in space and time for different patterns of motion in the atmosphere (fi).
2.5 Spectral Analysis
Spectra are often used as a tool to analyse the different fiequencies of wind. For
example. peaks in a spectra can be characteristics of local hourly wind conditions on the
micro or convective scale, or weather systems on the macro scale. Figure 2.4 shows two
different autospectra for wind velocity. The solid curve is based on measurements at
30 m and the dashed curve is based on measurements at a height of 100 m.
Measurements were taken during a one-year period on open terrain in Denmark and New
York State respectively. (6)
Period I I I I I 1 year 4days Iday 1 h 10min
I 1 s
Figure 2.4. Autospectra for wind velocity. The solid curve corresponds to measurements in Denmark at 30 m, and the dashed curve represents measurements at 100 m in New York State (6).
Some of the important properties of the autospectra observed in figure 2.4 now follow.
There is a great deal of movement lasting approximately 4 days, the same lifetime as a
fully developed weather system. Clear peaks are seen at 1 day and at !4 day for the
Denmark and New York State autospectra respectively. The amount of variance in the
range of approximately 10 minutes to 5- 10 hours is very low. This is referred to as the
spectral gap. "The spectral gap means that the wind climate and the turbulence in the
atmospheic boundary layer are mutually independent, so they may be treated separately
and superimposed (6)". See Figure 2.5 for an example of superposition. Also note that
the New York State data have rather high values between a few seconds and 5 minutes,
which are attributed to turbulence. The Denmark spectrum has the same tendency but it
is less pronounced. (6J
Figure 2.5. Gust wind velocity U + u, is separated into a wind climate component U and a turbulent component ug (or u' used in this thesis). Note that the turbulent component has been normaiized. (6)
Similar spectra from other locations show that the properties mentioned in the previous
paragraph are typicai in temperate zones (6). As a consequence of the spectral gap, mean
wind velocities based on a period of 10 minutes or 1 hour wilI not show much
di fference. (6)
CHAPTER 3 - EXPERJMENTAL APPARATUS AND METHODOLOGY
3.1 Selection of Solanvall@
Two separate Solarwalls@ were installed in early 1999 at the Canadian Coast Guard
Prescott Base, one on either side of the large Welding Shop door (see figure 3.1). The
West SoIarwallO (left of the door) was selected for experimentd purposes, as its surface
area did not become significantly shaded during the course of the day.
Figure 3.1. Two newly installed Solarwalls@ at the Canadian Coast Guard Prescott Base, one on either side of the Welding Shop door. Experimentation was carried out on the West Solarwall@ (lefi side of door).
A site map of the Prescott Base and const.ction drawings of the Solanvalls@ are
included in appendix B. The installation seen in appendix B is not a typical installation
as shown is figure 1.4, because some modifications had to be made due to a large
overhead Crane at ceiling level that ran the length of the welding shop. Outlet ducts were
lowered so that they would not impede the overhead crane (see figure 3.2). Normally
distribution ducting is mounted at ceiling level (as shown in figure 1.4) in order to take
advantage of the destratification benefits outlined in section 1.2. The two outlet ducts
and intake fans of the west Solarwall~ have been labelled as Duct 1, Duct 2, Fan 1, and
Fan 2 for future reference.
Figure 3.2. Overhead crane, two outlet ducts and two intake fans of the west Solarwall@ in the Prescott Welding Shop.
3 -2 Selection and Placement of Instruments
A number of instruments were required for the expenmentai set-up. Budget
restrictions limited the selection largely to existing equipment available within the
Department of Mechanical Engineering at RMC. However, a sonic anemometer and two
pressure transducers were purchased for this project. The equipment selected and a brief
description of their use and placement now follows.
3 -2.1 Sonic Anemometer
The b a i s for this study was to examine how three-dimensional flow afiected the
performance of a transpired solar collector. in order to characterize the flow across the
collector, an instrument to simultaneously measure the wind velocities in three
dimensions was required. Most cup anemometers only provide the velocity of a two-
dimensional flow and do not measure small or rapid fluctuations. Therefore, an
ultrasonic anemometer was selected for the purposes of this study. Uitrasonic
anemometers measure wind velocity based on the transit time of ultrasonic signals
between transducers.
The recently developed Young Model 8 1000 Ultrasonic Anemometer was acquired
for the expenmental set-up. It was selected because it was able to measure three-
dimensional wind velocities, and it was significantly less expensive than other sonic
anemometers found on the market ($4,000 Cdn vs. $8,000-$25,000 Cdn). This mode1
measures the three components of velocity in a cornmon volume. It also provides a good
range (0-50 d s ) , resolution (0.0 1 rn/s), threshold (0.0 1 d s ) , and accuracy (* 1 % rms for
0-30 mis). The Young Model 8 1000 also has the added benefit that one of its outputs is
air temperature, which it calculates fiom the speed of sound. The range of the sonic
temperature is -50 to +50 OC, with a resolution of 0.01 OC, and an accuracy of * 2 OC.
Further details on the specifications of the Young Mode1 8 1000 ultrasonic anemometer
are found in appendix C.
A speciai bracket was designed in order to mount the sonic anemometer at a given
distance fiom the wall. The supporting bracket was designed to be light weight yet
sturdy enough to keep the sonic anemometer securely in place without vibrating. It was
also designed to cause minimal obstruction to the main flow and to allow the sonic
anemometer to move parallei to the wall up to a distance of 0.6 t m (2 fi). The bracket
came apart in sections and included slotted connections for easy transport, mounting and
adjustment on site (see figure 3.3).
Only one sonic anemometer was use for this study due to their high costs. In order
to obtain a picture of the mean flow across the wdl it was decided to place the sonic
anemometer directly in the centre of the Solarwall@.
Figure 3.3. The sonic mernometer mounted on its support bracket directly in the centre of the west Solarwall@.
3.2.2 Pyranometer
A pyranometer is a standard instrument that measures both direct and diffuse
(reflected) solar radiation. "The World Meteorological Organization (WMO) descnbes
the pyranometer as an instrument for measuring solar radiation from a solid angle of 2n
stemdians into a plane surface and (with) a spectral range of 0.3 to 3.0 Fm (8)."
Beaubien et al. (8) divided pyranometers suitable for solar energy measurements into two
basic categories. Black surface pyranometers, which measure temperature rise of a black
surface referenced against a thermal mass or a reflective white surface, and photometric
pyranometers which convert radiant energy directly to electrical energy. Some black
surface pyranometers meet or exceed the WMO specifications for high quality
instruments suitable for use as secondary standard measurements. "The photometric
types, although less expensive to manufacture, have spectral responses govemed by the
semiconductor material, typically silicon, and are not classified by the WMO for
reference-grade applications (û)."
A Kipp and Zolen CM 1 O pyranometer (black surface pyranometer) was borrowed
from the Solar Calorimetry Laboratory of the Mechanical Engineering Department of
Queen's University. It was re-calibrated against two other pyranometers at the Queen's
Solar Calorimetry Laboratory in November 1999. The CM 1 O was mounted parallel to
the wall in order to determine the total amount of solar radiation seen by the SolanvdlB.
The pyranometer was rnounted on the east SolanvallQ as seen in figure 3.4, in order to
reduce the arnount of cable required to the data acquisition system.
Figure 3.4. View of the Kipp and Zolen CM 10 pyranometer mounted on the east Solarwall@.
3 -2.3 Temperature Measurement
Temperature measurements were carried using OrnegaB type K (chrorneValume1)
therrnocouples. Thermocouple measurements are based on the potential difference
between junctions of two dissimilar metals. In an effort to keep budget costs low. type K
thermocouples were chosen for measuring temperatures, as they were already available in
the Department along with type K shielded thermocouple wire.
In order to obtain a reading of a thermocouple source temperature, the cold junction
or reference junction temperature must be known. An Omega@ mode1 MCJ Electronic
Ice Point was used to provided a reference junction voltage equai to that of O OC junction.
The battery powered electronic ice point was placed in a shielded metai box that housed
the data acquisition connector block (to be discussed in section 3.3.1).
An OmegaB quick discomect thermocouple probe with an exposed junction tip was
inserted in each of the two outlet ducts (as seen in figure 3.5). One was also placed in the
metal box that housed the connector block. A fine gauge thermocouple was aiso
mounted on the SolanvallG3 with epoxy directly behind the sonic anemometer.
Figure 3.5. Placement of thermocouple probes and pitot-static tubes in the outlet of Duct 1 of the west Solarwall@.
3.2.4 Pressure Transducers
Pitot-static tubes comected to Setra model 264 %ery low differential pressure
transducers" were used to determine the velocities in the outlet ducts of the Solarwall@.
The pitot-static tubes were mounted near the centre of the long straight duct nuis as
shown in figure 3.5. They were mounted in this location in order to ensure the flow
would be as close to fully developed as possible for ease of calibration of the duct. The
Setra model 264 senses pressure difference, with a range of 0- 1.27 cm (0-0.5 inches)
water column, and converts this to a 0-5 Volt DC output. It has a static accuracy of 1%
full scale (or 0.0127 cm of water) in normal ambient ternperature environments.
3.2.5 Remote Weather Station
Local flow and temperature measurements where taken near the Solarwall@. using
the instruments mentioned in the previous pages. A measure of the local conditions of
the fiee Stream arnbient air was also required. A Davis "Weather Monitom'weather
station was used for this purpose. This weather station consists of a cup anemometer
with wind vane for measuing wind speed and direction. and a temperature and hurnidity
sensor. These sensors are wired into a display console that also measures baromeeic
pressure. A *'WeatherLink Data Logger@" was attached to the "Weather Monitor@" and
data were downloaded to a laptop PC using "WeatherLinkW software.
The cup anemometer was fixed to a tower 10 m fiom the ground, a standard height
used in meteorology. The tower is seen in figure 3.6. The weather station display
console was placed in the Helicopter Hangar Flight Office (see figure 3.6), and the
temperaturehumidi~ sensor was mounted under the eaves of a north-side wall as per the
manufacture's instructions (see figure 3 -7).
Helicopter Hangar
Figure 3.6. Helicopter Hangar and Flight Office. The cup anemometer was mounted on the tower and the weather station display console was placed inside the Flight Office. Note there is a construction trailer in the foreground that is not typically in this location.
Figure 3.7. Temperaturehumidity sensor shown mounted on the north wall under the eaves of the Flight Office.
The wind vane of the cup anemometer was oriented so that it would log the
oncoming wind direction, as is the practice in meteorology. The wind direction measured
by the cup anemometer was displayed as one of the 16 directions normally found on a
compass (Le. N, MuE, NW. ENE, E, etc). These 16 directions were converted to an
angle in degrees as shown in figure 3.8. The orientation of the Solarwall@ and sonic
anemometer were also included in figure 3.8. as references for future cornparisons of
performance based on wind direction. This reasoning will become more evident in the
following chapters.
Figure 3.8. Divisions of 16 possible cup anemometer wind directions. Orientation of the So larwall@ and sonic anemometer have been included for future re ference. Note that W for the sonic anemometer is positive in the upward direction.
3.3 Data Acquisition Svstem
3.3.1 Hardware
The data acquisition hardware for this project was placed on the second floor of the
Equipment and Systems Maintenance Shop, which was located directly beside the
welding shop. It was placed in this area and not in the Welding Shop in order to keep the
computer equipment fiee of the electrical noise and fine dust produced by the welding
process.
Shielded instrument wires were connected to a National InstrumentsTM CB-68LP
connector block, which was housed in a grounded metal box in order to reduce potentiai
noise. The connector block was comected to a National Instruments mode1 AT-MO-
16E-2 data acquisition board, which was installed in an IBM compatible penonai
computer. The sonic anemometer is capable of producing a digital output, and therefore,
was comected directly to the computer by means of a communication port.
3.3.2 Software
LabVIEW 5.0.1 was the software interface used h r the data acquisition and logging
process. LabVIEW is graphical prograrnming based software with data acquisition,
logging, and virtual instrumentation capabilities. Graphical prograrns were used and
created in LabVIEW in order to process and log signals, fiom both the data acquisition
board and the sonic anemometer. Copies of the graphical LabVIEW programs developed
are included in appendix D.
3.4 Lab Calibration of Equipment
3.4.1 Calibration of Sonic and Cup Anemometers
The sonic and cup anemometers were mounted in the RMC Wind Tunnel in order to
compare their output velocities with each other in both larninar and turbulent flow.
Turbulence was created by placing a screen mesh in front of the working section of the
wind tunnel. The output velocities were also compared to the wind tunnel velocity
calculated using a pitot-static tube and a Delfi water manometer. The results of this
testing are shown in appendix E. Note that the sonic anemometer had a resolution of
0.01 m/s and the cup anemometer had a resolution of 0.4 m/s.
Under both laminar and turbulent fiow conditions, the sonic anemometer had a
maximum difference in velocity of 1.3% (in the range of 4 to 22 m/s) when compared the
calculated velocity of the pitot-static tube. This was within the resolution capabilities of
the two measurement techniques, and therefore, no adjustrnents were made to the sonic
anemometer or its recorded data.
In turbulent flow conditions, the cup anemometer was found to be on average
0.46 rn/s below the reading of the sonic anemometer, close to its resolution capabilities.
Given that the cup anemometer and wind vane were to provide a general direction and
wind speed over a fifieen-minute time interval, its resolution and accuracy were
considered acceptable. No corrections were made to the recorded wind speeds.
3.4.2 Caiibration of Pressure Transducers
The Setra mode1 264 pressure transducers were caiibrated in the RMC wind m e 1
before use. This was done by comecting the pressure transducers to pitot-static tubes and
plotting their output voltages versus the wind tunnel static pressure. n i e pressure in the
wind tunnel was measured by another pitot-static tube comected a Delft water
manometer. The calibration curves obtained for the two transducers are shown in
appendix E. These two calibration curves were used in the LabVIEW data acquisition
program to provide direct pressure outputs in Pascals.
3.4.3 Comparison of Sonic Anemometer, Weather Station, and Thermocouple Temperatures
The sonic anemometer, weather station temperature sensor, and thermocouple
probes were placed in the wind tunnel for cornparison purposes. This testing was done in
conjunction with the pressure transducer calibration mentioned above. It was detennined
that the thermocouple temperature readings were on average 1.9 OC higher than the sonic
temperature reading dunng the 40 minute test. The weather station temperature sensor
was on average 1 .O OC higher than the sonic temperature. Thermocouple output readings
in a four-minute ice bath test were an average 0.74 OC. The sonic anemometer
temperatures were used as the reference readings and corrections were applied to
thermocouple measurements. The corrections applied are shown in appendix F.
Accurate temperature differences were considered more important than absolute readings.
3.4.4 Calibration of Solarwall@ Exhaust Duct Flow Rates
Calibration of one of the two Solarwdl@ exhaust ducts was done on site d e r al1 the
instruments were put in place. Because both of the exhaust ducts were similar, only one
calibration was carried out. The calibration was done by moving the pitot-static tube,
fiom its position roughly in the centre of the duct, to the duct wall and back. The
centreline profile was determined using this partial traverse by assuming symmetry and
fûlly developed flow. Syrnmetry and fully developed flow were again assurned to expand
the centreline profile to a two dimensional duct. Using this 2-D velocity profile, a duct
coefficient of 0.86 was caiculated (see appendix G).
3 -5 Uncertaintv
Uncertainties, accuracy, and the range for the instruments used in the experirnental
set-up are summarized in appendix H. The calculation of uncertainty for efficiency is
also included in this appendix.
3.6 Problems Encountered with the Experimental Apparatus
3 -6.1 Themocouple Readings
Temperature readings fkom the two thennocouples inserted in the outlet ducts wodd
sporadically read temperature values well below -1 000 OC. A very large negative
reading usually indicates a discontinuity in the thermocouple wires, however, no
discontinuity was found. No set pattern or source could be determined either for this
problem which occurred only on occasion. The problem also appeared in the output of
the thermocouple connected to the wall, but much less frequently when compared to the
outputs of the two duct thermocouples. Al1 thermocouple wires were shielded and
grounded to the cornputer ground. The wire fiom the thermocouple mounted to the wall
was nin outdoors while the wires fiom the duct thermocouples were strapped to pipes at
ceiling level in the welding shop. Higher sources of electronic noise in the welding shop
may have contributed to the higher instances of irregular values for the thermocouples
placed indoors. Even one temperature reading of less than -1 000 OC would invalidate
the mean interval reading for that penod. In order to correct this problem the data
acquisition program was modified to determine the number of times a large negative
valued appeared. If large negative numbers appeared less than twice in a sampling period
they were filtered out. If they appeared more than twice the data were discarded. A large
negative value rarely appeared more than once in a five-minute sampling period.
This effected data collected in the months of December 1999 and January 2000, and
resulted in a modification to the LabVIEW data acquisition program in late January to
circurnvent this problem.
3.6.2 Short Cycling and Flow Rate of Intake Fan 2
Problems were also encountered with short cycling of intake Fan 2, which was
connected to Duct 2. Intake Fan 2, unlike intake Fan 1 was controlled by a temperature
sensor which turned the fan on and off at a given set temperature of approximately SOC.
The temperature sensor wâs installed in the duct with the intention of shutting off Fan 2
when the air from the Solarwall@ was below 5°C. The fan did shut off when the
temperature fell below SOC, however, warm air nsing up Duct 2 from the room would
turn the fan back on just to be shut off again by the cold air from the Solarwall@ plenum.
When the temperature of the intake air from the SolanvaIl@ was less than 5OC, this
process would continually repeat itself. short cycling Fan 2 and providing inaccurate
temperature readings. The average pitot static pressure in Duct 2 was also found to be
significantly lower than that of Duct 1, when both intake fans were ninning continuously.
This led to an approximately 40% lower velocity flow rate in Duct 2 when compared to
Duct 1. Intake Fan 2 was shut off and the duct outlet covered in early February 2000, in
order to circumvent these problems, until a solution could be found and irnplemented by
the Prescott Base electrician. Further discussion and recommendations resulting fiom
this installation flaw will be dealt with in subsequent chapters.
3.6.3 Sonic Anemometer
The logging of sonic anemometer data failed on a number of occasions. The sonic
anemometer would often work fine for a number of days and then would suddenly fail to
communicate with the data acquisition system. Wire connections were checked and the
sonic anemometer was even brought back to RMC for testing. No cause for the sudden
failures could be determined until one raïny day in the beginning of Apnl when there was
no communication between the sonic and the data acquisition system. Wires were again
checked to no avail. A thin film of water was noticed on the lower instrumentation heads
of the sonic anemometer. These heads were dried off and communication between the
sonic anemometer and the data acquisition system was quickly re-established. From
looking at past data it was detemined that the sonic anemometer usually failed on very
rainy or snowy days, indicating that a build-up of liquid or snow impeded its ability to
work correctly. Nomdly these types of instruments are mounted on a tower to collect
weather data where wind would reduce the chances of a film from forming. In this
application the sonic was mounted in a relatively "sheltered" location near the wall.
3.6.4 Electronic Ice Point
The power of the battery in the electronic ice point slowly declined until the battery was
changed at the end of February. A correction, as detailed in appendix F, was applied to
temperature measurements taken between December and February. The data colIected
duing these months were mainly recorded when the sonic anemometer was located at a
distance of 30.5 cm (12 in.) fiom the Solarwall@. In order not to compare "apples with
oranges" or introduce M e r errors it was decided to analyse these Iimited data
separately. Anaiysis of the limited data recorded in February at a distance of 6 1 cm
(24 in) fiom the Solarwall@ (5 days and only 1 day over 600 w/m2) was not considered
prudent or necessary given the uncertainty of the correction factor applied to the
thermocouple temperatures.
3.6.5 Weather Station Temperature Sensor
The temperature sensor that was part of the remote weather station was installed as
per the manufacturer's instructions in the shade of the eves of a no& wall. It is suspected
that solar heating of the roof of the helicopter hanger influenced the temperature sensor,
because its measurements were much higher when compared to a portable sensor that
was used to double-check temperature readings. As a result, the sonic temperature was
used instead of the weather station temperature as a measure of the ambient temperature.
The consequences of this assumption will be discussed in the latter chapters.
CHAPTER 4 - RESULTS
As stated in the previous chapter, difficulties were encountered in simultaneously
recording al1 the required parameters for this study. Results presented here, unless
otherwise stated, will deal with data recorded every five minutes in the month of March
2000. Specifically Julian days 6 1-70, 74, 75, 8 1-88, and 90-92 inclusive (a total of 24
days). The data for al1 of these days will be referred to as the "March data set." During
this time the sonic anemometer was located in the centre of the Solarwall@ at a distance
of 61 cm (24 in) from edge of the cladding. Only one intake fan was in operation in the
month of March due to problems encountered with short cycling of the second intake fan
as discussed in section 3.6.2. The operating intake fan (Fan 1) was connected to what is
referred to as Duct 1.
4.1.1 Typical Data Acquisition Outputs
Figure 4.1 shows some typical data for a seven-day period (Julian days 82-88
inclusive). Figure 4.1 (a) shows the pitot static pressure in Duct 1, which was used to
calculated the veIocity and volume flow rates in the duct.
Figure 4.1 (b) represents the "total solar radiation" measured by the pyranometer,
which was mounted vertically on the wall. The pyranometer was mounted vertically in
order to measures the total solar radiation seen by the SolanvaIl@ including; direct beam,
difise, and reflected radiation. Note that on a very sunny day (e-g. Julian day 84) the
total solar radiation rises and falls smoothly with a more graduai slope at the very end of
the curve. The gradual dope at the end of the day is due to the di f i s e and reflected
radiation seen by the wall when there is no direct beam radiation. Note the large
fluctuations in Julian days 85-87, which are representative of partly cloudy days, and
Julian day 88, which is representative of a very overcast day.
Figure 4.1 (c) depicts the ambient temperature measured by the sonic anernometer
(sonic temperature), the temperature of the Solarwall@ cladding (wall temperature), and
the temperature of Duct 1. Al1 temperatures are in degrees Celsius (OC). Note that in the
evenings the wall temperatures and ambient sonic ternperatures tend to be almost equal.
This is logical as there is no heating of the Solarwall@ in the evenings. In the evenings
and on overcast days (e.g. Julian day 88), there is still a temperature rise of the air
(temperature Duct 1 - ambient sonic temperature), even though the wall temperature is
below the temperature in Duct 1. This is due to the recapture of heat loss from the
underlying block wall and convective heating of the air as it travels through Duct 1 (to be
discussed in further detail in section 4.2.2). Often there tends to be gradual cooling of the
ambient temperature after sundown and right up until dawn. Hence, comesponding
cooling of the wall and Duct 1 temperatures.
Figure 4.2 on the next page shows the history of the large scale fluctuations of the
mean wind velocities seen close to the Solarwall@ for the same period as figure 4.1 (Le.
Julian days 82-88 inclusive). LI is the mean horizontal velocity parallel to the wall
(positive to the east), Vis the mean velocity normal to the wall (positive towards the
wall), and W is the mean vertical velocity parallel to the wall (positive up). See figure 3.8
for the orientation of the sonic anetnometer with respect to the wall.
4.1.2 Measurements fiom the Weather Station Cup Anernorneter
As stated in section 3.2.5, a cup anemometer was mounted 10 meters above the
ground on a tower located beside the Helicopter Hangar. The anemometer provided a
general indication of mean wind speeds and direction over 15 minute intervals.
Figure 4.3 represents the distribution of wind direction for the March data set. Notice
that the predominant wind direction at the Prescott Base is fiom the southwest (or 225
degrees), an approach direction approxirnately parallel to the Solarwall@.
Wind Direction (degrea)
Figure 4.3. Wind direction distribution for the March data set.
Figure 4.4 shows the weather station cup anemometer wind speed distribution for
the March data set based on the Beaufort Scale. The classicd Beaufort Scaie was used to
represent the wind speed distribution because it provides a description of the effects of
wind at various intensities. The Beaufort Scale is summerized in Table 4.1 (5).
Light breeze Moderate breeze
Light airs Gentle breeze F res h brecze
Figure 4.4. Weather station cup anemometer wind speed distribution based on the Beaufort Scale for the March data set.
Beaufort Description of Speed Description of Wind Effects Number W ind W s )
Calm
Light airs
Light Breeze
Gentle breeze
Moderate breeze
Fresh breeze
S trong breeze
Moderate gale
Fresh gale
Strong gale
Less than 0.4 No noticeable wind.
0.4- 1 -5 No noticeable wind.
1 -6-3.3 Wind felt on face.
3 -4-5 -4 Wind extends Iight flag. Hair is disturbed. Clothing flaps.
5.5-7.9 Wind raises dust, dry soil, and loose paper. Hair disarranged.
8-0-1 0.7 Force of wind felt on body. Drifting snow becomes airborne. Limit of agreeable wind on land.
10.8- 13.8 Umbrella used with difficulty. Hair blow straight. Difficulty to walk steadily. Wind noise on ears unpleasant. Windbome snow above head height (blizzard).
13.9-17.1 Inconvenience felt when walking.
17.2-20.7 Generally impedes progress. Great difficulty with balance in gusts.
20.8-24.4 People blown over by gusts.
Table 4.1 Summary of Beaufort Scale (S.
4.2 Calculated Results
4.2.1 Air Temperature Rise vs. Total Solar Radiation
Figure 2, of appendix A, is a plot of temperature rise versus total solar radiation for
various flow rates. Appendix A was part of literature provided by Consenal Engineering
Inc. and Conserva1 S ystems Inc., the designers and manufactures of SolarwallB.
Figure 4.5, on the folIowing page, shows a similar plot prepared using data logged tiom
the Prescott Solarwall@ in the month of March 2000. As stated earlier, only one duct
was in operation in the rnonth of March due to problems encountered with short cycling
of the second intake fan. The airflow rate with just one fan in operation was roughly
0.0 1 m3/s per rnz of Solanvall@.
The performance lines depicted in figure 2 of appendix A for flow rates
B (0.01 m31s/m') and C (0.02 m3/s/m'), have been included in figure 4.5 for cornparison
purposes. Note that airflow rates (m3/s) are per rn' of Solmall@, hence, m3/s/m' as
shown in figure 2 of appendix A, or simply the suction velocity (v,) in fiont of the
SolanvallGQ in m/s. Performance line B, which is the sarne airflow rate for just one fan in
operation (0.01 m3/s/m2), is much higher than the Prescott data. However, performance
line C (0.02 m3/s/m') falls more closely to the temperature rises of the March data set.
This would suggest that the intake Fan 1 may only be making use of half of the area of
the Solawall@. However, this assumption will not be made for the results presented in
this chapter and the total area of the wall will be used for the calculation of efficiency.
The differences in efficiency are deemed more important than their absolute accuracy.
4.2.2 Temperature Rise due to Non-Solar Radiation
As mentioned in section 1.2, one of the secondary advantages of the SolanvaIl@
is that heat lost through the original exterior block wall is recaptured in the plenum
created between the block wall and the SolanvalI@ cladding. Figure 4.6 is a plot
created using data fiom the March data set, when the intake Fan 1 was lefi in
operation between 6 p.m. and 6 a.m. The temperature rise (temperature Duct 1 -
ambient sonic temperature) was plotted versus the ambient sonic temperature. One
can see fiom figure 4.6 that there is a ternperature rise even when there is no solar
heating present, and this temperature rise increases as the outdoor ambient
temperature decreases. It is also important to note that there is some convective
heating taking place as the air travels through the intake duct inside the room, in spite
of the fact that Duct 1 contains a thin layer of insulation which was designed to
reduce noise.
The Iarge scatter of the points, in figure 4.6, is mostly due to the fact that the
interior ternperature of the welding shop is not at a constant temperature (especially at
night). Temperatures inside and outside the shop also Vary fiom night to night, thus
affecting the heat transfer rate.
No correction was made for the temperature rise due to heat recovery fiom the
block wall and convection in the duct, due to the difficulty in calculating a heat
transfer coefficient that would apply under various solar radiation levels. This will be
discussed further in the next chapter.
-10 -5 O 5 10 15 20
Sonic Temp (deg C)
Figure 4.6. Temperature nse (temperature Duct 1 - arnbient sonic temperature) versus ambient sonic temperature. Data fiom March data set when the intake Fan 1 was left in operation between 6 p.m. and 6 a.m.
4.2.3 Efficiency and Effectiveness versus Solar intensity
As stated in section 2.2, the performance of a heat exchanger is usually based on
efficiency (equation 2.4) or effectiveness (equation 2.5), in which the latter is usually
the nom. Figure 4.7 is a plot of efficiency and effectiveness versus the total solar
radiation seen by the Solarwall49, based on the March data set. The data for
efficiency and effectiveness have been fùrther sub-divided in two, to show the
difference between when the solar intensity is increasing (to 9:40 a-m.) and when it is
decreasing (after 9:40 p-m.). The peak level of solar radiation seen by the Solarwall@
occurred at approximately 9:40 a.m. in the month of Manih. This is due to daylight
savings time and the fact that the orientation of the Solarwail@ was not directly to the
south. Efficiency and effectiveness decrease as the IeveI of solar radiation increased.
This is because radiation heat losses increase with increased surface temperature
(Stefan-Boltzman's law).
A wider distribution of data occurs at lower solar intensities and is a result of a
number of factors. At low levels of solar radiation, the temperature nse due to other
sources of heat (mentioned in section 4.2.2) has more of an effect. The distribution is
also greater afier 9:40 a.m., because as the solar intensity drops there is a slow release
of energy stored in the mass of the SolarwaIl@ and underlying block wall. Similarly,
partly cloudy days result in intermittent heating and cooling of die Sohwdl@, which
also causes greater fluctuations.
Uncertainty increases when the difference in temperature rise decreases at lower
solar intensities. Temperature rise is a key factor in detennining the uncertainty of
efficiency (see appendix H). Uncertainty in efficiency increases from a maximum of 8%
at solar radiation levels of 600 w/m2 to 14% at 200 w/rn2. Uncertainty and the release of
energy from the underlying block wall rnay be reasons why some effectiveness values
were greater than one, especially when solar radiation levels decreased afler 9:40 a-m..
The calculation of effectiveness was based on the temperature of one fine wire
thermocouple mounted to the centre of the west SolarwallB, with the assurnption that the
cladding was close to being isothermal. This assumption may not be valid for the low
flow rates encountered when only one fan was in operation. in reality temperatures were
probably lower near the centre of the wall, where the intakes were located, and higher
near the extremities. Because the thermocouple was mounted in the centre of the
SolarwaIlB (a region of I o w a temperature) it would cause effectiveness values to rise
(see equation 2.5). This may have also contributed to the extremely high effectiveness
values at low solar intensities.
Efficiencies were lower than expected, but were also a result of the low flow rate.
Kutscher et al. developed a mode1 that predicted constant efficiencies independent of
wind speed for suction velocity flow rates greater than 0.05 d s . At solar radiation
intensities of 700 w/m2, the efficiency was approximately 78 percent for an absorber
emissivity of 0.9 (3). However, this efficiency dropped to approximately 45-50 percent
for a suction velocity flow rate of 0.01 m/s (which is representative of our case).
4.3 Statistical Analysis
4.3.1 Selection of Data Used for Statistical Analysis
As stated previously, the March data set included data recorded every five minutes
in the month of March 2000, specifically Julian days 6 1-70, 74, 75,8 1-88, and 90-92
inclusive (a total of 24 days). The sonic anemometer was located 6 1 cm (24 in) from the
Solanvall@, and only one intake fan (Fan 1) was in operation during this period.
Prelirninary statistical analysis was done on the March data set where the solar radiation
was above 200 w/rn2. This data set will be referred to as the March data set (solar
radiation > 200 w/rn2). The statistical analysis was done using a software program called
SPSS for Windows release 10.0.0.
Considerable scatter was found in the March data set (solar radiation > 200 w/rn2).
Therefore, data where the solar radiation was above 600 w/m2 were chosen for m e r
analysis, because there was less scattenng of data. This data subset will be referred to as
the March data set (solar radiation > 600 w/m2). Further rational for choosing data above
600 ~ l m ' is given below.
The box plots in figure 4.8, show efficiency and effectiveness ranges for data with
solar radiation levels above 200 w/m3 and 600 W h 2 . The number of usable data
points (N) is 1023 and 483 respectively. The box plots were produced using SPSS, and
they show the rnedian and interquartile range of the data (Le. data broken down in four
ranges). ï k e y also show outliers (cases between 1.5 and 3 box lengths) and extremes
(more than 3 box lengths). The box length is the interquartile range or the range where
25% of the points fa11 above and below the median (i.e. 50% of the data). Figure 4.7 also
shows that the efficiencies for the March data set (solar radiation > 600 w/m2) fdl in a
much narrower range with fewer outliers and extremes, when compared to the March
data set (solar radiation > 200 w/m2).
The maximum uncertainty for efficiency was calculated to be between 6 and 8 % for
the March data set (solar radiation > 600 w/rn2). in order to avoid clutter and confusion
directly on the plots, error bars will not be shown but their size is simply stated here.
Eflïcicncy Effectivcness
Figure 4.8 Box plots of efficiency and effectiveness for the March data subsets (a) solar radiation > 200 ~ l m ' , (b) solar radiation > 600 w/rnZ. Circles represent outliers and stars represent extremes.
4.3.2 Analysis Based on Oncoming Wind Direction
Box plots of wind speed, solar intensity, ambient sonic temperature, and wall
temperature were plotted versus oncoming wind direction for the March data set (solar
radiation > 600 w/mZ), and are shown in figure 4.9. They are presented to depict the
ranges for these parameters for different oncoming wind directions. The nurnber of data
points (N) used to create the individual box plot for a given wind direction is included on
the x-ais. No data were available at solar radiation levels above 600 w/m2 for wind
directions less than 67.5 degrees. Wind speeds tended to be in a similar range for wind
directions above 180 degrees, and the ranges and medians of solar intensities tended to be
sirnilar for most wind directions. The arnbient outdoor temperatures, when solar
radiation levels were above 600 w/rn2, were between approximately -8 and 12 O C for
most of the data (a range of 20 OC). The coldest arnbient temperatures occurred when the
wind was blowing out of the north (360 degrees). The Solarwall@ cladding
ternperatures, when solar radiation levels were above 600 ~ l m ' , were between
approximately 20 and 41 O C for most of the data (a range of 21 OC). The coldest wall
temperatures also occurred when the wind was blowing out of the no*.
Wtnd Direction (drgrees 1
Wind Direction (degmsi
Figure 4.9. Box pIots of (a) wind speed, (b) total solar radiation, (c) ambient sonic temperature, and (d) wall temperature, plotted versus wind direction for the March data set (solar radiation > 600 w/rn2). Circles represent outliers and stars represent extremes.
Figure 4.9. Continued.
Figure 4.1 O is a box plot of the normalized estimated radiation losses from the
Solarwall@ as a function of wind direction. Data were normalized using the largest
estimated radiation loss which was calculated fiom equation 2.3 to be approximately
195 w/m2. Estimated radiation losses were calculated using equation 2.3. The
normalized radiation losses fell within sirnilar ranges when the wind was blowing fiom
the north (360 degrees) and from the southwest (225 degrees). However, the median
radiation loss were slightly higher when the wind was blowing from the north due to
colder ambient temperatures when the wind was blowing from this direction.
Wind Direction (degrees)
Figure 4.10. Box plot of the normalized estimated radiation losses as a function of wind direction for March data set (solar radiation z 600 w/m2). Data have been normalized using the largest estimated radiation loss. Circles represent outliers.
Box plots in figure 4.1 1 depicts the efficiency and effectiveness of the SolanvallQ as
a function of wind direction. Some wind directions have only a limited arnount of data
(N) available for analysis. These wind directions also tend to have a much wider range of
values. It is also important to mention that it difficult to make broad generalizations and
draw firm conclusions based on the limited data available in the data set (483 points).
However, some iogical explanations for the major differences due to wind direction now
follow.
One important observation of the plot of efficiency versus wind direction was that
the efficiency tended to be higher when the wind direction was from the northwest and
north, when compared to the southwest. The wind flows over top of the building when
the wind direction is fiom the northwest and north (3 15-360 degrees). As a result, a
recirculation or stagnation zone tends to develop as was shown in figure 2.1. This tends
to keep the heated boundary layer air fiom convective losses in fi-ont of the Solarwall@,
which results in increased efficiency.
When speaking about efficiency it is important to consider radiation losses, because
increased radiation losses would normally result in lower efficiencies. However this was
not the case. Figure 4.10 showed that median radiation losses tended to be slightly higher
for northerly wind directions, due to colder ambient temperatures when the wind was
fiom the north, compared to winds from the southwest.
Wind Direction (degrees)
Figure 4.11. Box plots of (a) efficiency, and (b) effectiveness, of the Solanvall@ as a function of wind direction for March data set (solar radiation > 600 w/mZ). Circles represent outliers and stars represent extremes.
The wind direction is roughly parallel to the Solarwall@ when the wind is fiom the
southwest (225 degrees). This would tend to carry away heat fiom the Solarwall@ and
rnay explain why efficiency levels are lowest in and around this wind direction.
A recirculation zone or stagnation zone was also expected to form when the wind
direction was fiom 270-295.5 degrees, a result of the sharp corner at the western edge of
the Solarwall@. Efficiencies tended to be slightly higher when wind was blowing from
these directions. Although efficiencies were similar, effectiveness values from wind
directions between 270-295.5 degrees were higher than those between 3 15-337.5 degrees.
This may have been a result of fewer radiation losses (as depicted in figure 4.10).
Winds speeds tended to be calm to light when the wind direction was flowing nearIy
perpendicular to the wall(ll2.5- 157.5 degrees). This may have resulted in a stagnation
zone in front of the Solanvall@, which led to higher efficiencies when compared to those
at 225 degrees (see figure 4.1 1 (a)). The efficiencies were even more pronounced when
the air was near still but still flowing towards the wall at wind directions between 90 and
1 12.5 degrees. Note that the effectiveness levels for wind direction 1 12.5 degrees
(figure 4.1 1 (b)) are comparatively low, again due to the relatively high radiation losses
shown in figure 4.10.
Figure 4.12 includes plots of efficiency and effectiveness as functions of wind
direction. Error bars show the range for 95% of the data. Note that the error bars are
quite large for most of those directions that have fewer than 1 O data. However, error bars
are relatively small for efficiency and for wind directions with more than 40 data points.
- - . - - - - - - - - - - - - - - - - - - - - - - - - - =-' . . . . . . . . . . . . . . . . . . . . . . 'il i
Wind Direction (degrees)
Figure 4.12. Plots of (a) efficiency, and (b) effectiveness as a hc t ions of wind direction. Error bars show the range for 95% of the data.
4.3.3 Analysis of Sonic Anernometer Wind Data
A study of wind data recorded using the sonic anernometer will now be presented.
The data presented will be for the March data set (solar radiation > 600 w/m2), when the
sonic anemometer was located 61 cm (34 in) fiom the SolanvaIl@, and only intake Fan 1
was in operation. The wind data were compared to efficiency in order to determine if any
performance trends were noticeable. Efficiency was chosen instead of effectiveness
because the values for efficiency were not as heavily influenced by radiation losses as
mentioned in the previous section.
Figure 4.13 illustrates the ranges of mean velocities in the x, y, and r axes. The
mean horizontal velocity (U) parallel to the wall had the widest range of data, with a
majority being negative. This at first seemed odd because the predominate winds from
figure 4.3 were from the southwest, suggesting a positive U velocity. Reasons for this
will be explained in chapter 5. Data for the mean velocity normal to the wall, V (positive
toward the wall), were more evenly distributed on both sides of the zero velocity mis.
This was because as the distance fiom the wall decreases to zero, the velocity V
approaches 0.01 m/s, which is the average intake velocity through the wall. The mean
vertical velocity parallel to the wall W (positive upwards) had a heavy distribution in the
positive direction. One reason for this was buoyancy, produced when the air was heated
by the wall and by the large grave1 filled planter directly in front of the Solanvall@
(shown in figure 3.3).
Figure 4.13. Efficiency versus mean velocities (a) U, (b) V, and (c ) W. March data set (solar radiation > 600 w/rn2).
W (mis )
Figure 4.13. Continued
Plots in figure 4.14 depict the efficiency versus the root mean squared (RMS) values
of the fluctuating components of velocity. Normally the RMS value is divided by the
mean velocity to produce the dimensionless parameter of turbulence intensity. However,
as seen in the plots of figure 4.13, many of the mean velocities were very small and
approached zero. As a result, this could produce extremely high levels of turbulence
intensity that are not illustrative of the effects of the fluctuations. It seerns logical to
assume that efficiencies tend to decrease as the RMS values of the flucniating
components increase (i.e. efficiency decreases as turbulence increases). A trend toward
linearity of these data is noted in the plots of figure 4.14.
5 1 O 1 5
RMS v' (Ws)
Figure 4.14. Efficiency versus (a) RMS u', (b) RMS v', (c) RMS w'. March data set (solar radiation > 600 w/m2).
O. 5
0 4
2' .; O 3 5
O. 2
O 1
0.0 .5 1 .O 1 5 2.0
RMS w' ( r n ~ s )
Figure 4.14. Continued.
No general trend is found in figure 4.1 5, the plot of efficiency versus the RMS of the
fluctuating component of temperature (2') . This makes sense, as temperature is a scalar
and there is no transport of fluid when this variable is Iooked at in isolation.
RMS 1' (dcgrres C)
Figure 4.15. Efficiency versus RMS t f . March data set (solar radiation > 600 ~ l m ' ) .
Figure 4.16 shows plots of efficiency versus the products of the mean of the
fluctuating components of velocity and temperature. The sign of the products of the
mean of the fluctuating components of velocity and temperature are important as they
indicate trends in fluid transport. A positive product indicates that the fluctuating
components of velocity and temperature would be either both positive or both negative.
This would indicate the transport of hotter than average fluid (t' positive) in a positive
direction (i.e. u' positive) to be replaced conversely by the transport of colder than
average fluid (f negative) in a negative direction (Le. uf negative). Essentially this means
that as hot eddies of fluid are transported away they are replaced by cold eddies of fluid.
The example shown above describes the turbulent heat transport in an easterly direction.
- 1 O - 5 O O
u't' (degres C ms)
Figure 4.16. Efficiency versus the mean of the products of the fluctuati~components of velocity and temperature where (a) n, (b) , and (c) w't ' . March data set (solar radiation > 600 ~ l r n ' ) .
w't' (degras C mis
Figure 4.16. Continued.
As c m be seen clearly in figure 4.16 (c), there was a trend to a positive product of
w't' , indicating the general transport of hotter than average fluid upwards due to
buoyancy (2' positive and w' positive). The product of (n) was negative indicating that
hotter air near the wall (t' positive), as a result of turbulent diffusion, was on average
transported away from the wall (v' negative) and was replaced by eddies of colder than
average fluid (t' negative and v' positive).
The plot of efficiency versus showed that the product of was both positive
and negative indicating that there was a transport of hotter than average fluid (f' positive)
in both directions. When the product of u't' was positive, hotter than average fïuid
(f positive) moved in an easterly direction (u' positive), and conversely colder fluid
(t' negative) moved in a westerly direction (ut negative). Alternately when product of
- u't' was negative, hotter than average fluid (z' positive) moved in a westerly direction (ut
negative) and conversely colder fluid (t' negative) moved in an easterly direction.
The absolute value of the negative products of in figure 4.16 (a) tended to be
larger than the positive products, indicating that "hotter" fluid on average tended to travel
in the negative direction (Le. off the wall in a westerly direction). Note that the mean
velocity U, in figure 4.13 (a), had an equally large range on both sides of the zero
velocity a i s . Hot fluid was still transported off the wall in an easterly direction (positive
direction), but its absolute value was not as great. The efficiency tended to drop as the
"hotter" fluid (larger positive t') lefl the wall surface in a westerly direction (u' negative).
This seems logical as the themial boundary layer, resulting from convective losses, would
tend to dissipate more readily off the western corner of the wall and would be held in
place on the east side by the concrete projection shown in figure 3.3.
CHAPTER 5 - DISCUSSION
The two main objectives of this study were to set up an experimental apparatus
complete with a data acquisition system at the Canadian Coast Guard Base in Prescott
and to determine experimentally how wind affected the performance of a Solarwall@.
Initially problems were encountered with the data acquisition system and they will be
discussed in the following section. Data for 24 days in the month of March 2000 were
successfully logged and analysed using a statistical software package. Results of this
analysis were presented in the previous chapter and will be M e r discussed here.
5.1 Problems Encountered with the Experimental Apparatus
5.1.1 Themocouple Readings
As stated in section 3.6.1, temperature readings fiom the two thermocouples inserted
in the outlet ducts would sporadically yield temperature values well below -1000 OC. No
set pattern or source could be determined for this problem which occurred only on
occasion. The problem also appeared in the output of the thermocouple c o ~ e c t e d to the
wall. but to a much lesser extent. Higher sources of electronic noise in the welding shop
may have contributed to the higher instances of irregular values for the thermocouples
placed indoors. The data acquisition program was modified in order to circurnvent this
problem by filtering out bad data.
5.1.2 Short Cycling and Flow Rate of Intake Fan 2
ProbIems were also encountered with the short cycling of intake Fan 2 as outlined in
section 3.6.3. The average pitot static pressure in Duct 2 was also found to be
significantIy lower than that of Duct 1, when both intake fans were ninning continuously.
This led to an approximately 40% lower velocity flow rate in Duct 2 when compared to
Duct 1. ïntake Fan 2 was shut off and the duct outlet covered, in order to bypass these
problems, until a solution could be found and implemented by the Prescott Base
electrician. This is why only the temperature and pressure readings for Duct 1 were used
in the March data sets.
The temperature sensor mounted in Duct 2 should be moved to another location,
preferably in the Solanvall@ plenum, or a back flow prevention system should be
installed in Duct 2 to prevent warm air from the shop tiom rising up the duct and starting
the fan. The dead band of the temperature sensor should also be increased in order to
prevent short cycling of Fan 2 when the temperature hovers near 5°C. The flow rate
provided by intake Fan 2 should also be checked against the designed flow rate and
corrected as required.
5.1.3 Sonic Anemometer
The logging of sonic anemometer data failed on a number of occasions. From
Iooking at past data it was determined that the sonic anernometer usually failed on very
rainy or snowy days, indicating that a build-up of liquid or snow impeded its ability to
work correctly. The sonic anemometer that was purchased for this study was a brand
new mode1 just put on the market by the manufacturer R.M. Young Company. It is
recornrnended that the manufacturer be contacted and appraised of this problem so a
suitable solution can be found to ensure continuous operation of the sonic anemometer in
inclement weather.
5.1.4 Electronic Ice Point
The power of the battery in the electronic ice point slowly declined until the battery
was change at the end of February. A correction, as detailed in appendix F, was applied
to temperature measurements taken between December and February. The data collected
during these months were mainly recorded when the sonic anemometer was located at a
distance of 30.5 cm (12 in.) fiom the Solarwall@. In order not to compare "apples with
oranges" or introduce fbrther errors it was decided to analyse these limited data
separately.
5.1.5 Weather Station Temperature Sensor
The temperature sensor that was part of the remote weather station was installed as
per the manufacture's instructions in the shade of the eves of a north wall. It is suspected
that solar heating of the roof of the helicopter hangar infiuenced the temperature sensor.
This resulted in inaccurate high temperature measurements fiom the sensor when the sun
was shining. Therefore, the sonic temperature was used instead of the weather station
temperature as a measure of the arnbient temperature. As shown in chapter 4,
temperature fluctuations and hot fluid transport fiom the wall were picked up by the sonic
anemometer even at a distance of 61 cm (24 in.) fiom the wall. This would indicate that
the sonic temperature would tend to be slightly wamer than the real ambient
temperature. However, the sonic temperature was still f a more indicative of the ambient
temperature when compared to temperature recorded by the weather station sensor.
Because the sonic temperature wouId tend to be warmer than the reai arnbient
temperature, the calculation of efficiency for this study may be low.
5.2 Tem~erature K s e
The suction velocity for the March data set with only intake Fan 1 working was
approximately 0.0 1 m3/s per m2 of SolanvaIl@. The volume flow rate was not close to
being doubled, as one might expect, when both fans were working because as stated
earlier, Fan 2 did not work as well as Fan 1. When only Fan 1 was working the system
could not produce the quoted temperature rise performance (i.e. line B) per total area of
Solarwall@. It is interesting to note that if only half of the surface area of the wall per
intake was considered, the flow rate in Duct 1 would be 0.02 m3/s per m2 of SolanvaIl@
(Le. performance line C). As was seen in figure 3.5, this flow rate coincided more
closely with the recorded values. Without some type of modelling one cannot assume
that if only one fan is running it oniy makes use of half of the energy collected by the
Solarwall@. Therefore, efficiencies shown in chapter 4 were calculated based on the
soiar energy received over the entire wall surface area when only intake Fan 1 was
working (Le. a flow rate of 0.0 1 m3/s per rn2 of SolanvaIl@), hence efficiencies were
lower than expected. Efficiencies were lower in al1 cases, but the differences in
eficiency were deemed more important than the absolute accuracy of their values.
No correction was made for the temperature rise due to the recapture of lost heat
fiom the block wall. Although the temperature of the air in the plenum varies, it can be
approximated for these purposes by the outlet temperature of Duct 1. The temperature of
Duct 1 as a function of wind direction is s h o w in figure 5.1.
Figure 5.1. Box plot of outlet temperature of Duct 1 as a function of wind direction for March data set (solar radiation > 600 ~ l r n ~ ) .
If the temperature in the plenum is approximated by the temperature in Duct 1, it can
be seen from figure 5.1 that the temperature in the plenum would be a minimum of 10°C
and would generally be over 15°C for most data. It was assurned that the average
temperature in the welding shop was between 15OC and 20°C, therefore, the A T of the
temperatures on either side of the block wall and the distribution ducting wouid be low.
As a result, there should have been little heat gain to the fresh air in the plenum from the
block wall or heat gain to the fiesh air in the distribution ducting from the air in the room,
when the solar intensity was above 600 w/rnZ. Therefore, no correction due to non-solar
heating was made for the March data set (solar radiation > 600 w/m2). In the future it is
recommended that instrumentation be installed to account for this non-solar related heat
tram fer.
5.3 Statistical Analvsis of Efficiencv and Effectiveness versus Wind Direction
It is important to state again that it is difficult to draw firm conclusions based on the
limited data set used for analysis. The March data set (solar radiation > 600 w/m2)
contained a total of 483 data points taken over 24 days of which only 15 days had solar
radiation levels above 600 w/m2. Notwithstanding, some comments about general trends
in differences in efficiencies and effectiveness when only intake Fan 1 was running will
be made.
Statistical analysis of the March data set (solar radiation > 600 w/m2) suggested that
efficiency and effectiveness were both influenced by the oncoming wind direction (see
figure 4.1 1). Wind speeds for this data set were typically in the light breeze range of the
Beaufort Scale (1.6-3.3 m/s), where wind is classified as being able to be felt on the face.
These low wind speeds and the suction effect of the SolanvaIl@, may be reasons why
greater differences in efficiency and effectiveness were not found.
Eficiency values in figure 4.1 1 (a) tended to be higher when the wind was flowing
over the building fiom the northwest and north (3 15-360 degrees), when compared to
when the wind was flowing parallel to the wall from the southwest (225 degrees). It is
suggested that a recirculation or stagnation zone tended to develop in front of the wall
when the wind was flowing over the top of the building (as described in section 2-32),
thus keeping the heated air generated by convection in front of the SolanvaIl@. The
eficiency also tended to be higher when the wind was flowing fiom the side and over top
of the building when it was coming from the direction between 270 and 295.5 degrees.
Winds fiom these directions would also tend to create stagnation and recirculation zones
in front of the Solarwall@ that would account for the increased values of efficiency.
Radiation losses were considered important due to the differences in ambient
temperatures for different wind directions. One would think that higher radiation losses
would produce lower efficiencies, however, this was not the case. It is suggested that the
recirculation and stagnation zones outlined in the previous paragraph tended to keep
warm air close to the wall, while this air tended to be swept away more readily when the
wind was flowing parallel to the waI1 fiom the southwest (225 degrees). Kutcher et al.
(3) showed that heat losses in their mode1 did occur when the wind was assumed to flow
parallel across the transpired solar collector. They also stated that these Iosses increased
with decreased suction flow rates (flows below 0.05 d s ) . They aIso concluded that at
lower flow rates collector temperature rises are higher, but efficiencies are lower and
wind effects are more important.
5.4 Sonic Anemometer Wind Data
From figure 4.13 it was shown that mean velocities recorded by the sonic
anemometer were equally scattered on both the positive and negative axes of the U and V
components of velocity, and tended to favou the positive axis of the W component of
velocity. It seems s m g e at first to observe the horizontal velocity (U) with equal scatter
on both side of the x-axis, given that the prevailing wind direction is out of the southwest
(225 degrees). A reason for this will be explained in the following paragraph. As the
distance to the wall approaches zero the velocity normal to the SolarwalI@ (V)
approaches the wall suction velocity (0.01 d s ) . This is the reason why velocities were
small and evenly distributed on both sides of the y-mis. Most of the data were on the
positive side of the -axis due to the effects of buoyancy.
5 -4.1 Mean Flow of Air at the location of the Sonic Anemometer
The ..-y plane around the sonic anemometer was broken down into quadrants and
classified by a number (1 -4) as shown in figue 5.2. The number indicates in what
general quadrant the mean velocity vector pointed in the x-y plane at the location of the
sonic anemometer. The sonic anemometer was located at 61 cm (24 in) fiom the
Solarwall@ for this andysis.
Quadrants in x-y plane with sonic anemometer at intersecton
SolanvaIl
Figure 5.2. Top view of the building. The x-y plane in front of the Solanvall@ was broken down into quadrants at the location of the sonic anemometer and classified by nurnbers 1-4.
The bar chart in figure 5.3 shows the distribution of the x-y plane velocity vector at
4 Concrete projection near overhead door
r
the sonic anemometer as a function of the oncoming wind direction. The x-y pIane
-
velocity vector generally pointed in quadrant 1 and 4 when the wind was blowing
horizontal to the wall out of the southwest (202.5-225 degrees), and generally in either
quadrant 3 or 3 for other wind directions. This would support the theory that a
recirculation zone exists when the wind is flowing over top of the building or from the
side of the building (oncoming wind directions between 247.5 and 360 degrees). It was
assumed that there is a barre1 rolling effect as shown in figure 2.1 when wind flows over
top of the building.
Figure 5.3. Velocity vector orientation in x-y plane as a function of oncoming wind direction. March data set (solar intensity > 600 w/m2).
Sketches in figure 5.4 provide a picture of possible wind flow and recirculation
patterns seen in the x-y plane for different oncoming wind directions. From figure 4.9(a)
it was seen that the wind speeds were generally very low for wind direction 112.5
degrees. and would indicate why the -Y-y plane velocity vector was in al1 quadrants.
Figure 5.4. Possible wind flow and recirculation patterns seen in the x-y plane for different oncoming wind directions (a) 202.5-225 degrees, (b) 3 15-360 degrees, (c) 247.5-292.5 degrees, (d) 67.5, 90, and 135 degrees. March data set (solar intensity > 600 w/rn2).
Fiogure 5.4. Continued
Figue 5.5. Box plot of efficiency versus wind quadrant direction fiom March data set (solar radiation > 600 w/m2).
A box plot of efficiency versus wind vector quadrant is presented in figure 5.5. It
shows that the mean efficiency was highest when the velocity vector was Iocated in
quadrant 2, in a general direction towards the wall. The efficiency was lowest in
quadrant 1 and 4, which generally occurred when the wind was fiom the southwest (225
degrees).
5.4.2 Fluctuating Components of Velocity and Temperature Measured by the Sonic Anemometer
Detailed observations in the previous chapter were made on the fluctuating
components of velocity and temperature measured by the sonic anemometer. A sumrnary
of these results with added comrnents are shown below.
Plots in figure 4.14 showed that efficiency tended to decrease with increased RMS
values of the fluctuating components of velocity. This is logical and is supported by
outdoor testing on a flat plate, where the heat loss coefficient was calculated to be mice
as large when compared to indoor wind tunnel tests. The differences were attributed to
higher turbulence intensities experienced outdoors (3).
Plots in figure 4.16 showed that there was a general transport of hotter than average
fluid up and away from the Solarwall@. with a corresponding replacement of colder than
average fluid in the opposite direction. Hotter than average fluid traveIIed in both
directions of the x-axis, with a general trend to lower efficiency in the negative x-a is .
The iower efficiencies in the negative axis are attributed to colder fluid being transported
to the wall by westerly winds.
CHAPTER 6 - CONCLUSION
The two main objectives of this study were achieved. The first objective was to set
up an experimentai apparatus complete with a data acquisition system at the Canadian
Coast Guard Base in Prescott. The second objective was to determine experimentdly
how wind affected the performance of a Solarwall@. Data for 24 days in the month of
March 2000 were successfully logged, and anaiysed using a statistical software package.
Analysis suggested that efficiency and effectiveness were both iniluenced by the
oncoming wind direction.
6.1 Experimental Apparatus and Method
There were unforeseen problems with instrumentation and equipment during this
study. Concluding remarks on the major problems encountered and their significance
fo1lows:
1. The average pitot static pressure in Duct 2 was found to be significantly lower than
that of Duct 1, when both intake fans were running continuously. This led to an
approximately 40% lower velocity flow rate in Duct 2 when compared to Duct 1.
92
The sonic anemometer occasionally failed to communicate with the data acquisition
system on very rainy or snowy days, indicating that a build-up of liquid or snow
impeded its ability to work correctly.
The sonic temperature (recorded at a distance of 6 1 cm from the Solanvall@) was
used instead of the weather station temperature as a measure of the ambient
temperature. This may be a contributing factor of why eficiency values tended to be
low for this study.
The flow rate with only intake Fan 1 working was approximately 0.01 m31s per m' of
Solarwall@. The volume flow rate was not doubled, when both fans were working
because as indicated previously, Fan 2 did not work as well as Fan 1. When only
Fan 1 was working, the system could not produced the quoted temperature rise
performance per total mZ of Solarwall@. If only half of the surface area of the wall
per intake were considered, the flow rate in Duct 1 would have been 0.02 m3/s per m2
of Solarwall@. Given this higher flow rate, the recorded values would coincide more
closely with the performance lines published by Conserval Engineering Inc.
Lower than expected air temperature rises based on a flow rate of 0.01 m31s per mZ of
Solarwall@, resulted in lower effkiencies. However, differences in efficiencies for
this snidy were deemed more important than the absolute accuracy of their values.
Temperature nses recorded during penods without solar radiation tended to increase
as ambient temperatures decreased (Le. penods between 6 p.m. and 6 a-m.). No
instrumentation was in place to account for the magnitude of this type of temperature
rise during the dav when the svstern was in operation. It was assumed that the
influence of this temperature nse was negligible for solar radiation levels above
600 w/m2.
6.2 Statisticd Analysis
As mention previously, lower than expected air temperature rises and efficiencies
were noted for the calculated flow rate per m2 of Solanvall@. based on oniy intake Fan 1
working. The calculation of eficiency was based on the total solar radiation received
over the entire wall surface area Differences in efficiency were deemed more important
than the absolute accuracy of their values for the purposes of this study. Some general
trends noted in performance for the Mach data set (solar radiation > 600 w/m2) are as
follows:
1. Statistical analysis suggested that eficiency and effectiveness were both influenced
by oncoming wind directions.
2. Wind speeds for the March data set were typically in the light breeze range. These
low wind speeds dong with the suction effect of the Solarwall@, may be reasons why
greater differences in efficiency and effectiveness were not found.
3. Effciencies tended to be higher when the wind was flowing fiom the side and over
the top of the building (wind directions 270 to 360 degrees), compared to efficiency
values when the wind was flowing parallel to the wall from the southwest (225
degrees). It is suggested that a recirculation or stagnation zone tended to develop
when the oncorning wind was between 270 and 360 degrees, which would be more
effective in keeping convective losses in front of the Solarwalt@. In contrast these
convective losses were greater when the wind was flowing paralle1 to the wall fiom
the southwest (225 degrees).
Boundary conditions near the wall accounted for the small and evenly distributed
mean normal velocities (0 on both sides of the y-axis. Solar heating of the
Solanvall@ and the large grave1 filled planters in fiont of the wall created a buoyancy
efXect which resulted in largely positive mean velocities in the vertical direction (m. The x-y plane around the sonic anemometer was broken down into quadrants and
classified by a number (1 -4) as show in figure 5.2. The direction of the mem
velocity fluid flow in the x-y plane was genemlly towards quadrants 1 and 4 when the
wind was blowing out of the southwest (202.5-225 degrees), and generally towards
quadrants 2 or 3 for other oncoming wind directions. Esciencies tended to be higher
when the general direction of the mean fluid flow was towards quadrant 2 (direction
towards the wall), and lower when the rnean flow was towards quadrant 1 and 4
(which generally occurred when the wind was from the southwest or 225 degrees).
Plots in figure 4.14 showed that efficiency tended to decrease with increased RbfS
values of the fluctuating components of velocity (i.e. efficiency tended to decreased
as turbulence increased).
Plots in figures 4.1 6 sho wed that there was a general transport of hotter than average
fluid up and away from the Solarwall@. Hotter fluid travelled in both directions of
the x-mis, however, lower efficiencies in the negative x-axis were attributed to cold
fluid being trans~orted to the wall bv westerlv winds.
CHAPTER 7 - RECOMMENDATIONS
7.1 Experimental Apparatus and Method
Dificulties were encountered with equipment and instruments as mentioned in
previous chapters. Before M e r study is carried out at the Prescott site it is
recommended that the following changes be implemented:
1. Equipment problems with the Prescott SoIarwall@ system should be rectified. The
temperature sensor mounted in Duct 2 (to tum intake fan 2 on and off) should be
moved to another location, preferably in the Solarwall@ plenum. Altemately. a back
flow prevention system should be installed in Duct 2 to prevent warm air fiom the
shop fiom rising up the duct and starting the fan. The solution may be as simple as
installing a lightweight hinged cover over the outlet of Duct 2. The dead band of the
temperature sensor should also be increased in order to prevent short cycling of Fan 2
when the temperature hovers near 5°C. The flow rate provided by intake Fan 2
should be checked against the designed flow rate and corrected as required.
2. It is recommended that the manufacturer of the sonic anemometer be contacted and
appraised of the problem of the instrument not working weIl in inclement weather. A
suitable solution should be found to ensure continuous operation of the sonic
anemometer.
3. The temperature sensor of the weather station should be moved to an alternate
location in order to provide for a more accurate reading of the ambient temperature.
4. The replacement of the battery-operated ice point with a fixed power source should
be pursued. This could include acquiring a new data acquisition connector block that
has an onboard temperature sensor for thermocouple cold-junction compensation.
5. Thermocouples could be placed just before the intake fans (instead of in the middle of
the outlet ducts as was done in this study) in order to eliminate any possible error
caused by temperature rise as the air travelled through the ducts.
6. Temperature rises during periods of little or no solar radiation were strongly
influenced by differences in welding shop and ambient temperatures, due to heat
Iosses recovered fiom the block wall (Le. the insulating effect of the plenum).
Thermocouples could be installed on either side of the block wall to account for the
magnitude of this non-soiar generated temperature rise. This would alIow for a more
accurate comparison of efficiencies versus wind direction, at lower solar intensities
and varying arnbient temperatures.
7. It is recommended that the data acquisition system be connected to an unintemiptable
power supply to ensure a continuous flow of data. Alternately, the computer could be
programmed to restart the data acquisition program after a power failure. The data
acquisition system could also be connected by a modem to enable remote monitoring
of the expenmental set-up and the downioading of data files. This would Save on
travel time to the site and result in better monitoring of equipment and instruments for
failures. Time and funding constraints precluded these from being implemented for
this study.
7.2 Recommendations for Further Study
This study was a preliminary look at how three-dimensional flow effected the
performance of a Solarwall@. A large portion of work of this research included
selecting, testing, installing, and debugging equipment. Good data was collected in the
final month of expenmental work, when oniy one intake fan was working (Fan 1) and the
sonic anemometer was at a distance of 6 1 cm (24") fiom the Solarwall@. It is
recomrnended that if a similar study is done in the future, that it be done over the course
of a heating season when both intake fans are operational. Future work should only be
done in Prescott when the changes recommended in the previous section are carried out.
The Prescott Solarwail@ system is not a typical installation seen in the field. and site with
a more standard installation as shown in figure 1.4 may prove to be more relevant for
fûture study.
The use of flow visualization a d o r the use of additionai sonic anemometers would
be beneficial in order to get a better idea of flow conditions around the building under
different wind conditions. Spectral analysis of data collected by the sonic anemometer
would dso be usetùl in detennining eddy sizes, because their length scales influence the
transport of heated air away fkom the SolanvalI@. Wind tunnel and computational fluid
dynamics (CFD) studies could also be carried out and compared to the results of this
expenmental research. Thermal imaging under different wind flows and solar intensities
could be useful in finding areas more susceptible to convective and radiative losses.
7.3 Sunnested Irnprovements to the Prescott Solarwall@ System
It was shown in this study that the Solarwall@ system installed at Prescott could
provide a significant temperature rise to fresh intake air. Workers in the welding shop
were sceptical as to added benefit of the Solarwall@. Initially they seemed disinterested
if the system was even working. A large part this disinterest was because they felt that
the system was just blowing cold air at them. There was often a temperature rise of
10 O C to 25 OC from the Solarwall@, but if the temperature was cold outside the
temperature blowing out of the Solarwall@ ducts was still well below a cornfortable room
temperature.
A standard Solarwall@ installation normally resutts in fiesh air being discharged at
ceiling level, which reduces stratification of the air temperature inside the room. Another
type of installation is where the pre-heated fresh air from the SolarwallQ is passed
through the building's heating system before it is enters the room. The latter type of
installation was not possible as the welding shop is heated mainly by overhead infiared
heaters. An overhead crane, which runs the length of the room, and three large roorn
exhausts at ceiling level led to the current design where the SolanvallO outlet ducts are
placed at eye level. This was done to avoid impeding the large overhead crane mounted
near the ceiling and to provide a suitable cross flow though the room (fiom the fresh air
SolanvaIl@ outlet ducts near the floor to the room exhausts on the opposite ceiling).
Some general suggestions will now be made to improve performance of the system from
an operational point of view, which are not directly related to the wind effects of this
study .
1. Educate workers as to how the Solarwall@ works and inform them of the actual
temperature rise recorded as a result of this study.
2. Look at a possible redesign of the location of Solarwall@ outlet ducts closer to the
ceiling, to make use of the destratification benefits and to avoid blowing cold air
directly on the workers. n i e modification or relocation of the three large ceiling
exhausts would also have to be considered (i.e. the exhaust pipes could be lowered
and shortened to stilI ensure an effective cross flow). The location, use and
orientation of electronic air purifiers in the Welding Shop should aiso be considered
in this redesign (they may not al1 be required given the added fiesh air flow fiom
Solarwall@ and the added use of the flexible exhaust hoods).
3. The Solarwall system could be placed on a timer to ensure operation only during
working hours. Altematively, motion sensors codd be install to ensure the system
was only ninning when the room was occupied.
4. An odoff ovemde switch should also be made accessible for use by the workers in
the welding shop, so that the system could be tunied off during times when no
welding was being done. This last option could Save energy costs but would only be
as effective as the training and will of the workers to use it.
7.4 Suggested Im~rovements to the Solarwall@ Design
This study suggested that e f~ciency gains were realized when recirculation or
stagnation zones were fonned in fiont of the Solanvall@. These areas of recirculation
and stagnation seemed to aid in keeping heat fiom being blown off the wall. It is
suggested that M e r research into harmonizing building design and SolarwallQ
installations be pursued, especially in areas of new construction. For example recessing
the Solanvall@ may be beneficid to its overall performance (see figure 1.1, the
installation on a Canadair building).
Different shapes and types of Solarwall@ cladding that would induce more localized
recirculation and stagnation areas may also increase performance. The increased
performance of new designs would have to be weighed against other factors including;
production and installation costs, and structural integrity requirements.
REFERENCES
1 . Conserva1 Solarwall "Cladding that Heats Fresh A i r and Heating for Industrial Buildings", pamphlet produced by Conserval Engineering Inc. and Conservai Systems Inc. Enclosed as Appendix A.
2. Kutscher CF., Christensen C.B., and Barker G.M. "Unglazed Transpired Solar Collectors: Heat Loss Theory", ASME Journal of Soiar Energy Engineering, Vol. 1 15, 182-1 88, August 1993.
3. Kutcher C.F. "Heat Exchange Effectiveness and Pressure Drop for Air Flow Through Perforated Plates With and U'ithout Crosswinds", Journal of Heat Tram fer, Vol. 1 16, 391-399, May 1994.
4. Dymond CS. and Kutscher C.F. " A Cornputer Design Model for Transpired Solar Collector Systerns", ASME Solar Engineering, Vol. 2, 1 165-1 173, 1995.
5 . Simiu E. and Scalan R.H.. *'Wind Effects on Structures." Second Edition. John Wiley & Sons, New York, 1986, Chapter 7.
6. Dyrbye C. and Hansen S.O., " Wind Loads on Structures", John Wiley and Sons. West Sessex England, 1997, Chapter 3.
7. "1 993 ASHRA E Handbook Fundamentals", Amencan Society of Heating, Refrigerating and Air Conditioning Engineers, Inc., Atlanta, 1993, Chapter 14.
8. Beaubien D.J., Bisberg A., and Beaubien A.F., "Investigations in Pyranorneter Design", Journal of Aerospace and Oceanic Technology, Vol. 15,677-686, June 1998.
9. Coulson K.L., "Solar and Terrestrial Radiation ", Academic Press, New York, 1975.
BIBLIOGRAPHY
Coulson, K.L., "Solar and Terrestrial Radiation ". Academic Press, New York, 1975.
Eckert, E.R.G., and Goldstein, R.J., " Measuremenfs in Heat Transfer ", Second Edition, McGraw-Hill Book Company, Washington, 1976.
Kays, W.M., and Crawford, M.E., "Convective Heat and iMass Transfer ", Second Edition, McGraw-Hill Book Company, Toronto, 1980.
Lunde, P .J .. "Solar Thermal Engineering, Space Heating and Hot Water Systems ". John Wiley & Sons, Toronto, 1980.
McQuiston, F.C., and Parker, J.D.. "Heating, Ventilation. andAir Conditioning: Analysis and Design ", Second Edition, John Wiley & Sons, Toronto, 1982.
Munson, B.R.. Young, D.F., and Okiishi, T.H., "Fundamentals of Fluid Mechanics ", John Wiley & Sons, Toronto, 1990.
~ z i s i k , M.N., "Heat Transfr, A Basic Approach ", McGraw-Hill Book Company, Toronto. i 985.
Sherman, F.S., " Viscous Flow ", McGraw-HiII, Inc., Toronto, 1990.
Upp, EL., "Fluid Flow Measurement ", Gulf Publishing Company, London, 1993.
White, F.M., "Fluid Mechanics ", Second Edition, McGraw-Hill Book Company, Toronto, 1986.
APPENDIX A
Pamphlets fkom Conserval on SoIarwalIB Entitled, "Cladding that Heats Fresh Air," and "Heating for Indusmal Buildings"
Conserval
CLADDING THAT HEATS FRESH AIR
Ycnn OC resevch and tuting h& m u l f e d in a tomlly new concept in solar hca8ng. lltc highcsr solar efficieaciu evcr obtaincd in ~ i r hcating and no glazing!
The al1 meral ~ ~ L . % R ~ ~ ~ ~ % e a ~ i n t e r e d to heat ouuide air aad can bc coupted ro mosl ventilaaoa faas. Whcn rucd with Conservai's air disrriburion syscm. additionai encrgy U savcd by dauaufying rhc cciling air. a
The S O L A R W A U ~ pancl looks likc a convcniional merai wrlI and is available in a choicc o f dJrk colon. n e pomw s u r t k t has tiny openings CO allow air fo p w h u g h picking up vimially al1 the solar hmt m c h i n g the mePl.
The m e n i clidding on rhe wall becomes the hcnter for ouuidc air entering the building. D ~ r k m e d hcau up when exposcd to the sun .
The SOLARWALL' cladding aIlows b i s heac IO be collccttd and put to use. It cven c o l l c c ~ hcat on cloudy days and ar night
millions of dollars esch year sm b a n g saved by corporations aad governmenu amund the worl with the B . SOLARWALL sysrcm.
wvi+immuiï HEATING SYSTEM
The sol= c i d d i n g is covercd with riny h o l a to dIow outside air to m v e l through the face of the cladding. .a outside Ur passes through the panel. ir sbsorbs the solar genemcd hear A venulauon f u i craces negmvc pressure in the w d l cavicy ro h w au rhrough the holes. The hor air rises to the top of the wdl whcrc it is u s d y collccted in an aanct ive cmopy pIcnum and d u c u d ro the ne-r fui ( fig. 1). Othcr designs inciude p d l e l m d mpcred Solamalls.
* m m D D a i p g m o l m i D I a a n a JduRImM ~ l l
WrSioiiri
FIgurc 2 Air-ccmpmre m e v% du ndl<ron for vuious ar-llow r~ la
C ( ~ ~ E R ~ L 200 wiiocat Road. Dominnm. Onnno M3J ZN5 a ?none 1416) 661 - 7 W Fax (416) 661-7146
The ~ o l a r w d l ~ d s o helps ro cool in summcr by prcvencing normal s o l v radiation h m s m h n g ihe bui1ding.s main wrill. Hot ;ut is thermally siphoncd up the wdl and venoiated rhrough holes a the rop of the cladding. leaving the mitin waII cool. B y - p i s dampers in summer d l o w non-heatcd Ur KO be drawn dirccrly into the building. mainuining indoor air qudi ty .
.Most wails. eve if well insulated will losc hcar The k SOLARWALL systcm is unique in chat h a p s i n g through chc wali is rcnirntd b x k inside the building togethcr with s o l v h u t absorbeci by rhe air. With vimally zero heat oss. !a plus the h u r gcnented on the wall. die SOURWALL h;is die highcst tnergy efficicncy avYlable.
IWOQR AIR PUAUTY
Propcr ventilation is ncccssvy CO m u t a i n a comiorr;lble and h d t h y indoor cnvironmcnr Au cight buildings may have lower heaùng bilis but s o m e u m a at the expense of indoor air quaiicy. The "sick building syndrome" is an issue. One of ctic best ways of solvinp diis problem according to ASMUE. is to inc ruse the~volurne of ouûrdc or vencïlaaon air bmught into a building. Qf course. ir rcquirts energy to h m the Ur. The Solvwal l h u e r c;ui d o the job with f r t t sol= h a and improve indoor air qtdicy.
~ N S ~ v & ~ Z J ? , Ridge L a Rd.. Sulu al. Buffalo. Z(Y 14216 USA D(CPhont (7161 835-4903 F a 1716) SU-1901
Figue 1 shows air tempennrrc Nc versus so1v radiacion f r various airrlow mtcs (A. B. C. D. E) h u g h die Solrrrwdl 8 For cxiunplc. on a s u ~ y &y the s o l v radiation would bc about wam per square mene. With s flow rae of 1 cfm/W (BI. die rcmperanuc rise would be dmosr 30'~. On cloudy days. it will hinction as a prchutcr widi a lower umpcnnirc rise.
Conserval
FOR INDUSTRIAL BUILDINGS A SOURWALL~ hci<td s r d e - u p systcrn for industriai buildings will provide frce h a u n g and irnprove indoor air q d i t y . The ur is hureci by solar energy. by wdl h-t loss rccovcry. and by urilizauon of sulitifid h u t 3t the cciling.
7 h e SOMWU@ h- is usually insuilcd on the south-facing w d of a building wherc the incoming frcsh air ;ibsorbs the h a of the s u ' s cncrgy. The air disaibucion sysrem rcclaims the suauficd h u t uapped ac the ctiling m d crutes n a d convection currcnrs inside the building char c ~ r y the h m down to die working levei for the comforr of thc cmployees.
By brïngxng in outsidc air. the system irnpmves the quality of the working environment and enabla die cxhaust fans CO work properly. Al1 lhis is done without addicionai opemung cost
Any type of wdl consuuction c m be convcncd inio a SOLARWALL@. In a rypicai insrallacion. J b u e concrcrc block wdI is covercd with SOURWALL" memi siding which k c o m e s the SOIS absorber. It is spaced away from the wdl to fonn an air Sap for the air enttring the system. (fig.1). A similv design is used for steel clad buildings.
At regular inrerv~ls dong the wdl n u r the roof. Conxrvai fan unis YC insrded to draw
rhe ourside sir through the SOURWALL~ cladding. Each fan hPs rnodulating outsidc air and rcnim dmpen. dischvgc Yr lernpennim sensor and controis. and flmc-retardant duct which distributes the solor h u t e d air dong the ccding of the plmt through numerocs prtcision opcnings.
SOUR HEdTUl MAKE-UP AIR
Poor air inlet fis 4
Factones ntzd a lot of u r m d h a u n e it wirhout s o l v c m be cxpcnsive. fn fzcr i r is cornrnon to sec l u g e gas o r j C t a m a r W C - u p f u s mm& orf k a u s e of rhc high opcmung costs. Cdnservd h3s solvcd chis proolcrn W I L ~
the SOL~RWAU@ m d Conservai i m systtm. In 3 cypicai plant the rempennirc of the hot jariufied ur 3i: die ccilinq im nsc CO over 30' C (W Fl in winter (f ige 2). The Conservai fuis cnable [hi, heat to be m f v m c d for w v die working Icvel. .At the s m c timc. the c o m m t supply of make-up air prcssunza the building. sropptng rhe infilmuon o i sold ar m d rcducxng uncorniomble Jmris dong the tloor t Fig.3) Dunng the surn e r monchs. when the additionai haring erfcct of rhe 3' S O U R W A L L is not qutrcd, outside air is brought drrccrly into the disuiburion d u c s thrnuyh by-pas dampers. When make-up air is no longer rcquircd md chr ran sysrcm is bhut Jown. the ouaide a r d m n c l o x sutorn;itic=lly. The utdirional insolmon with rhr S O L ~ R W A L L d s rcduca the b a r loss uid he!ps ro lowcr hat ing sosts. 5 The SOLARWALL h u e r complcncnrs the oprmion or the Ccinscsal fu i units by supplying ddirional herited Air into the systern. ~ n d i r d o e s 30 wich outstanding etficiency .
THE NEED FOR MME-UP AIR
The idcd working environment is frrt of al1 pollunnrs and ensurs ~n adquate m d conunuous supply of oxygcn. [f rhcse condiuons arc not mer. people becorne c d . sluggish and immble. absrntetrsrn increasei. momie sinks and producuvip Ings. The openuon of cxhausr fans lowen the air pressure insidc the building. If rnake-up air is not invoduccd in 3 conmllcd rnanner. ourside air w l l intilmte through m c k s in wdls. windows and doon in an aaempt to bdmce the pressure. Neglitivc pressure is a term used to indiure chis pressure diffennoal. Indusmal plans gcneraliy rcquire h m me-half ro four air changes cach hour depcnding upon the rvpe of p rocas involvcd. The eonmllcd inuke of f m h air is n a x s a q to: - cnsurc char exhaust fans purge the work XCI of conminlinrs - eiiminatc high vclocity cross drark through wtndows m d doon - ensure opmuon of n a m d d d t st;icks cornb bus non flues) so char down dm& do not refuse h;u;irdous cornbusuon producrs inro the work u e z Down dmfu c m dso cxnnguish pilot l i g h ~ . cause poor openrion of bumers and temperature controls. and producc rnoisnirc condensation in staçks and hezt cxchangm Imding to corroston damage - geneme a posiuve pressure whrch wiil d iminue rhe infiimtion of cold. uncorniomble dr;itts dong the plant rloor - climinarc diffcrenriai au pressures thTOughout Lhe plant causing doors ro close in an unconvollcd muincr. dangernus to personnel - conseme tirel. The infiltration of cold air at the penrnercr of rhe building I e d s to unduly high thermosrat scnings in an snernpt to correct the shanon . The exrra hex does nochmg CO irnprovc the coid mu and i r makcs rhe ir:nnI arcs of the plant honer. This lwds ro the conunuous use o i the cxhausr fms to dmw off die excessive hnr. For a cornplete expianauon of the n d for replacement s r rcter to "lndustnal Ventilauon. .A .Manual of Recommcndcd Pmc:tct" publishcd by the Amcncan Conference of Governmcnd Indusmal Hyycnisrs. The Manual aiso iilusrrjtcs die reiauvc etfiaencies of die vmous posraons for the inlcr and exhaust fans. It recornrnends that the inlet air be distnbuted cvcnly across the cciling. fi%. 4 shows the worst locxion. while Fig. 5 indicaca the best condition.
Site and Construction Drawings of the Solarwalls@ Installed at the Canadian Coast Guard Base in Prescott, Ontario, Canada
Canadian Garde côtière 1 Coast Guarâ canaciienne
BASE
SCL
HAT-SECTIEN VITH ANGLE
+ \2hrrn 31P. >@E. ri.$ VEFZIFY 3uSIDE CLEZRn~CZ AiWQOX Z5-m A8[3VE ;UP LE OF K l E Kl a W (THIS GiVES 7%- SSthCZ FER =AN CZVLrNG)
~ E C < SXE AND 30T7m C-EAGANCZ
OVE.?LPP na: SECTIENS :O@n ?ASEN VITH 4 S t R E v Z 3C3 CûNNECTiCN
1 I ! !
1 9926nnr I UR :0050nn= 70 E3GE CF 1 O I h PANEL <DE?EI\(DLUG ON CLEARANCE;
CIINCRE TC SCRE W INTfl LflW R l n
CONCRE 1 C SCRC W WITI1 WASllER INTII 1-DW R l l l
I-nm PER CLIP t \
CONCKE TE SCKE W W I TI-I WASt IEH
1 1 INTll L O W R l l l EVERY 4SOmn \ l\
1114xS5mri SEI-F IIRILI- llEX IJYLLIN IIEAlI SCKEW
1114xL35mm SELF I IRILl_ llEX t1EAD SCREW
11 14 x2Smn SEI-f INILI. iIEX STEEL SCREW t
FCILIR l'CR CIINN.
H14x25nm SC1.t- IIRII-L llEX I.IEAI1 NYt.flN I If:All SCRE W CVCKY 1-nw R l i i
LI 14 x25nrn SC1 . f nRil-1 llCX IICAII SCRCW NYI-IIN llCAll E V C R Y 450nv-1
APPENDIX C
Dr& ~~Instructions" for the Young Mode1 8 1000 Ultrasonic Anemometer
METEOROLOGICAL YOUNG INSTRUMENTS
INSTRUCTIONS
MODEL 81000 ULTRASONIC ANEMOMETER
OCTOBER 1999
MANUAL PN 81000-90
R. M. YOUNG COMPANY
2801 AERO-PARK DRIVE, TRAVERSE CITY, MICHIGAN 49686, U. S. A. TEL: (231 ) 946-3980 FAX: (231) 9464772
l[&@] MODEL 81000 YOUNO
ULTRASONIC ANEMOMETER
SPECIFICATTON SUMMARY
WNDSP W Range: Resolution: Threshold: Accuracy:
WND DIRECITON Aumuth Range: Elevation Range: Resolution: Accuracy:
SPEDOFSOUND Range: Rcsolution: Accuracy:
0-50 d s (1 12 mph) 0.01 mfs 0.01 m/s 21% mu (O - 30 m/s)
0-360 degrees 260 degrees 0.1 degree r 2* mis (O - 30 m/s)
300-360 mis 0.01 mis z 1% (0- 30 d s )
SONlC TEMPERATLIRE Range: -50 to 6 0 Co Rcsolution: 0.01 Co Accuracy: 22CO
GENERAL Air sample cdumn: 10 un high X 10 un diameter Air sample path: Sample ale: Output rate: Outout formats:
Baud Rates: Auxiliary Input:
Power Supply: Dimensions:
Weight:
INTRODUCTION
The YOUNG a l 000 Ultrasonic Anemorneter bnngs a new levcl of value to three dimensional sonic anemometry. This low cost unit boasts leahires and perfomanu ordinanty found on senson ust ing much more.
The 81000 measures wind vetouty aased on the transit tifne of ultrasonic signal5 sent behveen the Iransuucen. Oepending on ~ t s onentation and magnitude. air Row aiten the sonic signal transit lime. ay measuring Vie lansit tirne in eacn direCion along ail three paths. me three dimensional wind veloaty and speed of souna may be calarlaced. Fmm speed of sound. sanic temperature is denvea. Speed of sound and sonic temperature are coneded !or aoss- wind effecs.
Measurement data are available as voltage output signais or senal output usrng RS-232 or US485 connecions. Bath voltage and seriat output may be contigured for a vanety of output formats.
Operacing parameten rnay be edited using ordinary terminal sort- wôre on a PC. Simple menus make it easy. All parameten are storetj in nonvoIaCile memory.
Supenor environmental resutanec is achieved by using W stabi- lued thennoplastic. stainleu steel. and anodized aluminum campo- nenm. U e d n u l connections a n made vra an easily accessible jundon bar. The unit mounts on standard 1 incl pipe.
lScm 160 Hz (internal) 4 to 32 Hz iseledable) - Senal data (selectable) 3 voltage output channets O to 4000 mV RS-232 full duplex RS485 hall duplex (cm be t~ussed) 1200 10 38400 4 general purpose vollaçe inputs. 12-bit. 04000 mV 12 10 30 VOC. 3.5 wans Oveall heiçht 56 cm Support a m radius 17 un Mounting % mm (1.34 in) diameter
(standard 1 inch pipe) Sensor weight 1.7 kg (3.8 ib)
INITIAL CHECKOUT
Carefufly unpadc the unK and inspect for pnysical damage. Any damage should be reportCd to the sfiipper. The 81000 amves fully calibraleci and ready to use. A simple operational check rnay be perfomied as foilaws:
1. Remove jundion box wver and connec: power and s~gnal w i r u to leminais as indicalecl in mnng diagram under -8-232 annecion'. C a n n e RS-232 output to amputer COM port.
2. Using an ordinary serialcommunications program (like Hypertem). set ttie baud rate to 38400 with no flaw wntrol.
3. Appiy power ta the 81000 sensor. then wlI be a bnef delay for initialitjon then the un11 will begin 10 Output data. A continuous strearn of data will b@ output in the following fomaç speed (Spa-) azirnuth (space) elevatian (space) speed Of Sound (space) sonic temperature. Vcnfy Chat al1 values are present on me display. Typical output u show below
A threshoid levelo10.2 mis is pfeset fmm the facory. Wind below the threshold wili be shown as zero. In saII air, Soeed ml1 be zero. Azirnuüimay be any value hom O to 360. Belaw the threshoid Ievei, Vie last valid axirnuth nading will be Uuphyei. Elevation will remam zero untd the threshold ta exceedeû. Speed Of Sound ranges fmm 300 10 360 depending on temperature. At 20-C Che value is about 344. Sonic temperatun rnay be comparrd ;O a standard lhermometer and should a q m wthin a degree or Mo. If the duplayed values appear quesuonable or if any value is net displaymi. remove power and ch& al1 wnng connections. If the problem cannot be coneCed contact your YOUNG represenla- tlve.
4. Verrfy sensar nsporue by gentty blowing thmugh Ihe measuring scdon. Wind fmm the nom aide (marked 'N3. shauld pmaua a poutiveSPEED msponse and 3n AZlMUTHdbpiay comsponding to No* (ie: values around 360 or O ). Wmd fmm the opposite d W o n should produce vaiues indicating south. (around 180 ) and so foftb. Wind dawnward will pmduçt negative ELNATfON . values. upward will proauce positive values.
Aiter pmper operation is confimeci. Be sensor may be instalied. Facory senings may be changea by following the insrneions in the n e m seaion.
COMMAND MENU
Sending the €SC àiaader(ASCI127) three times in qui& suuxssion takes the unit out of OPERATE mode and auses the COMMAND MENUto appear.
Aocess eaci menu item by sending the chaacter asociated with the menu item of interest Charaaen may be uoper or lower case. Send X' to retum to OP=-TE mode. The following paragaphs explain the func3on of each menu item and assaciated sub-menu. The version number may Vary.
AVERAGING sets the number of autput vafues to use in caimlating an average. R ~ I S sening alters the net output rate of the sensar. Far example. if the output rate IS set to 4 Hz and the AVERAGE IS set to 8. the unitmll pmduce an outputonce every 2 seconds. (8 samples 14 output samples I second) = 2 samples I second.
BAUD sets the baud rate forsenal communication. r'aster baud rates may De required if the output stnng is bng and the output rate is fast (set OUTPüT RATE).
REPORT MODE sets the method by which wind measurements are taken. M WN calculates the averagevalue of all intemal samples aken !O detemine an output value for air veloaty. This mode is
REPORLsummarkes the current parameterseetings. Typicai values recommended for low wind veioaües (4 mis). MEDlAN finds a n shown below. the median value af al! intemal samples to detemine an output
value for air veloaty. This mode is rccommended for hqher PA-. LC<rm ( 0 1 CHAN OCLtY luSI CUlPIRC LEVEL -----------------------------*------------
velouties (>5 mis] sine it reduces the influence of outlien in
A 15-341 1 L9.610 SL6 the data seL AUTO swilches automatically beween MEAN and 4 ~ 9 . 5 ~ 0 4 1 4 MEDIAN at 5 mis tooffer optimal performance over an extended
3 15.2411 2 ~3.675 sr0 operating range. 5 23.750 S24
C :5.:46 1 26.675 1111 6 26.100 464 n0OE 1 -----------------
aJTmX m-7: CJSrp< :1 m 719- I ID-SPLLJ .UiXïEH EUXA?IOn SOS 7s 2 1 .-KM
'dWü tPEC!l WIZS: d a 31 -0 cuzw RA=: 4 HZ KI a ~ r ~ r u r r x c w
SAI(PLCs m l A Y t l U G t : O ),J) 5 - ':;& L I A i, ,,. .y ?<ODE; m OUT~TRATE seu the ratsatwhicisenal data is sent from the unrt.
!4A)(E ~ICKc:OW: Y 7 3 UMn KLWOL:Wt: ml: :SVAL10 MTA tt is influencecl by the nurnber of output values Deing averaged
M L ? ~ M P V t fORlU7: S?E=0. AZlrVTX. tZTtX7ICn (See AVERAGING). Higher output rates and longer output W L : ~ s a : o t~ to d a - 0-4090 r v suinas mav muire higher baud rates. The output rate also
SETUP
O ïü 540 C f f i AZ1NIE-i - 0-4000 SV
-60 '0 -40 CEG C C Z A t Z e W - 0-4000 i V :z11 -3 O :::s 11 10 4095 40911 40911 4095 20 en/¶ YS31 Z(S.7 Iüir 4t 'cc 14 v0C Nonnu
- . . determines the intemal number of samples taken to get a rneasurement Use the lower output rate senings for high velocties.
POLL CHAWCTER (ADDR) is used to set the address charader when the unit is operared in P O U CUSTOM format Any ~rintable ASCII darader may be used to identify mis panicutar ànernometer. Each anemometer on the buss should have a different address charader.
SETüP a l I M operating parameten to be altered to soit Lhe WedS of a panicular aoplication. A detailcd uolanation of each menu item mt:. t*00*1 : A
follows:
S M M L OüTFUT FORMAT sets the output string for senal output Preset and astom formats am available.
CUSTOM format allows the user 10 wnstnid anoutput string speafic to the needs of the application. Long strings may require higher BAUO ratuorbwerOü7PCTTRAfES. (Sec BAUD andOWPüT RAfE)
When CUSTOM is seleded the follawing message and menu appear:
W N t 4 are auxiliary voltage input channels 1 4 . The measure- ment for each channel is scaw to 0-4000. Normarly mis represents O to 4000 mMC. but other saling may be used.
UVW is the orthogonal u. v. and w wind speeds.All three values are oumut.
2 0 SPEED is the magnitude of the wind vectorin the w plane.
3 0 SPEED is the magnrtude of the wmd vedor in the thrte dimensronal space.
AZiMUTH is Vie 0.0-360.00 orientation angle of the wind vecor in the w plane.
ELNATION is tne 190.00 orientation angle of the wind veeor relative to the w axis.
SOS is the speed of sound.
Ts is Vie sonic temperature denved tram SOS.
RMYT sends wind speed and direction in a format suitable for the YOUNG Wind Tradrer display un& RS45 ouiputs must be used. When RMYF is seleaed. the baud rate is automaticaily set Io 9600. To access menu options. teminal softwam must be set 10 9600 baud as well.
NMEA sends wind s o c 4 and d indon in NMEA manne f o m t Trie sentence is NV1MWV.aaa.R.ss.s.NA whem aaa IS wind direc- tion angfe in d e g n u and u.s u wnd speed in knots. The baud rale is automatically set to a00.
user sends whefe A u a single alunanurnene addms daracer (sec POLL CHARACTEn). Uter recemng the pmp- eriy addesseci wmmand. the 81000 msponds wrV, the POLL CHARACTER fallowed by the -tom senal output ~Ving. Up to 32 anemometen may be nerworiced usmg tne Xi485 connec- mn. By assqning a unique adares to each devmi?. unrts may fun on the rame netwoftc and :espana wtth data oniy when addressed.
MRESHOLO secs the wind speed threshald (in &sec). Windvecor rnagndudes below the ttireshold are reponed as :ero.
UNlTS sets the wind speed units.
VOLTAGE OUTPUT FORMAT sets the values appeanng as voltage outputs. Full sa le output is 4000 mV for eac! cclannel.
ARer selecing the format a prompt for the scaling appears:
In UVW format scaling is shown as + or -. (ie: JO ta +40 m/s equals O Co4000 mV) In Speed Arimuth Uevaticn format. Speed is scaled as a positive range (ie: O 10 40 d s ) . Awnuth is scaled as O to 540a (muais O to 4000 mV). and E!evation is scalcd from 40 ln +ô0 degrees.
MPORTI\NT: The devia m u t be set for kustom' fomat and ;-box jurnpers rnust be in posrüons V2 & V3.
VOLTAGE INPUTS
The B l O W features 4 auxiiiary voltage inputs for connedon ofolher meteorological senson suc9 as temperature and humidity senson. Any voitage input of 4000 mVor less rnay beconneCed. Siqnal leveb a n output as numenal values on the autput string. See instruc3ons underSEFlL4L OUTPUTFORMAT. CUSTOM.
WARRANTY
i h s produd ts warrantcd to b e fret of defecs :n rnatenals and construaion for a pend of 12 months h m date af iniiiai purcnase. Liability is limited to npair or reolacement of defeme item. A cooy of the warranty polici may be obrained fmm R. M. Young Company
POLLCUSTOM famat allaws the 8lOW Co be polled ta rtspand with a cusrum stnng. Set CUSTOM above fordetaib cncomtruCing the stnng. When the output format 1s sel10 POUCUSTOM. the
--------- r-"------------------ 1
W U T l : : VIN: - R O U T E JITA L-2 I 1 V [ m - (32 TOWG WOEL 26700 I
v13UtZ '
V I N 2 - 0
FOR * C t W l 1 E HE*SURCKXTS k~~ VIC D V T U E N T I I L U N I S
I I
I I ON * E A S i S [ M ü W I C t I - 1 V I M - I
I I 4"x PUR I -PVR ElDW
I VlHl f mTQASWtc ' TEWPEIIATURE V(LTM;E OUTPUT f urO*3rcEtt7 VfrQ , ! - t n t r r var- R J T P U ~
I V l T H V O L I A C E I
QCT , c m r s
, ZCfCiKrCi ! 1
. - - - - R..u. ~ U N C CD. R A ~ = an. ur 496~56 U.S.A. 221-946-J980
J U N C BOX
NOTES: 1. MEASUREMENT VALUES FOR U. V. W.
ARE POSITIVE FCf? AIRFLOW IN DiRECTiQN OF ARROWS
WlND FROM E T 0 W = -U WlND FROM N T0 S = +V WIN0 UPWARDS = i w
APPENDIX D
LabVIE W Graphitai Programs used for Data Acquisition
-The ' d e v i c e ' is t h e c a c a a c q 2 i s i : i o c b o a r d lunber
-The cornpucer po:: connec:eC :O :ne s o n i c anemomecer i s i z i : i a ! i z e ~ by :ne serial ? o r Ini:.vi
an6 :he àa:a from :he s o n i c a r e cnen r e a c by scb vi 2 znc p l a c e ? i2:o +n &::&y.
- T e m p e r a t u r e , c r e s s u r e , a z d s o l a r r a d i a t b c m ê a s u r e m e c t s a r e a c q u i r e d f r o n :he c a c z
acquis : ion boa rd acd ? r o c e s s e C by :he TPS.vi ( C O roàuce no:se).
- S O G . r i c o m b i n e s t h e s o n i c a n e m o m e c e r a n d d o r a acq2is : :on b o a r d d z z z : o g e t h e r
wl:S a c o t z l è r r o r ccunc . The loqgea àaca is a l s o :ise s:am?ec. - . - - - - - - . - - - - - -- . . - - - - - - - -
Fron: ?onel
1 n c v t ce1 . L
.mg] :
P a g e 2 pl
d t c i c h e d co i e t r o a o i r symbol b e i o r i ---
- - -
uriceredd:.7i cr ies :O
D e c e r i i n e s ;$ i n ' '
er:or a c c ~ r c d (1 ~t f i 1'1 I 1 4
ilow control etc. 1 bu: fez size I
garr 3ilrOer
errer coae data bits
stop Dix
paricy Serial Port Inft-vi
Initialires che selected serial porc co tbe speciiied settings.
e r r o r code
m- I
C o n n e c t o r P a n e
nuu PT w a v e f o r m
channel ( O ) *;!!il - : . f , , , 5 i ? t . .1 .-. number of samples
sample rate (1000 sampleslsec) - b ~ l h ! . . ! . ! * device5r 8 . . :
AI A o q u i r e Waveform.vi
Acquires the specified number of samples at the specified scan rate and returns al1 the data acguired in scaled data
units. This V I calls the AI Waveform Scan V I from the Analog Input palette, using the follwing parameters:
( i l 6 1 device: the number of the plug-in data acquisition board. You must specify device.
(string] channel: specifies the analog input channel to acquire from. The default input is channel O. See the description
of the Analog Input Group Config VI for a detailed description of this parameter and the valid syntax for the channel
strings.
(i32) number of samples: the number of samples the VI acquires before the acquisition is complete.
(sgll scan rate: the number of samples per second to acquire,
(sgll hiqh limit: specifies the maximum scaled data expected at the input channel. LabVIEW uses the high and low limits
to set programnable board features such as gain, polarity, and input range.
(sgl) l o w limit: specifies the minimum scaled data expected at the input channel. LabVIEW uses the high and low limits to
set programmable board features such as gain, polarity, and input range.
O u t p u t V a l u e s :
((sgl]) waveform: a one-dimensional array that contains scaled analog input data.
( s g l ) actual sample period: the time between samples, the inverse of the actual sample rate the VI used to acquire the
data. This may differ slightly £rom the requested sample rate, depending on Ihe hardware capabilities.
C o n n e c t o r P a n e
1-CJC T e a p
T e m p l
T e r n p 2
P r e s s u r e 1
1 - roiai i n r
T e n p 3 ~ e i p p r e i i o l . v i
Th i s vi acquires data using software timing. Data acquistion device number a n d the number of s a m p l e s required is input.
T h e mean of the temperatures, pressures, and total solar radiation is calculated by the mean.vi [already in system) and
outputs are displayed. An error check is also included so large negative temperatures are noted for future processing.
P a n e 1
- - 1
CL; !N; :ig ; -: "1 O
-7 c l
r - i Ti- , '='!
L. 1
Jrci :n arzay foraac Lron z 3 e data acqu~s:r:on Cev:ce L;.e 1 0 0 data taken eve:y 1100 ml d:e averrged d
averapes aioaq utck array 7a:~er !:sa the SOSLC r c e a o ~ e c e r a:e coab:ncd L ~ C J a s:=gIe array and scortd
s ~ ~ p t d f:!e by C!XS V î .
iat Panel
II; -;@pl 21
C o n n e c t o r P d n e
Digits of Precision character string
saiaples l a s 1 date logged
l d s t tine logged
croate data string l.vi
A string containing both s o n i c anemometer and data acquistion board values is time s t a m p e d . T a b s are a l s o inserted s o
that the files are easily read by a spreadsheet.
F r o n t P a n e l
APPENDIX E
Caiibration Plots of the Sonic and Cup Anemometers, and the Setra Mode1 264 Pressure Transducers in the RMC Wind Tunnel
Testing was carried out in the RMC Wind Tunnel in a turbulent flow field in order
to veri@ the accuracy of the sonic and cup anemometers. Turbulence was created by
placing a screen in front of the wind tunnel working section. Results of this test are
plotted in figure E. 1. The velocity of the cup and sonic anemometers were ploned versus
the velocity calculated using a pitot-static tube and a Delft water manometer.
0 . - . .
O 2 4 6 8 10 12 14 16 18 20 Velocity Calclattd using Pitot-Static Tube (mis)
Figure E. 1. Sonic and cup anemometer velocities versus the velocities calculated using a pitot-static tube and Delft water manometer.
Two Setra mode1 264 pressure transducers had to be calibrated before use. The
transducers were connected to pitot-static tubes using flexible tubing and were calibrated
in the RMC wind tunnel versus the pressure measured using a pitot-static tube and a Delft
water manometer. The calibration curves seen in figure E.2 were used in LabVIEW to
convert the output voltages of the two transducers directty to pressures (units of Pascals).
O 0.5 1 1.5 2 2.5 3 3.5 4 4.5 5 Tnnsducer Output Voltage (V)
Figure E.2. Calibration curves for two Setra 264 pressure transducers.
Themocouple Temperature Corrections
As stated in section 3.4.3, the sonic anemorneter and thermocouple probes did not
measure the same temperature, but there was a consistent difference in the measurements.
As seen in figure F. 1, the power in the battery of the electronic ice point slowly declined
between the months of Decernber and Februaiy, causing a drift in the thermocouple
measurements. Figure F. 1 is a time senes plot that shows the temperature difference
between thermocouple 3 and the sonic anemometer, when the Solarwall@ was left in
operation during penods of no solar radiation (between 6 a.m. and 6 p.m.). The time
series is based on the Julian caiendar where Julian day O represents 1 January 2000.
Therrnocouple 3 was mounted beside the sonic anemometer in December and January
and on the SolarwallQ in February and March. "Ideally" there should be no difference in
these readings as they both measured the outside temperature. There was not very much
data for figure F.l because of problems encountered with equipment, and because the
SolanvaIl@ was often turned off at night during these months. Figure F.2 shows the
same data after the correction was applied.
As seen in figure F.3, the temperature difference between thermocouple 3 (wall
temp) and the sonic anemometer is approximately 1.25 OC, for the month of March. This
value was subtracted from al1 thermocouple measurements in the March data set. The
result of this correction is shown in figure F.4.
Figure F. 1 . Temperature difference (temperame thermocouple 3 - sonic anemometer temperature) versus Julian day, during periods of no solar radiation (between 6 a.m. and 6 p-m.). Julian day O represents I January 2000.
Ir-
Figure F.2 Corrected temperature difference (temperature thermocouple 3 - sonic anemometer temperature) versus Julian day. during periods of no solar radiation (between 6 a.m. and 6 pm) .
Figure F.3. Temperature difference (wall temperature - sonic anemometer temperature) versus Julian day, during periods of no solar radiation (between 2 a-m. and 4 a-m.). Julian day 6 1 is 1 March 2000.
Julun i h y
Figure F.4. Temperature difference (wall temperature - sonic anemometer temperature) versus Julian day, during penods of no solar radiation (between 2 a.m. and 4 a.m.), after a temperature correction of -1.25 OC.
Calibration of Solarwall@ Outlet Ducts
Caiibration of one of the two Solarwall@ exhaust ducts was done on site after al1 the
instruments were put in place. Because both of the exhaust ducts were similar, only one
calibration was carried out. A duct coefficient of 0.86 was caiculated using the velocity
profile seen in figure G. 1. The calibration was done by rnoving the pitot-static tube, from
its position roughiy in the centre of the duct, to the duct wdl and back. The centreline
profile was determine using this partial traverse by assuming symmetry and fully
developed flow. Symmetry and fùlly developed flow were again assumed to expand the
centreline profile to a two dimensional duct.
-20 -15 -10 -5 O 5 1 O 1.5 20
Distance frorn center of Duct I (cm)
Figure G. 1. Velocity profile of Duct 1.
APPENDIX H
SUMMARY OF UNCERTAINTY
Table H. 1 below surnrnerizes the uncertainty, accuracy, and ranges of the
instruments used in the experimental set up. The 'hecertainty of the thermocouple
rneasuements were assumed to be approximately 0.2 OC. based on the differences of
thermocouple readings during testing done in the RMC wind tunnel. The accuracy of the
pyranometer was assurned to be the maximum allowable for a second class pyranometer
base on WMO standards (9).
Table H. 1. Summary of uncertainty, accuracy, and ranges of the instruments used in the expenmental set up.
instrument Sonic anemometer velocity Sonic anemometer temperature Thermocouple temperature (type K) Pyranorneter Setra pressure transducers
Cup anemometer velocitv
From equation 2.4, the eficiency for the Solanvall@ can be calculated to be.
Uncertainty 0.01 m/s
0.01 OC
0.2 OC '
0.10 % full scale
0.40 m/s
Accuracy + 1 % rrns (0-3 O mk)
+ 2 OC
2.2 OC
k 2% I 1% full scale or
1.25 Pa
Range 0-50 rn/s
-50 to 50 OC
-200 to 1250 OC
0- 1 -27 cm water, (0-0.5 in water), or
or 0- 125 Pa
where vd is the velocity in the duct (mis), Ad is the duct area (m2), and 0.86 is the duct
coefficient calculated in appendix G. If Tm= Tm - Tonb , and assuming p, Ac, &, and c,
are al1 constant, the uncertainty for eficiency becomes:
The velocity in the duct is given by,
where PI is the pressure in Duct 1. Therefore the uncertainty for vd is
Substituting H.4 into H.2 gives
For the worst case scenario of the March data set (solar radiation > 600 w/m2)
where, Tou, = 283 "K, T,,= 10 O C , and PI = 38 Pa, results in an uncertainty of efficiency
of 8%. Under these same conditions but with 1, = 200 w/m2, the maximum uncertainty
increases to 14%, and decreases to 6 % when Ic = 1000 w/m2.