垂下液膜式水平管蒸发器的换热特性

采用层流和紊流两种模型对一水平管外垂下液膜的强制对流蒸发换热性能进行了数值计算．对管顶部的冲击滞止区和管侧部的自由绕流区分别采用不同的坐标变换方法进行微分方程组简化．根据滞止区计算结果确定自由绕流区的初始边界条件，排除了以前类似计算中人为假定计算边界条件的缺陷．紊流计算采用壁面函数法．数值计算结果确认了液膜蒸发量对换热系数的影响可以忽略，液膜内温度分布不能近似为线性分布．计算结果和作者的实验数据及其他研究的实验数据进行了比较，实验值处于层流解和紊流解之间，更靠近紊流解．对水和Ｒ１１两种工质，紊流解和实验值吻合得很好

Evaporation Heat Transfer of Falling Liquid Films on Horizontal Tube Evaporator

Laminar model and turbulent model were used to calculate the heat transfer coefficient of falling liquid films on horizontal tube evaporator. Different coordinate alternations were used to simplify the differential equations for stagnation region and free surface flow region respectively. The boundary conditions of free surface flow region were ditermined by the calculated results of stagnation region. Wall function method was used for turbulent calculation. Calculations show that effects of film evaporation can be neglectable and the temperature field of liquid film can not be approximated to linear distribution. The comparisons of experimental results with numerical solutions show that the experimental data are between laminar solutions and turbulent solutons, but are closer to the turbulent analysis.