两级R744超市中央制冷系统节能特性

Performance of R744 commercial centralized refrigeration systems

比较了以二氧化碳(R744)为工质的超市中央制冷系统制冷技术方案,包括普通两级制冷(CB)、旁通压缩两级制冷(PC)和多引射器-旁通压缩耦合两级制冷(EJ),讨论了配置空调系统(AC)之后的功耗变化。根据计算得到,在环境温度20℃以上,相较于CB系统,PC系统的功耗减少了6.8%～12.3%;EJ系统功耗降低了6.3%～17.5%。在耦合了AC系统之后,相较于PC-AC系统,EJ-AC系统的功耗降低了4.9%～6.5%。与R404a系统相比,超市两级R744系统都有明显的节能效果。

Three R744 supermarket refrigeration systems are compared,including conventional booster system(CB),booster system with parallel compression(PC) and multi-ejector booster system with parallel compression(EJ).The parallel compressors in PC and EJ systems work under lower pressure ratio and consequently the energy of compressors decreases.In EJ systems,expansion valves are substituted by ejectors,so that the irreversible loss in the system could be lower.The airconditioning system integrated with PC and EJ system are also discussed respectively.The optimal high side pressure of each system is confirmed.The value of high side pressure becomes larger when the outdoor temperature increases.When the ambient temperature is fixed,the multi-ejector system features the lowest high side pressure.The power consumption of each system is obtained by the simulation models.The results indicate that the power consumption of PC could be decreased,ranging from 6.8% to 12.3% compared to CB.And for EJ,the power consumption is even smaller,where the gap is 6.3% to 17.5%.Compared with HFC(hydrofluorocarbon),such as R404a,the R744 supermarket refrigeration system is of great energy saving potential in warm climates.