Effect of lubricating oil on flow boiling heat transfer of low GWPrefrigerant R-1234yf in a horizontal small-diameter tube

实验研究了润滑油对低GWP制冷剂HFO-1234yf在内径为2 mm和4 mm的小口径管内流动沸腾换热的影响。实验结果表明，随着油品质量分数的增加，蒸汽品质较低时的局部换热系数增大，起泡现象加剧。在高品质区，换热系数随油品质量分数的增加而单调减小。通过目视观察，展示了不同质量流量和热流密度下的成型现象和流型。随着含油质量分数的增加，压降从无油时的1.7倍增加到4.8倍。

The effects of lubricant oil on flow boiling heat transfer of low GWP refrigerant HFO-1234yf in small-diameter tubes with inner diameter of 2 and 4 mm were experimentally investigated. Experimental results showed that with increasing oil mass fraction, the local heat transfer coefficient increased at lower vapor quality due to intensified foaming phenomena. However, the heat transfer coefficient decreases monotonically with oil mass fraction in high quality region. The forming phenomena and flow patterns at different mass flux and heat flux were illustrated by the visual observation. With increasing oil mass fraction, pressure drop was larger from 1.7 to 4.8 times than that for oil free.