Performance evaluation of heat pump dryer

A batch type heat pump assisted dehumidified air dryer was developed successfully with a medium range of temperatures (30-41 degrees C) for safe drying of heat sensitive crops. Dehumidification system of the developed heat pump dryer (HPD) maintained the relative humidity (RH) of air entering the drying chamber below 40%. The inlet drying air temperature decreased during early hours of drying followed by rapid rise between the 2nd and 10th h, after which the temperature was almost stable. The RH of inlet and exhaust drying air increased initially and decreased subsequently with drying time as product became drier. The HPD was found to have a specific moisture extraction rate between 0.55 and 1.10 kg/kWh. Energy consumption for HPD for 24 h of operation was found less (4.48-5.05 kWh) than the hot air dryer (5.65-9.6 kWh) while operating under different drying conditions. Better quality dried sweet pepper (Capsicum annuum L.) was obtained in HPD owing to lower drying air temperature.