润滑油对水平强化管降膜蒸发传热特性的影响

Effect of Lubricating Oil on Heat Transfer Performance of Falling Film Evaporation on Horizontal Enhanced Tube

实际制冷系统中的制冷剂含有压缩机的润滑油.本文研究了制冷剂中润滑油不同含油率时水平管降膜式蒸发传热特性.工质为R134a,含油率分别为0.5%、1.2%、5.1%,蒸发温度为6,℃,热流密度范围为30～65,kW/m^2,工质喷淋密度分别为0.13,kg/（s·m）,0.17,kg/（s·m）、0.21 kg/（s·m）,测试段采用表面强化的铜管.实验结果表明：含油率从0.5%增大到5.1%,管外传热性能逐渐提高,当喷淋密度增加,管外换热系数也会提高,但随着含油率的增加,换热系数的增加幅度不大;一定含量的润滑油能增大R134a 水平管降膜蒸发的换热系数.

In engineering practice,refrigerant contains lubricating oil form compressor in the refrigerating system. In this study,the impact of different oil contents on evaporation of falling film on horizontal enhanced tube was dis-cussed. Experiments were conducted for R134a at the saturation temperature of 6,℃ on enhanced copper tube,with oil contents being 0.5%,1.2% and 5.1%,respectively,and heat fluxes ranging from 30,kW/m2 to 65,kW/m2, sprinkle densities being 0.13,0.17,and 0.21,kg/(s·m). The experimental results show that heat transfer coefficient of the outside horizontal enhanced tube increases with both oil contents growing from 0.5% to 5.1% and increasing sprinkle densities. However,with the augments of oil contents,the increases of heat transfer coefficient are nearly insensitive to the increasing sprinkle densities. In certain range of content,lubricating oil can improve heat transfer coefficient of R134a falling film evaporation.