Experimental Investigation on Dill Drying in a Solar - Assisted Heat Pump Dryer

Abstract

In this study, a solar dryer assisted with heat pump was developed and thin layer drying of dill was carried out at air temperatures of 40, 50, and 60ºC and air velocities of 0.5, 1 and 1.5 ms - 1 . Also, the drying rates, Specific Moisture Extraction Rate (SMER), and energy consumption were evaluated. Dill samples were dried from initial moisture content of 90% to the final moisture content of 10% in 195 - 275 minutes without assisted heat pump, and with assisted heat pump in 80 - 140 minutes. By using heat pump, the drying rate increased wi th increase in temperature at a given air velocity, thus, reducing the drying time. Increase in the air velocity at a given temperature improved the drying rate. By increasing the air velocity from 0.5 to 1.5 m s - 1 , drying time decreased up to 42%. The spe cific moisture extraction rate values were found to vary between 0.078 and 0.18 K g Kw - 1 h - 1 . The minimum value of energy consumption was 3312 kJ at air temperature of 60ºC and air velocity of 1.5 m s - 1 . Also, the total energy consumption of dryer with heat pump was reduced by 19%, which reflects the higher energy efficiency. Keywords : Drying rate, Energy efficiency, Solar drying