2.2. Twin layer solar tunnel dryer

The twin layer solar tunnel dryer is used in the drying experiment. This dryer consisted of solar collector and solar drying region, 80 W solar module and one 24 V DC (direct current) fan at the air inlet of the solar collector for providing the required air flow (Figure 1).

Twin layer solar tunnel dryer Photo.

The dryer is 24 m long (8m long collector and 16m long drying section) and 2 m wide. It stands on 0.8m high brick plinth. UV-stabilized polythene sheet (transmittance. 88–90%) is used for covering both the collector and drying region. The collector region is painted black for absorbing solar radiation. In the dryer there are sixty 0.81m² wide trays arranged in two layers loaded one over the other 30 at top and 30 at bottom for drying products on them. Hand-operated pipe and crank arrangement is used to open or close the plastic cover to easily load and unload a product to be dried.