R410A-油混合物在7mm水平直光管内流动沸腾的换热特性 Ⅰ.实验研究

Heat Transfer Characteristics of R410A-Oil Mixture Flow Boiling in a 7 mm Horizontal Straight Smooth Tube Ⅰ.Experimental Study

实验研究了环保替代制冷工质R410A-润滑油混合物在水平直光管内的流动沸腾换热特性．实验测试管长度2m、外径7mm．实验工况的蒸发温度为5℃，质量流率为200-400kg／（m^2·s），热流密度为7．56～15．1kW／m^2，入口干度x=0．2～0．7，干度变化为0．2，油的平均质量分数wno=0～5％．实验结果表明，R410A-油混合物管内流动沸腾的换热系数随质量流率的增大而增大；在x〈0．7的工况下，油的存在总是增大换热，当wno从0增长到5％时，换热系数最大可增加61％．在x=0．8的高干度情况下，换热系数在wno=1％时达到最大值，然后随着wno的增大换热系数逐渐降低．

Experimental study of the heat transfer characteristics of R410A-oil mixture flow boiling in a horizontal smooth tube was performed to investigate the influence of oil concentration, vapor quality and mass flux on the heat transfer coefficient. The length of the test tube is 2 000 mm, and the outside diameter is 7.0 mm. The experimental parameters include the evaporating temperature of 5℃, the mass flux from 200 to 400 kg/（m^2· s）, the heat flux from 7.56 to 15. 1 kW/m^2 , the inlet vapor quality from 0. 2 to 0.7, and oil concentration from 0 to 5%. The test result shows that the heat transfer coefficient of the R410A-oil mixture increases with the mass flux; the presence of oil enhances the heat transfer coefficient when the vapor quality is less than 0. 7; the heat transfer coefficient can be enhanced by 61% as the oil concentration increases from 0 to 5%. When the vapor quality is 0.8, the heat transfer coefficient gets the maximum value at the oil concentration of 1%, and then it decreases with the increasing of oil concentration.