Design of solar tray tomato drier

Abstract

Drying is one of the oldest, cheapest and most common methods of preservation and storing agricultural products. Open air sun drying of agricultural products is the traditional method employed in most of the developing countries. Sun drying is used to denote the exposure of a commodity to direct solar radiation and the convective power of the natural wind. Many of our food crops have 80 to 90 per cent moisture content and most of these need to be removed for long term storage. In practice, most of the dryers used have an operating efficiency of 50-60 per cent and this indicates that significant amounts of energy are used in the post-harvest activity. A small scale village level solar dryer for tomato was designed in Mainefhi subzone using locally available materials. The theoretical design of the solar dryer was composed of the solar collector, blower, drying chamber and chimney. Designing a solar collector parts which include solar collector area, absorber surface area, selection of suitable blower with the recommended capacity, designing solar drying chamber area and sizing of drying chamber and chimney were the specific aim of the study. The results on the basis of calculations and assumptions with the recommended value were obtained. The solar dryer with collector area of 2.26 m2 and drying capacity of 5kg was designed to dry tomato from 90 per cent to 8 per cent moisture content wet bulb during the sunshine hours, 8.21 hrs per batch. After drying, 5kg of tomato was reduced to 0.544kg of tomato.