Comparative Evaluation of a Square Shaped Mixed Mode Cabinet Solar Dryer with a Circular and Rectangular Cabinet Solar Dryer (PDF)
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Comparative Evaluation of a Square Shaped Mixed Mode Cabinet Solar Dryer with a Circular and Rectangular Cabinet Solar Dryer
Three different mixed mode solar dryers (square, circular and conventional) of the same volume and collector surface area were developed with available materials obtained from the market and evaluated.
The dryers were evaluated using crayfish (Procambarus clarkii), okra (Abelmoschus esculentus L.) and yam (Discorea rotunda) in order to evaluate their efficiencies.
1.5kg of crayfish was taken and prepared for the experiment. The material was divided into two, one half for the dryer, and the other for open air drying.
No load and loaded test was carried out for three days respectively. The moisture content of 78% (w.b) for 0.750kg of crayfish reduced to 12% (w.b) during the period of drying.
The drying rate in the circular mixed mode cabinet solar dryer was found to be higher than the conventional and the square shaped solar cabinet dryers.
During the course of drying, after the crayfish was put inside the drying chamber, the temperature of the drying was monitored at an hour interval as well as the relative humidity.
The water content of the product was also checked at an hour interval until there was no more change in the weight of the product.
It was observed that the product dried faster with the circular mixed mode cabinet solar dryer than with the conventional and square shaped cabinet solar dryer.
As a result of the highest temperature attained in the circular mixed mode cabinet solar dryer, it was evaluated that the rate of moisture removal of crayfish was highest in the circular dryer. All the dryers performed better than open air drying.
TABLE OF CONTENT
Table of Content iv
List of Figures ix
CHAPTER ONE: INTRODUCTION 1
1.1 Background of the study 1
1.1.1 Sun Drying 2
1.1.2 Solar Drying 3
1.2 Statement of the problem 4
1.3 Objective of the study 7
- Scope of the study 7
1.5 Significance of the study 8
CHAPTER TWO: LITERATURE REVIEW 9
2.1 Theory of drying 9
- Agricultural products drying mechanism 9
- Economic and environmental benefits of solar dryers 10
- Drying principles 11
- Solar Drying Technology 12
2.6 Classification of solar dryers 12
2.7Application of solar dryers 14
2.7.1 Solar drying of agricultural products 14
- Solar drying of marine products 17
- Working Principle 18
2.8.1 Open Sun Drying (OSD) 18
- Direct Solar Drying (DSD) 19
- Indirect Solar Drying (ISD) 20
CHAPTER THREE: MATERIALS AND METHOD 22
3.1 Materials 22
- Study area 23
- Materials used for the experiment 23
- Design considerations 23
- Design calculation 24
- Fabrication of machine 31
- Machine description and operation 31
3.8 Method 36
3.8.1 Preparation of material (crayfish) 36
3.8.2 Evaluation performance of the dryer 36
CHAPTER FOUR: RESULTS AND DISCUSSIONS 38
4.1 Heated air rate curve 38
4.2 Loading Test 41
4.2.1 Diurnal variation of relative humidity 41
4.2.2 Diurnal variation in temperature curves for each day (crayfish) 44
4.3 Moisture Content Determination 46
4.4 Comparison of the square shaped dryer with the circular and conventional dryer 47
4.4.1 Temperature variations 47
4.4.2 Diurnal relative humidity variations 50
4.5 Solar drying of crayfish 52
4.6 Solar drying of okra 54
4.7 Solar drying of yam 56
CHAPTER FIVE: RECOMMENDATION AND CONCLUSION 58
5.1 Conclusion 58
5.2 Recommendation 59
More than half of the energy in the world is gotten from the sun’s energy. Drying is one of the methods used to preserve food products for longer periods.
The heat from the sun coupled with the wind has been used to dry food for preservation for several thousand years.
Solar thermal technology is a technology that is rapidly gaining acceptance as an energy saving measure in agriculture application (Ekechukwu, 2000).
It is preferred to other alternative sources of energy such as wind and shale, because it is abundant, inexhaustible, and non-polluting.
Solar air heaters are simple devices to heat air by utilizing solar energy and it is employed in many applications requiring low to moderate temperature below 80°C, such as crop drying and space heating (Mujudar, 2007)
Drying is the oldest preservation technique of agricultural products and it is an energy intensive process.
High prices and shortages of fossil fuels have increased the emphasis on using alternative renewable energy resources.
Drying of agricultural products using renewable energy such as solar energy is environmental friendly and has less environmental impact.
Different types of solar dryers have been designed, developed and tested in the different regions of the tropics and subtropics (Norton, 2000).
The major two categories of the dryers are natural convection solar dryers and forced convection solar dryers.
In the natural convection solar dryers the airflow is established by buoyancy induced airflow while in forced convection solar dryers the airflow is provided by using fan operated either by electricity/solar module or fossil fuel.
Now the solar dryer designed and developed for and used in tropics and subtropics are discussed under two headings (Mujumbar, 2007).
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