SOLAR DRYING OF AGRICULTURAL PRODUCE

Abstract

Drying or dehydration of material means removal of moisture from the interior of the material to the surface and then to remove this moisture from the surface of the drying material. Solar drying equipment would yield clean, dust free and good quality of agriculture produce. A dryer would make the drying process much faster as compared to that in open field drying normally adopted by the farmers. Moreover, the damage caused by birds, pests, rats and insects and by weather is reduced giving about 20 — 30 % higher output of crops. Attempts have been made to increase the efficiency of cabinet dryer. Through one such attempt, a "Reverse Absorber Cabinet Dryer" (RACD) is developed. In a RACD, the solar energy is directed and concentrated by a parabolic reflector on to the bottom of the absorber plate and gets absorbed. The crop is kept above the top of absorber plate (not in contact with the absorber plate) in trays. Atmospheric air drawn in by natural convection effect flows over the top of the absorber plate. The hot air then flows through the crop, removing moisture from the crop. In the present work, an experiment investigation has been carried out to study the drying process in a Reverse Absorber Cabinet Dryer: • Three different crops namely Wheat, Peas and Paddy are tested. The mass of the crops to be dried is varied. Also dryer system parameters viz vent width (V) and duct depth (D) are varied to study their effect on the drying process and on the performance of the system. The hourly variation of temperatures of the crop, plate and fluid and moisture removed are observed and recorded. The variation of solar radiation is also recorded. The instantaneous efficiency, total efficiency and daily efficiency were evaluated. Typical trends observed are critically examined. Some of the typical characteristic revealed are presented and discussed.