Evaluation of Energy Aspects of Apple Drying in the Hot-Air and Infrared Dryers

Drying is an energy-intensive process. In general, heating and evaporation require large quantities of energy. This study has been conducted to evaluate analysis for dying apple slices in two drying systems including hot-air convection and infrared drying. The apple samples were dried at temperatures of 90, 120 and 150°C and radiation intensity of 0.22, 0.31 and 0.49 W/cm² in the hot-air and infrared dryer, respectively. The results showed that the minimum energy consumed for drying apple slices in infrared dryer was 1 kW h while minimum energy consumption in hot air dryer was 7.02 kW h. Also, the specific energy consumption in IR dying was about 82-86% shorter than that of hot-air drying. The value of SEC of apple under IR and hot air drying was ranged from 110.35 to 71.78 kWh/kg_water and 635.53 to 501.15 kWh/Kg_water, respectively. The calculated value of moisture diffusivity varied from 3.499×10-7-4.746×10-7 m²/sec and 3.671×10-7-5.101×10-7 m²/sec and the value of energy activation were found to be 140.1 and 94.62 kJ moL^-1 for IR and hot air drying, respectively. Therefore, one way to improve drying operations is to use infrared energy.