低温冷库热气融霜冷凝热的季节匹配度分析

Analysis of the seasonal matching degree on condensation heat of hot gas defrosting for low temperature cold stores

在对低温冷库冷负荷构成进行分析的基础上,分析了制冷系统冷凝热随季节(即环境温度)变化的特点,定义了"季节系数",即冬季与夏季能用于热气融霜的冷凝热量之比,其意义是季节对制冷系统冷凝热量的影响程度,季节系数小说明影响程度大,即冷凝热量与季节的匹配度差,反之说明影响程度小、匹配度好。讨论了制冷剂为R22和R404A的制冷系统在不同名义冷凝温度下的季节系数的特点。结果表明:季节系数随制冷剂和名义冷凝温度的不同而不同,在名义冷凝温度一定时,R22的季节系数比R404A的小;而对同一种制冷剂,名义冷凝温度越低,季节系数越小;且R404A的季节系数受名义冷凝温度的影响更为明显。本研究为热气融霜技术的工程设计与推广提供了参考。

The constitution of cold load of a low temperature cold store was analyzed, and on this basis, the variance of the refrigeration system＇s condensation heat with the seasons （i. e. ambient temperature） was studied. To evaluate the impact of seasons on condensation heat of a refrigeration system, COS （ the coefficient of season） was defined as the ratio of the heat which could be used for hot gas defrosting in winter and that in summer. Smaller COS indicates the greater impact degree, which means the matching degree of condensation heat and seasons is poor, and vice versa. COS for the refrigeration systems are obtained under different nominal condensation temperatures using R22 or R404A as the working fluids. The results indicate that the COS is affected by the kind of refrigerants and the nominal condensation temperatures. The COS of R22 is smaller than that of R404A at the same condensation temperature. COS is also found decreasing with the nominal condensation temperature. And COS of R404A is more significantly influenced by the nominal condensation temperature than that of R22. These findings provide a theoretical basis for engineering design of hot gas defrosting and the application of this technology.