CO_(2)跨临界平行压缩与闪气旁通能效及应用浅析

Efficiency and application analysis of parallel and flash gas bypass cycle in CO_(2)transcritical system

随着工商业制冷行业对环保要求的不断增加,二氧化碳作为制冷剂已经得到了越来越多的认可。在中国,部分工商业制冷设备使用的是二氧化碳与氨或氢氟烃类制冷剂的复叠系统。而在欧洲或国内的一些大型商超行业二氧化碳双级增压系统已经越来越普遍。由于环境温度对二氧化碳跨临界制冷循环的影响,特别是在高气冷器出口温度时,使其在节流时产生大量能量损耗和不能被用来参与制冷的大量闪发气体。这些闪发气体只能进一步被节流并被压缩机重新吸入压缩做功,带来更多的损耗。随着技术的革新,平行压缩已经被广泛证明可以在高环境温度下使二氧化碳跨临界制冷系统更加节能。通过对平行压缩以及闪气旁通系统的能效进行模拟计算和对比分析发现:当气冷器出口温度在37℃时,平行压缩COP提高近20%。同时,在跨临界系统的应用当中需要考虑压缩机、中间压力、高压等对整个系统能效的影响。

With the rapid development of industry and commercial refrigeration business,using CO_(2)as a refrigerant is considered more and more in refrigeration systems.In China CO_(2)is mostly used in a cascade system which is compounded with ammonia or HFCs.In Europe however,it is quite common to apply a trans critical booster system especially in supermarket application.Considering the effect of ambient temperature or sink temperature on the system,a mass of losses and flash gas happened during the expansion process.The flash gas contribute nothing to refrigeration but need to be throttled again and goes in to the compressor to compress it,which is an additional loss of power.With the development of CO_(2)trans critical system,parallel cycle is proven as an option to optimize the COP of the system especially in high ambient temperature.After analyzed the efficiency of both parallel and flash gas bypass system,it turns out that parallel system has a efficiency improvement of 20%at the outlet gas cooler temperature is 37℃.Besides during actual application of trans critical system,the selection of compressor,intermediate pressure and high pressure also have a great effect on the system's efficiency.