Elzaidabi, Abdalla Ali Mohamed (2009) Low energy, wind catcher assisted indirect-evaporative ...

233 Pages·2016·15.5 MB·English

by  Christine Middleton

Low Energy, Wind Catcher Assisted Indirect - Evaporative
Cooling System for Building Applications

Abdalla. A. M. Elzaidabi

Thesis submitted to the University of Nottingham
for the degree of Doctor of Philosophy
September 2008
Contents
Abstract ………………………………………………………………………....viii
Publications ……………………………………………………………………….x
Acknowledgements ………………………………………………………….. .. .xi
Nomenclature …………………………………………………………………....xii
List of tables……………………………………………………………………..xiv
List of figures………………………………………………………………….....xv
C h a p t e r 1
1.0 Introduction ………………………………………………………………….2
1.1 The project aims……………………………………………………………...5
1.2 Research objectives…………………………………………………………..5
1.3 Research methodology……………………………………………………….6
1.4 Thesis layout………………………………………………………………….8

Chapter 2: Buildings Ventilation
2.0 Introduction: scope of this chapter ………………………………………....11
2.1 Purpose of the Ventilation ………………………………………………….11
2.2 Types of buildings ventilation ……………………………………………...13
2.2.1 Infiltration ……………………………………………………………...13
2.2.2 Purpose-provided ventilation ………………………………………….14
2.3 Mechanical ventilation ……………………………………………………..15
2.3.1 Types of mechanical ventilation ……………………………………….15
Abdalla Elzaidabi, PhD thesis, 2008 Page ii
2.3.2 Advantages and disadvantages of mechanical ventilation……………..18
2.4 Natural Ventilation ……………………………………………………….....19
2.4.1 Natural ventilation concept …………………………………………….19
2.4.2 Elaborations of the Basic Strategies …………………………………....23
2.4.3 Advantages of Natural Ventilation ……………………………………..25
2.4.4 Disadvantages of Natural Ventilation ………………………………….25
2.5 Natural ventilation and indoor air quality …………………………………..26
2.6 Natural ventilation and passive cooling ………………………………….....27
2.7 Solar induce ventilation ……………………………………………………..28
2.7.1 Solar Chimney ………………………………………………………….28
2.7.2 Trombe wall …………………………………………………………....30
2.8 Wind-induced natural ventilation …………………………………………...31
2.8.1 Wind Cowl ventilation ……………………………………………….....31
2.8.2 Wind Catcher / Wind tower …………………………………………….34
2.8.2.1 Historical background of wind catcher …………………………..35
2.8.2.2 Principles of modern Wind catchers ……………………………..38
2.8.2.3 Advantages of the modern wind catcher ………………………....40

Chapter 3: Evaporative cooling and psychometric energy Core
3.0 Introduction…………………………………………………………………42
3.1 Evaporative cooling ………………………………………………………...42
3.2 Evaporative coolers ………………………………………………………...45
3.3 The Psychrometric chart and Air Properties ……………………………….47
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3.4 Factors affecting evaporation rate ………………………………………….48
3.5 Evaporative cooler designs …………………………………………………52
3.5.1 Direct evaporative cooling (DEC) ……………………………………..52
3.5.2 Indirect evaporative cooling (IEC) …………………………………….57
3.5.2.1 Factors affecting the (IEC) performance ………………………...59
3.5.3 Direct- indirect evaporative cooling (Two stage Evaporative
Cooling)………………………………………………………………………... 60
3.6 Conclusions……………………………………………………………….....61

Chapter 4: Experimental evaluation of the performance of an Indirect
Evaporative Cooling system employing a (PEC)

4.0 Scope of the chapter ………………………………………………………...64
4.1 Introduction ………………………………………………………………....64
4.2 System description ………………………………………………………….68
4.3 Operation of the PEC System ……………………………………………….69
4.4 Experimental setups ………………………………………………………...70
4.5 Results and discussion ……………………………………………………....72
4.5.1 Results of the 1 kW pre – prototype …………………………………...74
4.5.2 Results of the 2 kW pre – prototype …………………………………...76
4.5.3 Results of the 3 kW pre – prototype …………………………………...77
4.5.4 Discussion of the results ……………………………………………….80
4.6 Improvements of the performance of the PEC cooling system …………….80
4.6.1 Performance of the modified system ……………………………………..82
4.6.1.1 Effect of the air flow passage ………………………………………..82
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4.6.1.2 Effect of the pads surface wetting area ……………………………...83
4.7 Design and construction of a full prototype PEC unit ……………………..84
4.7.1 Geometrical description ……………………………………………….84
4.7.2 Performance evaluation of the prototype system ……………………...86
4.8 Conclusions ………………………………………………………………....90

Chapter 5: Psychrometric Energy Core (PEC) integrated –Wind
Catcher System

5.0 Scope of the chapter ………………………………………………………...92
5.1 Introduction and background ……………………………………………….92
5.2 System Description …………………………………………………………95
5.3 Fabrication of the system ………………………………………………….100
5.4 System operation …………………………………………………………..103
5.4.1 Cooling mode ………………………………………………………....103
5.4.2 Ventilation mode ……………………………………………………...104
5.5 Flow verification using Computational Fluid Dynamics (CFD) …………..105
5.5.1 Methodology …………………………………………………………..105
5.5.2 Results of the modelling ……………………………………………....116
5.6 Conclusions ………………………………………………………………....120

Chapter 6: Experimental evaluation of the combined PEC wind
catcher system

6.0 Introduction ……………………………………………………………….122
6.1 Test methodology …………………………………………………………122
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6.1.1 Test Rig setup .......................................................................................124
6.2 Tests results and discussion ……………………………………………….126
6.2.1 System air pressure drop ……………………………………………...127
6.2.2 Effect of the internal fans on the temperature, relative humidity and the air
flow at a given wind speed and ambient temperature …………………….......127
6.2.2.1 The effect on temperatures when supply and exhaust fan off …...129
6.2.2.2 The effect of fans and water flow rate on the air humidity ……...130
6.2.3 Impact of the ambient temperature, air flow rate and water flow rate on
evaporative cooling rate ………………………………………………………..132
6.2.4 The effect of PEC channel width size ………………………………....135
6.3 Cooling load & COP ……………………………………………………....142
6.4 Discussion of the results …………………………………………………...144
6.5 Conclusions ………………………………………………………………...149
Chapter 7 General Discussion and Conclusions
7.1 General discussions ………………………………………………………..152
7.1.1 Performance of a three pre-prototype PEC …………………………....153
7.1.2 Combined PEC wind catcher system, design and experimental
evaluation……………………………………………………………………....154
7.2 Recommendation for further research ……………………………………..155

References ……………………………………………………………………..158
Bibliography ……………………….................................................................164

Appendix I ……………………………………………………………………..171
Abdalla Elzaidabi, PhD thesis, 2008 Page vi
Appendix II …………………………………………………………………..186

Appendix III ………………………………………………………………….193

Appendix IV…………………………………………………………………..197

Appendix V…………………………………………………………………...202

Appendix VI ………………………………………………………………….205

Abdalla Elzaidabi, PhD thesis, 2008 Page vii
Abstract
Increased consciousness of the environmental problems has aroused people’s
interest of renewable energy systems, especially the application of green features in
buildings.
The demand for air conditioning / cooling in domestic and non-domestic buildings is
rising throughout the world; this increases the reliance on conventional fuels and the
global warming effect from greenhouse gas emissions. Passive cooling and energy
efficient design can substantially reduce reliance on fuel based heating and cooling.
Passive and Hybrid Downdraught Cooling, in different forms, is now technically
viable in many parts of the world. This has been established through a combination
of research projects.
In some hot arid regions, a major part of the energy consumed consists of air-
conditioning requirements. Alternative methods, using passive cooling techniques,
can assist in reducing the conventional energy consumption in buildings.
Evaporative cooling, which can be tracked back several hundreds of years in ancient
Egypt and Persia [1–3], is one of the most effective strategies, because of the
enormous latent heat needed for evaporation of water.
Green features are architectural features used to mitigate migration of various air-
borne pollutants and transmission of air from outside to indoor environment in an
advantageous way [9].

The reduction of fossil fuel consumption and the associated decrease in greenhouse
gas emissions are vital to combat global warming and this can be accomplished, in
Abdalla Elzaidabi, PhD thesis, 2008 Page viii
part, by the use of natural ventilation. To assess the performance of several
innovative cooling systems devices and to develop improved models for more
established technology, quantitative measurement of output was necessary. This was
achieved in this study by the development of simply constructed low energy cooling
systems which were calibrated by the innovative use of wind and water as a source.
These devices were found to be consistent and accurate in measuring the
temperature and cooling load from a number of devices. There were some problems
in the original evaporative units. Therefore, a number of modifications have to be
made to enhance the systems performance. The novel Windcatcher – PEC cooling
system was assessed and different cooling loads were achieved.

Abdalla Elzaidabi, PhD thesis, 2008 Page ix
PUBLICATION

The following articles has been published by the author during preperation of this
thesis.

1- Elzaidabi, A. A.; Omer, S. A and Riffat, S. B. (September 2007) Development
and Experimental Evaluation of Indirect Evaporative Cooling System Employing a
Psychometric Energy Core System, SET6th, Chile, Santiago.
2- Elzaidabi, A. A.; Omer, S. A and Riffat, S. B. (August 2008) Experimental
evaluation of a novel combined Wind catcher - indirect evaporative cooling System
for cooling application in buildings, SET7th , Seoul, Korea.
3- Elzaidabi, A. A.; Shauli Ma, Omer, S. A and Riffat, S. B. (August 2008)
Experimental performance of a novel Liquid Desiccant Dehumidification

System. SET7th, Seoul, Korea.

(cid:1) Other publications during author research period are:

1- Elzaidabi, A. A.; Omer, S. A, Design approach for sizing a hybrid fuel cell-solar
system for building energy, ATE - 2007- 410R1 (under review).
2- Elzaidabi, A. A.; Omer, S. A, (2006) Fuel cells a technology for sustainable
renewable energy supply- an approach for a hybrid fuel cell-solar system for
building energy, ses.org – Sudan.
3- Garba, M. M., Elzaidabi A., Omer, S. and Riffat, S.B, (2008), Environment and
Experimental Evaluation of Passive Solar Cooking System for Sustainable
Applications, SET7th, Seoul, Korea.
Abdalla Elzaidabi, PhD thesis, 2008 Page x