制冷机是依靠消耗外功将低温热源(低于环境温度的热源)中的热量转移到高温热源(环境温度热源)中去的机器。实现制冷的循环可以有许多种,但从热力学的观点去分析,最完善的制冷循环只有一个。这个热力学最完善的循环,应该是可逆的制冷循环。它是由两个与低温热源及高温热源无温差的换热过程和两个等熵过程所组成的循环。与热机循环的热效率概念相似,在相同的高温热源和低温热源温度的条件下,衡量制冷循环热力学完善程度的指标,也就是经济性的指标是制冷系数ε,它是制冷量 Q_0和耗功 W 的比值ε=Q_0/W。制 Chillers are machines that rely on external work to transfer the heat from a low-temperature heat source (a heat source below ambient temperature) to a high-temperature heat source (ambient temperature heat source). There are many ways to achieve refrigeration cycle, but from the viewpoint of thermodynamics, there is only one most perfect refrigeration cycle. The thermodynamically perfect cycle should be a reversible refrigeration cycle. It consists of two with low temperature heat source and high temperature heat source without heat transfer process and two isentropic processes composed of the cycle. Similar to the concept of thermal efficiency of the thermal cycle, the measure of the degree of thermodynamic improvement in the refrigeration cycle under the same conditions of high-temperature heat source and low-temperature heat source temperature, that is, the economic indicator is the refrigeration coefficient ε, which is the cooling capacity Q_0 and work W The ratio ε = Q_0 / W. system