Dehumidifier batch drying - effect of heat-losses and air-leakage

The performance of a dehumidifier dryer is influenced strongly by the opera ting temperature and humidity. This paper shows how heat conduction and air leakage losses can cause the temperature of a dehumidifier kiln to collaps e in a batch drying process, resulting in increased drying time and energy use. By means of a dynamic simulation model it is shown that heat loss due to an uninsulated floor alone may be sufficient to prevent a kiln reaching its normal operating temperature. It is shown that the effect of heat losse s is exacerbated when the dehumidifier capacity is modulated for humidity c ontrol. Auxiliary heating can prevent temperature collapse in a poorly insu lated kiln, This maintains the drying speed but adds considerably to the en ergy used. To avoid these difficulties the insulation and air seals of a de humidifier dryer should be appropriate to the power dissipated by the dehum idifier and fans. An example is presented in which sealing and insulating t he kiln yields a reduction of 44 per cent in the drying time, a reduction o f 32 per cent in energy use, and an increase of 168 per cent in net operati ng revenue. Copyright (C) 2000 John Wiley & Sons, Ltd.