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PROJECT TOPIC- DESIGN, DEVELOPMENT AND PERFORMANCE EVALUATION OF AN ACTIVE SOLAR DRYER FOR BIOMATERIAL PROCESSING

PROJECT TOPIC- DESIGN, DEVELOPMENT AND PERFORMANCE EVALUATION OF AN ACTIVE SOLAR DRYER FOR BIOMATERIAL PROCESSING

ABSTRACT

An active solar dryer was designed, developed and the performance evaluation undertaken. The dryer has 3 main sections: The solar collector, heat storage unit and drying chamber with the following dimensions 160cm x 95cm x 10cm, 85cm x 65cm x 35cm and 95cm x 75cm x 70cm respectively. The dryer is incorporated with a suction fan that enhances air flow in the chamber. Tests were conducted during the dry and wet seasons in March and June respectively to indicate if the suction fan used has effect in both seasons. The different drying methods: open sun drying, solar drying without suction fan and solar drying with suction fan were used for the test. Also, different root / tuber crop products: cassava, yam, sweet potato, cocoyam, ginger and turmeric were used. Statistical analysis using ANOVA was used to determine the effect of the different drying methods and crop types on the drying rates. Results from the dry season test show that solar drying with suction fan gave highest drying rate of 0.1125kg/hr when used to dry yam. Also, the least drying rate was obtained when open sun drying was used to dry turmeric. Also, results from the wet season test show that solar drying with suction gave highest drying rate of 0.048125kg/hr when used to dry yam. The least drying rate was obtained when open sun drying was used to dry cassava. The use of suction fan reduces drying period and therefore enhances drying of agricultural products. Indication showed that the value of the relative humidity within the drying chamber was lower when the suction fan was in use. The dryer has actual capacity of 15kg / batch. The collector has maximum heat gain / efficiency of 1682.3W and 94.4% respectively. The products dried with the solar dryer were of better quality than those dried with open sun drying method because they retained their colour and also free from mould after storage for about 3 months. 

CHAPTER 1

INTRODUCTION

1.1 Drying of Agricultural Products

Drying refers to the removal of moisture from agricultural materials until the moisture content of the product is in equilibrium with the surrounding air usually 12 to 14 percent moisture, wet basis. Successful drying depends on enough heat to draw out moisture, dry air to absorb the released moisture and adequate air circulation to carry off the moisture. The key factor in drying is to remove moisture as quickly as possible at a temperature that does not seriously affect the flavor, texture and colour of the product. If the temperature is too low in the beginning, microorganisms may grow before the product is adequately dried, but if the temperature is too high and the humidity too low, the product may harden on the surface. This makes it more difficult for moisture to escape and the product does not dry properly. Dried foods are tasty, nutritious, light weight, easy-to- prepare, and easy-to-store and use (David, 2000). The energy input is less than what is needed to freeze or can, and the storage space is minimal. The nutritional value of food is only minimally affected by drying. Vitamin A is retained during drying, however it is light sensitive and food containing it should be stored in dark places (Herringshaw, 1997). Vitamin C is destroyed by exposure to heat, although pretreating foods with lemon, orange, or pineapple juice increases vitamin C content (David, 2000). Dried foods are high in fibre and carbohydrates and low in fat, making them healthy food choices (Kerr Barbara, 1999). Dried Foods that are not completely dried are susceptible to mold. Microorganisms are effectively killed when the internal temperature of food reaches 145o F (Herringshaw Doris, 1997)
According to Kerr Barbara (1999), nutritionally dried food is ranked by the United State Food and Drug Agency as better than canning and freezing. She states that the tastes are related to the food, but there is some uniqueness in their flavour and texture. Dennis Scanlin (1997) also found that by reducing the moisture content of the food to between 10 and 20%, yeast, bacteria, mold, and enzymes are all prevented from spoiling it. The flavour and most of the nutritional value are preserved and concentrated. Drying permits long-term storage of agricultural products without deterioration, since extended storage periods are becoming increasingly important with the large amount of crop being stored and carried over through another storage year by the government and industry.

PROJECT TOPIC- DESIGN, DEVELOPMENT AND PERFORMANCE EVALUATION OF AN ACTIVE SOLAR DRYER FOR BIOMATERIAL PROCESSING

1.2 Objectives

i. To design an active solar dryer with heat storage unit.

ii. To evaluate the effect of suction fan in solar crop drying system.

iii. To undertake the performance evaluation of the dryer using different drying methods / crops.

iv. To determine the drying rate of different root / tuber crops using the solar dryer.

1.3 Scope of the Study

1. The design and development of an active solar dryer with both direct and indirect mode of solar collection.

2. The study evaluates the performance of the dryer with respect to drying rate and dried quality of various biomaterials.

3. It also evaluates the effect of the suction fan on the drying rate of crops.

4. The study determined the drying rate of the following root crops: cassava, yam, sweet potato, ginger, cocoyam and turmeric.

5. The study examined the temperature and relative humidity variations within the drying chamber.

PROJECT TOPIC- DESIGN, DEVELOPMENT AND PERFORMANCE EVALUATION OF AN ACTIVE SOLAR DRYER FOR BIOMATERIAL PROCESSIN

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