carbon dioxide solar assisted heat pump by

CARBON DIOXIDE SOLAR ASSISTED HEAT PUMP

SYSTEM FOR SPACE COOLING AND HEATING

BY

YEHYA A.A BARADEY

A thesis submitted in fulfilment of the requirement for the

degree of Doctor of Philosophy in Engineering

Kulliyyah of Engineering

International Islamic University Malaysia

FEBRUARY 2018

http://www.google.com.my/url?url=http://www.iium.edu.my/educ&rct=j&frm=1&q=&esrc=s&sa=U&ei=KHqFVJaTIZKyuATNwoGoBw&ved=0CBMQFjAA&usg=AFQjCNH8CPBB4-yr6XSF1EeEZS5f3iT02w

ii

ABSTRACT

Solar assisted heat pump (SAHP) system is a conventional heat pump system where

solar energy is the main or supplementary heat source. In the normal installation, heat

rejection occurs directly to the ambient air as waste heat. In tropical countries such as

Malaysia, air conditioners are running almost in every building, so that the amount of

waste heat from the heat pump systems is huge. It is more prudent to exploit this heat

for other applications such as water heating, drying, and desalination instead of

throwing it away. Meanwhile, SAHP systems usually operate by HCFC synthetic

refrigerants such as R134a. Synthetic refrigerants cause Global Warming and Ozone

Depletion. Replacing the synthetic refrigerants by CO2 in heat pump systems will be

more environmentally friendly. In current contribution, carbon dioxide was used as

refrigerant to improve the performance of the system and to make it environmentally

friendly. Waste heat from the gas cooler was utilized to provide hot water for

domestic applications as well as to operate the desalination unit. Dryer was placed as

secondary gas cooler to provide additional cooling for the refrigerant which increases

the COP of the system. Solar energy was integrated in the system as supplementary

heat source to decrease the work done by the compressor and therefore improve the

performance of the system. The modified system was designed, built and

experimentally tested to study its performance, and to investigate the feasibility of the

system. The system consisted of R744 trans-critical compressor, air finned-tube room

evaporator, evaporator collector to provide heat to the refrigerant, internal heat

exchanger, Air Gap Membrane Desalination Unit (AGMD), air convective dryer,

water tank, water flat plate solar collector, and two gas coolers. The experimental part

was carried out on the R744 test rig at NTNU. The AGMD unit and the water flat

plate collector were experimentally tested on the rooftop in IIUM. Simulation for the

system components was conducted using the commercial release of ANSYS FLUENT

FLOW 14.5 and MATLAB software. Results showed that the system was able to

provide hot water with temperature of 56oC for domestic applications. Water solar

collector, which was used to provide hot water during the day, provided hot water at

same temperature as well. Effect of inlet temperature of coolant in the first gas cooler

was studied and it was concluded that the higher inlet temperature the lower COP.

Impact of ambient temperature on the performance of the air convective dryer was

theoretically studied. Theoretical results showed that the higher ambient temperature

the higher outlet temperature of the refrigerant (R744) from the dryer, which

negatively influences its performance. Effect of ambient temperature on the

coefficient of performance of the system was also carried out. It was concluded that

increasing the ambient temperature has negative impact on both heating and cooling

COP of the system. Heating and cooling COPs of the system were recorded as 4.1 and

3.4 respectively. Production rates of fresh water from the AGMD unit under different

inlet temperatures of seawater were experimentally examined. Results showed that

maximum amount of produced fresh water obtained was 45.3 Ml/hr at inlet

temperature of feed water of about 55oC..

iii

خلاصة البحثABSTRACT IN ARABIC

أنظمة المضخات الحراريه التي تعمل بمساعدة الطاقة الشميسة هي عبارة عن مضخات حراريه

اعتيادية تكون فيها الطاقة الشمية هي المصدر الاساسي او الثانوي للطاقه. هذه الانظمة صممت

الهواء الخارجي. عادة ما يتم طرد لشفط او أخذ الحراره من داخل الابنية المغلقه وطردها الى

الحراره المأخوذه من الابنية للحصول على مناخ داخلي مناس الى الهواء الطلق مما يساهم في

مشكلة الاحتباس الحراري ومشكلة طبقة الاوزون. تلك الطاقة ) الحراره( تعتبر حرارة مهدرة بلا

ريق بذل طاقة اوليه للضاغط الذي يجعل فائدة على الرغم من ان الحصول عليها لا يتم الا عن ط

من فرق الضغط للمائع سببا لاستمرارية الدائرة الحراريه للنظام. في دولة استوائيه مثل ماليزيا

حيث يتم تشغيل انظمة التكييف تقريبا في كل الابنية والجامعات والمستشفيات على مدار اليوم ,

فان استغلال هذه الطاقه لتشغيل انظمة اخرى مثل تكون الطاقة المهدره سنويا ضخمه جدا. لذلك

انظمة التجفيف وتحلية المياه او حتى توليد مياه ساخنة للاعمال المنزليه يكون اكثر جدوى واكبر

نفعا. اضافة الى ذلك فان هذه الانظمه تعمل حاليا بمواثع وغازات مضره للبيئه ومسببة للاحتباس

قد تم حظره عالميا بسبب تلك المشاكل. في الاونة الاخيره , الحراري. الكثير من هذه الغازات

الكثير من الابحاث العلمية التي اجريت عالميا, تأكد ان استخدام غاز ثاني اكسيد الكربون لتشغيل

الانظمة الحرارية يجعل هذه الانظمه صديقة للبيئة مما قد يحد او يقلل من مشكلة الاحتباس

الحراريه للنظام. الرسالة المقدمه تتضمن تصميم نظام حراري يعمل الحراري ويزيد من الكفاءه

بمساعدة الطاقة الشمسية لتوليد مياه ساخنه تلزم للاعمال المنزليه, ولتشغل نظام تجفيف منزلي ,

ولتوليد وحدة تحلية المياه للشرب من مياه البحر. المشروع كان بالتعاون مع الجامعة النرويجية

لوجيا في مدينة تروندهايم في النرويج. التجارب العملية لتقييم عمل النظام للعلوم والتكنو

الحراري قد اجريت في الجامة النرويجية للعلوم والتكنلوجيا بينما التجارب العملية الخاصه بوحدة

تحلية المياه ونظام تسخين المياه عن طريق الطاقة الشمسية قد اجريت في ماليزيا وتحت الظروف

ية الماليزيه وذلك لاسباب تتعلق بالدعم المالي للمشروع والوقت.تاكيد نتائج التجارب المناخ

العملية للنظام قد تم من خلال استخدمام برناج الانسس وبرنامج الماتلاب.النتائج النظرية التي تم

لمشغل الحصول عليها كانت متقاربة جدا مع النتائج العملية. أطهرت النتائج ان النظام الحراري ا

65عن طريق ثاني اكسيد الكربون قادر على تزويد مياه ساخنه للاستخدام المنزلي بدرجه حراره

درجه مئويه. المياه الساخنه المزودة عن طريق النظام الشمسي وفق المناخ الماليزي يمكن ان

مجفف( تصل الى نفس درجة الحرارة تقريبا. تأثير درجة حرارة الجو على عمل نظام التجفيف )ال

قد تمت دراسته وقد اظرت النتائج انه كلما زادت درجة حرارة الجو كلما زادت درجة حرارة

الغاز وهذا بدوره يقلل من كفائة نظام التجفيف. بالمقابل تمت دراسة تأثير درجة حرارة الجو على

رة. معامل الاداء للنظام واظهرت النتائج ان معامل الاداء يتناقص مع ازدياد درجة الحرا

للتسخين والتبريد 4.1و 1.4التجارب العملية التي اجريت اظهرت ان معامل الاداء للنظام هو

ملتر لكل 16.4على التوالي. كما اظهرت النتائج ان اعلى نسبة مياه محلاه تم الحصول عليها هي

. ساعه

iv

APPROVAL PAGE

The thesis of Yehya A.A Baradey has been approved by the following:

_____________________________

Mohammad Nurul Alam Hawlader

Supervisor

_____________________________

Meftah Hrairi

Co-Supervisor

_____________________________

Ahmad Faris Ismail

Co-Supervisor

_____________________________

MD Ataur Rahman

Internal Examiner

_____________________________

Armin Hafner

External Examiner

_____________________________

Kim Choon Ng

External Examiner

v

DECLARATION

I hereby declare that this thesis is the result of my own investigations, except where

otherwise stated. I also declare that it has not been previously or concurrently

submitted as a whole for any other degrees at IIUM or other institutions.

Yehya A.A Baradey

Signature ........................................................... Date .........................................

vi

INTERNATIONAL ISLAMIC UNIVERSITY MALAYSIA

DECLARATION OF COPYRIGHT AND AFFIRMATION OF

FAIR USE OF UNPUBLISHED RESEARCH

CARBON DIOXIDE SOLAR ASSISTED HEAT PUMP SYSTEM

FOR SPACE COOLING AND HEATING

I declare that the copyright holders of this dissertation are jointly owned by the

Student and IIUM.

Copyright © 2018 Yehya A.A Baradey and International Islamic University Malaysia. All rights

reserved.

No part of this unpublished research may be reproduced, stored in a retrieval system,

or transmitted, in any form or by any means, electronic, mechanical, photocopying,

recording or otherwise without prior written permission of the copyright holder

except as provided below

1. Any material contained in or derived from this unpublished research may

only be used by others in their writing with due acknowledgement.

2. IIUM or its library will have the right to make and transmit copies (print

or electronic) for institutional and academic purposes.

3. The IIUM library will have the right to make, store in a retrieved system

and supply copies of this unpublished research if requested by other

universities and research libraries.

By signing this form, I acknowledged that I have read and understand the IIUM

Intellectual Property Right and Commercialization policy.

Affirmed by Yehya A.A Baradey

……..…………………….. ………………………..

Signature Date

vii

DEDICATION

To my beloved parents, wife and brothers

viii

ACKNOWLEDGEMENTS

The author would like to express his sincerest gratitude to the main supervisors Prof.

Dr. Mohammad Nurul Alam Hawlader and Co- supervisors Prof. Dr. Meftah Hrairi

and Prof. Dr. Ahmad Faris Ismail for giving me the opportunity to carry out this

research work under their supervision and would like to express my appreciation for

their patience, support and\ guidance.

Special thanks and appreciation to Department of Energy and process

Engineering at Norwegian University of Science and Technology- Trondheim,

especially Prof. Dr. Armin Hafner, and Prof. Dr. Olav Bolland, for giving me

opportunity to conduct my experimental work of my PhD project in NTNU and for

their kind hospitality during the experimental campaign. Warm thanks and

appreciation to Dr.Eng. Ángel Álvarez Pardiñas, and Krzysztof Banasiak for all

efforts they spent in training me on the R744 Test Rig.

I would like to record my warmest appreciation to my beloved parents, my

wife and my brothers for their patience and continuous support throughout my study,

their love and affection have made it possible for me to continue my studies up to this

moment.

Last but not least, I would like to thank Mechanical department, Faculty of

Engineering and all IIUM staff whose direct and indirect support helped me to achieve

my master’s degree. Special thanks go to the Malaysian people for their hospitality

throughout my staying period in their wonderful country.

ix

TABLE OF CONTENTS

Abstract ........................................................................................................................ ii Abstract in Arabic ........................................................................................................ iii Approval page .............................................................................................................. iv

Declaration ................................................................................................................... v Copyright ..................................................................................................................... vi Dedication .................................................................................................................... vii Acknowledgements ...................................................................................................... viii Table of contents .......................................................................................................... ix

List of Tables ............................................................................................................... xii

List of Figures .............................................................................................................. xiii List of Abbreviations ................................................................................................... xxi

CHAPTER ONE: INTRODUCTION ...................................................................... 1 1.1 Overview ................................................................................................... 1 1.2 Concept of Waste Heat Recovery ............................................................. 2

1.3 Construction of the Thesis ........................................................................ 5 1.4 Problem Statement .................................................................................... 5

1.5 Research Philisophy .................................................................................. 8 1.6 Research Objectives .................................................................................. 9 1.7 Research Methodology.............................................................................. 9

1.8 Expected Outcomes ................................................................................... 10 1.9 Limitations of the Research ...................................................................... 12

1.10 Research Milistone .................................................................................... 13

CHAPTER TWO: LITERATURE REVIEW ......................................................... 14 2.1 Introduction ............................................................................................... 14

2.2 Solar Assisted Heat Pump (Sahp) Systems ............................................... 15 2.3 Sahp System For Heating And Cooling .................................................... 17

2.4 Sahp System For Drying ........................................................................... 22 2.5 Desalination Technology .......................................................................... 25

2.5.1 SAHP System for Desalination ........................................................ 25

2.5.2 Membrane Desalination Technology ............................................... 27 2.6 Solar Collectors ......................................................................................... 28

2.7 Why Carbon Dioxide ................................................................................ 30 2.7.1 Carbon Dioxide Trans-critical Cycle ............................................... 33 2.7.2 Thermo physical properties of Carbon Dioxide (R-744) ................. 35

2.7.3 Heat Transfer Coefficient of R-744 Compared to R-134a ............... 37 2.7.4 Carbon Dioxide SAHP Systems at low Ambient Temperature ....... 38 2.7.5 COPs of Carbone Dioxide HP Systems ........................................... 38 2.7.6 Greenhouse Gases Emission of Refrigerants ................................... 40

2.7.7 Comparison between R-744 and R-134a Compressors ................... 41 2.8 Effect of Carbon Dioxide Refrigerant On Human Health ........................ 44 2.9 Effect of Refrigerant Charge On the Trans-Critical Co2 Cycle ................ 44 2.10 Optimal Heat Rejection Pressure of Carbon Dioxide in Sahp .................. 45 2.11 Expansion For Carbon Dioxide Sahp ........................................................ 48

x

2.12 Irreversibility in the Co2 Trans-Critical Cycle.......................................... 49

2.13 Summary ................................................................................................... 52

CHAPTER THREE: RESEARCH METHODOLOGY ........................................ 53 3.1 Introduction ............................................................................................... 53 3.2 System And Experiments .......................................................................... 53 3.3 Components of the Sahp System .............................................................. 59

3.3.1 R744 Compressor ............................................................................. 59

3.3.2 Air Finned-Tube Room Evaporator ................................................. 60 3.3.3 Ethylene Glycol – CO2 Evaporator .................................................. 61 3.3.4 Ethylene Glycol – CO2 Gas Cooler (1st Gas Cooler) ....................... 62 3.3.5 Water – CO2 Gas Cooler (2nd Gas Cooler)....................................... 63 3.3.6 Internal Heat Exchanger .................................................................. 64

3.3.7 Expansion Valves ............................................................................. 65

3.3.8 Oil Separator and Pressure Measuring Devices ............................... 65

3.3.9 Carbone Dioxide (R744) Refrigerant ............................................... 65 3.3.10 Mass Flow Meter Devices ............................................................. 66 3.3.11 Experiment’s Set Up Flow Chart ................................................... 67

3.4 Complementary Components .................................................................... 67

3.4.1 Convective Air Dryer ....................................................................... 67 3.4.2 Water (Liquid) Flat Plate Solar Collector ........................................ 69

3.4.3 Water Tank ....................................................................................... 69 3.4.4 Air Gap Membrane Desalination Unit (AGMD) ............................. 70

3.4.4.1 Auxiliary Equipment ........................................................... 72

3.5 Modeling Ans Simulation of the Sahp System ......................................... 73 3.5.1 Compressor Modeling ...................................................................... 73

3.5.2 Modeling of Flat Plate Solar Collector (Liquid Collector) .............. 74

3.5.3 Coefficient of Performance of the System (COP) ........................... 78

3.6 Cfd Simulation Using Ansys Fluid (Flow) ............................................... 78 3.6.1 Gas Coolers ...................................................................................... 79

3.6.1.1 Governing Equations ........................................................... 81

3.6.1.2 CFD Simulation Procedures ................................................ 81

3.6.1.3 Generating the Mesh ............................................................ 82 3.6.1.4 Setting up the model ............................................................ 84

3.6.2 Evaporators .................................................................................... 89 3.6.2.1 Multiphase Flow .................................................................. 89 3.6.2.2 Ethylene Glycol- CO2 Evaporator ....................................... 91

3.6.2.3 Air Finned-Tube Room Evaporator ..................................... 92 3.6.3 Air Convective Dryer ....................................................................... 93

3.7 Summary .................................................................................................... 94

CHAPTER FOUR: RESULTS AND DISCUSSION .............................................. 96 4.1 Introduction................................................................................................ 96 4.2 T-S And P-H Diagrams of the System ...................................................... 97

4.3 System Performance .................................................................................. 98 4.3.1 R744 Compressor ............................................................................. 98 4.3.2 Ethylene Glycol- CO2 Gas Cooler (1st Gas Cooler) ......................... 100

4.3.2.1 Experimental Results ........................................................... 100 4.3.2.2 CFD Simulation Results ...................................................... 102

xi

4.3.3 Internal Heat Exchanger ................................................................... 113

4.3.4 Water – CO2 Gas Cooler (2nd Gas Cooler)....................................... 115 4.3.4.1 Experimental Results ........................................................... 115

4.3.4.2 CFD Simulation Results ...................................................... 115 4.3.5 Air Finned Tube Room Evaporator.................................................. 118

4.3.5.1 Experimental Results .......................................................... 118 4.3.5.2 CFD Simulation Results .................................................... 120

4.3.6 Ethylene Glycol - CO2 Evaporator ................................................... 127

4.3.6.1 Experimental Results ......................................................... 127 4.3.6.2 CFD Simulation Results ..................................................... 131

4.4 Complementary Components .................................................................... 136 4.4.1 Air Convective Dryer ....................................................................... 136 4.4.2 Water (Liquid) Flat Plate Solar Collector ........................................ 141

4.4.3 Air Gap Membrane Desalination Unit (AGMD) ............................. 145

4.5 Coefficient of Performance of the System (COP) ..................................... 146

4.6 Summary .................................................................................................... 147

CHAPTER FIVE: CONCLUSION .......................................................................... 149 5.1 Conclusion ................................................................................................. 149

LIST OF PUBLICATIONS ...................................................................................... 153

REFERENCES ........................................................................................................... 154

APPENDIX A ............................................................................................................. 161 APPENDIX B ............................................................................................................. 164

APPENDIX C ............................................................................................................. 172

APPENDIX D ............................................................................................................. 175 APPENDIX E ............................................................................................................. 181 APPENDIX F ............................................................................................................. 182

APPENDIX G ............................................................................................................. 184 APPENDIX H ............................................................................................................. 185

APPENDIX I .............................................................................................................. 188 APPENDIX J .............................................................................................................. 190

xii

LIST OF TABLES

Table 1.1 Research Milestone 13

Table 2.1 Characteristics of Some Refrigerants 41

Table 2.2 Some Symptoms of Inhaling CO2 45

Table 3.1 Boundary Conditions for 1st Gas Cooler 87

Table 3.2 Solution Methods Used for Gas Coolers 87

Table 3.3 Under Relaxation Factors for Gas Coolers 88

Table A.1 Thermo-physical Properties of R744, and Ethylene Glycol

50% in the 1st Gas Cooler 161

Table A.2 Thermo-physical Properties of Water at Different Temperature 162

Table A.3 Thermo-physical Properties for the Refrigerant (R744) and

Water in the 2nd Gas Cooler 162

Table A.4 Thermo-physical Properties of Refrigerant (R744) and

Ethylene Glycol 50% in Evaporators 162

Table A.5 Thermo-physical Properties of Ethylene Glycol 50% at

Different Inlet Temperature to Evaporator 163

Table A.6 Boundary Conditions for 2nd Gas Cooler 163

Table E.1 Additional Experimental Results 181

Table H.1 Experimental Data Shown in Figure 5.87 185

Table H.2 Incident Solar Radiation [W/m2] of 9th of May 187

Table J.1 Experimental Results of AGMD 190

xiii

LIST OF FIGURES

Figure 1.1 Energy Consumption for District Heating in Sweden through

Several Decades 4

Figure 1.2 Flow Chart of Research Methodology 11

Figure 2.1 Diagram of SAHP system for water heating 15

Figure 2.2 Example of Carbon Dioxide Commercial Dryer 24

Figure 2.3 Types of membrane distillation: A) DCMD, B) AGMD, C)

VMD, D) SGMD 28

Figure 2.4 Different types of Collectors Worldwide 2012 29

Figure 2.5 Thermodynamic properties of Carbon Dioxide 35

Figure 2.6 Pressure- Temperature Phase Diagram of Carbon Dioxide. 37

Figure 2.7 COP behavior of CO2 system and conventional (baseline)

system at varying ambient temperature 38

Figure 2.8 Calculated COP as a function of the evaporation temperature

tE 40

Figure 2.9 Pictures of R-134a and Carbon Dioxide Compressors 42

Figure 2.11 Comparison of Power Consumption from R-744 and R134

Compressors 43

Figure 2.12 Comparison between relative Energy Consumption of CO2 and

R-134a Compressors used for Coca Cola Double Door Bottle

Cooler and Coca Cola Vending Machine with Fans, Lights and

Motors 44

Figure 2.13 Effect of Outlet Temperature of the Gas Cooler on the Optimal

Heat Rejecting Pressure of CO2 Trans-critical Cycles with

Throttling Valve and Expander 47

Figure 2.14 Effect of Evaporating Temperature on the Optimal Heat

Rejecting Pressure of CO2 Cycles with Throttling Valve and

Expander 48

Figure 2.15 Results of Expansion process for CO2 trans-critical Cycle 49

Figure 3.1 Schematic Diagram of Carbon Dioxide Solar Assisted Heat

Pump System for Space Cooling, Water heating, Drying, and

Desalination 54

xiv

Figure 3.2 P-h diagram of Carbon Dioxide Trans-critical Cycle 56

Figure 3.3 Schematic Diagram of Carbon Dioxide Heat Pump System

Located at NTNU- Experimental Room Number 3 58

Figure 3.4 Picture of the Complete R744 HP System at NTNU 59

Figure3.5 Flow Chart of the Experiment 66

Figure 3.6 Schematic of Water Tank 69

Figure 3.7 Schematic of Air Gap Membrane Desalination 71

Figure 3.8 Cross Section of the Liquid Solar Collector 77

Figure 3.9 Simulation Flow Chart 80

Figure 3.10 Preview of Fluids inside Inner and Outer Tubes in Ethylene

Glycol- CO2 Gas Cooler 82

Figure 3.11 Named Selections Preview for Ethylene Glycol- CO2 Gas

Cooler 83

Figure 3.12 Mesh Preview for Ethylene Glycol- CO2 Gas Cooler 83

Figure 3.13 Mesh Quality Report 84

Figure 3.14 Setup Options Ethylene Glycol- CO2 Gas Cooler 84

Figure 3.15 Preview of General Settings of the Model 85

Figure 3.16 K-epsilon (2eqn) Choices 86

Figure 3.17 Solution Initialization and reference frame for 1st Gas Cooler 88

Figure 3.18 Gas-Liquid Flow Regimes in Vertical Tube 91

Figure 3.19 Model Options Followed in Simulation of the Room

Evaporator 93

Figure 4.1 Figure 4.1: T-S Diagram of the solar assisted heat pump

system 97

Figure 4.2 P-h Diagram of the solar assisted heat pump system 97

Figure 4.3 Suction pressure [bar] of the Compressor 98

Figure 4.4 Discharge pressure [bar] 99

Figure 4.5 Variation of Refrigerant Temperature with Discharge pressure

at Constant Suction Pressure 99

xv

Figure 4.6 Mass Flow Rate [kg/m] of Refrigerant (R744) 100

Figure 4.7 Experimental Inlet and Outlet Temperatures of the Refrigerant

(R744) and Ethylene Glycol 50% in the 1st Gas Cooler 101

Figure 4.8 Pressure Drop/ Difference of R744 in the 1st Gas Cooler 101

Figure 4.9 Mass Flow Rate [kg/m] of Ethylene Glycol in the 1st Gas

Cooler 102

Figure 4.10 Scaled Residual 103

Figure 4.11 Static Temperature Contour of the Refrigerant in 1st Gas

Cooler 104

Figure 4.12 Contour of Total Temperature of Refrigerant in 1st Gas Cooler 104

Figure 4.13 Contour of Static Temperature for Inner Tube of the 1st Gas

Cooler 105

Figure 4.14 Contour of Static Temperature of Ethylene Glycol in 1st Gas

Cooler 105

Figure 4.15 Contour of Static Temperature of Outer Tube of the 1st Gas

Cooler 106

Figure 4.16 Contour of Static Temperature for All Parts of the 1st Gas

Cooler 106

Figure 4.17 Static Pressure Contour of R744 in 1st Gas Cooler 107

Figure 4.18 Contour of Dynamic Pressure (Pascal) of R744 108

Figure 4.19 Contour of Refrigerant (R744) Velocity (m/s) 109

Figure 4.20 Contour of Wall Shear Stress for R744 Tube 109

Figure 4.21 Contour of Wall Shear Stress for Ethylene Glycol Tube 110

Figure 4.22 Contour of Static Temperature of Refrigerant for Water- CO2

Gas Cooler (1st) 111

Figure 4.23 Contour of Static Temperature of Water for water- CO2 Gas

Cooler (1st) 111

Figure 4.24 Contour of Static Pressure of Refrigerant in Water- CO2

Gas Cooler (1st) 112

Figure 4.25 Effects of water Inlet Temperature on Outlet Temperature of

both Refrigerant and Water in 1st Gas Cooler 113

xvi

Figure 4.26 Inlet and Outlet Temperature of R744 in the Internal Heat

Exchanger 114

Figure 4.27 Pressure Drop/ Difference in the Internal Heat Exchanger 114

Figure 4.28 Inlet and Outlet Temperature of R744 in the 2nd Gas Cooler 115

Figure 4.29 Scaled Residual for 2nd Gas Cooler 116

Figure 5.30 Contour of Static Temperature of Refrigerant (R744) in 2nd

Gas Cooler 117

Figure 4.31 Contour of Static Pressure of Refrigerant (R744) in 2nd Gas

Cooler 117

Figure 4.32 Contour of Static Temperature of Water in 2nd Gas Cooler 118

Figure 4.33 Outlet Temperature of R744 in the Room Evaporator 119

Figure 4.34 Pressure Drop/Difference [bars] in the Room Evaporator 119

Figure 4.35 Inlet Temperature of Air in the Room Evaporator 120

Figure 4.36 Plate Temperature in the Room Evaporator 120

Figure 4.37 Scaled Residual 121

Figure 4.38 Static Temperature of R744 in the Room Evaporator 121

Figure 4.39 Contour of Static Temperature of Fins and Copper tube in the

Room Evaporator 122

Figure 4.40 Contour of Static Pressure for R744 (Pressure Difference) in

Room Evaporator 122

Figure 4.41 Contour of Velocity Magnitude (m/s) of Refrigerant 123

Figure 4.42 Contour of Phase 1 (Gas Phase) of Refrigerant 124

Figure 4.43 X-Y Plot of Phase 1(Gas Phase) of the Refrigerant 125

Figure 4.44 Contour of Phase 2 (Liquid Phase) of the Refrigerant 125

Figure 4.45 X-Y Plot of Phase 2 (Liquid Phase) of the Refrigerant 126

Figure 4.46 Contour of Specific Heat of the Two Phase of Refrigerant 126

Figure 4.47 X-Y Plot of Density of the Two Phase of Refrigerant 127

Figure 4.48 Outlet Temperature of Refrigerant (R744) from Ethylene

Glycol-CO2 Evaporator 128

xvii

Figure 4.49 Difference between Inlet and Outlet Temperatures of Glycol in

Ethylene Glycol-CO2 Evaporator 128

Figure 4.50 Inlet Temperature of Glycol in Ethylene Glycol-CO2

Evaporator 129

Figure 4.51 Pressure Drop (Difference) of Refrigerant (R744) in Ethylene

Glycol- CO2 Evaporator 130

Figure 4.52 Amount of Heat [KW] Given to Ethylene Glycol in

Evaporator 130

Figure 4.53 Scaled Residuals for Ethylene Glycol- CO2 Evaporator 131

Figure 4.54 Contour of Static Temperature of the Refrigerant (R744) in

Ethylene Glycol – CO2 Evaporator 131

Figure 4.55 Contour of Static Pressure of the Refrigerant (R744) in

Ethylene Glycol – CO2 Evaporator 132

Figure 4.56 Contour of Volume Fraction for phase 1 (Gas) of the

Refrigerant (R744) in Ethylene Glycol – CO2 Evaporator 133

Figure 4.57 X-Y Plot of Volume Fraction for phase 1 (Gas) of the


Figure 4.58 Contour of Volume Fraction for phase 2 (Liquid) of the


Figure 4.59 X-Y Plot of Volume Fraction for phase 2 (Liquid) of the


Figure 4.60 Contour of Static Temperature of Ethylene Glycol in Ethylene

Glycol – CO2 Evaporator 135

Figure 4.61 Outlet Temperature of Refrigerant (R744) and Ethylene

Glycol from Evaporator at Different Inlet Temperature of

Ethylene Glycol 136

Figure 4.62 Scaled Residuals 137

Figure 4.63 Contour of Static Temperature of Refrigerant (R744) in Dryer 138

Figure 4.64 Contour of Static Temperature of Fins and Tube of the Dryer 138

Figure 4.65 Contour of Static Pressure of Refrigerant (R744) in Dryer 139

Figure 4.66 Contour of Velocity of Refrigerant (R744) in Dryer 140

Figure 4.67 X-Y Plot of Turbulent Reynolds Number of the Refrigerant

(R744) in Dryer 140

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Figure 4.68 X-Y Plot of Effective Prandtl Number of the Refrigerant

(R744) in Dryer 141

Figure 5.69 Outlet Temperature of Water from the Solar Collector 142

Figure 4.70 Incident Solar Radiation [From 10 am to 4 pm] of 9th of May 142

Figure 4.71 Outlet Temperature of Water from the Collector at Different

Ambient Temperature 143

Figure 4.72 Useful Energy Gained by the Collector at Different Incident

Solar Radiation and Different Ambient Temperature 144

Figure 4.73 Effect of Incident Solar Radiation and Inlet Temperature of

Water on the Collector Efficiency 144

Figure 4.74 Inlet and Outlet Temperatures of feed water (Seawater), and

Coolant Water to the unit 145

Figure 4.75 Production Rate of fresh water from the AGMD Unit 146

Figure 4.76 Experimental and Calculated Heating and Cooling COP of the

System 147

Figure B.1 X-Y Plot of Total Pressure of R744 in Ethylene Glycol- CO2

Gas Cooler 164

Figure B.2 X-Y Plot of Absolute Pressure of R744 in Ethylene Glycol-

CO2 Gas Cooler 164

Figure B.3 X-Y Plot of Static Temperature of Refrigerant in 1st Gas

Cooler 165

Figure B.4 X-Y for Total Temperature of Refrigerant in 1st Gas Cooler 165

Figure B.5 X-Y for Static Temperature of Inner Tube of the 1st Gas

Cooler 166

Figure B.6 X-Y for Static Temperature of Ethylene Glycol in 1st Gas

Cooler 166

Figure B7 X-Y Plot of Total Temperature of R744 in water-CO2 Gas

Cooler at 10 oC Inlet Temperature 167

Figure B8 X-Y Plot of Total Temperature of Water in water-CO2 Gas


Figure B9 X-Y Plot of Total Temperature of R744 in Water-CO2 Gas


Figure B10 X-Y Plot of Total Temperature of Water in Water-CO2 Gas


xix

Figure B11 X-Y Plot of Total Temperature of R744 in waster-CO2 Gas

Cooler at 21.7 oC Inlet Temperature 169

Figure B12 X-Y Plot of Total Temperature of Water in waster-CO2 Gas

Cooler at 21.7 oC Inlet Temperature 169

Figure B.13 Electric Current (A) for the Electric Heater of Ethylene Glycol

in the 1st Gas Cooler 170

Figure B.14 Electric Current (A) for Pump of Ethylene Glycol in the 1st

Gas Cooler 170

Figure B.15 Amount of Heat Given by the Electric Heater to Ethylene

Glycol in the 1st Gas Cooler 171

Figure C.1 Electric Current (A) for Fan of Air Finned- Tube Evaporator 172

Figure C.2 X-Y Plot for Static Temperature of R744 in the Room

Evaporator 172

Figure C.3 X-Y Plot of Static Pressure for R744 (Pressure Difference) in

Room Evaporator 173

Figure C.4 X-Y Plot of Dynamic Pressure (Pascal) for Two Phase R744 173

Figure C.5 X-Y Plot of Velocity Magnitude (m/s) of Refrigerant 174

Figure D.1 Electric Current (A) for the Pump of Ethylene Glycol in

Evaporator 175

Figure D.2 Electric Current (A) for the Electric Heater of Ethylene Glycol

in Evaporator 175

Figure D.3 Preview of Mesh for Ethylene Glycol – CO2 Evaporator 176

Figure D.4 Contour of Static Temperature for Inner Tube in Ethylene


Figure D.5 Contour of Static Temperature for Outer Tube in Ethylene


Figure D.6 X-Y Plot of Static Temperature of the Refrigerant (R744) in

Ethylene Glycol- CO2 Evaporator 177

Figure D.7 X-Y Plot of Static Temperature of Ethylene Glycol in






xx





Figure F.1 X-Y Plot of Static Temperature of Refrigerant (R744) in Dryer 182

Figure F.2 X-Y Plot of Static Pressure of Refrigerant (R744) in Dryer 182

Figure F.3 Turbulent Viscosity of the Refrigerant (R744) in the Air

Convective Dryer 183

Figure H.1 Useful Energy Gained by the Collector at Different Incident

Solar Radiation and Different Inlet Temperature of Water 186

Figure I.1 Volumetric, Mechanical, and Isentropic Efficiencies of the

compressor at different discharge pressure and 45 bars suction

pressure 188

Figure I.2 Mass Flow Rate of the Refrigerant at Different Compressor

Speed 188

Figure I.3 Electric Current (A) of the Compressor in Experiments 189

xxi

LIST OF ABBREVIATIONS

Ac Area of Collector

Cb Bond Conductance

Cp Specific Heat Capacity

c Clearance Volume

Di Inner Diameter of Tube

F Fin Efficiency

F’ Collector Efficiency Factor

FR Collector Heat Removal Factor

h Specific Enthalpy

hc Convective Heat Transfer Coefficient

I Solar Radiation

K Thermal Conductivity

Mass Flow Rate

N Rotational Speed of Compressor

n Polytropic Index

P Pressure

P1 Suction Pressure

P2 Discharge Pressure

Qu Useful Energy Gain/rejected

t Time

T Temperature

Tpm Mean Plate Temperature

U Overall Heat Transfer Coefficient

UL Overall Heat Loss Transfer Coefficient

Wc Compressor Work

α Collector absorptance

τα Transmittance absorptance product

β Collector Tilt

η Efficiency

μ Kinematic Viscosity

xxii

ρ Density

σ Boltzman’s constant

ε Emittance

δ Plate Thickness

1

CHAPTER ONE

INTRODUCTION

1.1 OVERVIEW

Solar energy is the most attractive form of renewable energy as it comes from the sun,

and available almost every day (Hermann, 2004). Some studies showed that the

current global energy consumption is about 15 TW, while the total energy that could

be gained from solar sun is about 85 TW. It means that solar energy alone has a

capacity to meet the current world energy demand (Sukki et al., 2010). The

applications of solar energy nowadays are very wide. For instance, it could be

converted directly to electricity using Photovoltaic or dish systems. Solar assisted heat

pump (SAHP) systems have recently received great attentions from researchers. These

systems have been considered the most promising as they environmentally friendly,

efficient, and bring various thermal applications for domestic and industrial usage,

such as water heating, drying, space cooling, space heating, refrigeration, and

desalination of water ((Zakaria, 2010), (Shaochun, 2009)). Heat pump (HP) system is

a conventional vapor compression air conditioning system which collects or absorbs

the heat from a heat source, usually air conditioning room, and dissipates it to the

atmosphere. Solar assisted heat pump (SAHP) system is a conventional heat pump

system where solar energy is main or supplementary heat source.

HP systems are designed in order to cool down the interior space by removing

the heat from it and reject it to ambient air through the condenser. In the normal

installation, heat rejection occurs directly to the ambient air, but recently many

applications have been proposed by different researchers in order to recover the

wasted heat. The dissipated heat from the heat pump could cause many problems such

2

as air pollution and global warming. At the same time it could be used in a useful way

in drying, water heating and desalination of seawater, especially in the buildings

running air-conditioner all the day such as hotel and hospitals. By utilizing the waste

heat from air conditioners for various applications, the HP system work on the idea of

recovering or reusing the waste heat.

1.2 CONCEPT OF WASTE HEAT RECOVERY

According to (Senda, 2012), energy conversation coupled with waste heat recovery

have recently become the most major attractive topics for research in most

industrialized countries since the beginning of twenty first century. This great

attention started from the seventieths of last century due to the fact that the oil is a

finite energy source, the significant increase in its prices till now, and the problems

appeared due to the political conflicts as well. Increase in the cost of the fuel has great

effect on the running cost of the fuel based systems. In vehicles, for instance, air

conditioning systems added nearly 35% extra cost (Pathania & Mahto, 2012), so that

the reduction of the air condition load by exploiting the waste heat from the engine

will leads to a significant reduction in the consumed fuel by the vehicles. In addition,

the huge production and usage of oil during the last century led to climatic changes

and problem such as global warming and Ozone depletion due to accumulation of

carbon dioxide and increase its percentage at the atmosphere layer.

Waste heat recovery concept requires all possibilities and efforts in preventing

any potential losses of any form of energies which must be reused or exploited instead

of throwing it away. It includes, for instance, designing and implementation useful

and efficient systems to recover the waste heat from air conditioning systems (Reay,

1979). Waste heat can be either used in different process at same systems, such as

carbon dioxide solar assisted heat pump by

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