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Federation of European Heating, Ventilation and Air-conditioning Associations
Address:
Rue Washington 401050 Brussels
Belgium
www.rehva.eu
[email protected] Tel: +32 2 514 11 71
Fax: +32 2 512 90 62
Federation of European Heating, Ventilationand Air-conditioning Associations
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Federation of European Heating, Ventilation and Air-conditioning Associations
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Federation of European Heating, Ventilation and Air-conditioning Associations
Ventilation EffectivenessREHVA Guidebook no 2
AUTHORS
Elisabeth Mundt, Professor, KTH-
Royal Institute of Technology,
Stockholm, Sweden (editor)
Hans Martin Mathisen, Ph.D.,
Sintef, Trondheim, Norway
Peter V. Nielsen, Professor,
Aalborg University, Denmark
Alfred Moser, Ph.D., ETH, Zrich,Switzerland
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Federation of European Heating, Ventilation and Air-conditioning Associations
CONTENTS1. VENTILATION EFFECTIVENESS IN A NUTSHELL (3 p)2. SYMBOLS AND TERMINOLOGY (4 p)
3. WHY VENTILATION EFFECTIVENESS (5 p)
4. TYPICAL CONTAMINANTS AND CONTAMINANTSDISTRIBUTION IN VENTILATED ROOMS (6 p)
5. THEORY AND DEFINITIONS (8 p)
6. MEASUREMENTS (12 p)
7. PREDICTION OF AIR QUALITY BY COMPUTATIONAL FLUIDDYNAMICS (4 p)
8. CASE STUDIES (21 p)
9. DEFINITIONS OF VENTILATION EFFECTIVENESS INDIFFERENT COUNTRIES (1 p)
10. APPENDIX 1 (1 p)
11. REFERENCES (4 p)
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Federation of European Heating, Ventilation and Air-conditioning Associations
VENTILATION EFFECTIVENESS
includes
A
Indices representing the
ability of a system toexchange the air in the room
air change efficiency,
local air change index,
B
Indices representing the
ability of a system to removeair-borne contaminants
contaminant removal
effectiveness (CRE), local air quality index,
a
a
P cP
c
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Federation of European Heating, Ventilation and Air-conditioning Associations
INTRODUCTORY CHAPTERS
1. VENTILATION EFFECTIVENESS IN A NUTSHELL
2. SYMBOLS AND TERMINOLOGY
3. WHY VENTILATION EFFECTIVENESS
Keep concentration low
Point source Q cs
ce
Point sensorP
cs
ce
Point source Q
Concentration field resulting from point source Q
Distributed source Q
cs
ce
Point sensor P
Distributed source Q, mean concentration
cs
ce
a
a
P
c
c
P
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-5 0 5 10 15 20
0
1
2
3
4
es
eP cc
4 TYPICAL CONTAMINANTS AND CONTAMINANTS
DISTRIBUTION IN VENTILATED ROOMS
Return opening
The location of a return
opening may have a very
large influence on the
concentration
distribution, although it
only has a small influence
on the velocity
distribution.
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4 TYPICAL CONTAMINANTS AND CONTAMINANTS
DISTRIBUTION IN VENTILATED ROOMS
Displacement ventilation and vertical concentration gradient
The idea behind displacement ventilation is to accept a variation in the
concentration distribution with a high value below the ceiling and a low
value in the occupied zone.
0,950,90
0,800,70
0,950,90
0,800,70
73,0exp
c 76,0exp
c
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5 THEORY AND DEFINITIONS
AirChangeEfficiency
qv
qv
Age
0 n=V/qv
P
What is the mean age of the air in theroom?
Mean age of air in the exhaust2 x Room mean age of air
a
=
The mean age of air in the exhaustis always equal to the nominal time constant
n
a
The room mean age of air can not be less than half the nominal time constant!
Thus the air change efficiency < 100 %
2
n
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5 THEORY AND DEFINITIONS
AirChangeEfficiency
Fully mixed flow
n
n
%50a
Displacement flow
n
nn 2
%100%50 a
Short-circuit flow
n
n
%50a
Piston flow
n2n
%100a
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Contaminant Removal effectiveness, CRE
5 THEORY AND DEFINITIONS
Concentration in the exhaust
Mean concentration in the roomCRE =
ec
c
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6 MEASUREMENTS
Injection of tracer gas
Flowmeter
(Rotameter)or mass flow
controller
Injection
point
Closing
valve
Pressure control valve
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6 MEASUREMENTS
Routines for how to measure and calculate the ventilation effectiveness
Alternative 2
Tube from gas bottle
Alternative 1
Tube from gas bottle
Exhaust air
concentration
Local room air concentrations
Switch
Analyser
5 10 15 20
Time (minutes)
Concentration(ppm)
This part of the curve could be
used to calculate the decay
For calculation of the tail the
calculated decay is used
cn
ci-1
ci
ti
ti-1
c0
2
4
6
8
10
12
14
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6 MEASUREMENTS
Commissioning
2. Incorporate commissioning
specificationsDesign
3. Review project design
4. Develop commissioning plan
5. Develop prefunctional checklist
6. Execute prefunctional checklist
8. Approve p refunctional checklist
9. Develop functional tests and
diagnostic monitoring plan
10. Execute monitoring and
functional plans
12. Accept equipment performance
13. Develop final commissioning report
1. Develop team
Installation
Acceptance
Post-acceptance
11. Is equipment
in compliance?
7. Are expected
results realised?
7A. Correct deficiencies
No
Yes
11A. Correct deficiencies
No
Planning
2. Incorporate commissioning
specificationsDesign
3. Review project design
4. Develop commissioning plan
5. Develop prefunctional checklist
6. Execute prefunctional checklist
8. Approve p refunctional checklist
9. Develop functional tests and
diagnostic monitoring plan
10. Execute monitoring and
functional plans
12. Accept equipment performance
13. Develop final commissioning report
1. Develop team
Installation
Acceptance
Post-acceptance
11. Is equipment
in compliance?
7. Are expected
results realised?
7A. Correct deficiencies
No
Yes
11A. Correct deficiencies
No
Planning
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7 PREDICTION OF AIR QUALITY BY
COMPUTATIONAL FLUID DYNAMICS
Contaminant distribution around a sedentary person, contaminant source at the floor
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The exposure of a standing person from different surfaces with the same emission
7 PREDICTION OF AIR QUALITY BY
COMPUTATIONAL FLUID DYNAMICS
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8 CASE STUDIESDescription and Design Values, Measured Results, Discussion of Results
Auditorium
15,8 m
21,5m
6m
3,6m
3,8 kW ceiling light
320 seats
Measurement column
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8 CASE STUDIESAuditorium
20 25Temperature, C
23,8 C
24,8 C
20,7 C
22,4 C
Room width: 21.5 m
19 m
890 ppm CO2
420 ppm CO2
0 1 2
Local air quality index
0,85- 0,97
0,56-0.82
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8 CASE STUDIES
Office in town hall
Office in town hall Full scale experiments
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Federation of European Heating, Ventilation and Air-conditioning Associations
8 CASE STUDIES
Office in town hall
Carpet as contaminant source Concentration profiles
0
1
2
3
0 1 2 3 4 5Dimensionless concentration (c/c e)
Height(m)
New system
Old Sys tem
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Federation of European Heating, Ventilation and Air-conditioning Associations
8 CASE STUDIESIndustrial building
Mixing ventilation
Displacement ventilation
Section A-A
Measuring position
A
A
75 m38 m 24 m
25 m
5m8
m
A
A
75 m38 m 24 m
Section A-A
25 m
5m8
m
Measuring position
10 14 18 22 26
4
3
2
1
(min)P
Height (m)
Mixing ventilation
Displacement ventilation
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Federation of European Heating, Ventilation and Air-conditioning Associations
8 CASE STUDIES
Homogeneous emission techniques
Laboratory hall Subdivision of the room
7 m
4 m
13,2 m
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Federation of European Heating, Ventilation and Air-conditioning Associations
8 CASE STUDIESHomogeneous emission techniques
Local mean age of airLocal concentrations with point sources
Computed local meanage of air in the sub-
volumes between the
two layers
0,35 0,42 0,50 0,54
0,28 0,35 0,45 0,60
0,27 0,28 0,43 0,63
0,33 0,33 0,48 0,57
1
0
1
0
c/ce
1
0
1
0
c/ce
1,33 m above the floor
Floor level
The shadowed ellipses
show the positions of
the two 750 W air
convectors at the floor
level
1
0
1
0
c/ce
1,33 m above the floor
Floor level
The shadowed ellipses
show the positions ofthe two 750 W air
convectors at the floor
level
1
0
1
0
c/ce
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