COMPARISON OF PERFORMANCE OF DIRECT SOLAR AIR WITH WATER BASED SOLAR AIR HEATING FOR DRYING APPLICATIONS

摘要

Drying of food products is one of the most widely practised activities through out the world. Almost all the crops have to be dried in order to improve the shelf life of the product. A study by Ali [1998]has shown that various food items, to the tuneof 65 million tons, worth Rs.76,000 crores per annum, are lost during post-harvest phase because of unavailability of proper treatment technology. The important advantages of drying of agricultural products are possibility of earlier harvest, preventionof field losses, reduced spoilage, good marketability, better product quality and lesser transportation cost. Food products are sensitive to temperature and therefore temperature control becomes essential to control the quality of the product. Products that have been dried at lesser temperatures prove to be of better quality and fetch higher prices in the market. Ho-Hsein [2005] compared the effect of temperature on the quality of the product and concluded that gradual drying at lesser temperature improves product quality. Tropical species of fish can withstand temperatures of 45-50deg C before proteins are denatured or cooking starts as reported by Bala [1998]. In the case of seed preparation, a maximum temperature of 43 deg C is recommended because high kernel temperature impairs germination. High temperature also affects the chemical structure of the grain. The desirable temperature for certain food products is given in Table-1 ( Sodha et al. [1987a]).