不同制冷剂对气悬浮压缩机电机冷却及系统性能的影响

Influence of Different Refrigerants on Motor Cooling Process and System Performance of Compressor with Gas Bearings

电机冷却是保障气悬浮离心制冷压缩机可靠运行的关键。本文建立了气悬浮离心制冷压缩机的数学模型,分析了不同制冷剂(R134a、R1234yf、R1234ze(E))对电机冷却过程和制冷系统性能的影响。研究结果表明:采用R1234ze(E)时电机内部温度最高,电机永磁体最高温度比采用R134a和R1234yf时高60~90℃;采用3种制冷剂时电机的绕组平均温度均随冷却入口温度的升高而降低;采用R134a和R1234yf时永磁体最高温度均随冷却入口温度的升高而降低,采用R1234ze(E)的永磁体最高温度随冷却入口温度的升高先增后降,在冷却入口温度约为25℃时最高。冷却入口温度每上升4.5℃,电机冷却回路的出口干度下降约3%~5%。带电机冷却支路的系统与传统系统相比,电机温度可以控制在更安全的运行范围之内,但采用R134a、R1234yf、R1234ze(E)的系统COP分别降低1.23%~1.82%、1.23%~1.65%、1.14%~1.17%。

Motor cooling is key to the reliable operation of centrifugal refrigeration compressors with gas bearings.A mathematical model of a centrifugal refrigeration compressor with gas bearings was devised,and the influences of different refrigerants on the motor cooling process and refrigeration system performance were analyzed.The results show that the internal temperature of the motor reaches the highest when R1234ze(E)is used,and the maximum temperature of the permanent magnet of the motor is 60-90℃higher than that with R134a and R1234yf.When using the three refrigerants,the average winding temperature of the motor decreases with an increase in the cooling inlet temperature.When R134a and R1234yf are used,the maximum temperature of the permanent magnet decreases with an increase in the cooling inlet temperature.When R1234ze(E)is used,the maximum temperature of the permanent magnet first increases and then decreases with the increase in cooling inlet temperature.The maximum temperature is reached when the cooling inlet temperature is approximately 25℃.The outlet vapor quality of the motor cooling circuit decreases by approximately 3%-5%when the cooling inlet temperature increases by 4.5℃.Compared with traditional systems,systems with motor cooling branches can control the motor temperature within a safer operating range.However,systems using R134a,R1234yf,and R1234ze(E)have COPs reduced by 1.23%-1.82%,1.23%-1.65%,and 1.14%-1.17%,respectively.