A model to predict R134a refrigerant leakage through the radial clearance of rolling piston compressors

In this paper a non-isothermal two-phase model for oil–R134a refrigerant mixture flow is presented to predict the R134a leakage through the radial clearance of rolling piston compressors. The flow is divided in a liquid single-phase region and in a two-phase region, in which the homogeneous model is used to simulate the flow. The refrigerant leakage is determined using the mixture mass flow rate and the refrigerant mass fraction variation along the flow. The results are obtained for inlet pressures varying from 200 to 700 kPa, inlet temperatures ranging from 40 to 60 °C, and minimal clearances between 10 and 60 μm. The results are firstly compared to existing isothermal model data, showing that there is a significant difference between the leakage flow rates predicted by isothermal and non-isothermal models. Finally, a useful general equation for compressor designers is proposed to calculate the refrigerant leakage for a large range of operation conditions.

► Refrigerant leakage is modeled by a non-isothermal two-phase oil-refrigerant mixture flow. ► The existing isothermal two-phase models are shown to overestimate the leakage. ► A general equation to estimate the refrigerant leakage is proposed. ► This equation can be used in a computational code for simulating the whole compressor.