Development of an air recirculating tray dryer for high moisture biological materials

Fruits and vegetables are highly perishable and deterioration in quality and quantity occurs due to poor storage and processing facilities at the production site in developing countries like India. Dehydration of vegetables using a recirculatory dryer is possible but limited, in practice. The recirculatory dryers so far developed have a drawback of non-uniform drying along the length of the trays. Hence an effort was made to solve this problem. A recirculatory cabinet dryer of capacity 5 kg/batch using a central air distribution system was designed and developed. The dryer was tested with blanched potato chips. At a constant air flow rate of 1.5 m(3)/min and 65 degreesC temperature, it took about 3 h time to reduce the moisture content from 856.94% (dry basis) to 9.98% (dry basis). The heat utilization factor (HUF) and thermal heat efficiency (THE) of the developed dryer were found to be 18.94% and 22.16%, respectively. (C) 2001 Elsevier Science Ltd. All rights reserved.