Pool boiling heat transfer characteristics of R-1233zd(E) on smooth tube subject to POEC-220 lubricant oil

Abstract

Pool boiling heat transfer characteristics of low pressure and low GWP refrigerant R-1233zd(E) alternative to R-123 and R-245fa on a smooth copper tube are investigated with the influence of POE (polyolester)-lubricant oil POEC-220 (220 cSt). The experiments were conducted at a saturation temperature of 10°C, and 26.7°C in 10−90 kWm−2 heat flux range. The mass concentration of POEC-220 oil varied from 1−10%. The obtained results exhibit that the addition of POE lubricant to the pure low-pressure refrigerant R-1233zd(E) degraded the heat transfer performance. The average degradation of heat transfer coefficients (HTCs) for mass concentration of oil 1%, 3%, 5%, and 10% are 9.40%, 7.16%, 15.31%, and 42.87% respectively when compared to that of pure refrigerant. It is found that the nucleation sites are especially reduced at the bottom part of the test tube. Yet, either Augmentation or reduction of HTC with the presence of lubricant oil is mainly attributed to the absolute pressure (low/medium/high) of the working refrigerant/fluid/system/evaporator, the mass concentration of oil, boiling surface, and applied heat flux. However, augmentation in the HTC with less oil addition (e.g., less than 5%) can be seen for absolute pressures between 150 and 700 kPa.