双级螺杆式制冷机组油冷却控制系统的改进

Improvement on oil cooling control system for two-stage screw refrigeration unit

对双级螺杆式制冷机组油冷却控制系统及油冷却负荷进行分析计算,发现热力膨胀阀冷冻能力与不同工况的实际运行情况无法匹配是造成板式换热器板片温度大幅波动的主要原因。试验证明该温度波动造成板式换热器热疲劳。采用对电子膨胀阀开度进行自动调节的PID控制系统,换热器板片温度的波动幅度大幅降低,油温稳定在设定目标值,符合设计与使用要求。此控制方式特别适用于多变量、非线性和不断变化的系统。

The oil cooling control system is analyzed for two-stage screw refrigeration unit and its oil cooling load is calculated.It is found that the refrigerating capacity and operation condition of thermal energy expansion valve doesn't match the actual operation under various working conditions.It is the main reason for the wild temperature fluctuations of plate heat exchanger.It is testified that the temperature fluctuations cause the thermal fatigue for plate heat exchanger.By PID control system which can automatically control the degree of opening of electronic expansion valve,the temperature fluctuation range for plate heat exchanger is sharply reduced.The oil temperature holds steady at target value.It conforms to using and design requirements.This control mode is particularly suited for the multivariate,nonlinear and shifting system.