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Title of Thesis

Experimental Investigation and Mathematical Modeling of a Low Energy Consuming Hybrid Desiccant Cooling System for the Hot and Humid Areas of Pakistan

Author(s)

Anjum Khalid

Institute/University/Department Details
Department of Mechanical Engineering / NED University of Engineering & Technology, Karachi
Session
2008
Subject
Mechanical Engineering
Number of Pages
222
Keywords (Extracted from title, table of contents and abstract of thesis)
Investigates, Mathematical, Desiccant, Significantly, Demonstrated, Absorber, Staggered, Desiccant, Hybrid, Mathematical, Modeling, Humid

Abstract
This experimental and simulation study investigates the potential of using a solar assisted hybrid desiccant cooling system (SHDCS) for air conditioning applications for Pakistan. A review of literature reveals that compared to the conventional vapour compression cycle this cycle could offer saving in overall primary energy. Since the cycle is based on supply of conditioned ventilation air it has significantly lower environmental impact.
A gas fired hybrid desiccant cooling test rig has been installed at the Energy Conservation Laboratory
NED to study the performance of various components. These experiments enabled understanding of the system and helped develop effect of individual components on the system performance. Important parameters of system components established from the experiments were used as input to the TRNSYS simulation model.
The simulation studies have been based on a well established transient energy software TRNSYS.Specific to this work a mathematical model of Modified Cooler was prepared from basic principles and added as module to TRNSYS. Addition of this component resulted in an increases of the COPp-s by a factor of 1.065 for the weather of Lahore. Besides COP; all system parameters showed an improvement due to the addition of this component.
Six case studies based on SHDCS have been performed for Karachi and Lahore. The results so obtained established that the advantage of using SHDCS depends on the climatic conditions. SHDCS offers considerable promise for Lahore i. e., it shows that of the seven month summer cooling season the desiccant cooling system alone suffices for three month – April, May and October. However for Karachi summer, characterized by high humidity, SHDCS does not provide acceptable temperature and humidity conditions without auxiliary air conditioning.
The source of thermal energy needed for regeneration plays an important part in the overall success of the desiccant cooling scheme. To reduce the use of conventional energy, in this case natural gas, a solar collector has been included in the study. Micro analysis of the flow and heat transfer phenomenon taking place inside inclined solar air collector was studied using CFD software, which demonstrated that low heat transfer between air and absorber can be improved by using staggered fins. It was also shown that the fin configuration coupled with low flow velocity helped increase heat transfer in the absorber duct by increasing heat transfer area, mixing and residence time.
Energy, economic and environmental impact of the solar collectors was also studied and payback periods for energy, Carbon emission and monetary investment have been found to be 1.5 years, 1 year and 14 years respectively.
The success of the desiccant cooling system is strongly associated with cost of the thermal energy. Combined heat and power systems offer an opportunity of providing this energy at no additional cost. The latter study has been suggested to be taken up as future work.
 

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3,222 KB
S. No. Chapter Title of the Chapters Page Size (KB)
1 0 CONTENTS

 

iii
67 KB
2

1

BACKGROUND OF THE PRESENT STUDY

1.1 Introduction
1.2 Aims and Scope of Research
1.3 Research Objectives
1.4 Formulation of Problem
1.5 Research Methodology
1.6 Structure of the Thesis
1.7 Conclusion

1
266 KB
3 2 OVERVIEW OF THE RELEVANT LITERATURE

2.1 Previous Works
2.2 Overview of Cooling Technologies
2.3 Conclusion

11
338 KB
4 3 BASIC PRINCIPLES OF ADSORPTION

3.1 Introduction
3.2 Adsorption Principles
3.3 Classification of Adsorbents
3.4 Desiccant Cycle
3.5 Theory of Desiccant Wheel
3.6 Conclusions

36
378 KB
5 4 EXPERIMENTAL WORK

4.1 Introduction
4.2 Description of System
4.3 Data Logging System
4.4 Rig Operation
4.5 Solar Assisted Desiccant Cooling System
4.6 Performance Indices
4.7 Component Performance Calculations
4.8 Analysis of Measurement Results
4.9 Conclusions

48
400 KB
6 5 MODIFIED EVAPORATIVE COOLER

5.1 Introduction
5.2 Evaporative Cooling
5.3 Modified Cooler and its Modeling
5.4 Integration of Modified Cooler Model in TRNSYS
5.5 Procedure for Creating a New TRNSYS Component
5.6 Validation of Modified Cooler Model
5.7 Modified Cooler Simulation Results
5.8 Conclusion

76
321 KB
7 6 MODELING OF DESICCANT COOLING SYSTEM

6.1 Introduction
6.2 TRNSYS Simulation Procedure
6.3 Project Setup in TRNSYS simulation studio
6.4 Solver Schemes
6.5 Simulation of Desiccant Cooling System in TRNSYS
6.6 Weather Input File
6.7 Climatic Conditions and Regeneration Temperature
6.8 Component Parameter Settings
6.9 Calculation Method in TRNSYS
6.10 Validation of TRNSYS Model
6.11 Simulation Case Studies
6.12 Results and Discussion
6.13 Conclusion

92
555 KB
8 7 SOLAR COLLECTOR DESIGN FOR SOLAR ASSISTED DESICCANT COOLING

7.1 Introduction
7.2 Pakistan’s Solar Energy Resources
7.3 Solar Collector
7.4 Practical Considerations for Solar Collectors
7.5 Solar Air Collector
7.6 Thermal Analysis of Solar Air Collector
7.7 Modeling Procedure in CFD
7.8 Modeling Solar Air Collector – Fluent Analysis
7.9 Results and Discussion - Fluent
7.12 TRNSYS Simulation of Solar Collector
7.13 Conclusions

129
692 KB
9 8 LIFE CYCLE ASSESSMENT OF SOLAR AIR COLLECTOR

8.1 Introduction
8.2 Energy Scenario of Pakistan
8.3 Life Cycle Analysis
8.4 Life Cycle Assessment of Solar Air Collector
8.5 Calculation of Energy, Environment and Monetary Indicators 164
8.6 Results and Discussion
8.7 Conclusions

160
233 KB
10 9 CONCLUSIONS AND PROSPECT FOR FUTURE WORK

9.1 Introduction
9.2 Conclusions
9.3 Suggestions for Further Work

177
117 KB
11 10 APPENDICES

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