The Limit Inlet Temperature of Refrigeration Centrifugal Compressor to Avoid Phase Change

From the polytropic compression progress to compress the refrigerant to the same pressor ratio, the polytropic work to be consumed will reduce with the decrease of inlet temperature. However, the refrigerant may liquefied if the inlet temperature is low enough. Though the principle that the acceleration of coming fluid may result in liquefaction has been proved by numerical and experimental method, and the liquefaction inside the Supercritical-Carbon-Dioxide centrifugal compressor has been wildly study, there isn’t an easy method to predict whether the inlet condition may cause liquefaction inside the compressor.

We find that fluid flow the space near the suction face of leading edge (SNSL) is similar to the flow in converging nozzles if the mass flow is less than design condition and the angle of attack is negative, and small mass flow makes it similar to flow through converging-diverging nozzles. The maximum velocity in absolute coordinate system (MVIA) in SNSL of medium mass flow condition can be larger than that of large mass flow condition.

We proposed a method to predict the critical inlet temperature of refrigeration centrifugal compressor to avoid phase change. The predicted critical temperature shares the same trend with the numerical results. Liquefaction will occur inside the compressor when the inlet temperature is lower than the critical temperature. The critical temperature will first raise and then down as the mass flow increases, which should be taken into consideration while designing a refrigeration centrifugal compressor or adjusting the operation condition.