solar cooling (case study)

بسم الله الرحمن الرحيم

Faculty of engineering

"Mechanical engineering department"

Solar cooling

Prepared by: Hamzeh shehadeh Mahmoud Khader Tariq al Rjoub Advised by:

Pro. Afif Hasan.

A graduation project submitted to

The Mechanical Engineering Department in partial fulfillment

Of the requirements for the degree of B.Sc. in mechanical engineering

Birzeit

May 2010Contents

Page

Abstract IAbstract in Arabic IIIAcknowledgment IVChapter One: Introduction 1

Chapter Two: Solar energy 5

2.1Solar Radiation 6

2.1.1 The solar constant 6

2.1.2 Measurement of solar radiation

2.1.3 Solar radiation angles 9

2.2 Solar collectors 18

2.2.1 Flat-plate collectors 18

2.2.2 Evacuated tube collectors 23

2.2.3 Concentrating Solar Collector 31

Chapter Three: Solar refrigeration 39

3.1Absorption cycle 40

3.1.1 The structure of absorption chiller 40

3.1.2 The principle of absorption chiller 41

3.1.3 The coefficient performance of the ideal absorption cycle 43

3.1.4 Market available chilled water systems 44

3.1.5 Cost analysis 46

3.2 Adsorption cycle 47

3.2.1 The cycle consists of four periods 47 3.2.2 Advantages of the adsorption cycle 47 3.2.3 Disadvantages of the adsorption cycle 48

3.3 Electricity (Photovoltaic) Driven systems 48 3.4 Desiccant cooling cycles 49

3.4.1 How desiccants work 49 3.4.2 Advantages of desiccant cooling system 50 3.4.3 Applications 50 3.4.4 Types of desiccant cycle 50

Chapter Four: Solar energy cooling case study 55

4.1 Case description 56

4.2 Construction elements description 56

4.3 Thermal resistance for walls, windows and doors 57

4.4 Load calculation 60

4.4.1 Sample calculation for the Multipurpose Hall (120 seat hall) 60

4.4.2 The load results for the ground and 1st. floors 62

4.5 Solar system design 65

4.5.1Collector Calculation 65

4.5.2 Collector installation 67

4.5.3 Double jacket Storage tank 69

4.5.4 Boiler (back up) Calculation 69

4.5.5 Solar system pump selection 70

4.5.6 Expansion Tank selection 73

4.6 Duct design 74

4.7 Chilled water distribution 77

4.7.1 Fan coil selection 77

4.7.2 Chilled water pump selection 77

4.8 Economic analysis for solar energy cooling case study 80

4.9 Conclusions and recommendations 84

Chapter Five Adsorption refrigeration 86

5.1 Introduction 87

5.2Adsorption refrigeration 87

5.3Working pair’s selection 91

5.4 Lab. Scale adsorption ice maker 94

5.4.1 Adsorption ice maker model components 94

5.4.2 Components description 95

5.4.3 Lab scale experiment 96

5.4.4 Conclusions and recommendations 98

References 100AppendicesAppendix A.1 Arch plane for case study law building in Birzeit University Appendix A.2 Wall sectionAppendix A.3 dimension of doors and windows of the case study buildingAppendix B.1 Absorption chiller catalogue Appendix B.2 CPC solar collector catalogueAppendix B.3 Boiler catalogue

Appendix B.4 Pumps catalogue

Appendix B.5 Expansion tank catalogue

Appendix C.1 Palestine climatologically

Appendix C.2 Cooling design condition

Appendix D.1 Pressure drop figure to steel duct

Appendix D.2 Duct sizing

Appendix D.3 Fan coils catalogue

Appendix D.4 pill of quantity

Table of Figures

Figures #No Name page2.1 Pyranometer 82.2 Pyheliometer device 82.3 Diversity of season 92.4 Angle of sun radiation 102.5 Tilt angle and season 111.6 The zenith angle 112.7 The declination angle 122.8 The latitude angle 132.9 The azimuth angle 132.10 The hour angle 142.11 the length of day at different latitude angle

with variation of season14

2.12 The solar radiation 152.13 the variation of solar Insolation at 21 June

and 21 December at different latitude17

2.14 The variation of solar radiation at different latitude during full year

18

2.15 A typical liquid Flat Plate Collector 192.16 the heat flow through a Flat Plate solar

collector20

2.17 Typical solar energy collection system 202.18 efficiency versus ΔT/I 232.19 evacuated tube collector& hot water storage 242.20 Insulation of evacuated tube 252.21 The construction of evacuated tube 252.22 direct flow model and its efficiency 262.23 indirect flow model and its efficiency 262.24 glass-to-metal seal model and its efficiency 272.25 thermosyphoning principle 282.26 flat plate fins 292.27 V-shaped fins 292.28 the efficiency for flat plate collector and for

evacuated tube collector30

2.29 Cylindrical concentrator 322.30 Absorber 32

2.32 Parabolic concentrator 332.33 Cross Section of Cylindrical parabolic

Concentrating Collector33

2.34 Parabolic Trough Solar Field Technology 352.35 Field of Compact Linear Fresnel Reflectors 352.36 Field of Compact Linear Fresnel Reflectors 362.37 Field of Solar Furnace 362.38 Parabolic Dish 373.1 absorption chiller 403.2 component of absorption refrigeration cycle 413.3 pressure versus temperature 423.4 working principle of absorption chiller 423.5 schematic for the absorption cycle 433.6 Single effect absorption chiller 443.7 double effect absorption chiller 453.8 annual total cost versus cooling capacity for

both chiller compression and absorption46

3.9 Working principle of desiccant cycle. 493.10 solid desiccant cooling system 513.11 desiccant wheel 523.12 liquid desiccant cycle 534.1 Installation of CPC-18 OEM collector 674.2 dimension of CPC-18 OEM collector 674.3 installation angles of the CPC-18 OEM

collector68

4.4 The case study solar system component 724.5 The supply duct of offices (1,2and3) in1st

floor74

5.1 Adsorption cycle represented in a Clapeyron-Clausius diagram

88

5.2 Lab. scale adsorption ice maker 94

List of Tables

Table #No Name page2.1 comparison between flat plate and evacuated

tube29

2.2 Temperature range of solar collector 383.1 Advantage and disadvantage for the solar

vapor compression refrigerator48

3.2 Comparison between solid and liquid desiccant cycle

54

4.1 Specifications of an 40 ton absorption chiller 644.2 The dimensions of the CPC -18 OEM

collector68

4.3 Selected fan coil specification for ground floor

77

4.4 Selected fan coil specification for first floor 774.5 Fixed cost for absorption chiller working

system80

4.6 Fixed cost for absorption chiller working system

81

4.7 Life cycle cost absorption chiller compare with electrical chiller

84

5.1 charcoal/methanol pair experiment data 965.2 silica-gel/water pair experiment data 97

Nomenclature

FR Collector heat removal factorI Intensity of solar radiation(W/m2)TC Collector average temperature(Co)Ti Inlet fluid temperature(Co)Ta Ambient temperature(Co)Ul Collector overall heat loss coefficient(W/m2Co)Qi Collector heat input(W)Qu Useful energy gain(W)Qo Heat loss(W)τ Transmission coefficient of glazingα Absorption coefficient of platem Mass flow rate of fluid through the collector(Kg/s)Rth Thermal resistance (m2Co/W)

Awindow Area of the windows(m2

)

ΔT The difference in temperatures(Co)SHGF Solar heat gain factor W/m

2

SC Shading coefficient

CLF Cooling load factor

V¿

infVolumetric flow rate of infiltration air(L/s)

Δw The difference in moisture content between two regions (moisture continents Kg/Kg Dry Air )

CLTD Cooling load temperature difference

fu Usage factor

fb Ballast factor

c p Constant pressure specific heat(KJ/Kg.Co)

η Efficiency

G Solar irradiance(W/m2)

ηo Optical efficiency

ζ collectorCollector efficiency

qu Useful heat required(W)

Q s Heat storedρ

Density of water Kg/m3

Re Reynolds number

Abstract

In light of the global struggle for energy and because of the high prices of oil and

its negative impact on the environment intensives the approach to renewable energy

sources, especially solar energy , innovations and development of many systems in the

various parts of the world. In order to take the advantage of solar energy in several areas,

including electrical energy production, heating and cooling, as a result of the mentioned

factors this work has been selected, which looks at ways to harness solar energy for

cooling.

In this project a range of cooling systems that takes the advantage of solar energy

had been offered, in terms of the principle of work and of the thermal analysis of these

systems. In addition a cooling system for an existing building by using the absorption

cooling system had been designed, also an economic comparison between absorption

chiller used in the design and an electric chiller with the same cooling capacity, In

addition a model for an adsorption ice maker had been built to investigate the working

conditions of the adsorption cycle.

It had been founded at the end of the working in this project that to cool two floors

of the annex-of the law building in Birzeit University with an approximate 800 m2 area an

adsorption chiller of capacity 40 tons refrigeration is needed, a 15 solar collectors of type

CPC OEM-18 and a 34KW water boiler had to be adopted to run the chiller.

The economic study reveals that the life cycle cost for operating the absorption

chiller 25 years equals (776500 $ ) and (1094800 $ ) for the electrical chiller so the

installation of the absorption chiller instead the electrical chiller is justified , the study

also shows that the payback period for the absorption chiller equals 4.7 years.

The last part of the project shows that for the adsorption ice maker to work

efficiently the pressure inside the system must be lower than (9 cm Hg), also at the same

working conditions the performance for the system that uses charcoal/methanol pair is

better than that uses silica-gel/water pair, also it had been found that the distance between

the generator and the evaporator and the relative position of them plays a very important

role in the operation of the adsorption ice maker.

المستخلص

في ظل الصراع العالمي على الطاق�ة و بس�بب األس�عار المرتفع�ة للب�ترول وأث�ره الس��لبي على البيئ��ة مم حف��ز التوج��ه إلى مص��ادر الطاق��ة المتج��ددة وخصوص��ا الطاق��ة الشمسية, فقد تم ابتكار وتطوير العديد من األنظمة في مختل��ف أنح��اء الع��الم لالس��تفادة من الطاقة الشمسية في ع��دة مج��االت منه��ا إنت��اج الطاق��ة الكهربائي��ة والتس��خين وأيض��ا التبريد نتيجة لما ذكر من عوامل فقد تم اختيار هذا العم��ل ال��ذي يبحث في ط��رق تس��خير

الطاقة الشمسية في التبريد.

في هذا المشروع تم عرض مجموعة من أنظمة التبريد باالستفادة من الطاقة الشمسية من حيث مبدأ العمل وأيضا التحليل الحراري لهذه األنظمة , حيث انه تم عRرض تصميم لنظام تبريد لمبنى قائم باستخدام نظام االمتصاص للتبريد, إضافةT إلى ذلك يحتوي

هذا المشروع مقارنة اقتصادية للمقارنة بين نظام تبريد يستخدم وحدة تبريد تعمل على.مبدأ اإلمتصاص ونظام أخر يستخدم وحدة تبريد كهربائية

وقد تبين في نهاية عملنا القائم على تبريد طابقين من بناء ملحق كلية الق��انون في بواسطة نظ��ام تبري��د يس��تخدم وح��دة امتص��اص ذات2م 800جامعة بيرزيت ومساحتهما

T الى 40قدرة CPC مجمع للطاقة الشمسية من ن��وع 15 طن تبريد ، ويحتاج النظام أيضاOEM-18 كيلو واط . 34 ومرجل لتسخين الماء بقدرة

وكشفت الدراس��ة اإلقتص��ادية ال��تي اج��ريت في ه��ذا المش��روع أن تكلف��ة دورة حي��اة دوالر( و)776500 س��نة يس��اوي )25النظ��ام المس��تخدم لوح��دة تبري��د اإلمتص��اص لم��دة

دوالر( للنظ��ام المس��تخدم لوح��دة تبري��د كهربائي��ة ، و أيض��ا تظه��ر الدراس��ة1094800سنة.4.7فترة استرداد مبلغ اإلستثمار لنظام اإلمتصاص يساوي االقتصادية أن

وفي نهاية المشروع قRدmم تصميم لوحدة تبريد تعمل على مبدأ اإلدمصاص وهي وحدة صغيرة صممت من أجل التعرف على كيفية عمل وحدة التبريد التي تعمل على مبدأ

.اإلدمصاص

وقد اتضح انه لتشغيل المبرد العامل بكيفية اإلدمصاص يجب أن يتوفر داخل النظام

سم زئبق( ، وعند تشغيل النموذج في نفس ظروف العمل واألداء9ضغط أقل من )

تبين أن زوج الفحمsilica- gel/water و الميثانولباستخدام زوج الفحم الحجري/

كما إنه وجد أن المسافة بين المولد والمبخر ووضعالميثانول أكفأ من نظيره ,الحجري/

كل منهم بالنسبة لألخر يلعب دورا هاما جدا في تشغيل مبرد اإلدمصاص.

.

شكر واهداء

في بداية االمر نحمد الله عز وجل على اتمام هذا المشروع، ونزجي جزيل الشكر وعظيم

االمتنان الى من تجرعوا الكأس فارغا ليسقوننا قطرات الحب وكلت اناملهم ليقدموا لنا لحظة سعاده وحصدوا األشواك عن دروبنا ليمهدوا لنا طريق العلم والدينا االعزاء واخوتنا

واخواتنا.

إلى الشموع التي ذابت في كبرياء.......لتنير كل خطوة في دربناT للعلم واألخالق لتذلل كل عائق أمامنا ........فكانوا رسال

T لردع أعدائنا يا من شعلتم مصباح آمالنا وجعلتم العلم سببا(إليكم أساتذتنا الكرام)

وأخص بالذكر األستاذ المشرف على مشروعنا

د. عفيف حسن

الى كل من ساهم في اتمام عمل هذا المشروع واخص بالذكر االستاذ عزمي

في دائرة الكيمياء

الى من حزنوا بحزننا وفرحوا بفرحنا وتقبلوا شكوى همومنا زمالئنا األعزاء

Chapter One

Introduction

Introduction:

Now a day the governments all over the world are concerned with how to expand

the usefulness of the renewable energy sources. Scientists all over the world are now

trying to find new methods to extract the power from the alternative energy sources and

to increase the efficiency of the available methods. All these efforts have been made so as

to reduce the dependence on the energy come from fossil fuels mainly as the world

generates 85% of its energy from fossil fuels. But this source is non-permanent source of

energy and it can be vanish any time and its price depends on the political situation

between countries as its price increase whenever there are wars.

If we know that only 0.54% of the energy consumed in the world is generated from

solar power then we must work seriously on developing the methods used to extract this

power from the sun especially in the regions that have a good solar potential, and

Palestine is one of them.

The interest in solar cooling systems first started to increase due to the oil crisis in

the 1970s, and then later, in the 1990s, because of ecological problems related to the use

of CFCs and HCFCs as refrigerants. Such refrigerants, when released into the

atmosphere, deplete the ozone layer and contribute to the greenhouse effect. Furthermore,

with the increase in energy consumption worldwide, it is becoming even more urgent to

find ways to use the energy resources efficiently as possible. Thus, machines that can

recover waste heat at low temperature levels such as absorption and adsorption machines

can be an interesting alternative for wiser energy management.

The conventional adsorption cycle had been presented extensively in the literature

and it mainly includes two phases:

A- Adsorbent cooling with adsorption process, which results in refrigerant evaporation

inside the evaporator and, thus, in the desired refrigeration effect. At this phase, the

sensible heat and the adsorption heat are consumed by a cooling medium, which is

usually water or air.

B- Adsorbent heating with desorption process (also called generation), which results in

refrigerant condensation at the condenser and heat release into the environment. The heat

necessary for the generation process can be supplied by a low-grade heat source, such as

solar energy, waste heat, etc.

In comparison with mechanical vapor compression systems, adsorption systems

have the benefit of saving energy, if powered by waste heat or solar energy, simpler

control, no vibration and lower operation costs. In comparison with liquid absorption

systems, adsorption systems can be powered by a large range of heat source

temperatures, starting at 50 ℃ and going up to 600℃ or even higher. Moreover, the

latter system does not need a liquid pump or rectifier for the refrigerant, does not present

corrosion problems due to the working pairs normally used, and it is less sensitive to

shocks and to the installation position. These last two features make it suitable for

applications in locomotives, busses, boats and spacecrafts. Although adsorption systems

offer all the benefits listed above, they usually also have the drawbacks of low coefficient

of performance (COP) and low specific cooling power (SCP).

This project has been divided into five chapters: the first chapter which contains an

introduction to the project.

The second chapter under the title of solar energy discusses the solar radiation and

changes throughout the year through the study of angles and mathematical formulas as

well as a collection of graphs and tables. Then it will show a range of solar collector

types and discuss its temperature characteristics and cost to compare between them. The

chapter has also reviewing a series of graphs and tables that shows the properties of these

collectors.

Chapter three, under the title of solar cooling discusses how we can use solar energy

for cooling purposes through a review of a range of cooling techniques those included

absorption, adsorption, desiccant cooling in terms of the principle of their respective

work and thermal analysis of these techniques.

Chapter four, this chapter contains a design for a cooling system using absorption

cycle to cool the Annex Building of the Faculty of Law at Birzeit University.

Calculations using mathematical equations for the design and selection of the appropriate

absorption air conditioning chiller had been shown in this chapter, also solar collectors

had been selected to obtain the energy needed to run the chiller. This chapter also

contains a presentation of an economic study done on the predesigned cooling system for

the law building to compare between two systems the first on uses absorption chiller and

the second one uses electrical chiller by evaluating the life cycle cost for both of them

during 25 years, the study shows the number of years required to recover the overall cost

of the system that uses the absorption chiller.

Chapter five, this chapter contains a brief description of the adsorption cycle; also it

shows the principles of choosing working pairs for the system. This chapter contains the

details of the construction of an adsorption ice maker lab. scale model , the data gained

from operating of the lab. Scale model using charcoal/methanol and silica-gel/water pairs

were shown in this chapter.

Chapter Two

Solar energy

2.1Solar Radiation

The sun is a sphere of diameter 1 .39×109m and its average distance from the earth

is1 .49×1011 m . The interior of the sun is extremely hot, with temperature of many

millions of degree. The surface temperature is approximately 6000 K, one can define the

effective black body temperature of the sun as the temperature of black body radiating the

same amount of energy per unit surface area as the sun. The effective black body

temperature of the sun is 5762 K other effective temperature could also be define for

example, the temperature of black body with the same wave length of maximum

radiation. as the sun is approximately 6300K

Two type of solar radiation reach us, the first one is director beam radiation which

is the solar radiation received from the sun without having been scattered by the

atmosphere. Diffuse radiation on the other hand, is the solar radiation received from the

sun after its direction has been changed by scattering is the atmosphere. Diffuse radiation

is sometimes referred to as sky radiation and diffuse radiation on a surface is termed the

total or global radiation.

Irradiance is the term given to rate at which radiant energy is incidence on a surface

per unit area of the surface. Using SI unit’s irradiance is measured inW /m2. Integrating

irradiance over a period of time gives the irradiance or isolation with J /m2units.

2.1.1 The solar constant

The radiation emitted by the sun is nearly constant. The intensity of this radiation can

be characterized by the solar constant I 0 .The solar constant is defined as the solar

irradiance at normal incidence just outside the earth atmosphere , When the sun – earth

distance is at its mean value of 1 . 49×1011 m (Due to eccentricity of the earth’s orbit the

radiation incident on the earth varies with season by ±3 .3 %) .

Measuring solar constant is very difficult due to atmosphere effect, but satellite

technologies helped in measuring it to have a value of 1372.7 W /m2.

The actual solar power that reaches the earth is obviously less than the solar constant

due to many factors including the fact that sun rays must penetrate 150 Km thick

atmosphere before reaching the earth, so much of the radiation is absorbed or scattered or

reflected as a result. Clouds and smog also limited the portion of solar radiation that

reaches the earth. [1]

2.1.2 Measurement of solar radiation

The two common methods which characterize solar radiation are the solar radiance

(or radiation) and solar insolation. The solar radiance is an instantaneous power density in

units of kW/m2. The solar radiance varies throughout the day from 0 kW/m2 at night to a

maximum of about 1 kW/m2. The solar radiance is strongly dependant on location and

local weather.

The solar insolation is the total amount of solar energy received at a particular

location during a specified time period, often in units of kWh/(m2 day). While the units

of solar insolation and solar irradiance are both a power density (for solar insolation the

"hours" in the numerator are a time measurement as is the "day" in the denominator),

solar insolation is quite different than the solar irradiance as the solar insolation is the

instantaneous solar irradiance averaged over a given time period.

There are two basic types of instruments used to measure solar radiation, pyranometer

and pyheliometer.

Pyranometer: has a hemispherical view of surroundings and is used to measure

total, direct and diffuse solar radiation on a surface, also known as solar meter.

See fig 2.1.

Pyheliometer: has a restricted view, about 5o and is used to measure direct or

beam solar radiation it follows the sun with two axis tracking see fig 2.2.

Pyranometer is used also to measure diffuse radiation by using a shadow band to

black the direct sun view.

Sunshine duration:

Campball-Stokes sunshine recorder is used to measure sunshine duration. It uses a solid

clear glass sphere as a lens to concentrate the solar beam on the opposite side of the

sphere. A strip of heated paper marked with time graduations is mounted on opposite side

of sphere where the beam is concentrated, and it burns the paper, the length of the burned

part of strip gives duration of bright sunshine. [2]

Figure(2.1) : Pyranometer[2]

Figure (2.2): Pyheliometer[2]

2.1.3 Solar radiation angles:

The earth rotates at its axis and complete one rotation every day. And it revolute about

the sun every year once, this revolution creates the season.

Figure (2.3): shows creational of season due to revolution [3]

Misconception:

The people think that it is summer when the sun is close to earth and its winter when it is

furthest from the earth. This wrong see figure (2.3). The main reason for change of

season is not the distance it is the tilt angle of earth.

How the tilt change the season:

The earth is tilted at 23.45o toward the Polaris:-

When the earth is tilted toward the sun it is summer

When the earth in not tilted its equinox

When the earth is tilted in the opposite direction its winter.

Figure (2.4): solar irradiance angle

From figure (2.4) we see that when the angle is increasing its projection (cosine the

angle) is decreasing

Cos90<cos60<cos30<cos10

So the intensity of sun light is increasing and this will cover less area and heating it more.

Figure (2.5) shows how the tilt angle creates the summer and winter seasons [4]

We see that the when it is summer above horizontal it is winter below it and conversely

when it is winter above horizontal it is summer below and this is due to the tilt angle of

the earth.

During one year the position of earth with respect to the sun is changed and this affected

the solar radiation on the earth .there are several angle affect the solar radiation:-

The zenith angle: the angle between vertical and sun light. Its symbol is θ z

Figure (2.6): the zenith angle [4]

We see that when it is summer the zenith angle is bigger than it is winter so the

sun is high in summer and low in winter (height of sun depend on the sine of

zenith angle) .this difference of height is due to the inclination of earth’s axis.

The elevation angle (altitude): angle between horizontal and sunlight.

Declination angle: the angular position of the sun at solar noon with respect to the

plane of equator. δ=23.45sin360(284+n)

365

Figure (2.7): The declination angle [4]

Latitude: the angle between the horizontal line and the line to the center of

earth…….∅

Figure (2.8): The latitude angle [4]

Azimuth: the angle between south meridian and sun light projection.

A=sin−1( cos δ sin ωsinθz

)

Figure (2.9): The azimuth angle [4]

ω=hour angle that it is the angular displacement of the sun east or west of local

meridian. That it is 15o for each hour from solar noon.

For example ¿0 at solar noon .

B: tilted angle of the collector.

Incidence angle θi :the angle between sun light line and the normal line on the

collector.

Figure (2.10): The hour angle (ω) [4]

Day length:

Figure (2.11): The length of day at different latitude angle with variation of season [5]

Day light hours = 2× cos−1 [− tan∅ tan δ ]

15

Sidereal day: the time that it takes for the earth to rotate with respect to the stars =23 hour

and 56 minutes and 4.091 second.

Solar day: the time it takes for earth to rotate with respect to the sun=24 hours.

The solar radiation:

Figure (2.12) the solar radiation [6]

Diffuse radiation results from the scattering of sun rays by clouds and other

atmosphere gases. Total energy reaching a collector surface is equal to the sum of the

direct beam radiation and the diffuse radiation.

On bright sunny day diffuse radiation is 10% of total radiation while on a partly

cloudy diffuse radiation is 50% of total. But on a completely overcast day diffuse

radiation is 100%.

The collecting surface will receive the same diffuse radiation for any orientation of

the surface because the diffuse radiation is assumed to be uniformly over the sky.

The direct radiation En= Eoτ m …..The collector surface is normal to the sun radiation

Eo= solar constant

τ =transmission coefficient

τ =0.1 ……overcast day

τ =0.8…... clear day

m=air factor mass

m=secθ z

When the collector surface is aligned at angle β the equation become:

Ei= Encosθ i

The general equation that include diffuse radiation:

Et=Encosθ i+FIEd+F2ρ (Encosθ z+Ed)

Et=total solar radiation

ρ =ground reflectivity of diffuse radiation

F1= (1+cos β

2) ……………Sky to collecting surface

F2= (1−cos β

2)……………..ground to surface

F1+F2=1

South-facing tilted surface:

When the collectors face is toward the south so the best tilt angle β is that the angle make

the incidence angle =0 at solar noon

cosθ i ,t=sin (∅−β )sin δ +cos (∅−β ) cos δ cosω

At θi , t=0 at solar noon ω=¿0

1=sin (∅−βn )sin δ+cos (∅−βn )cos δ cos o

This lead to:-

1=cos (∅−βn−δ ) hence ∅−βn−δ=0

βn=∅−δ

δ is taken∈t hebaddest day∈radiation∧¿ is t h e Dec .22

Non-south facing tilted surface:

cosθ i ,t=sin (∅ z )cos ( A−γ ) sin β+cos (∅ z ) cos β

This lead to A−γ=0

So A=γ

1 ¿sin (∅ z ) sin β+cos (∅ z ) cos β

This lead to β=θ z

So the surface is rotated about a vertical axis holding A=γ and tilt angle

β is continuously adjusted ¿maintain β=θ z

Figure (2.13): The variation of solar Insolation at 21 June and 21 December at different latitude [6].

The last figure shows the variation of solar Insulation at 21 June and 21 December at

different latitude.

Figure (2.14) :The variation of solar radiation at different latitude during full year [6]

The solar radiation and climate information in Palestine is attached to the appendix C.1

2.2Solar collectors:

2.2.1 Flat-plate collectors:

A flat plate is the most common type of solar thermal collector, and is usually used

as a solar hot water panel to generate solar hot water. A weatherproofed, insulated box

containing a black metal absorber sheet with built in pipes is placed in the path of

sunlight. Solar energy heats up water in the pipes causing it to circulate through the

system by natural convection (thermosyphon). The water is usually passed to a storage

tank located above the collector. This passive solar water heating system is generally

used in hotels and homes in sunny climates such as those found in southern Europe.

These collectors heat liquid or air at temperatures less than 80°C.

For these purposes, the general practice is to use flat-plate solar energy or evacuated

tube collectors with a fixed orientation (position). The highest efficiency with a fixed flat-

plate collector or evacuated tube collector is obtained if it faces toward the sun and slopes

at an angle to the horizon equal to the latitude plus about 10 degrees. Solar collectors fall

into two general categories: non-concentrating and concentrating.

There are many flat-plate collector designs but generally all consist of (1) a flat-plate

absorber, which intercepts and absorbs the solar energy, (2) a transparent cover(s) that

allows solar energy to pass through but reduces heat loss from the absorber, (3) a heat-

transport fluid (air, antifreeze or water) flowing through tubes to remove heat from the

absorber, and (4) a heat insulating backing. One flat plate collector is designed to be

evacuated, to prevent heat loss.

The first accurate model of flat plate solar collectors were developed by Hottel and

Whillier in the 1950s

Figure (2.15) a typical liquid Flat Plate Collector [7]

Thermal analysis of flat plate collector:

Figure (2.16): shows the heat flow through a Flat Plate solar collector. [7]

Figure (2.17) shows the schematic of a typical solar system employing a flat plate solar collector and a storage tank.

Figure (2.17): Typical solar energy collection system [1]

If I is the intensity of solar radiation, in W/m2, incident on the aperture plane of the solar collector having a collector surface area of A in m2, then the amount of solar radiation received by the collector is:

However, as it is shown Figure (2.16), a part of this radiation is reflected back to the sky,

another component is absorbed by the glazing and the rest is transmitted through the

glazing and reaches the absorber plate as short wave radiation.

Therefore the conversion factor indicates the percentage of the solar rays penetrating the

transparent cover of the collector (transmission) and the percentage being absorbed.

Basically, it is the product of the rate of transmission of the cover and the absorption rate

of the absorber. Thus,

As the collector absorbs heat its temperature is getting higher than that of the surrounding

and heat is lost to the atmosphere by convection and radiation. The rate of heat loss (Qo)

depends on the collector overall heat transfer coefficient (UL) and the collector

temperature.

Thus, the rate of useful energy extracted by the collector (Qu), expressed as a rate of

extraction under steady state conditions, is proportional to the rate of useful energy

absorbed by the collector, less the amount lost by the collector to its surroundings. This is

expressed as follows:

It is also known that the rate of extraction of heat from the collector may be measured by

means of the amount of heat carried away in the fluid passed through it, that is:

Equation 4 proves to be somewhat inconvenient because of the difficulty in defining the

collector average temperature. It is convenient to define a quantity that relates the actual

useful energy gain of a collector to the useful gain if the whole collector surface were at

the fluid inlet temperature. This quantity is known as “the collector heat removal factor

(FR)” and is expressed as:

The maximum possible useful energy gain in a solar collector occurs when the whole

collector is at the inlet fluid temperature. The actual useful energy gain (Qu), is found by

multiplying the collector heat removal factor (FR) by the maximum possible useful

energy gain. This allows the rewriting of equation (4):

Equation (7) is a widely used relationship for measuring collector energy gain and is

generally known as the “Hottel-Whillier-Bliss equation”. A measure of a flat plate

collector performance is the collector efficiency (η) defined as the ratio of the useful

energy gain (Qu) to the incident solar energy over a particular time period:

The instantaneous thermal efficiency of the collector is:

If it is assumed that FR, τ, α, UL are constants for a given collector and flow rate, then the efficiency is a linear function of the three parameters defining the operating condition: Solar irradiance (I), Fluid inlet temperature (Ti) and Ambient air temperature (Ta). Thus, the efficiency of a Flat-Plate Collector can be approximated by measuring these three parameters in experiments. The result is a single line (ΔT/I – Curve) shown in Figure (2.18)

Figure (2.18) efficiency versus ΔT/I [7]

The collector efficiency η is plotted against (Ti – Ta)/I. The slope of this line (- FR UL) represents the rate of heat loss from the collector. For example, collectors with cover sheets will have less of a slope than those without cover sheets. There are two interesting operating points on Figure (2.18).

1) The first is the maximum collection efficiency, called the optical efficiency. This occurs when the fluid inlet temperature equals ambient temperature (Ti= Ta). For this condition, the ΔT/I value is zero and the intercept is FR (τ α).

2) The other point of interest is the intercept with the ΔT/I axis. This point of operation can be reached when useful energy is no longer removed from the collector, a condition that can happen if fluid flow through the collector stops (power failure). In this case, the optical energy coming in must equal the heat loss, requiring that the temperature of the absorber increase until this balance occurs. This maximum temperature difference or “stagnation temperature” is defined by this point. For well-insulated collectors or concentrating collectors the stagnation temperature can reach very high levels causing fluid boiling and, in the case of concentrating collectors, the absorber surface can melt [7]

2.2.2 Evacuated tube collectors:

it is solar panel was built to reduce convective and heat conduction loss (vacuum is heat

insulator).It is one of solar radiation collector, which uses the solar energy to heat water

for different applications such as heating and cooling at high temperature range (77 Co -

177 Co) better than flat plate .now evacuated tubes are using in domestic application

instead of flat plate specially in cloudy region.

Figure :( 2.19) Evacuated tube collector& hot water storage [8]

Structure:

The evacuated tube collector may contain 6,8or16….. Tubes dependent on the

application, each tube consist of two glass tubes. The outer tube is made from strong

transparent borosilicate glass that is able to resist impact from hail. The inner tube is also

made of borosilicate glass, but coated with a special selective coating, which has an

advantages such that it is excellent solar heat absorption and smaller heat reflection

properties .It is also good antifreeze collector because its manifold is insulated with rock

wool so the temperature of header is rarely to fall below 10 Co . The cylindrical design of

tubes ensures effective collection of solar energy throughout entire day because the

incidence angle is always equals 0o.

Figure (2.20): Shows how the manifold is insulated with thickness of rock wool [9]

Figure (2.21): The construction of evacuated tube [9]

From last figure the heat pipe condenser area is large as possible to increase the heat

transfer between the tube and the fluid inside the manifold.

Construction type of evacuated tube:

Direct flow (heat pipes)

Figure (2.22): The construction of direct flow model at left a graph shows the collector efficiency versus

collector inlet temperature at different values e= (0.05, 0.01), e = emissivity [10]

Indirect flow

Figure (2.23): The indirect flow model with a graph of collector efficiency versus collector inlet

temperature at different value of the emissivity. [10]

Metal absorber with glass-to-metal seal

Figure (2.24) A Metal absorber with glass-to-metal seal model beside a graph observes the relation between

the collector efficiency versus collector inlet temperature at different value of the emissivity. [10]

Performance of evacuated tube collector:

Collector efficiency: as useful heat divided by solar radiation on the collector surface.

ζ=qu

AI

qu=useful heat

qu=AFR¿

So ζ=FR τα−F R

IU ¿

FR=heat removed factor.

α= absorptivity of absorber plate.

τ =cover transmittivity.

U=overall conductance heat transfer coefficient between the plate and the ambient air.

Ti=fluid inlet temperature.

Ta=ambient air temperature.

A=collector area

I=solar radiation falling into the per unit area.

How does the water circulates in the tubes?

1. Active system: this system uses the pump to circulate the water in tubes which are

opened to the manifold and this type of tubes is called pressurized tube.

2. Passive system: there is no need for pump to circulate the water; it circulates on

thermo siphon principle.

Thermosyphon system: - use sunlight to circulate water or heat absorbing fluid through

the solar collectors to the storage tank using the thermosyphon principle that hot water or

fluid rises and that dark surface absorb heat.

Figure (2.25): Circulation of water depending on thermosyphoning principle [11]

Installation of evacuated tube:

1. Open loop system: the water is circulated in collector and heated directly from

sun, then it goes to the storage tank .this system is installed when the climate is

frost –free and the quality of water is good.

2. Closed system: use a second fluid which is heated from sun then it flows directly

to water storage tank in order to heat water. This system is useful when the quality

of water is not good and when the climate is frost prone. [11]

Reflector types:

Flat sheet

Figure (2.26): Flat plate fins [12]

V-shaped fins

Figure (2.27): V-shaped fins[12]

Table (2.1): Comparison between flat plate and evacuated tube:-

Evacuated tube Flat plate

performance Best performance in cold, cloudy day Best performance in warm

sunny days

Cost More expensive Less expensive

cleaning Difficult to clean Easier to clean

Area Have less collector area May have larger collector

area

More efficient when ∆t>45Co Historically more reliable

Evacuated tubes are better than flat plate because the incidence angle =0o throughout

entire day .but flat plate angle = 0o just at noon.

Figure (2.28): Shows that the efficiency for flat plate collector and for evacuated tube collector [10]

Figure (2.28) shows that the efficiency of flat plate becomes =0 when the collector inlet

temperature is >75 Co but the efficiency of vacuum tube is still >60% in winter solstice

where both collectors efficiency will not reach zero value in summer.

Orientation of evacuated tube collector:

Evacuated tube collectors are customarily installed in a fixed position .tilted toward the

south with the angle β such that:

β=∅−δ

∅=latitude angle

δ=declinatiopn angle

0<δ<−23 during winter an average value=-12o, and ∅=32o∈ palestine so β=44o

0<δ<23During summer an average value =12o and ∅=32o in Palestine so β=20o

[10]

2.2.3 Concentrating Solar Collector:

In the last decade, much attention has been given to concentrating solar collectors,

which are capable of reaching higher temperatures compared with other collectors.

Several designs of solar collectors have been developed over the years in order to

improve their performance, a simple design that combines a static parabolic or cylindrical

reflector with a tracking absorber positioned along a path, the static reflector concentrate

sun light onto a linear thermal absorber. For any change in the incident angle, the

reflected rays will always intersect in different points of the tracking path, therefore, it

would be possible to track the sun movement simply by positioning the collector on the

correct position of the tracking path, without moving the reflector.

Usually a parabolic Trough concentrator is installed east- west aligned with one

degree of freedom for tracking, about its axis at latitude of 40° N for the summer

Season.

1- Cylindrical Reflector Tracking Path :

It can be easily demonstrated that, for cylindrical reflector the tracking path is a

circle. As shown in Fig (2.29)

Figure (2.29): Cylindrical concentrator [13]

Figure (2.30): Absorber. [13]

2- Parabolic Reflector Tracking Path:

It is well known that a parabola has a point focus at a normal incidence; nevertheless,

it can be shown that for any other incidence angle, all rays are concentrated into an area.

Therefore the smallest possible region intersecting all of the reflected radiation will be

the absorber position as shown in Fig (2. 30) the analysis consisted in a ray tracing

computation of the average concentration ratio versus sun angle. The concentration

(intersection) ratio CR of the collectors defined as the ratio of the effective aperture area

and absorber tube area.

Figure (2.31): Parabolic concentrator. [13]

Figure (2.33) Cross Section of Cylindrical parabolic Concentrating Collector [14]

The instantaneous efficiency of parabolic trough is found by:

ηc=η∘−U c(T r−T a )

I cC R

Where η∘ : Optical efficiency.

T r : Temperature of absorber.

T a : Temperature of ambient air.

U c : Overall heat transfer coefficient of the collector.

I c : Solar radiation on collector.

And CR : Concentration ratio.

CR=Aa

A r

Where Ar : Area of absorber.

Aa : Area of aperture.

Losses from absorber in the parabolic trough are smaller because of smaller area

comparing to the flat plate, but losses due to radiation are higher. A disadvantage of the

parabolic trough is that it requires tracking of the sun such that the aperture area is normal

to suns direction. [14]

Primary Types of Solar Collectors:

1. Parabolic Trough.

Figure (2.34): Parabolic Trough Solar Field Technology [15]

2. Compact Linear Fresnel Reflector.

Figure (2.35): Field of Compact Linear Fresnel Reflectors.[15]

• A series of long, shallow-curvature mirrors

• Focus light on to linear receivers located above the mirrors, which is appearing in

the Fig (2.35) bellow.

Figure (2.36): Schematic Field of Compact Linear Fresnel Reflectors. [15]

Lower costs compared to parabolic troughs

• Several mirrors share the same receiver

– Reduced tracking mechanism complexity

• Stationary absorber

– No fluid couplings required

– Mirrors do not support the receiver

• Denser packing of mirrors possible

– Half the land area

3. Solar Furnace.

Figure (2.37): Field of Solar Furnace. [15]

Solar furnaces are used for:

- High temperature processes à “Solar Chemistry”

- Materials testing

A field of heliostats tracks the sun and focuses energy on to a stationary parabolic

concentrator which refocuses energy to the receiver.

Receivers vary in design depending on process:

Batch or continuous process

Controlled temperature and pressure

Collection of product (gas, solid, etc.)

4. Parabolic Dish & Engine.

Figure (2. 37): Parabolic Dish. [15]

Mature and Cost Effective Technology: Large utility projects using parabolic dishes are

now under development.

Technical Challenges Have Been:

Development of solar materials and components

Advantage: High Efficiency

Demonstrated highest solar-to-electric conversion efficiency

Potential to become one of least expensive sources of renewable energy. (Still

true with development of Fresnel reflectors?)

Advantage: Flexibility

Modular - May be deployed individually for remote applications or grouped

together for small-grid (village power) systems.

5. Solar Central Receiver (Solar Power Tower)

6. Lens Concentrators.

Table (2.2): Temperature range of solar collector [15]

Motion Collector type Absorber type Concentration

ratio

Indicative

temperature

range (°C)

Stationar

y

Flat plate collector (FPC) Flat 1 30-80

Evacuated tube collector (ETC) Flat 1 50-200

Compound parabolic collector (CPC) Tubular

1-5 60-240

Single-

axis

tracking

5-15 60-300

Linear Fresnel reflector (LFR) Tubular 10-40 60-250

Parabolic trough collector (PTC) Tubular 15-45 60-300

Cylindrical trough collector (CTC) Tubular 10-50 60-300

Two-axes

tracking

Parabolic dish reflector (PDR) Point 100-1000 100-500

Heliostat field collector (HFC) Point 100-1500 150-2000

Chapter ThreeSolar refrigeration

3.1Absorption cycle:

As stress increased on generation and distribution of electricity in the world, there is a

need to look for solution .one of these solutions is absorption technology which is

operated by environmentally friendly substances, and utilizes waste heat from different

sources.

3.1.1 The structure of absorption chiller:

Figure (3.1) Schematic for absorption chiller [16]

The absorption chiller consists of:

Condenser

Evaporator

Absorber

Generator

Throttling valve

Pump

3.1.2 The principle of absorption chiller:

The main reason for inventing is to reduce consumption of electricity, so the researcher

wanted to replace the compressor which is the element that consume the electricity with

other elements could achieve the same process. These elements from fig (3.1) are

generator, absorber and pump.

The process:

The vapor exist from evaporator with low pressure so to increase its pressure using

pump it must absorbed by a liquid solution to form liquid phase then this solution is

pumped using the pump and is delivered to the generator with high pressure (the pump

couldn’t pressurize vapor) .then the generator- which is operated by solar energy –

separates the vapor from the solution by adding heat to the vapor-liquid solution .then the

vapor moves to the condenser in order to reject the heat then it passes through the

throttling valve whose purpose is to provide a pressure drop to maintain pressure

difference between generator and absorber. After that the water with low pressure with

low pressure enters the evaporator here the water evaporates at low pressure and takes

heat from surroundings causing cooling effect. Then the vapor repeats the cycle. [17]

Figure (3.2) the main component of absorption refrigeration cycle [18]

Figure (3.3): The basic process- close cycle on pressure versus temperature. [19]

Figure (3.4) working principle of absorption chiller on pressure versus temperature [19]

Why using pump if it also consume electricity?

The function of pump is to pressurize the liquid which its density (lower specific

volume) is higher than the density of vapor (higher specific volume) so the pumping of

liquid consumes less electricity than compressing vapor according to the following

equation:

w=∫Pdv

w=work done on liquid or vapor.

P=pressure of the fluid.

dv =differential of specific volume of the fluid.

3.1.3 The coefficient performance of the ideal absorption cycle:

COPabs=refrigeration rate

rate of heat additionat generator

In certain respects applying the term COP to the absorption system is unfortunate because

the value is appreciably lower than that of the vapor-compression cycle (0.6-versus 3 for

example). The comparatively low value of COPabs should not be considered prejudicial

to the absorption system to; because the COPs of the two cycles are defined

differently .the COP of the vapor-compression cycle is the ratio of the refrigeration rate

to the power in the form of work supplied to operate the cycle. Energy in form of work is

normally much more valuable and expensive than energy in form of heat.

The absorption cycle can be thought of as a combination of a power cycle and

refrigeration cycle.

Figure (3.5) a schematic for the absorption cycle [20]

Ts source temperature, Ta ambient temperature, Tr refrigerating temperature. For an ideal

power cycle.

qg

w=

T s

T s−¿ Ta¿

For an ideal refrigerator

qe

w=

Tr

Ta−¿ T r¿

Using the definition of COPabs for an absorption cycle above,

COP=qe

qg

=T r ¿¿

[20]

3.1.4 Market available chilled water systems:

Single effect absorption : many products for operation with hot water steam in

the capacity range>100KW .typical opeation temperature 80 Co-110Co. Figure

(45)

Figure (3.6) Single effect absorption chiller [21]

Double effect absorption:often directly fired system .operating temperature

130Co-160Co. Figure(3.7)

Figure (3.7) Double effect absorption chiller

Solution types: Lithium bromide

Water is the refrigerant and the aqueous lithium-bromide solution represents the

solvent, the refrigerant 'water' avoids an application below 0 Co

Lithium-bromide salt in aqueous solution is non-caustic, nearly non-toxic,

noncombustible and odorless.

Are used almost exclusively for the generation of cold water in the field of air

conditioning.

Cold-water outlet temperatures up to +5°C may be achieved,

Working pressures in the evaporator and in the condenser are in the deep vacuum

range.

They are designed as compact sets and are manufactured serially and

economically in large quantities.

1. Ammonia-water

Ammonia is the refrigerant and water represents the solvent.

Ammonia is caustic, has a pungent smell and is toxic, but on the other side

The pungent smell alerts in time thus avoiding damages to health in general.

Ammonia/Air mixtures are barely inflammable but may be explosive in the

Case of high percentages of ammonia between 15.5 and 27 % by volume.

Ammonia dissolved in water is caustic.

Ammonia is considerably lighter than air.

At atmospheric pressure above - 33.4 deg.C, ammonia is gaseous, hence

Plants with evaporation temperatures < - 33 deg.C are working in the vacuum.

Deep temperatures down to -60 deg.C (-65 deg.C) may be achieved.

[22]

3.1.5 Cost analysis:

Figure (3.8) Relation between annual total cost versus cooling capacity for both chiller compression and

absorption. [23]

Figure (3.9) shows the relation between annual total cost versus cooling capacity for both

chiller compression and absorption. This graph shows that the total cost of absorption

chiller is higher than the compression chiller.

3.2 Adsorption cycle:

The interest in adsorption systems first started to increase due to the oil crisis in the 1970s, and then later, in the 1990s, because of ecological problems related to the use of CFCs and HCFCs as refrigerants. Such refrigerants, when released into the atmosphere, deplete the ozone layer and contribute to the greenhouse effect. Furthermore, with the increase in energy consumption worldwide, it is becoming even more urgent to find ways to use the energy resources as efficiently as possible. Thus, machines that can recover waste heat at low temperature levels—such as adsorption machines— can be an interesting alternative for wiser energy management. The heat necessary for the generation process can be supplied by a low grade heat source, such as solar energy, waste heat, etc. [24]

3.2.1 The cycle consists of four periods:1: HEATING AND PRESSURISATION: During this period, the adsorber receives heat while being closed. The adsorbent temperature increases, which induces a pressure increase, from the evaporation pressure up to the condensation pressure. This period is equivalent to the "compression" in compression cycles.2 : HEATING AND DESORPTION + CONDENSATION: During this period, the adsorber continues receiving heat while being connected to the condenser, which now superimposes its pressure. The adsorbent temperature continues increasing, which induces desorption of vapor. This desorbed vapor is liquefied in the condenser. The condensation heat is released to the second heat sink at intermediate temperature. This period is equivalent to the "condensation" in compression cycles.

3 : COOLING AND DEPRESSURISATION: During this period, the adsorber releases heat while being closed. The adsorbent temperature decreases, which induces the pressure decrease from the condensation pressure down to the evaporation pressure. This period is equivalent to the "expansion".

3.2.2 Advantages of the adsorption cycle: In comparison with mechanical vapor compression systems, adsorption systems have the benefit of saving energy, if powered by waste heat or solar energy, simpler control, no vibration and lower operation costs. In comparison with liquid absorption systems, adsorption systems can be powered by a large range of heat source temperatures, starting at 50 C and going up to 600 C or even higher. Moreover, the latter system does not need a liquid pump or rectifier for the refrigerant, does not present corrosion problems due to the working pairs normally used, and it is less sensitive to shocks and to the installation position. These last two features make it suitable for applications in locomotives, busses, boats and spacecrafts.

3.2.3 Disadvantages of the adsorption cycle: Although adsorption systems offer all the benefits listed above, they usually also have the drawbacks of low coefficient of performance (COP) and low specific cooling power (SCP). However, these inconveniences can be overcome by enhancing of the heat and mass transfer properties in the adsorber, by increasing the adsorption properties of the working pairs and by better heat management during the adsorption cycle. [24]

3.3 Electricity (Photovoltaic) Driven systems:

A vapor compression refrigeration system is the most widely used cooling system because of high efficiency and reliability. Electricity, as the main energy source, is used as the driven energy for almost vapor compression system. Solar energy can be integrated with vapor compression cooling system by both photovoltaic cells and solar thermal collectors with Rankin engines.

The main component of the vapor compression refrigeration system is a compressor. The compressor for the solar driven system is a direct current (DC 12 or 24 volts) compressor since the electricity output from the PV cell is the direct current. Inverter is needed to convert DC electricity to Ac electricity when using AC compressor.

Battery is needed to prolong the cooling period when there is lack of sunlight. Battery’s capacity is generally 340 Amp-hour. The size of the PV array depends on the available insulation of each area. The small application such as vaccine box or a cooling box is more economic than the large one. The power-driven compressor requires Rankin engine to convert heat from the solar thermal collectors into a useful work for the collector. [25]

Table (3.1): Advantage and disadvantage for the solar vapor compression refrigerator [33]

Advantage DisadvantageHigh COP For a PV system, installation cost is high

and it requires battery for energy backup. Simplicity for the refrigeration system Noisy from compressor Long term experience that is easy to

maintenance when the problem happens Required high technical Knowledge for PV

system Low price Refrigerant can be leaked

Required little maintenance

3.4 Desiccant cooling cycles Desiccants are materials which can attract and hold moisture. Nearly any material is a desiccant-even glass can collect a small amount of moisture. But desiccants used in commercial equipment are selected for their ability to hold large amounts of moisture .for example the silica gel packets often sealed into vitamin bottles can hold moisture equal to about 20% of their dry weight. Liquid desiccant materials can hold even more moisture.

3.4.1 How desiccants work: Desiccants remove water vapor by chemical attraction caused by differences in vapor pressure. When air is humid, it has a high water vapor pressure. In contrast, there are very few water molecules on a dry desiccant surface, so the water vapor pressure at the desiccant surface is very low. Water molecules move from the humid air to the dry desiccant in order to equalize this pressure differential.

With desiccants as shown in Fig (3.9), moisture removal occurs in the vapor phase. There is no liquid condensate. Consequently, desiccant dehumidification can continue even when the dew point of the air is below freezing. This is different from cooling-based dehumidification, in which the moisture freezes and halts the process if part of the coil surface is below 32°F.

Figure (3.9) working principle of basic cycle.

Desiccant change the vapor to heat

One aspect of desiccant wheel behavior can be confusing to the first-time user of the technology; air leaves a desiccant wheel dry, but warmer than when it entered the wheel. For example, if air enters a desiccant wheel at 70°F and 50%Rh, it will leave the wheel at about 100°F and 4% Rh. This non-intuitive behavior becomes easier to understand the reverse of evaporative cooling. When water is sprayed into air, it evaporates by using part of the sensible heat in the air—so the dry bulb temperature falls as water vapor is added to the air. Desiccants produce the opposite phenomenon. As water vapor is removed from air, the dry bulb temperature of the air rises. The amount of temperature rise depends on the amount of water removed. More water removal produces a greater temperature rise as shown in figure (3.14). The initial user naturally asks: how can desiccant systems save cooling energy if dehumidification adds sensible heat to the air? Part of the answer is that some heat is moved to reactivation by a heat exchanger. The rest of the answer depends on the application. For example, if air is dry, it may not be necessary to cool it if the space is already overcooled—as in a supermarket. Alternatively, dry air can be cooled using low-cost indirect evaporative cooling such as cooling towers, or with highly efficient vapor compression systems operating at high evaporator temperatures. In such cases, desiccants can save energy and energy cost.

3.4.2 Advantages of desiccant cooling system:

* Since only air and water are used as working fluids and no fluorocarbons are required thus there is no danger to ozone layer depletion.

* Significant potential for energy savings and reduced consumption of fossil fuels achieved. Electrical energy requirements are 25% less than the conventional V-C refrigeration system. Source of input thermal energy are solar, waste heat and natural gas.

* Since Desiccant systems operate at near atmospheric pressure, their construction and maintenance is simple.

3.4.3 Applications:

Large latent loads and low humidity requirements e.g. Hotels, supermarkets, auditoriums, ice rinks, pools, Ventilation air etc.

3.4.4 Types of desiccant cycle:

1. Solid desiccant cycle.2. Liquid desiccant cycle.

1- Solid desiccant cycle:

Figure (3.10) solid desiccant cooling system

Dry desiccant systems continuously remove moisture from the air using a corrugated ceramic composite, impregnated with desiccant, formed into a wheel. Generally, silica gel is used as the composite. Moist process air, which has a high vapor pressure, passes through the upper portion of the rotating desiccant wheel. The desiccant, which has a low vapor pressure, absorbs the moisture. The dry process airstream then passes through the conventional refrigeration coil, where the temperature is lowered to design conditions.

The dry desiccant wheel is effective only until it is saturated. Once it is, a scavenger hot airstream is forced through the desiccant wheel to remove moisture. After it is regenerated, the desiccant is cooled to lower its vapor pressure, and then rotated back into the moist airstream, where the dehumidification cycle repeats. As shown in Fig (3.10).

Descent wheel

The Figure (3.11) shows the basic desiccant component—the wheel. The desiccant material, usually a silica gel or some type of zeolite, is impregnated into a support

structure. This looks like a honeycomb which is open on both ends. Air passes through

the honeycomb passages, giving up moisture to the desiccant contained in the walls of the honeycomb cells. The desiccant structure is formed into the shape of a wheel. The wheel constantly rotates through two separate airstreams. The first air stream, called the process air, is dried by the desiccant. The second air stream, called reactivation or regeneration air, is heated. It dries the desiccant.

Figure (3.11) desiccant wheel

Dry Desiccants material:1. Silica Gel2. Titanium Gel3. Dry Lithium Chloride4. Natural Zeolites

5. Activated Alumina

Advantage of silica gel as desiccants:-

Silica gel has many other properties that recommend it as a desiccant.

-It will adsorb up to 40% of its own weight in water vapor. This adsorption efficiency is approximately 35% greater than typical desiccant clays, making silica gel the preferred

choice where weight or efficiency are important factors.- It has an almost indefinite shelf life if stored in airtight conditions.- It can be regenerated and reused if required. - It is a very inert material; it will not normally attack or corrode other materials.- It is non-flammable.

2- Liquid desiccant cycle:

Figure (3.12) liquid desiccant cycle

Liquid desiccant technology has been in use for many years, primarily in process applications requiring dehumidification and humidity control. In some applications, it may be more energy efficient than traditional defrost or dry desiccant systems.

The air to be dehumidified is passed through a desiccant solution spray. The solution has a lower water vapor pressure than the air and the air is dehumidified.

The water extracted from the air will dilute the concentration of the liquid desiccant and over time, subsequently reduce its effectiveness. To maintain the desiccant at a fixed concentration, it is fed to a regenerator section. At the regenerator the liquid desiccant is heated, which raises the vapors pressure in the air causing moisture to transfer to the desiccant. The heated desiccant is sprayed into an air stream of outdoor air and the moisture is released and exhausted to the outdoors. The regenerated desiccant is then cooled and reused. As shown in Fig (3.12)

Liquid desiccant systems can be used with any type of refrigerant or refrigeration system. Mediums include salt (sodium chloride, calcium chloride or lithium chloride) and propylene glycol.

Liquid desiccants solution:-

1) Calcium and lithium chloride use is not permitted with edible food product.2) Sodium chloride, temperatures are limited to approximately -6F (-21.1C), but its use

is permissible around edible food product.

The biggest problem with inorganic salt solutions is that they are highly corrosive. Thus, there is the potential for increased maintenance costs.

Propylene glycol is well-suited for liquid desiccant systems used in food processing operations.

Does not have corrosive characteristics. Is antimicrobial. Is effective as a food preservative. Is more effective than the inorganic salts at lower temperatures.

Application of liquid desiccant system:-

The liquid desiccant is its ability to supply biologically uncontaminated air. The solutions used kill bacteria on contact. Additionally, there are no wet surfaces, such as those found on cooling coils, to promote bacterial growth. This makes liquid desiccants ideal for use in healthcare facilities and in sensitive industrial applications such as pharmaceuticals.

The table bellow explains Comparison between solid and liquid desiccant cycle:

Table (3.2) Comparison between solid and liquid desiccant cycle

SOLID DESICCANT LIQUID DESICCANTLess degree of dehumidification More drying capabilityInexpensive materials like Silica gel, , alumina

Costly materials like LiBr,LiCl,Cacl2Glycols with water

Pressure drop is higher Pressure drop is lowerAdsorption – desorption is notContinuous

Adsorption – desorption iscontinuous

Easily coupled with conventional VC&AC system

Modifications are necessary forcoupling

Chapter Four Solar energy cooling case study

4.1 Case description:

In this chapter we want to design an air conditioning system using absorption chillers instead of using electric chillers. For this design the extension of the law building in Birzeit University was taken as our case, this building consists of three floors, Basement floor which is used mainly as archive and small store, ground floor which has a large hall that contains 120 seat so we can consider it as a lectures room and the first floor which contains the teachers offices and two multipurpose rooms.

The first thing that would be done is to calculate the cooling load, after that the required equipment should be chosen such as chillers, fan coil units, and solar system component. After that the ducts design should be done, finally economic analysis and bay back period to absorption working system compare with electrical working system could be calculated.

4.2 Construction elements description:

1- Walls :

External walls: which consists of five layers that are:

5 cm stone+17 cmconcrete+3 cm polyet h ylene insulation sh eet+10 cm blockb+2cm palster

.

Internal walls: which consists of 3 layers that are :

2 cm plaster+10 cmblock+2cm plaster.

Exposed ceiling : which consists of 4 layers that are :

2 cm asph alt+(25cm concretecombined wit h17 cm block)+2 cm palster.

Non-exposed ceiling : which consists of 5 layers that are :

1 cm(borcelane)+3 cmcement+1 cm sand+2 cm palster+

(25 cm concrete combined wit h17 cm block ).

Floor : which consists of 4 layers that are:

1 cm stone (borcelane )+3cm cement+15 cm sand+15 cm concrete

The wall section is shown in the wall section plane in the appendix A2. In this building the glass used is double glass and the external doors are from

iron and the internal ones are from wood. The architecture planes of the building can be found in the appendix A1.

4.3 Thermal resistance for walls, windows and doors:

For external walls:∑ R th=R stone+R concrete+Rinsulation+Rbrick+Rplaster+Rair(¿+out)

R stone=0.052.2

Rconcrete=0.171.75

Rinsulation=0.030.03

Rbrick=0.10.9

Rplaster=0.021.2

Rair ∈¿=0.13¿

Rair out=0.04

∑ R th=1.176

¿all heat transfer coefficient= 1

∑ Rth

=0.85Watt

℃ .m2

For non-exposed ceiling:

∑ Rt h=Rceramic+Rcement+Rsand+Rconcrete+Rbrick+Rpalster

+Rair (¿+out)

Rstone=0.011.6

Rcement=0.031.4

Rsand=0.10.3

Rconcrete=

0.251.75

∧0.08

1.75

Rbrick=0.170.95

Rplaster=0.021.4

Rair∈¿0.02

∑ Rth=0.476

¿all heat transfer coefficient=2.1Watt

℃ .m2

For exposed ceiling :

∑ Rth=Rasphalt+Rconcrete+Rbrick+Rpalster+Rair (¿+out)

Rasphalt=0.020.7

Rconcrete=0.381.75

∨0.211.75

Rbrick=0.170.95

Rplaster=0.021.4

Rair∈¿0.1

Rair out=0.04

∑ Rth=0.375


℃ . m2

For exposed ceiling :

∑ Rt h=Rasp h alt+Rconcrete+Rbr ick+Rpalster+Rair (¿+out)

Rasp h alt=0.020.7

Rconcrete=0.381.75

∨0.211.75

Rbrick=0.170.95

Rplaster=0.021.4

Rair∈¿0.1

Rair out=0.04

∑ Rt h=0.375


℃ . m2

For floor :

∑ Rt h=Rstone+Rcement+Rsand+Rconcrete+Rair (¿+out)

Rstone=0.011.6

Rplaster=0.031.4

Rsand=0.150.3

Rplaster=0.151.75

Rair∈¿0.15

Rair out=0.09

∑ Rt h=0.855

¿all heat transfer coefficient= 1

∑ Rt h=1.17

Watt

℃ .m2

¿all heat transfer coefficient for t h e single galss=3Watt

℃ . m2

¿all heat transfer coefficient for t heexternal doors=7Watt

℃ . m2

¿all heat transfer coefficient for t h e internal doors=3.5Watt

℃ . m2

The room’s height is 4 meters. The windows and the doors dimensions are shown in table 1and 2 respectively in

appendixes A3.also in Appendix C.2 the temperature and relative humidity indoor and outdoor can be found.

4.4 Load calculation:

4.4.1 Sample calculation for the Multipurpose Hall (120 seat hall) in the ground floor:

1) Windows glass load:

qglass=q trans+qsolar=ug Awindow ΔT + A∗SHGF∗SC∗CLF

Taking into account the orientation of windows to the sun the following data for the load gained:

Space qglass (W )

120 seat hall 3955

2) Infiltration load:

Qinf=qs+ql=1 .23∗V¿

inf∗ΔT+3000∗V¿

inf∗Δw

The following data were obtained for the load:

Space q (W )

120 seat hall 6048

3) Transmission through walls:

For external walls:

qS , walls=uwall∗Awall∗CLTDwall

For internal walls:

q int . walls+roof∧ceiling=uwall×Awall×ΔT

Taking into account the orientation of the walls to the sun and the internal walls and the floor were included the following data were obtained for the load:

space qwalls−total q floor+ceiling (W )

120 seat hall 3107 5169

4) Lights radiation load

fu×fb=0.79

q lights=( area×20 )×0 .79×0 . 85

Thus, the load obtained is:

Space 120 seat hall

q light (W ) 3223

5) Appliances load

Assuming proper equipments in hall (computers, speakers and displaying machine)

Thus, the load obtained:

Space q (W )

120 seat hall 3936

6) People & ventilation load:

q lights=( watt−rating )×fu×fb×CLF

Assuming the number of people in each room and the time of occupancy and the activity type as follows:

1) Assuming to have 120 persons, and assumed as a lecture attendance, then the load equals the value follows.

Space q (W )

120 seat hall 12765

Total load for the 120 seat hall:

space Qlatent(KW)

Q sensible(KW)

Qtot (KW)

TR

120 seat hall 7.3 32.9 40.2 11.4

4.4.2 The load results for the ground and 1st. floors:

For the ground floor:

1- Multipurpose hall (120 seat hall) KW BTU/H

TOTAL COOLING LOAD (KW) 40.20039079 137167.601

2- Sound rooms KW BTU/H


3- Entrance lobby KW BTU/H


For the 1st floor:

1- Corridor KW BTU/H


2- Office # 5 KW BTU/H










7- For multipurpose room #1 KW BTU/H


8- For multipurpose room #2 KW BTU/H


The total load needed for ground and 1st. floors = 144 kilowatt = 40 RT.

So we need an absorption chiller of capacity 40 ton refrigeration , we have select a hot water fired absorption chiller manufactured by Sanyo company the specification of the chiller selected is shown in table 4.1

Table 4.1 Specifications of a 40 ton absorption chiller:

Item Scope of Works Qty Unit Price

(USD)

Total Price

(USD)

AATo supply Sanyo Hot Water LiBr Absorption Chiller H Series, model: LCC-E02 with total cooling capacity of 40 USRT inclusive of the following features:

- Chilled water, Temp.out: 8ºC, Temp.in:13ºC

- Cooling water, Temp.out: 37ºC, Temp.in:31ºC

- Hot Water, Temp.out: 83ºC, Temp.in:88ºC

- Power Supply : 415V/ 3phase / 50HZ

- Single effect

- High efficiency part load operation

- Digital intelligent microprocessor integrated control

- Four crystallization prevention safety controls

- Patented Li-Br solution

- One year equipment warranty

1 Nos. 69,000.00 69,000.00

(1) This quotation is based on CFR - Ramallah, Palestine.

(2) Solar District Cooling (M) Sdn. Bhd. is the sole-distributor for Dalian Sanyo absorption chiller.

(3) Exclude all mechanical, electrical and structural works.

4.5 Solar system design:

4.5.1Collector Calculation:

A- Case one :

This case related with Initial load to heat the water from 18C∘ to 88 C

∘

which is request as Heat source for the chiller. And this case neglected

because large number of solar collector. (Also in Appendix C.1 the climatologically average temperature)

Depending of the collectors catalogue CPC “Evacuated tube collector” in appendix B2

ζ =60% With T out collector =88°

and T in collector =18

Flow rate request 0 .947

kgs (from chiller catalogue) in Appendix B.1

Q=mC p

¿

ΔT

= 0 .947×4 . 17(88−18 ) = 276.4293 KW (Initial load)* The area of collectors request to cover this load

ζ collector=qu

AGWhere:ζ collector : Efficiency of the collector. qu : Useful heat required (Watt).A: Area of the collectors (meter).

G: Average Summer Insolation on A Horizontal Surface in Ramallah (W

m2 )

And G= 740 W

m2 (from solar data in Appendix C1).

A=276429 .3740×0 . 6

= 622.5885m2

* The area of each collector from (collector catalogue in Appendix B.2) is 3.41m2

* Number of collectors is 183

B- Case Two:

This case related with steady load for the chiller heat source, which is used in our solar system.Where:T in : Hot water enter the chiller is 88 C

∘.

T out : Hot water out flow from the chiller is 83 C∘ . (From the chiller

specification) * The total heat required is

Q=mC p

¿

ΔT

= 0 .947×4 .17(88−83 )

=19.7449 KW* The efficiency of the collectors in this case 58% depending on the collector average temperature. (Appendix B.2)*The area of the collectors request is

A=19744 . 9740×0 . 58

= 46 m2

* The number of collector is 14

⇒For the safety due to thermal losses in system we added another collector to become

15 collectors.

4.5.2 Collector installation:

This type of collectors is installed in the way shown in figure (3.1)

Figure 4.1 shows the way to install CPC-18 OEM collectors

The dimensions of each collector is shown in figure (4.2) and table (4.2)

Figure 4.2 shows the dimension of CPC-18 OEM collector

Table (4.2) the dimensions of the CPC -18 OEM collectors

The installation angles of the collectors and the free space between them is shown in figure (4.3)

Figure (4.3) shows the installation angles of the CPC-18 OEM collector and the free space between the collectors.

The catalogues from where we took the information about the chiller and the collector can be found respectively in appendix B.1 and B.2

4.5.3 Double jacket Storage tank:

The double jacket storage tank designed to store 60% of the evacuated tube heat

collection during 8 hour.

Q s=ρ Vc ( t s−tm)

Q s= Heat stored, KJ

ρ=Density of water, Kg /m3.

V= Volume, m3

.

c p = specific heat, KJ / Kg⋅K

t s=Storage temperature, ∘ C

tm= Minimum useful temperature,

∘ C

V=(19 . 7449 KW×8×60×60 )×0 .6980×4 . 17×30

=2 .74 m3

The volume of chosen storage tank is 2.5 m3

to decrease initial heating load on the

boiler.

4.5.4 Boiler (back up) Calculation:

A 34KW boiler can cover the entire initial load to increase water temperature from

18C∘ to 88 C

∘ in storage tank request as Heat source for the chiller, but the time for this

process take 5.96 hour, after this time chiller turn on.

Q= m

timeC p ΔT

34 KW =2500

time×4 . 17×(88−18 )

Time=5.96 h

⇒ If the efficiency of the boiler had been taken 90%, then the time required to cover all

the heating load would be 6.65 hour.

The selected boiler is Buderus G115E/G115 S with heating capacity of 34 KW, the

boiler specification shown in (Appendix B.3).

4.5.5 Solar system pump selection

In order to select a suitable pump, we must cover the largest head to be sure that

the pump will cover all of our system.

The optimal velocity should be chosen in closed loop heating system not exceed

10 ft/s the velocity taken to be 8 ft/s which equal 2.5 m/s.

In order to calculate the total head of the circulated pump, that is on the line

between double jacket storage tank and solar collectors with flow 0.947 Kg/s. total pipe

length estimated by 44 meter.

Pump head and losses calculation:

The diameter of the pipe had been calculated to be 1 in =0.0254m

Velocity assumed not exceed 8ft/sec = 2.5 m/sec for not noisy system and less friction losses, and volumetric flow rate 0.978 L/sec with ρ= 968 kg/m3 at 85o for water L= 44 mρ= 968 kg/m3 at 85o for water μ= 451x10-6 N.s/m2 (at 85o) from heat transfer tables.D=1” =0.0254 mV=2.5 m/s

Re= ρ VDμ

=968×2.5×0 .0254

451×10−6=136 .3×103

⇒ Turbulent flow

Frictional losses in pipesε= 0.05 mm

εd

=0 .050 .0254

=1. 97×10−3

⇒ From moody chart f=0 . 025

ΔH f=f ×(LD )×

V1

2

2 g

ΔH f=0. 025×(440 .0254 )×2. 52

2×9 .81=

13.8 m

Frictional losses in elbows:

# of elbows = 6X (1 Tee+ 5 elbows 90 degree)

ΔH=K×V

12

2 g

Where; K: is the factor of fittings which is for elbows=0.95

ΔH=6×(0 . 95× 2. 52

2×9 . 81)=

2m Frictional losses in valves:

3 valve (gate valve, fully open)

K=0.3

ΔH l=K×V

12

2g

⇒ ΔH l=3×(0 .3× 2.52

2×9 . 81)=0.3m

pressure drop in CPC 18 OEM evacuated tube collectors

From a catalogue in (Appendix B.2) is 100 mbar = 1 m for each one.*The 15 CPC evacuated tube collector connected as shown in figure 4.1, five rows in parallel each one has three CPC 18 OEM evacuated tube collectors. And the largest length of the pipe go through 3 collector. For 3 collectors = 3 m at flow rate 11.7 L/min.Total Head =13.8+2+0.3+3 =19 m

The selected pump (1) with flow rate 3.5 m3 /hand head 19 m is circulated

Salmson LRL 203-13/1.1 pump.

Other selected pumps. Pump (3) 3.5 m3 /h flow rate and total head 12 m is

circulated Salmson LRL 203-10/0.55 pump. And pump (2) 0.43m3 /h flow rate and total head 5 m. is circulated Salmson LRL 404-13/0.25 pump. The specification of the pump selected shown in (Appendix B.4).

The figure (4.4) bellow show the case study solar system component

Figure (4.4): The case study solar system component.

4.5.6 Expansion Tank selection:

It is considered as an important unit in heating system. It is necessary to contain the extra volume of water when its temperate rises to high degree, so this tank designed so that its active volume will contain the extra volume of water.

* The system volume

Pipe volume= total length ¿ π /4×(0 .0254 )2

= 0.0223 m3

Collectors manifold volume each one 10 liter ⇒ total volume = 150 liter

⇒V system=0. 1723m3

V t=V s

[ (v2 /v1)−1 ]−3 α( t2−t1)( Pa /P1)−( Pa / P2)

Where :

t1= lower temperate (18∘C ).

t2= higher temperate (100∘C ).

v1= specific volume of water at t1=0.001m3 /kg .

v2= specific volume of water at t2=0.001044m3 /kg .

α = liner coefficient of thermal expansion (11. 7×10−6 m /m .k ).

Pa = atmospheric pressure 101.3 Kpa.

P1 = pressure at t1 = ρ×g×H pump (181 Kpa) , H pump = 19 m.

P2 = maximum pressure of the system = 270 Kpa

V t=0 . 1723[(0 .001044 /0 . 001)−1 ]−3×11. 7×10−6 (100−18 )

(101.3 /181 )−(101 .3 /270)

⇒Volume of expansion tank (2) = 0.0383

After sample calculation the volume of expansion tank (1) is 25 liter.

So according to this values (ZILMET) expansion tank type will be selected which about 35 Liter for expansion tank (2) , and 25 liter expansion tank(1) respectively. And the specification of (ZILMET) expansion tank type shown in the catalogue in (Appendix B.5).

4.6 Duct design:-

Depending on equal friction method there is a sample calculation for duct sizing, which is supply three offices (1,2and3) in1st floor as shown in Appendix A.1, and in figure (4.5).

Figure (4.5): The supply duct of offices (1,2and3) in1st floor.

For the comfort condition the air flow velocity in main duct supply assumed to be 5m

s

In main duct (section one upstream)

Q0=1367.6 CFM=0.65m3\s & air velocity 5

ms

By using pressure drop loss chart (Appendix D.1)∆ PL

=0.65 Pa¿

Q=V × A

V=990 ft\min

A=π4

D eq

So……Deq=1.33 ft

But Deq=2 a× ba+b

And aspect ratio ¿ba

=2:1

b =2a

So Deq=2a=b=0.405

a=0.203 m

b=0.405 m

Section two (downstream1)

∆ PL

=0.65 Pa¿ Remain the same value for all following cases

Q1 =1368-413=955 CFM=0.45 m3\s &∆ PL

=0.65 Pa¿

And From pressure drop loss chart

So Deq=2a=b=0.36m

a=0.18m

b=0.36m

For section three of the duct(downstream two)

Q2=955-425=530 CFM =0.25 m3\s

From pressure drop loss chart

So Deq=2a=b=0.28m

a=0.14m

b=0.28m

Branches:-

The Fig (4.5) show the distribution of branches

A) Q1=413CFM =0.195 m3\s


So Deq=2a=b=0.26m

a=0.13m

B) Q2=425CFM =0.2 m3\s


So Deq=2a=b=0.28m

a=0.14m b=0.28m

Static pressure

Static pressure drop = duct length *

ΔPL

= 0.65*15

= 9.75 Pa

Dynamic pressure drop

Assume a dynamic loss coefficient of 0.3 for upstream to downstream

For (A)

∆ P=Co( ρV 2

2 )V=Q

A

V=4 × 0.45

π × 0.362 =4.4 m/s

∆ Pu-d =0.3( 1.2 × 4.42

2 )=3.5 Pa

For (B)

V=QA

V=4 × 0.195

π × 0.262 =3.7 m\s

∆ Pu-d =0.3( 1.2 ×3.72

2 )=2.5 Pa

FTP=∑ ∆ PL

li+∑Co( ρ V 2

2 )=0.65(2+5+8) +3.5+2.5=15.75 Pa

All duct distribution and sizing for ground and first floor explained respectively in Appendixes A1, D2.

4.7 Chilled water distribution

4.7.1 Fan coil selection:

After the calculation of the cooling load and the CFM request for each duct design as shown in Appendix A.1. A Petra DC type fan coil ( chilled water medium static) were selected to cover all the cooling load for the ground and first floor with Catalogue specification in Appendix D.3 , the table (4.3)and (4.4) bellow show the selected one .

Ground floor

Table (4.3): Selected fan coil specification for ground floor.

Fan coil number (As shown in Appendix

A.1)

Fan coil type Fan coil air flow (CFM) Fan coil chilled water flow(GPM)

1 DC 30 2286 15.32 DC 30 2286 15.33 DC 24 1908 11.474 DC 24 1908 11.47

First floor

Table (4.4): Selected fan coil specification for first floor .

Fan coil number (As shown in Appendix

A.1)

Fan coil type Fan coil air flow (CFM) Fan coil chilled water flow(GPM)

1 DC 18 1507 8.982 DC 16 1312 7.723 DC 18 1507 8.984 DC 14 1200 7.325 DC 18 1507 8.98

4.7.2 Chilled water pump selection:

All the fan coil need 95.6 GPM chilled water, which is 6 .03×10−3 m3/ s .

3 .38×10−3 m3 /s For the ground floor and 2 .65×10−3 m3 /s for the first floor. by

assuming the optimal velocity 2 .5m / sof chilled water for not nosey cooling system. A cross diameters were calculated for each length as flow rate distribution and the largest length which selection pump depend on is 8 meter with pipe diameter 2``, 4 meter with

diameter 1

12

``

and 20 meter with diameter

3``

4 .

L= 8 mρ= 980 kg/m3 at 10o for water μ= 451x10-6 N.s/m2 (at 10o) from heat transfer tables.D=2``=0.0508 mV=2.5 m/s

Re= ρ VDμ

=980×2.5×0 .0508

451×10−6=275 .9×103

⇒ Turbulent flow

Frictional losses in pipesε= 0.05 mm

εd

=0 .050 .0508

=9×10−4

⇒ From moody chart f=0 . 021

ΔH f=f ×(LD )×

V1

2

2 g

ΔH f=0.021×(80 . 0508 )×2 .52

2×9 .81=0 .97m

For pipe L=4m

D=1

12

``

=0.0381 m

ΔH f =0.67m

For pipe L=20m

D=

34 =0.01905m

ΔH f =8.7m

Frictional losses in elbows:

The equivalent length calculation

Leq=KDf

Where; K: is the head loss coefficient of fittings which is for elbows=0.95 and for

Tee =1.8.

⇒

For elbow:

= 4.76 m

⇒

Leq=10 m

ΔH ( fitting )=1. 8 m

The head loss for water collector= 0.8m.

ΔH( total )=1. 8+0 . 8

¿2 .6 m

pressure drop in fan coil as shown in fan coil (1) catalogue in Appendix D.3 as

average is 5ft of water =1.55 m.

⇒

All calculation above for supply line, which nearly same of return line.

Leq

Total head = (supply line*2) +fan coil head loss

=2 (0. 97+0 .67+8 .7+2. 6 )+1. 55=27 . 5 m

⇒

As shown above from the calculation, the pump required to supply a fan coil

with chilled water 22 cubic meter per hour and total head 27.5 m, depending on

this calculation Salmson LRL 203-16/1.1 pump was selected with specification

( appendix B.4)

4.8 Economic analysis for solar energy cooling case study:

The case study economic analysis period time is 25 year (absorption chiller

working system), compare with (vapor compression chiller working system).

Two systems operate for 3 months, 8 hour per day

Assuming

Interest rate (d) =8%

Prices inflation (f) =10%

Investments:

Absorption Chiller working system:

Table (4.5): fixed cost for absorption chiller working system

Electrical Chiller working system:

Table (4.6): fixed cost for absorption chiller working system

The fixed cost shown in table (5, 6) respectively is depending on pill quantity in Appendix D.4

Operating Cost:

Absorption chiller working system:

Equipment (#No) Cost($)Absorption chiller (1) 69000Solar Collectors(15),1500$/collector

22500

Boiler (1) 2160

Pumps (4)

810670620350

Fan coils (9) 950$/fan coil 8500Storage tank(double jacket insulation)(1)

2430

Expansion tank (2) 67$/tank 130Pipes, fittings and insulation 670Duct+ insulation 1900installation 10000Total cost 119740

Equipment(#No) Cost($)Electrical chiller (1) 40000Fan coil(9),950$/fan coil 8500Pipes, pump and fittings 1240Duct+ insulation 1900installation 5000Total cost 56640

For boilerAssume that the boiler is operated 3 times 6.65 hour per year (to increase the

water temperature from18C∘ to 88 C

∘which is request as Heat source for the

chiller (3 months).

Cost of diesel=mf

.

ρ× price per liter($)×time(sec)

Where:

¿ mf : foil consumption of boiler=0.014 Kg/s (Boiler catalogue in Appendix B.3)

ρ : Diesel density=0.85.

Diesel price per liter=1.6$

Time: 3*6.65*60*60= 71820(sec)

⇒ Cost diesel/year =0.0140.85

×1.6 ×71820(sec)

=1890$/year

Each pump consumes 3 KW electrical powers. Cost of Electricity =Electrical consumption for four pumps=

¿of pumps× ( power (KW )× price($ /kwh)×total hour )

= 4 ( pumps)× ¿

=1750$/year

Each fan coil consumes 12 KW electrical powers.Electrical consumption of fan coils (9 fan coils)/year=9 × (12 (KW )×0.203 ($ /kwh)× 720(hour ))

=15780$/year

Absorption chiller consumes 2KW electrical powers.

Electrical consumption for the chiller/year=2(KW )× 0.203($ /kwh)×720(hour )

=290$/year

Total consumption of electricity=1750$/year +15780$/year +290$/year

=17800$/year

Maintenance = 3000$/year

Total operating cost= Total consumption of electricity/year + Maintenance+ Cost diesel/year

=17800$/year+3000$/year+1890$/year

=22690$/year

Annual cost=annual operating cost+ capital cost*FCR

FCR=interest +depreciation

FCR=d+ d

(1+d )n

=0.08+ 0.08

(1+o . o8 )25

=0.092

=22690$/year +119740*0.092

=33700$/year

Electrical chiller working system:

For 40 TR COP=1.2

Electrical chiller consumes120KW electrical power.

Electrical power consumption of electrical chiller/year=120(KW )×0.203($ /kwh)×720 (hour )

=17500$/year

Fan coil electricity consumption (9 fan coils) =15780$/year

In this working system just one pump has been working to distribute chilled water.

Pump consumption=¿

=440$/year

Total electricity consumption/year= Electrical power consumption of electrical chiller/year+ Fan coil electricity consumption/year+ Pump consumption/year

=17500$/year+15780$/year+440$/year

= 33700$/year

Maintenance/year =2000$/year

Total operating cost/year = Total electricity consumption/year+ Maintenance/year

=33700$/year+2000$/year

=35700$/year

Annual cost=annual operating cost+ capital cost*FCR

Annual cost=35700+56640*0.092

=40900$/year

Life cycle cost

PWF

1. For future

PWF=1

(1+d )n

=1

(1+0.08 )25

=0.1462. For annual payment :

PWF= 1

d−f×(1−[ 1+ f

1+d ]n)

= 1

0.08−0.1×(1−[ 1+0.1

1+0.08 ]25)

=29.1

Table (4.6): Life cycle cost absorption chiller working system (A), compare with electrical chiller working system (B) during 25 years.

Cost item Cost option A, Cost option B,

First cost ( investment) 119740$ 56640$

PWF 1 1

Present worth 119740$ 56640$

Annual operating cost 22690$/year 35700$/year

PWF 29.1 29.1

Present worth 660000$ 1038900$

Salvage value 22000$ 5000$

PWF 0.146 0.146

Present worth - 3212 -730

Life cycle cost 776500$ 1094800$

From table above (4.6) it’s easy to note that life cycle cost for absorption chiller working system less than electrical chiller working system, this lead cooling with absorption chiller is better.

Payback period:

=[ investment of (B−A )−SALVAGE VALUE OF (B−A)× PWF ]

annual operatingcost of (A−B)

=4.7 years

4.9 Conclusions and recommendations:

It’s clearly appear that the initial cost of instillation of absorption chiller working

system costly more than electrical chiller installation for the same cooling

capacity, but if you look father on time with operate system ,the life cycle cost for

the electrical chiller is being more costly than absorption chiller.

The economic study reveals that the life cycle cost for operating the absorption

chiller 25 years equals (776500 $ ) and (1094800 $ ) for the electrical chiller so

the installation of the absorption chiller instead the electrical chiller is justified ,

the study also shows that the payback period for the absorption chiller equals 4.7

years.

Chapter fiveAdsorption refrigeration

5.1 Introduction:

The need for energy is constantly increasing and is leading to an increase in the price

of energy; however energy sources are getting scarce. Therefore, the search for an

efficient technology has become a necessity. Heating and cooling systems are

technologies that consume energy; and the demand for these systems is increasing in

every aspect. Therefore, the development of anew refrigeration and heat pump systems

that is driven by cogeneration of waste heat or renewable energy sources is highly

desirable.

Since the adsorption chillers are usually driven by heat, they can contribute to

reducing the energy consumption by utilizing non-fossil fuels, such as waste heat from

the cogeneration process or alternative renewable energy resources, besides that

adsorption chillers contributes in minimizing the depletion in the ozone layer and

adsorption chillers are CFCs free this makes those chiller a strong competitive to the

electrical refrigeration systems.

The correct selection of the adsorbent-adsorbate pair is the first step to increase the

performance of the system, Activated carbon-methanol adsorbent–adsorbate pair is

widely used in adsorption refrigeration systems that needs very low temperatures such as

ice making applications in literature activated carbon-methanol adsorbent–adsorbate pair

has the highest coefficient of performance among the adsorbent-adsorbate pairs.

5.2Adsorption refrigeration:

Adsorption in literature is the process of absorbing liquids and gases by using solid

materials, and the adsorption cooling cycle is one of the refrigeration cycles that utilize

heat to drive the refrigerant throughout the cycle instead of using a mechanical

compressor.

When a porous solid is exposed to a gas for which it has an affinity, forces of

attraction act between the individual gas molecules and the atoms or ions composing the

solid, at the interface of the two phases. The unbalanced forces at the phase boundary

result in the adsorption of the gas by the solid. The solid is referred to as the adsorbent

while the gas is referred to as the adsorbate.

The evaporation of the adsorbate takes its energy from the environment which gives

us the cooling effect and the regeneration of the adsorbate adsorbed by the adsorbent

needs a heat which is taken from the low temperature heat sources, the evaporation and

the regeneration of the adsorbate through the system completes one cycle.

One operating cycle of the system will consist of four distinct steps, described and

presented graphically in the Clapeyron-Clausius diagram of Figure (5.1).

Assumption: The system evaporator is named as vessel B and the

generator is named as vessel A and those vessels each have a control valves.

Figure [5.1] an adsorption cycle represented in a Clapeyron-Clausius diagram

Step 1: Isosteric heating of the wet adsorbent (charging stage):

At the beginning of the cycle, point 1 in Figure 5.1, the adsorbent of vessel A

contains the maximum amount of adsorbate within its pores, i.e. the adsorbent is wet. The

ratio X of adsorbate mass to the dry mass of adsorbent at this point is Xmax. The valve

between the adsorbent vessel A and the condenser/evaporator (vessel B)is initially closed.

As heat Qd at temperature Td is applied to vessel A containing the wet adsorbent, the

pressure of the adsorbate in vessel A will increase to the condenser pressure, Pc, with no

change in X.Therefore, the ratio of mass of adsorbate to mass of adsorbent is Xmax

(point 2 in Figure5.1). The process between points 1 and 2 is referred to as the isosteric

(constant mass ) heating of the wet adsorbent.

Step 2: Desorption and condensation of adsorbate (charging stage):

At point 2 (Figure 5.1) the valve connecting the adsorbent vessel A to the condenser

(vessel B) is opened. Heat Qd continues to be supplied to the adssorbent in vessel A and

desorption of the adsorbate from the adsorbent occurs until the adsorbent vessel A and

the condenser (vessel B) reach the equilibrium pressure. The adsorbate gas from vessel A

flows to the condenser (vessel B) , Where it is condensed to its liquid state.Heat of

condensation Qc is rejected at temperature Tc. The desorption of the adsorbent in vessel

A

At a constant pressure Pc continues until the adsorbent reaches the temperature Td

and the ratio of mass of the adsorbate to mass of adsorbent is at the minimum value

Xmin. i.e. the adsorbent is dry (point 3 in Figure 5.1(. The valve connecting the adsorbent

vessel A to the condenser/evaporator (vessel B) is now closed.

Step 3: Isosteric cooling of the dry adsorbent (discharge stage):

At point 3 (Figure 5.1) the adsorbent within the adsorbent vessel A has a minimum

amount of adsorbate within its pores, Xmin. The adsorbent is at a temperature Td, and is

separated from the adsorbate in liquid form that is contained within the

condenser/evaporator (vessel B). The valve is kept closed. As the adsorbent vessel A

cools, the pressure of the adsorbate contained within the pores of the adsorbent decreases

to the evaporator pressure Pe with no change in the ratio of mass of the adsorbate to mass

of the adsorbent, Xmin (point 4 in Figure 5.1). The process between point 3 and 4 is

referred to as the isosteric (constant mass) cooling of the adsorbent.

Step 4: Evaporation of the adsorbate and adsorption (discharge stage):

At point 4 (Figure 5.1) the valve connecting the adsorbent vessel A to the

evaporator (vessel B) is now opened. Heat Qe is supplied to the evaporator so that the

liquid adsorbate within the evaporator returns to its gaseous state. Heat continues to be

supplied to the evaporator B and the equilibrium pressure is achieved as the adsorbate gas

flows from vessel B to the adsorbent vessel A. Adsorption at a constant pressure Pe

continues until the adsorbent in vessel A reaches the temperature Ta. At this point, the

ratio of mass of adsorbate to mass of adsorbent that can be contained within the pores of

the adsorbent is at the maximum value Xmax. (Point 1 in Figure 5.1). Heat of adsorption

Qa is released during this process. This last process completes one operating cycle.

If the adsorption system is used for storage applications, the operating cycle

described above is discontinuous. Assuming an ideal cycle, the charging phase consists of

steps 1and 2, where the temperature required to charge the system is Td and the heat to be

stored is Qd. Heat can be stored indefinitely as long as the valve connecting the adsorbent

vessel A and the condenser/evaporator (vessel B which contains the liquid adsorbate)

remains closed at the end of step 2.

Adsorption system performance:

Adsorption cycles performance parameters are usually measured in terms of the

cycle coefficient of performance (COP) and its specific cooling power (SCP) COP is

defined as the ratio of the useful thermal energy moved in or out of the cycle (Qev) to that

of the high temperature thermal energy used (Qd) it can be expressed as:

C . O . P=Q ev

Qd

(1)

The performance for solar powered adsorption cycles can be measured by its solar

coefficient of performance (SCOP) which is the ratio between the useful energy output to

the total solar energy insolation on the collector surface (I)

C . O . P=Q ev

I (2)

Another term that is useful in showing the cycle performance is specific cooling

power (SCP) which is expressed as:

S . C . P=Q ev

τ cycle × M e (3)

Me is the total mass of adsorbent and τcycle is the cycle time.

[26]

5.3Working pairs selection:

There are several working pairs for solid adsorption. For the successful operation of

a solid adsorption system, careful selection of the working medium is essential. It is

because; the performance of the system varies over a wide range using different working

pairs at different temperatures.

The advantages and disadvantages of different working media and their properties

are listed and discussed in this section. For any refrigerating application, the adsorbent

must have high adsorptive capacity at ambient temperatures and low pressures but less

adsorptive capacity at high temperatures and high pressures. Thus, adsorbents are first

characterized by surface properties such as surface area and polarity. A large specific

surface area is preferable for providing large adsorption capacity, and hence an increase

in internal surface area in a limited volume inevitably gives rise to large number of small

sized pores between adsorption surfaces. The size of the micro-pores determines the

effectiveness of adsorptivity and therefore distribution of micro-pores is yet another

important property for characterizing adsorptivity of adsorbents.

In order to select an adsorbent for refrigeration applications we must look at the

following properties:

High adsorption and desorption capacity, to attain high cooling effect.

Good thermal conductivity, in order to shorten the cycle time.

Low specific heat capacity.

Chemically compatible with the chosen refrigerant.

Low cost and widely available.

In order to select an adsorbate for refrigeration applications we must look at the

following properties:

High latent heat per unit volume;

Molecular dimensions should be small enough to allow easy adsorption;

High thermal conductivity;

Good thermal stability;

Low viscosity;

Low specific heat;

Non-toxic, non-inflammable, non-corrosive; and

Chemically stable in the working temperature range.

A survey of the favored working adsorbate shows that methanol and water operates

at sub atmospheric saturation pressure at the operating temperatures needed and ingress

of air immediately results in system malfunction. Ammonia doesn't have this problem

because its outward leak could be tolerated for some time, but its saturation pressure of

13 bar at 35 ℃ condensing temperature is quite high. In the case of methanol with a

normal boiling point of 65 ℃ , the law saturation pressures could be exploited

advantageously to detect leakage, since it most necessarily result in abnormal increases in

pressure and poor performance.

Ammonia, methanol and water, all have relatively high latent heat values of 1368,

1102 and 2258 KJ/Kg.℃ respectively and their specific volumes are low, on the order of

about 10-3m3/Kg.

Ammonia is toxic and corrosive, while water and methanol are not, but the problem

with alcohols is that they are flammable.

Water is the most thermally stable with adsorbents, closely followed by methanol

and ammonia in that order. However, water cannot be used for freezing purpose because

of its freezing temperature is 0 ℃this makes methanol a favored adsorbate for pairing

with a stable adsorbent.

Various kinds of working pairs for adsorption refrigeration have been studied, and

they include both physical and chemical adsorption working pairs. The main physical

adsorbents are activated carbon, zeolite and silica gel, and accordingly, the physical

adsorption working pairs are mainly activated carbon-methanol, activated carbon-

ammonia, zeolite –water and silica gel �� water. In recent years, the working pairs

activated carbon (HFC-134A) and activated carbon dimethyl ether were also investigated.

As water is the refrigerant normally used with zeolite or silica gel, the evaporating

temperature is never lower than 0℃. Compared to other physical adsorption working

pairs, the main advantage of the utilization of activated carbon as adsorbent is the low

evaporating temperature that can be reached, as the refrigerants most employed are

ammonia or methanol. Due to the low evaporation temperature of these refrigerants, these

pairs are more suitable for ice making technology.

A study published by the ''Institute of Refrigeration and Cryogenics, Shanghai Jiao

Tong University, Shanghai 200030, China'' titled '' The performance of two adsorption

ice making test units using activated carbon and a carbon composite as adsorbents ''that

constrains on studying the best ''activated carbon/adsorbate'' pair reveals that the best

choice for a refrigeration pair is the ''activated carbon/methanol'' pair which has

adsorption quantity of 59% larger than that of ''activated carbon/ammonia''.

Another study for ''Meunier F, Douss N" titled '' Performance of adsorption heat

pumps: activated carbon/methanol and zeolite/water pairs'' shows that the C.O.P of the

heat pump used in the test which uses activated carbon/methanol pair is 0.4-0.5 but the

C.O.P of the same heat pump undergoes the same operating conditions is 0.3.

For all the purposes listed above and because we want to build an adsorption ice

maker model which means very low temperature application we have selected activated

carbon-methanol pair as working pair.

[27]

5.4 Lab. Scale adsorption ice maker:

In order to investigate the adsorption cycle behavior we built an adsorption ice maker

model, the model were built by using glass ware components.

5.4.1 Adsorption ice maker model components:

Figure [5.2] Lab. scale adsorption ice maker.

1- Vacuum pump: which is used to reduce pressure inside the system.

2- Evaporator: which contains the adsorbate and the refrigeration effect is extracted

there.

3- Heat exchanger) Condenser) to reduce the temperature of the adsorbate when it is

desorbed from the generator.

4- Generator: which contains the adsorbent where the heat is added to the cycle.

5.4.2 Components description:

A- Evaporator:

The evaporator is the part of the model from where the cooling effect is extracted so

the construction of the evaporator depends on the way we want to utilize this effect in our

case we want only to investigate the process working conditions so we want to measure

the temperature of a known amount of water surrounds the evaporator so we can choose

the any shape of the evaporator (cubic box or a spherical shape) so we choose the

spherical shape as the glass sphere can sustain larger pressure on it .

B- Generator (Adsorber):

The generator is the part of the model to be heated and its shaped is determined

according to the way we want to heat the adsorbent material some shapes are made like a

flat plate water collector as the adsorbent material is arranged so that the water passages

passes through the material which is the most common type but in our model we use a

spherical container to but the adsorbent inside it and we immerse it inside paraffin oil

container and we use to heat the oil as it has a boiling temperature 200 rather than water.

C- Condenser:

The most common types of condensers are:

1- Finned type heat exchangers: This type of heat exchangers are used in the small

adsorption units as the heat to be rejected is small and this type of heat exchangers

depends on the natural convection which is a poor process , when one decide to

use this type of heat exchangers then there must be another pipe that is not finned

which connects the generator with the evaporator so as to make sure that the

adsorption process happens and the adsorbate not to condense and return back to

the evaporator.

2- Shell and tube heat exchanger: this type can be used with the small and large units

and this type can be used alone as the connection between the evaporator and the

generator this means more simple construction and large heat rejection capacity,

For all reasons above and because the glass Finns gives no effect as the thermal

conductivity for the glass is very low then we use the shell and tube heat

exchanger as the condenser of the unit [28].

5.4.3 Lab scale experiment:

In this section we show the results obtained from the experiments done using the

model.

Table (5.1): charcoal/methanol pair experiment data.

TimeTevap. (C

∘

) Tcond. (C∘

) Tgen. (C∘

) Tamb. ((C∘

) Pressure

(cm Hg)

11:20 23 23 22 23 67

11:50 22.8 23 22 23 66

12:20 22.5 23 22 23 65

12:50 22 23 22.5 23 64

01:30 21.5 23 22.7 23 63.5

01:40 21 23 22.8 23 63

01:50 20.3 23 23 23 62

02:10 20 23 25 23 60

02:30 20 23 29 23 58

02:50 20.2 19 39 23 56

03:00 20.6 19 50 23 50

03:20 21 19 60 23 48

03:50 21 19 71 23 43

04:10 21 19 83 23 39

04:30 21 19 92 23 38

Comments on data:

From 11:20 we evacuate the system and then inject the methanol into it,

Adsorption process ends at 01:50, so the adsorption cycle takes 2.5 hours.

The desorption process starts at 01:50 till 04:30, so the desorption process takes 2

hours and 40 minutes.

The amount of methanol adsorbed by the charcoal is 25 ml water.

Table (5.2): silica-gel/water pair experiment data

TimeTevap. (C

∘

) Tcond. (C∘

) Tgen. (C∘

) Tamb. (C∘

) Pressure

(cm Hg)

11:10 20 19 21 23 68.3

11:28 20 19 21 23 68.2

11:36 20 19 21 23 67.8

11:50 19.5 19 21.4 23 67.6

12:00 19.5 19.5 21.8 23 67.5

12:15 19.3 19.5 21.8 23 66.9

12:30 19 19.6 22 23 66.8

12:50 19 18 22 23 66.5

01:20 19 18 23 23 65

01:50 19.3 18 36 23 64

02:30 19.5 18 48 23 60

03:00 19.6 18 60 23 58

03:30 19.6 18 76 23 55

04:00 19.6 18 85 23 53

04:30 19.6 18 95 23 50

Comments on data:

From 11:10 we evacuate the system and then inject the water into it, Adsorption

process ends at 12:50, So the adsorption cycle takes 100 minutes.

The desorption process starts at 01:50 till 04:30, So the desorption process takes 2

hours and 40 minutes.

The amount of water adsorbed by the silica-gel is 14 ml water.

The following experiment was done in order to calculate the latent heat of

the methanol.

We put an 40 ml methanol in the evaporator and then we open the system

on the vacuum pump and the result was that the 40 ml evaporated in 15

minutes and this evaporation decreases the temperature of a liter water 6

degrees Celsius.

Cooling amount Q equals

Q = m ×c p ×∆ T = 0.04 × 0.787 ×2.55× 6=481.6 Joule

Latent heat of methanol equals:

Latent heat = 0.4816 ÷ (0.031 ×6 )=2.5KJouleKg .℃

5.4.4 Conclusions and recommendations :

The adsorption pairs doesn't work on the same working conditions that the

charcoal starts the desorption process at 71 ℃ but the silica-gel starts the

desorption process at 76 ℃ .

Silica-gel/water system needs lower pressure inside the system than that is

needed by the systems that uses activated-carbon/methanol pair.

The model built has two drawback the first the pipes weren't lubricated so that

the refrigerant were stuck on the condensers' wall and didn't flow to the

evaporator because the adhesive bond between the methanol and water with

the glass is high so we found difficult to turn the refrigerant back in to the

evaporator. The second thing is that the condenser was very long this was the

greatest obstacle we found when operating the system. So we found that the

generator and the evaporator must be close to each other and this distance is

also proportional to the system size and the cooling capacity and if we

recommend to be approximately 20 cm, Also we recommend to solve the

lubrication problem the condenser must be put under the generator directly so

the refrigerant by gravity will flow to the evaporator.

The charcoal used in the experiment was of an unknown origin and we didn't

know its' adsorptivity and we recommend to use activated carbon which has a

better adsorptivity or charcoal fibers.

References:

[1] Active Solar Collectors and Their Applications, Ari Rabal, Center for Energy and Environmental Studies, Princeton University (New York Oxford University 1985).

[2] Renewable Energy note book, Dr, Afif Hasan ,(Birzeit University 2009).

[3] Solar angles, http://www.docudesk.com, 12/9/2009.

[4] Sun Earth Relationships-www.vistech.net/users/rsturge/dateline.html

[5] The Season http://eeyore.astro.uiuc.edu/~lwl/classes/astro100/fall03/

[6] Solar Electric Systems University of Delaware, ECE Spring 2008 C. Honsberg

[7]- Analysis of a Flat-plate Solar Collector, Fabio Struckmann , Dept. of Energy Sciences, Faculty of Engineering, Lund University, Box 118, 22100 Lund, Sweden.

[8] Evacuated blood collection tube, www.bd.com , 20/9/2209.

[9] Evacuated tube collector www.toodoc.com, 20/9/2209.

[10] Flat vs evacuated tube, www.energymatters.com.au, 20/9/2209.

[11] Conversion energy, renewable energy sources: Sorenson,

[12] Evacuated tube solar hot water collector www.solarwaterwise.com.au , 20/9/2209.

[13] Optical Performance Analysis for Concentration Solar collector Applying Parabolic and Cylindrical Stationary Reflector , Jun Dog , Zhifeng Wang Institute of Electrical Engineering , Chinese Academy of Sciences, Beijing 100080,P.R. China.

[14]- Enhancement in Thermal Performance of Cylindrical Parabolic Concentrating Solar Collector, K.D.P.SINGH and S.P. SHARMA , Department of Mechanical Engineering,NIT,Jamshedpur,INDIA{[email protected];[email protected]},Received 13 January 2009, Accepted 26 January 2009.

[15]- Types of Solar collector, http://en.wikipedia.org , and 10/9/2009.

[16] Absorption Chillers for Buildings: www . eren . doe . gov / power / , 23/9/2209.

[17] Dorgan, C.B., Leight, S.E. and Dorgan, C.E., 1995, Application guide forAbsorption cooling/refrigeration using recovered heat, Am. Soc. Heat. Ref Air-Cond. Engrs (ASHRAE), Atlanta, GA

[18] Cooling cycle2006 www . escenter . org , 20/9/2209.

[19] (PDF SHC (solar heating and cooling international energy agency

[20] Air conditioning and refrigeration book, Jerold W.jones , 2nd edition.

[21] Absorption chiller for building www.energy.wsu.edu/cfdocs/tg/12.htm.

[22] Absorption chiller Niebergall, W., 1959, Sorptions-Kältemaschinen, Vol. 7 of Handbuch der Kältetechnik, Ed. R. Plank, Springer-Verlag, Berlin

[23] Direct-Fired Absorption Chillers: Student: Anya WIndira Supervisor: Prof. Dr. Ing. B. Stanzel.

http://www.escenter.org/

http://www.eren.doe.gov/power/

[24] - An energy efficient solar ice maker, K.SumathyDepartment of Mechanical Engineering, University of Hong Kong, Hong Kong

[25]- Solar energy refrigeration by liquid-solid adsorption technique, Watheq Hussein, Al najah-university (2008).[26] Investigation of an Adsorption System for the Seasonal Storage of Heat Applied to Residential Buildings, Maria Mottillo, and January 2006. [27] Technology development in the solar adsorption refrigeration systems, K. Sumathy and K.H. Yeung, Li Yong, May 2002. [28] Solar energy refrigeration by liquid-solid adsorption technique, Watheq Hussain, January 2008.

Appendix A.3

Table 1 Dimensions of the doors in the building in millimeters [arch. Plane].

Table 2 Dimensions of the windows in the building in millimeters [arch. Plane].

Appendix B.1

Absorption chiller catalogue

Appendix B.2

Collector catalogue

Appendix B.3

Boiler catalogue

Appendix B.4

Pumps catalogue

Appendix B.5

Expansion tank catalogue

CAL-PRO CE drawing 20013

Technical table for standard closed expansion tank (ZILMET) product red colour.

Appendix C.2Cooling load design condition & calculation variable

Table (1): Cooling load calculation variables.

Wall Direction CLTD SHG CLF SCNorth 15.155

117 0.75 0.83North East 18.143

445 0.2 0.83East 19.72

691 0.19 0.83South East 17.977

571 0.24 0.83South 15.404

350 0.32 0.83South West 18.807

571 0.49 0.83West 20.55

691 0.52 0.83North West 18.973

445 0.51 0.83

Table (2): Temperature and relative humidity for the design conditions.

Inside design conditions(summer)Temp. inside ( C )

23

Relative humidityФ

47%

Outside design conditions(summer)Temp. outside ( C )

35

Relative humidityФ

62%

Appendix D.1

Figure of pressure drop in straight, circular, sheet-metal, 20∘

C air, absolute roughness 0.00015 m

Space Duct length(m)

Main duct Friction loss Pa

m

Number of section

Section length(m)

Number of Branches

Size of section

(m×m

)

FTP(Pa)

Hall 120 seat #2x12 0.45 4 3 0 0 .53×0 . 26 18.8

3 0 0 .45×0 .233 0 0 .39×0 .23 0 0 .13×0 .07

Entrance lobby #2x8 0.48 3 2.7 0 0 .451×0.74 8.5

7.7 0 0 .42×0.212.7 0 0 .32×0 .16

Appendix D.2

Duct sizing of case study

Table 1 : Ground floor duct sizing.

Table 2: First floor duct sizing.

Space Duct length(m)

Main duct

Friction loss

Pam

Number of

section

Section length(m)

Number of

Branches

Size of section

(m×m

)

Size of branches

(m×m

)

FTP(Pa)

Multipurpose #2x8 0.45 3 2.7 0 0 .4×0 . 33 8.5

2.7 0 0 .37×0. 182.7 0 0 .28×0 . 14

Office(4,5) 3 0.5 2 3 1 0 .372×0 . 186 39.8

4 0 .304×0 .152 0 .304×0 .152Corridor 7 0.6 3 2 0 0 .38×0 . 16 10.4

2.5 0 0 .34×0 .172.5 0 0 .27×0.137

Office(1,2,3) 15 0.65 3 2 1 0 .405×0 .2 0 .26×0.2 15.75

5 1 0 .36×0. 18 0 .36×0.188 0 .28×0 . 14

Appendix D.3

DC Fan coil catalogue

Figure (1): Ceiling Basic Models with Plenum.

DCP fan coil designed for concealed ceiling installation above false ceiling with ducted supply air distribution and free return of air above false ceiling. The plenum encloses the fan section of the basic unit. Unit of this type consist of a coil, fan and flat filter.

Figure (2): fan coil water strainer

Appendix D.4

Pill of quantity

Equipment Type/Model Quantity Explanations

Absorption chiller Sanyo /LCC-E02 1 Cooling capacity 40 RT

Fan coilsPetra/DC fan coils 9 Medium static pressure

Pumps

Salmson LRL 203-13/1.1

1 Flow rate 3.5 m3 /hand head

19 m


1 3.5 m3 /h flow rate and total

head 12 m


1 0.43m3 /h flow rate and total head 5 m


1 22m3 /h flow rate and total head 27.5 m

Expansion tanks

(ZILMET) expansion tank(2)

1 35 Liter

(ZILMET) expansion tank(1)

1 25 liter

Storage tank Double jacket 1 2.5 m3

Evacuated tube solar collectors

CPC-18 OEM collector

15 3.41m2

area for each one

Boiler Buderus G115E/G115

S1 heating capacity 34KW

pipes

steel 1/2 inch

quantity In length

60 meter

steel 3/4 inch 100 meter

steel 1 inch 44 meter

steel 1

12 inch

8 meter

steel 2 inch 16 meter

Fittings

elbow 90 30 with pipe size

tees 10 with pipe size

water collectors 5suitable for fan coils chilled water

distribution

valves 30 globe and gates

Ducts square ducts 9Total area can be founded in

appendix D.2

Insulator

Duct insulator For all the supply duct surface

area

Chilled water supply

pipe 100 meter pipe

solar cooling (case study)

Documents

solar refrigeration

solar collectors

solar constant

variation of solar radiation

solar system design

solar radiation angles

measurement of solar

adsorption cycle