R600a/CO_2一级分凝和二级分凝自复叠制冷循环的性能研究

Performance Study on R600a/CO_2 Auto-Cascade Refrigerating Cycle with One-Step Dephlegmation and Two-Step Dephlegmation

基于天然工质应用于自复叠制冷循环的研究,对一级分凝和二级分凝自复叠制冷循环进行了理论分析,讨论了使用天然工质R600a/CO2作为非共沸制冷剂时制冷剂的配比、冷凝温度、蒸发温度和冷凝蒸发器冷凝侧出口过冷度对2种循环系统性能的影响.结果表明:2种循环均存在最佳的制冷剂配比,其中二级分凝循环还存在最佳中间温度;在一定的冷凝温度和蒸发温度下,二级分凝自复叠制冷循环与一级分凝自复叠制冷循环相比,性能系数大,单位质量制冷量大,压力比高;随着冷凝温度和蒸发温度的升高,二级分凝循环的性能系数提高得更多.

Theoretical analyses on auto-cascade refrigerating cycle with one-step dephlegmation and two-step dephlegmation were performed to discuss the influence of composition, evaporating temperature, condensing temperature and supercooling on the system performance when using non-azeotropic mixture refrigerant R600a/CO2. The results show that each cycle has an optimal mixture composition ratio of the mixture refrigerant, and an optimal middle temperature exists in two-step dephlegmation cycle. Moreover, at the certain evaporating temperature and condensing temperature, coefficient of performance, refrigerating output by unit mass refrigerant and compression ratio of two-step dephlegmation cycle are greater than those of one-step dephlegmation cycle. When evaporating temperature and condensing temperature increase, the difference of performance between two-step dephlegmation cycle and one-step dephlegmation cycle is greater.