Vacuum far-infrared drying of apple

This paper describes the experimental results on the drying of the apple slices by infrared radiation under vacuum condition. The investigation of vacuum far-infrared drying processes was conducted on the experimental set-up that is designed to imitate industrial batch dryer. The experimental conditions have been chosen such that heaters temperature and absolute chamber pressure have been in the range used on the industrial dryer. Apple slices were dried at four vacuum pressures 20, 40, 60 and 80 kP and five temperature of heatres, 120, 140, 160, 180 and 200ºC which were kept constant during the single experiments. Based on experimental drying data, it was found that the drying time decreased with an increase of temperature of heaters and the decrease in the absolute chamber pressure. It was also concluded that the influence of the temperature of heaters has more significant effect on reducing of the drying time than the vacuum pressure.