Abstract: The flow patterns of R32 were observed for its condensation heat transfer in a smooth horizontal circular tube with inner diameter of 2 mm. The experiments were conducted with the method of visualization under mass fluxes of 100, 200, 400 kg·m^-2·s^-1 at the condensation temperature of 40℃. Plug, slug, annular-wavy and annular flow patterns were observed. The results show that with the increase of mass flux, the annular flow regime becomes large and corresponding vapor quality is smaller when the annular flow changes to intermittent flow. The transition line between the two patterns is a slash line. It is because the shear in the vapor-liquid phase interface increases with the mass flux, which promotes the conformation of the annular flow. With dimensionless numbers, a correlation is proposed for predicting the boundary of intermittent flow and annular wavy flow. Compared the results with other five flow pattern maps, Yang-Shieh model can predict the experimental results relatively well.

Key words: R32, flow, condensation, heat transfer, minichannel, horizontal small tube

摘要： 采用可视化的方法，对流体R32在内径2 mm 的水平光滑圆管内冷凝换热的流型进行了观测实验，实验设定的流体饱和温度为40℃，质量流量分别为100、200、400 kg·m^-2·s^-1。观测到的主要流型为塞状流、弹状流、环波状流和环状流。通过实验观察，发现随着流量的增加环状流的流型区域增加，流型由环波状流转换成间歇流的干度推迟，其分界线为一条斜线，主要是由于随着流量的增大，气液表面剪切力增大促进了环波状流的形成。借鉴量纲1准则数提出间歇流与环波状流分界线公式。将实验值与其他5种流型模型进行了对比分析，发现只有与Yang-Shieh模型比较吻合。

关键词: R32, 流动, 凝结, 传热, 小通道, 水平光滑管