机房空调负落差长连管系统膨胀阀前过冷度研究

机房空调在负落差长连管安装方式下会产生启动时低压报警和过冷度较小等问题,对机组运行的稳定性、可靠性和性能产生影响。本文理论计算R407C制冷剂名义工况下不同负落差时膨胀阀前过冷度和压缩机排气压力,发现膨胀阀前过冷度与负落差呈负相关关系,制冷剂在膨胀阀中可能会闪发。基于此,采用带储液罐的空调机组,试验分析储液罐分别位于冷凝器出口处和膨胀阀进口处时膨胀阀前的过冷度,结果表明,储液罐位于膨胀阀进口处可以有效保障膨胀阀前过冷度并降低压缩机排气压力。

Study on degree of subcooling before expansion valve of long connecting pipe system with negative height difference for computer room air-conditioning

Low pressure alarms during startup and low degree of subcooling occur in computer room air-conditioning when long connecting pipe is installed with negative height difference,which affect the system stability,reliability and performance. The degree of subcooling before the expansion valve and discharge pressure of compressor are theoretically calculated at different negative height differences for refrigerant R407C under nominal condition. It’s found that the degree of subcooling before the expansion valve is negative related with the negative height difference,and the refrigerant can flash in the expansion valve. On the basis of these,the experimental study on the degree of subcooling before expansion valve is performed on the air-conditioning unit with receiver located at the outlet of condenser or at the inlet of expansion valve. The results show that the receiver equipped at the inlet of expansion valve could guarantee the degree of subcooling effectively and lower discharge pressure of compressor.