R134a卧式螺旋管内沸腾两相流型与传热特性实验研究

在蒸发温度为5～15 ℃、热流密度范围为5～20 kW·m^-2、工质质量流速变化范围为50～500 kg·m^-2·s^-1和干度范围为0.01～0.9的条件下，对R134a在卧式螺旋管内的沸腾两相流型及传热特性进行了实验研究。利用可视化技术对流型进行了观察分析，发现在相同工况条件下，卧式螺旋管上升段和下降段的流型有所不同，特别是形成环状流之前存在明显不同的过渡流型，分别为波环状流型和超大气弹流型，因此，对上升段和下降段分别建立了流型图。获得了传热系数随工质的干度、质量流速和热流密度等参数的变化关系，发展了R134a在卧式螺旋管内流动沸腾传热系数的计算关联式。

Study on Two-Phase Flow Boiling Patterns and Heat Transfer of R134a in Horizontal Helically-Coiled Pipe

The experimental study on flow boiling patterns and heat transfer of R134a in horizontal helically-coiled pipe was presented. The experiment was carried out at saturation temperature from 5 to 15 ℃, with the refrigerant mass flux varying from 50 to 500 kg·m^-2·s^-1, heat flux varying from 5 to 20 kW·m^-2, and the vapor quality ranging from 0.01 to 0.9. The flow patterns were observed and analyzed through visualization experiment. It is found that the flow patterns in the upflow and downflow sections are different under the same conditions, especially the transition flow patterns before the annular flow are obviously different, which are wave annular flow and super slug flow in the upflow and downflow sections, respectively, so two different flow pattern maps are proposed for the upflow and downflow sections, respectively. The effects of vapor quality, mass flow rate and heat flux on the boiling heat transfer coefficients were obtained, and the new correlation was developed for predicting the flow boiling heat transfer coefficients of R134a in horizontal helically-coiled pipe.