充注量对小型CO2制冷系统影响的实验研究

摘要

In order to study the effects of refrigerant charge on the performance for a small carbon dioxide refrigeration system, many experiments under different charge were carried out. The effects of changing the refrigerant charge on condensing pressure, evaporating pressure, power of system, condensingt empera-ture and evaporating temperature were discussed. By combining the system, pseudo critical condition was analyzed. The results indicate that undercharged carbon dioxide systems could result in decrease of the evaporator pressure and condenser pressure, improve of suction temperature and exhaust temperature of the compressor, COP is low. However, overcharged carbon dioxide systems could increase the power of system, decrease COP. The outlet hot side of internal heat exchanger reaches pseudo critical temperature after the plant works for a while, meantime the suction temperature and exhaust temperature drop suddenly. The point-in-time of sudden-drop temperature comes in advance constantly along with the increase of the refrigerant charge. This study may provide theoretical guidance on how to determine optimal refrigerant charge and how to maintain efficient operation of the small carbon dioxide refrigeration system.%为了研究充注量对小型二氧化碳制 冷系统的影响,利用一套展示柜二氧化碳制冷系统,进行了不同充注量的实验.讨论了充注量对二氧化碳制冷系统吸排气压力、运行功率、吸排气温度的影响.同时,结合本系统,对假临界现象进行了分析,结果表明:充注量不足,蒸发、冷凝压力低,压缩机吸、排气温度高,系统COP较低；充注量过多,系统运行功率高,系统制冷系数降低；系统运行一段时间后,回热器热侧出口达到假临界温度,吸、排气温度产生突降；随着充注量的增加,吸、排气温度突降点前移.本研究可为跨临界二氧化碳制冷系统最佳充注量的确定及如何维持系统高效运行提供理论指导.