在制冷装置中,蒸发器表面的温度低于冷间空气的温度和冷藏货物表面的温度,以致产生水蒸气分压力差;使冷间内空气及冷藏货物中的水分不断地移向蒸发器表面,并凝结成霜。蒸发器表面结霜,使传热热阻增加,传热系数降低。对空气冷却器来说,还导致空气通路变窄,空气流动阻力增大,风量减 In the refrigeration unit, the temperature of the evaporator surface is lower than the temperature of the cold air and the temperature of the surface of the refrigerated goods, so that a partial pressure of water vapor is generated; the moisture in the cold air and the refrigerated goods is continuously moved to the evaporator surface , And condensed into a frost. Evaporator frosting surface, so that heat transfer resistance increases, heat transfer coefficient decreases. For air coolers, it also leads to narrowing of the air passage, increased air flow resistance, reduced air flow