竖直管外气液逆流环状降膜速度与温度分布

建立了竖直管外环状降膜气液逆流传热传质条件下稳态层流降膜一维速度分布和二维温度分布模型,以及膜厚和降膜表面热通量的数值计算方法。表面热通量的模型计算值与实验值在气体Reynolds数Re_g<1200的范围内吻合较好,表明基于界面摩擦因子求解模型的方法在两相均为层流条件下是可靠的。模型显示了降膜速度分布和温度分布的非线性特征,降膜表面附近陡降的温度梯度表明,减小膜厚是强化降膜传热传质过程的有效途径。

Velocity and temperature profiles in annular falling films outside vertical tube with counter-current gas flow

A theoretical model was derived for the steady state one-dimensional velocity distribution and two-dimensional temperature distributions in annular laminar liquid films falling down on the wall outside a vertical tube with heat and mass transferring from the interface to counter-current gas flow.Based on the model,liquid film thickness and interfacial heat flux could be predicted if shear stress was obtained.From the good agreement of experimental data and predicted values of the interfacial heat fluxes within the range of gas flow Reynolds number Re_g<1200,the method of using interfacial friction factor to solve the model was reliable under laminar conditions of the two phases.The model simulation results revealed the non-linear characteristics of velocity and temperature distributions in the film.The sharp temperature gradient close to the gas-liquid interface indicated that it was an effective way to enhance heat and mass transfer by reducing film thickness.