Design analysis and studies on some solar air heaters

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DESIGN ANALYSIS AND STUDIES ON SOME SOLAR AIR HEATERS

VINOD KUMAR SHARMA

THESIS SUBMITTED TO THE

INDIAN INSTITUTE OF TECHNOLOGY, DELHI FOR THE AWARD OF THE DEGREE OF

DOCTOR OF PHILOSOPHY

CENTRE FOR ENERGY STUDIES

INDIAN INSTITUTE. OF TECHNOLOGY, DELHI

JULY, 1982

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*

* TO MY PARENTS

* * * * * * * * * * * * * * * * * * * *

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it CERTIFICATE

It is certified that the thesis entitled, "Design analysis and studies on some solar air heaters" has been completed by Mr. V. K. Sharma under my supervision. It

is original in nature and I have permitted the candidate to submit it for the degree of Doctor of Philosophy in Solar Energy.

(H. P. Garg)

M.Sc., Ph.D.

Professor, Centre of Energy Studies

Indian Institute of Technology New Delhi 110016

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ACKNOWLEDGEMENT

It is my great pleasure and privilege to express profound indebtedness to Professor H.P. Garg for his invaluable supervision, perennial source of help, ever- lasting inspiration, stimulating discussions and unstinting guidance and unfailing help in suggesting the problems at all stages of this work as a consequence of which the present study reached fruition. To me instead of being formal and official, he has always been informal, cordial and homely.

Grateful thanks are due to Prof. M.S. Sodha, Prof. S.S. Mathur, Prof. S.P. Sabberwal, Prof. B.C.

Raychaudhari, Dr. G.N. Tiwari and Dr. S.C. Kaushik for their active interest and support.

The most valuable suggest ions and discussions with Dr. A.K. Bhargava and Dr. B. Bandyopadhyay were invaluable in planning, execution, and interpretation of the problem for which I wish to express my heart felt thanks and gratitude.

Due interest shown by Dr. A.R. Shukla,

Dr. P.K. Bansal, Dr. Ashvini, Dr. Kandpal, Mr. Avinash, Mr. R.C. Agnihotri, Mr. S.N. Garg, Dr. (Ms.) Usha Singh and all other faculty members of the Centre of Energy Studies is thankfully acknowledged.

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I wish to appreciate the cooperation extended by technical and administrative staff of the Centre of

Energy Studies throughout the course of the work. In particular, I am thankful to Shri V.K. Jain and

Mr. Ramesh Kumar Rohella.

It gives me great pleasure to appreciate

Mrs. Shashikala for patiently typing the manuscript and also Mr. Jagdish for making the drawings.

Finally, I feel it my duty to thank Tata Energy Research Institute, Bombay, for the financial assistance during the course of the present study.

(VINOD KUMAR SHARMA)

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SUMMARY

This dissertation deals with the analytical and experimental analysis of flat-flate solar air heaters both of conventional and of novel type. The main objective of this thesis is to study the effect of various climatiQ#

design, and operating parameters on the performance of fixed configuration type of few conventional and novel

type of solar air heaters in conventional and unconventional modes of operation.

The transient analysis of solar air heater has been attempted in order to determine the dependence of the

transient behaviour on various design parameters. Thorough analysis of heat balance equations of different components of a solar air heater along with experimental validation in some cases, is reported. T-\Jith the help of computer models, the author has seen the effect of flow rate, plate length, selective coating, thermal capacitance, metallic plate thick- ness etc. in a single attempt. The periodic responses

have also been studied for different combinations of Para-- meters, Moreover, an air heater in nonconventional mode of operation has also been studied. This is achieved by making air flow rate time dependent.

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Detailed theoretical analysis of three different

configurations of double exposure solar air heaters has been attempted vigorously. A self consistent periodic analysis of multiple pass solar air heater has been developed

the very first time. So far no meaningful theoretical comparison of this novel type of solar air heater is done with other possible mode of conventional solar air heaters.

The author has developed the theory of a multiple pass solar air heater where air makes four passes before exit.

In this study a single plate air heater with maximum of four glass cover plates is considered. The performance of the system with 1,2 and 3 passes was also conducted.

The effect of number of glass cover plates on the 1, 2, 3 passes has also been investigated.. It is noted that multiple pass solar air heater proposed in this thesis performs much better for low flow rates and large plate length. For small plate length and high flow rates

addition of cover plates does not effect the performance of 2 or 3 passes 'air heater. Moreover, study of aA two pass solar air heater is also reported. The aim of this study was to analyse in as much detail as possible, theoretically, two pass solar air heater and to compare its performance with possible configurations of conventional solar air heater.

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The performance results of two matrix air heater with single and double glazing, using waste iron scraps from the lathe machine, are also presented. These results are compared with those of a conventional type air heater.

Moreover, experimental investigation on a prototype rock- bed solar collector, attempted the first time are also

included. Apart from presenting in brief the basic idea of rock-storage system, it also deals with experimental observations of thermal decay of rock storage mediLmi, its preliminary economic analysis and an overall discussion about its applicability.

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TABLE OF CONTENTS LIST Or FIGURES

LIST OF TABLES NOMENCLATURE CHAPTER -- I

GENERAL INTRODUCTION CHAPTER .- II

TRANSI?IT ANALYSIS OE A SOLAR AIR HEATER OF THE SECOND KIND AND A COMPARATIVE STUDY OF THE STEADY STATE ANALYSIS AND THE PERIODIC ANALYSIS

1-22

23-62

2.1 INTRODUCTION 23-25

2.2

TRANSIENT ANALYSIS OF A SOLAR AIR 25 HEATER OF SECOND KIND

2.2.1 Model Formulation 27-33

2.2.2 Experiment 33-36

2.2.3 Numerical Inputs 36

2.2.3.1 Meteorological data

36

2.2.3.2

Radiative heat transfer coefficient 36-38 2.2.3.3 Natural convective heat transfer 38-39

coefficient

2.2.3.4 Other parameters 39-40

2.2.4 Result and Discussion 41-47 2.3 A COMPARATIVE STUDY OF THE STEADY 48

STATE ANALYSIS AND THE PERIODIC ANALYSIS OF THE AIR HEATER

2.3.1 Energy Balance on Air Heater 48-50

2.3.2 Steady State Solution 50-51

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2.3.3 Periodic Analysis 51-52

2.3.4 Meteorological Data and Fourier Coeff- 52-60 icients

2 .4 CONCLUSION 61-62

CHAPTER

III

EVALUATION OF THE PERFORMANCE OF THE AIR HEATERS; 63-102 CONVENTIONAL DESIGNS AND IN NONCONVENTIONAL MODE

OF OPERATIONS

3.1

3.2 3.2.1 3.2.2

3.2.3 3.2.4 3.3

3.4 INTRODUCTION

EVALUATION OF THE PERFORMANCE OF THE AIR HEATERS OF C CNVENTIONAL DESIGNS Structure of the Air Heaters

Mathematical Modelling Numerical Inputs

Result and Discussion

AN AIR HEATER IN NONCONVENTIONAL MODE OF OPERATIONS

CONCLUSION

63-65 65-66 66-69 69-74 74-78

78-91 91-•97

CHAPTER - I V

THEORETICAL ANALYSIS-OF SOME CONFIGURATION OF DOUBLE EXPOSURE SOLAR AIR HEATERS

4.1 INTRODUCTION

4.2 MATHEM'1TICAL FORMULATION 4.3 NUMERICAL INPUTS

4.3.1 Meteorological Data

4.3.2 Dimensions and Physical Constants 4.3.3 Heat-transfer Coefficients

4.4 RESULT AND DISCUSSION 4.5 CONCLUSION

103-128

103-105

105-112

113

113 113-116

116-117

118-119

128

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5.3.

5 .2 5.2.1 5.2.2 5.2.3 5.3 5.3.1 5.3.2 5.4

INTRODUCTION

STUDY OF A TWO PASS SOLAR AIR HEATER

Mathematical Modelling

Numerical Inputs

Result and Discussion

MULTIPLE PASS

SOLAR AIR HEATER

Theoretical Formulation

Numerical Inputs CONCLUSION

129-174 129-131 132 132-136 136-138 138-144 144-145 145-152 152-173 173-174

CHAPTER - V

THEORY OF A MULTIPLE PASS SOLAR AIR HEATERS

CHAPTER - VI

PERFORMPNCE STUDIES ON SOLAR AIR

HEATER WITH

175-233 POROUS ABSORBERS.

6.1 INTRODUCTION 175-179

6.2

STUDIES ON SINGLE AID DOUBLE GLAZED 179-180 MATRIX TYPE SOLAR AIR HEATERS

6..2.1 Performance Equation 180

6.2.2 Experimental Procedure 180-181

6.2.3 Air Heaters Tested 181

6.2.3.1 Type-I : Matrix type solar air heater 182.

6.2.3.2 Type-II: Matrix type solar air heater 182-184 with wire mesh

6.2.4 Result and Discussion 184-208 6.2.5 Preliminary

_Energy

and

Economic Analysis

208-212 6.3 INVESTIGATION OF ROCK-BED

SOLAR

212 COLLECTOR CUM STORAGE SYSTEM

6.3.1 Theoretical Consideration 212-215 6.3.2 Collector

Construction

215-218

6.3.3 Instrumentation 218

6.3.4 Performance 218-230

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Xi Folio 6.3.5 Preliminary Economic Analysis of the ' - 230-232

System

6.4 •CONCLUSION 232-233

REFERENCES 234-237