冷干机在正常情况下，蒸发器表面有一层膜状冷凝水存在。在计算蒸发器冷负荷时已经考虑到这一情况。如果蒸发温度降得很低，使换热铜管表面温度在零度以下，水蒸气就会在铜管表面凝结成霜，由此产生的问题是
冷干机在正常情况下，蒸发器表面有一层膜状冷凝水存在。在计算蒸发器冷负荷时已经考虑到这一情况。如果蒸发温度降得很低，使换热铜管表面温度在零度以下，水蒸气就会在铜管表面凝结成霜，由此产生的问题是：
Under normal circumstances, there is a layer of film condensation water on the surface of the evaporator. This has been taken into account when calculating the cooling load of the evaporator. If the evaporation temperature is very low, so that the surface temperature of the copper pipe is below zero, the water vapor will condense on the surface of the copper tube into frost, the problem is:
①水蒸气“升华为霜”比“凝结为露”要多吸收约15%的冷量；
Water vapor "sublimation" as frost "condensation" to absorb more than 15% of the amount of cold;
②霜的热导率只有水的1/4，使管外空气不能充分冷却，而同时管内蒸发温度却有进一步降低的趋势，如此循环的结果，必将给制冷系统带来许多不良后果（譬如产生“液压缩”）；
The thermal conductivity rate of only 1/4 of water frost, the air outside the tube can not be fully cooled, while tube evaporation temperature has further decreased, so the results will bring many adverse consequences to the refrigeration system (such as "liquid compression");
③从空气流通径讲，霜的存在会使空气阻力增加，使供气压力降低，严重时甚至会使气路堵塞；
Speaking from the air circulation, the presence of frost will increase the air resistance, so that the supply pressure is reduced, and even serious gas road blockage;
④从系统能耗来讲，蒸发温度过低导致压缩机制冷系数大幅下降，能耗增加。所以含湿量很大的压缩空气进入冷干机工作时，冷媒在管内的蒸发温度至少应保证蒸发器铜管表面温度在零度以上。试图通过定时化霜的办法来降低蒸发温度，冷干机是不能接受的。
From the energy consumption of the system, the evaporation temperature is too low, which leads to the decrease of the compressor refrigeration coefficient and the increase of energy consumption. Therefore, a large amount of compressed air into the cold dry machine, the refrigerant in the tube evaporation temperature should be at least to ensure that the surface temperature of the evaporator tube above zero. It is not acceptable to try to reduce the evaporation temperature by the method of timing defrosting.
