Comparison of drying characteristics of tomatoes with heat pump dehumidifier system, solar-assisted system and natural drying

Abstract

The effect of heat pump, solar-assisted system and natural drying (solar drying) systems on the drying time, geometry, energy consumption and physical conditions of tomatoes was experimentally determined. Tomatoes were cut into either halves or quarters before drying. Besides heat pump dehumidifier (HP) and solar-assisted systems (SAS) at the drying air speed of 2 m/s on average, natural drying (ND) was also used for drying experiments. Drying performance of HP was the best. In terms of drying time, HP was 50% better than ND and 30% better than SAS. The highest moisture extraction rate (MER) was 0.237 kg w/h in tomato quarters dried in HP, the lowest value was 0.125 kgw/h tomato quarters dried in ND. The highest specific moisture extraction rate (SMER) (1.573 kgw/kWh) was found for tomato quarters dried in SAS while the lowest one (0.078 kgw/kWh) was for tomato halves dried in HP. In general, SMER values of tomato quarters were higher than those of tomato halves dried under same conditions. Heat pump system presents great advantages for tomatoes such as faster drying speed, less influence by environmental factors (rain, dust, insects) and less dependence on environmental conditions.