Recent progress in pool boiling heat transfer of low GWP refrigerants with the effect of POE lubricant oil

The recent research on pool boiling heat transfer of low global warming potential (GWP) refrigerants under the effect of polyolester (POE) lubricating oils are summarized in this article. Recently, several low GWP refrigerants have been developed as alternatives to the high GWP refrigerants such as hydrofluorocarbons (HFCs). However, it is crucial to comprehend how lubricating oil affects the performance of low GWP refrigerants in terms of compatibility and pool boiling heat transfer (commonly seen in flooded evaporators). The overview suggests that the low GWP refrigerants are compatible with POE oil. Whereas, its heat transfer performance depends on the mass concentration of oil present in the refrigerant. In addition, the pool boiling performance of the low GWP refrigerant is also affected by other factors such as evaporator pressure, saturation temperature, heat flux, and thermophysical properties of refrigerant and oil mixture. The analysis of available heat transfer coefficients (HTCs) for refrigerant-oil mixture shows that the heat transfer performances of the enhanced surfaces are very sensitive in the presence of oil; whereas, it is less severe on a smooth surface. On smooth surfaces, a refrigerant-oil mixture (3% mass concentration) could augment the HTCs as compared to the pure refrigerants subject to evaporator pressure/saturation temperature. In contrast, the simulation studies show that the oil additives always deteriorate the HTCs compared to the pure refrigerant.