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

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 ۴۰, ۵۰, and ۶۰ºC and air velocities of ۰.۵, ۱ and ۱.۵ ms-۱. Also, the drying rates, Specific Moisture Extraction Rate (SMER), and energy consumption were evaluated. Dill samples were dried from initial moisture content of ۹۰% to the final moisture content of ۱۰% in ۱۹۵-۲۷۵ minutes without assisted heat pump, and with assisted heat pump in ۸۰-۱۴۰ minutes. By using heat pump, the drying rate increased with 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 ۰.۵ to ۱.۵ m s-۱, drying time decreased up to ۴۲%. The specific moisture extraction rate values were found to vary between ۰.۰۷۸ and ۰.۱۸ Kg Kw-۱ h-۱. The minimum value of energy consumption was ۳۳۱۲ kJ at air temperature of ۶۰ºC and air velocity of ۱.۵ m s-۱. Also, the total energy consumption of dryer with heat pump was reduced by ۱۹%, which reflects the higher energy efficiency.