基于VOF算法，编写用户自定义函数（UDF），采用FLUENT软件建立了椭圆横管外降膜流动和换热的计算模型。根据CFD模型，计算和分析了在不同长短轴比e下管外降膜速度分布、压力分布、液膜内温度分布和管外换热分布的变化规律。模拟所得和实验数据基本吻合。研究结果表明：长短轴比e的变化影响了管外液膜速度分布、压力分布和膜内温度分布；相比圆管，椭圆管的管外膜内液体流速更快。壁面压力沿周向逐渐减少并在X=0.9附近快速回升；随e的增加，周向压力最小值位置逐渐向后推移。局部Nu数分布与压力分布在趋势上存在一致性。当e=1.65附近时，椭圆的换热性能最优；最后，通过对管形的研究分析，提出横管的传热分区模型。

Based on VOF algorithm and user defined function (UDF) , a physical model was established for elliptical transverse tube falling film flow and heat transfer by FLUENT. According to the CFD model, the velocity distribution, pressure distribution, temperature distribution inside the liquid film and the change of the distribution of heat transfer were calculated and analyzed under different ratio between long and short axes. The data of simulation are basically consistent with the experimental data. The results show that the velocity distribution, pressure distribution and temperature distribution of the liquid film are affected by the change of the ratio between long and short axes. Compared with a circular tube, the liquid flow rate in the tube of the elliptical tube is faster. Wall pressure gradually decreased along the circumferential direction and rapid recovery near the X=0.9.With the increase of ratio between long and short axes, the position of the minimum value of the circumferential pressure is gradually increased.The local Nu in X=0.9 reaches the minimum value.The local Nu distribution is consistent with the pressure distribution on the trend. When e=1.65 is near, the heat transfer performance of ellipse is optimal. At last, the heat transfer model of horizontal tube is presented through the study and analysis of the tube shape.

TK172

国家自然科学基金项目（51306156）；西南科技大学博士基金项目（11zx7106）.