蒸发器积霜对冷库热工状况的影响

Effect of evaporator frost on thermal condition of cold storage

为了探讨冷库蒸发器积霜对冷库热工状况的影响,为冷库及时化霜和无霜运行提供科学依据,试验选用10t3HP的双温双控冷库为研究对象,动态监测了蒸发器积霜前和积霜后两段时间内库温、霜温、蒸发器进风口与出风口温差、冷库耗电量,绘制了蒸发器外表面的三维温度场。试验结果表明:蒸发器积霜前,库温周期变化较为稳定;积霜后,冷库运行周期由3个阶段变为风机运行和制冷2个阶段且库温最低温度逐渐升高,达不到设定下限,周期变化幅度减小,用时缩短。积霜后的霜温周期最低值达到霜温设定下限,冷库不能在正常设定的范围内运行,蒸发器的制冷效率明显下降。蒸发器积霜使进风口与出风口温差减小;冷库运行12h的耗电量增加147.06%。积霜后蒸发器外表面三维温度场显著不同,各点温度都有所下降,偏离设计的最低温度。试验表明,冷库运行过程中不积霜运行是冷库节能安全运行的重要因素。

In order to explore the influence of evaporator frost on the thermal conditions of cold storage, this paper provides the scientific basis for the cold storage in a timely manner of frost and frost-free operation. The ten tons and three HP and dual temperature controlled cold storage is studied, dynamically monitoring cold storage temperature, frost temperature, the temperature difference of evaporator air inlet and outlet and power consumption, and three-dimensional temperature field of the outer surface of the evaporator is drawn. The results show that before evaporator frosted , the cycle change of cold storage temperature is more stable. Cold storage operation cycle consisting of three phases turns into two stages of fan running and cooling, and the lowest cold storage temperature is gradually increased so that it can not reach the setted lower limit. The changing range of cycle is reduced and time is shortened. After evaporator frosted , frost temperature cycle minimum value reaches setted lower limits and cold storage could not operate within the scope, then the cooling efficiency of the evaporator is decreased. The temperature difference of the air inlet and outlet is reduced because evaporator frost and cold storage power consumption increased by 147.06 % to run 12 hours. Three-dimensional temperature field in the outer surface of the evaporator is significantly different and every point temperature has dropped so that it deviates from the designed minimum temperature. The tests show that evaporator with no frost is an important factor to keep cold storage energy saving and operating safe.