自复叠制冷循环中混合工质泄漏性能的研究

Study on leakage of mixture refrigerant in auto-cascade refrigeration cycle

尽管自复叠制冷循环越来越广泛的用于深冷及普冷领域,对于循环中工质泄漏特性的研究却较少。以非共沸混合工质两相区的等温泄漏为基础,分析了在自复叠循环装置中各部件的泄漏对工质组成的影响,其中发生在冷凝器出口处、气液分离器和蒸发器出口处的泄漏对工质组成影响较大。以采用非共沸混合工质R600 a/CO2的自复叠低温冷冻箱为例,研究了不同泄漏点不同泄漏率的泄漏特性。结果说明当工质泄漏时混合工质组成和循环性能发生变化,在蒸发器出口处的泄漏对循环性能影响最大;当泄漏引起循环工质组成发生较大变化时,压缩机变容量和变压力比调节能力明显降低,此时系统不能满足设计工况的要求,工作性能变差。

Although auto -cascade refrigeration cycle was widely used in cryogenic and refrigerating field, there was less study related to the leakage characteristics of refrigerant in the cycle. The influence of leakage in each part of auto - cascade device on composition of refrigerant was analyzed based on the isothermal leakage of non - azeotropic refrigerant in two - phase area. The influence of leakage at exit of condenser, vapor - liquid separator and evaporator on the refrigerant composition is bigger. Taking the auto - cascade cryogenic compartment using non - azeotropic refrigerant R600a/CO2 for example, the leakage characteristics of different leakage point and ratio were studied. The results show that refrigerant composition and performance of cycle is changed when refrigerant leaks out. The influence of leakage at exit of evaporator is maximal. When composition of refrigerant changes much due to the leakage, the adjusting ability of capacity and pressure ratio of compressor reduces obviously. In the case, the system can not meet the requirement of working condition and the performance of cycle is worsen.