ABSTRACT

The fabrication of the solar dryer was successful and test were carried out for various performance comparisons such as No-load and Load performance of the dryer and direct sun drying comparison and noticeable differences was noticed in the final moisture content such that the maximum temperature recorded in the drying chamber and solar collector for No-load are 44.5 and 52 respectively and also for when the cabinet is loaded the above stated temperatures are 66 and 76.5 for a highest temperature of 34.5 and least temperature of 23 but an optimum temperature of 27, thereby giving the solar dryer an exergetic efficiency between 70and 80 . The tests were carried out between the hours of 9am and 5pm. The solar store that is to release heat to the drying chamber in the night was found to have its highest temperature at 43. All these performances are due to the fact that rain falls virtually every day and if not a rainy day then it is was a cloudy day such that the sun is not shining at its peak. The load result was accomplished using red sweet pepper and yam food samples.

TABLE OF CONTENTS

Title page i

Abstract ii

Certification iii

Dedication iv

Acknowledgement v

Table of contents vi

List of figures xi

List of Tables xii

List of Plates xiii

CHAPTER ONE 1

1.1 General Background 1

1.2 Aim And Objective 3

1.2.1 Aim 3

1.2.2 Objective 3

1.3 Scope Of The Project 4

1.4 Justification 4

CHAPTER TWO 5 

2.0 Literature Review 5

2.1 Solar Radiation 5

2.1.1 Solar constant 5

2.2 Domestic Solar Dryer 9

2.2.1 Features 9

2.3 Multi-Rack Variable Inclination Solar Dryer 10

2.3.1 Features 10

2.4 Solar collectors 12

2.4.1 Covers 12

2.4.2 Absorbers 13

2.4.3 Insulation 13

2.4.4 Vents and Pipes 13

2.4.5 Solar Heating 13

2.4.6 Flat-plate collectors 14

2.4.7 Evacuated-tube collectors 15

2.5 Thermal storage 16

2.5.1 Heat stores 18

2.6 Performance evaluation of an enhanced fruit solar dryer using concentrating panels 19

2.7 Basic theory of operation 22

2.8 Materials and methods 24

2.8 Solar dryer performance evaluation 26

CHAPTER THREE 29

3.0 Methodology 29

3.1 The Transparent Surfaces 29

3.1.1 Solar Loads through Transparent Surfaces 3.1.1.1 Fenestration 29

3.1.1.2 Fenestration Heat Balance: Solar Heat Gain through Glass 29

3.2 The Solar Collector 33

3.2.1 Factors Affecting Collector's Efficiency 33

3.2.2 Energy Balance on a Flat Plate Collector 34

3.2.2.1 Loss of Energy 35

3.2.3 Transmission Losses 36

3.3 Thermal Storage 38

3.4 Equations for Exergetic Analysis 39

3.5 Design Calculations and Construction 41

3.5.1 Design Considerations 41

3.5.2 Collector's Tilt Angle 41

3.5.3 Absorber Plate 42

3.5.4 Glazing Material 42

3.5.5 Heat Losses 42

3.5.6 Air Circulation 43

3.5.7 Air Leakage 43

3.5.8 Air Temperature 43

3.5.9 Dryer Capacity 44

3.5.10 Drying Time 44

3.5.11 Energy Storage 44

3.6 Design Calculations 45

3.6.1 Initial Data 45

3.6.2 Calculation of the Required Transparent Area of the Drying Chamber 45

3.6.3 Calculation of the Collector's Area 49

3.6.3.1 Sun's Declination 'δ' 49

3.6.3.2 Hour Angle, 'H' 50

3.6.3.3 Solar Altitude, 'β' 50

3.6.3.4 Solar Azimuth, ‘ϕ' 50

3.6.3.5 Surface Azimuth ' ϕ ' and Solar- Surface Azimuth 'ν' 50

3.6.3.6 Angle of Incidence '' 51

3.6.3.7 Direct Normal Solar Intensity; '' 51

3.6.4 Collector's Inclination: Vertical and Slanting Heights 55

3.7 Heat Storage Medium 55

3.7.1 Calculation of Heat Stored 56

3.8 Construction Cost Analysis 56

3.9 Material Selection and Equipment Description 58

3.9.1 Material Selection 58 

3.9.1.1 Transparent Surfaces 59

3.9.1.2 Absorber Plate 59

3.9.1.3 Thermal Storage Material 60

3.9.1.4 Thermal Insulators 60

3.9.1.5 Drying Cabinet 60 

3.9.1.6 Drying Trays 61

3.9.2 Equipment Description 62

3.9.2.1 Solar Collector 62

3.9.2.2 Drying cabinet 63

CHAPTER FOUR 64

4.0 Results and Discussion 64

4.1 Result of Various Data 64

4.1.1 Result of no-load readings 64

4.1.2 Result of load readings(YAM) 70

4.2 Mass of loaded cabinet (with red sweet pepper) and control measure 72

4.3 Heat required 74 

4.4 Hourly Efficiency 76

CHAPTER FIVE 79

5.0 Conclusion and Recommendation 79

5.1 Conclusion 79

5.2 Recommendation 79

REFERENCES 80

APPENDIX 83