PERFORMANCE EVALUATION AND COMPARISON OF MIXED MODE FORCED CONVECTION SOLAR TUNNEL DRYER AND PYRAMID DRYER FOR SPINACH LEAVES

A forced convection mixed mode tunnel and pyramid type solar dryers has been fabricated for drying of leafy vegetable such as spinach leaves. The performance of the fabricated driers is evaluated by carrying drying experiments at Miraj, District Sangli. Solar drying of spinach leaves is carried at different air velocities. Initially 2.28 kg of fresh spinach leaves (Initial moisture content of spinach is 90.7% w.b) are dried in both the dryers at air velocity 0.4m/s, 0.5m/s, 0.6m/s and 0.7m/s and performance of the dryer is compared. It is observed that 0.5 m/s air velocity is optimum for drying of spinach in tunnel type dryer while 0.6 m/s for pyramid type dryer. The temperature of the drying chamber of tunnel and pyramid dryers remains higher than the ambient temperature. For spinach the average system drying efficiency of the tunnel type drier varies from 26.72% to 20.99 % whereas of pyramid type dryer varies from 20.93% to 18.30%. The observed result of the present work shows that the proposed forced convection mixed mode tunnel type solar drier is good for drying spinach.