EVAPORATIVE COOLING FOR THERMAL COMFORT IN BUILDINGS

Transcription

1 EVAPORATIVE COOLING FOR THERMAL COMFORT IN BUILDINGS by DEV ANAND HINDOLIYA Submitted in fulfillment of the requirements of the degree of Doctor of Philosophy to the CENTRE FOR ENERGY STUDIES INDIAN INSTITUTE OF TECHNOLOGY, DELHI JANUARY, 2005

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3 To My Parents

4 CERTIFICATE This is to certify that the thesis entitled "Evaporative Cooling for Thermal Comfort in Buildings" being submitted by Mr. Dev Anand Hindoliya for the award of the degree of Doctor of Philosophy is a record of original bonafied research work carried out by him under my guidance and supervision. The matter contained in this thesis has not been submitted in part or in full to any other university or institute for the award of any degree/diploma. Dr. S.C. Mullick) Professor Centre for Energy Studies Indian Institute of Technology, Delhi New Delhi

5 ACKNOWLEDGEMENTS I express my deepest sense of gratitude and indebtedness to my supervisor Prof. S.C. Mullick for his invaluable guidance, keen interest and inspiration throughout this research work. I am indebted to Prof. T.C. Kandpal for his constant encouragement, valuable suggestions and support throughout this research work. I avail this opportunity to express my sincere thanks to Pro. M.K.G. Babu, Head, C.E.S., Dr. Avinash Chandra, Dr. S.C. Kaushik, Dr. R.S. Agrawal and Dr. Sanjeev Jain and Dr. Subodh Kumar for their help and encouragement. I owe thanks to Dr. Ashvini Kumar, Dr. Krishan Kant and Dr. Naiem Akhtar for many fruitful discussions and encouragement during this work. I am very grateful to the Secretary, Department of Man Power Planning and Technical Education, Government of Madhya Pradesh, for sponsoring me for carrying out this research work. I am thankful to my colleagues Mr. Rakesh Singhai, Mr. B.K. Chourasia, Mr. Varun Jain, Mr. R.P. Tiwari, Mr. S.Y. Khan, Mr. Atul Chamola, Mr. Pallav Purohit and Mr. Ishan Purohit for their help and support. I wish to convey my thankfulness towards Mr. Kundan Singh Devgan, Mr. M.P. Verma and Mr. O.P. Chawla for their invaluable help during experimental work. I express my deep sense of gratitude for my wife Mrs. Hemlata Hindoliya for her sacrifices, endless tolerance, moral support and providing necessary help during preparation of this thesis. My children Shashank and Disha gave me enthusiastic support during this work. I am thankful to them. I am also thankful to my younger brothers Mr. Amar Nath, Mr. Anil and Mr. Arun for their support and keeping me free from other responsibilities towards family. (Dev Anan. Hindoliya)

6 ABSTRACT High energy consumption and ozone layer depletion due to use of CFCs in vapour compression based air conditioning has shifted the attention -of common user towards low energy consuming devices such as evaporative coolers. Therefore, there is a renewed interest in this area. The present work is a modest attempt to study several aspects associated with the direct evaporative cooling in buildings related to comfort, its geographic range, building parameters, sizing etc. The thesis begins with an introduction and review of available literature on relevant topics. The study to assess the possibilities of achieving thermal comfort using direct evaporative cooling under four of the presently delineated climatic zones based on annual data, has been presented in Chapter 2. In Chapter 3, weather data for 60 Indian cities has been analyzed to determine utilization potential of direct evaporative cooling in India. This work resulted in changed climatic zones that are based on detailed weather data for the summer months and are pertinent to evaporative cooling. The potential hours described in this chapter, were also used to prepare bin data which is required to calculate energy saving of a DEC compared to that of vapour compression system. Some issues related to sizing of DEC have been studied in Chapter 4. The work has resulted in a modified thumb rule for sizing a DEC. Chapter 5 deals with saturation efficiency and its experimental correlations. Simple correlations for saturation efficiency, have been obtained for two different types of aspen pads from experimental data. The correlations have been used to obtain supply condition for simulation of buildings. Chapter 6 takes into account the effects of orientation of wall(s) of a building on room air conditions. The study has been extended to determine the possibilities of employing evaporative cooling when

7 load due to exposure of exterior surfaces increases. It was found that by having the suitable ACH and indoor air motion (velocity), the comfort can be obtained in the building. Chapter 7 presents a study to determine the effects of some building design/constructional parameters on room air conditions in a building cooled by an evaporative cooler. It is seen that effect of glazed area is more prominent than other factors. Effect of roof transmittance is prominent compared to that of wall. Chapter 8 summarizes the principal findings of the present work.

8 CONTENTS CERTIFICATE ACKNOWLEDGEMENT ABSTRACT LIST OF FIGURES 1. INTRODUCTION Evaporative Cooling The Indoor Air Requirement and Evaporative Cooling Eco-Friendly Nature and Cost Effectiveness Energy Conservation with Evaporative Cooling Thermal Comfort and its Assessment Effect of Saturation Efficiency of a DEC and Indoor Air Velocity 1.11 on Room Conditions 1.7 Review of Previous Work in Relevant Areas Evaporative Coolers: Various Types and Performance Passive Evaporative Cooling Solar Energy Utilization for Space Cooling Desiccant Assisted Evaporative Cooling The Present Study DIRECT EVAPORATIVE COOLING FOR THERMAL COMFORT IN A BUILDING IN FOUR CLIMATE ZONES OF INDIA Representative Locations in Different Climatic Zones of India The Room Specifications and Simulation Parameters 2.3

9 2.3 Analysis of Room Conditions Hot and Dry Climatic Zone Composite Climatic Zone Moderate Climatic Zone Warm and Humid Climatic Zone Thermal Sensation of Occupants Concluding Remarks ASSESSMENT ^17 UT" "ATIn N pntr.nti Ai. OF DIRECT EVAPORATIVE COOLING FOR INDIA The Available Weather Data Base Limiting Ambient Conditions Utilization Potential of Direct Evaporative Cooling The Evaporative Cooling Zones Energy Saving Potential of Direct Evaporative Cooling Estimation of Input Power Estimation of Energy Saving Computation of Seasonal Energy Saving for Delhi Concluding Remarks SIZING OF A DIRECT EVAPORATIVE COOLER Sizing of a DEC using Load Calculation Solar Radiation on Wall(s), Roof and Window Heat Gain Through Building Components Indoor Design Temperature 4.4 ii

10 4.2 Use of Thumb Rule Modified Thumb Rule Effect of Internal Sensible Load Concluding Remarks EXPERIMENTAL CORRELATIONS FOR SATURATION EFFICIENCY OF A DIRECT EVAPORATIVE COOLER 5.1 Experimental Test Facility Mixing Chamber Receiving Chamber Discharge Chamber Blower Flow Nozzles Specification of a Direct Evaporative Cooler Used for 5.4 Experimentation 5.3 Experimental Determination of Cooler Saturation Efficiency Correlations for Saturation Efficiency Concluding Remarks THERMAL COMFORT IN A ROOM FOR DIFFERENT ORIENTATIONS OF WALL(S) USING DIRECT EVAPORATIVE COOLING The Specifications of the Room and Simulation Parameters The Effects of Orientation and Exposure of Exterior Surfaces Achieving Thermal Comfort Concluding Remarks 6.14 iii

11 7. EFFECTS OF BUILDING DESIGN PARAMETERS ON THERMAL COMFORT IN AN EVAPORATIVELY COOLED BUILDING Room Specifications and Simulation Parameters Effect of Solar Absorptance of Exterior Wall(s) Effect of Solar Absorptance of Roof Effect of Thermal Resistance of Exterior Walls Effect of Heat Capacitance of Exterior Walls Effects of Size and Number of Glazing of Window Sensitivity Analysis Concluding Remarks CONCLUSIONS REFERENCES APPENDICES A Assessment of Thermal Comfort for a few Ambient Conditions: A case Study B- FORTRAN Program for Computation of Sol-Air Temperature on Different Walls and Roof of a Building C - Representation of Hourly Values of Ambient Conditions for Summer Months of April, May and June for Major Cities of India D- Heat Transfer Coefficients in Aspen Cooling Pads iv