重力对R134a在矩形小通道内冷凝过程的影响

为研究重力对小通道冷凝过程的影响，采用VOF模型对制冷剂R134a在水平放置的边长1mm方形截面小通道内的冷凝换热过程进行数值模拟.模拟过程考虑重力、表面张力和界面剪切力的综合作用，表面张力采用CSF模型.结果表明:重力对矩形小通道冷凝换热的影响不明显，蒸气在通道横截面上呈近似圆形分布；通道较短时重力对液膜的汇聚作用不明显，达到一定长度后重力作用凸显.研究结果为天舟一号货运飞船搭载的蒸发与冷凝科学实验研究项目冷凝空间实验方案设计提供了理论依据. 

Effect of Gravity during Condensation of R134a in a Rectangular Minichannel

In order to study the effect of gravity on the condensation of R134a in a horizontal single square minichannel with 1mm side length, a Volume of Fluid (VOF) method is adopted to simulate the condensation process. The influence of gravity, surface tension and gas-liquid interfacial shear stress are taken into account. The Continuum Surface Force model is chosen for surface tension. Results denote that the lowest velocity and temperature appears at the corner of channel, where condensation occurs first. The distribution shape of the steam in the cross section of the channel is approximately circular and the condensation increases along the flow direction. In square minichannel, the effect of gravity on condensation can be neglected and the condensation is dominated by surface tension and gas-liquid interfacial shear stress at low and high inlet mass velocity respectively. The influence of gravity in condensation film is unobvious when the minichannel is short. In long minichannel, the condensation accumulates in the bottom of channel because of gravity which is not benefit for condensation heat transfer.