切应力作用下层流饱和蒸发降膜的传热特性

处于切应力作用下的层流饱和蒸发降膜，作为一种重要的气液流动形式，其热质传递过程与目前多数文献研究的冷凝液膜明显不同。基于力平衡和能量平衡分析，从理论上建立了在同向或反向切应力作用下层流饱和蒸发液膜传热特性的物理模型，推导出液膜厚度和传热系数与流动长度、界面切应力、界面对流换热强度、雷诺数间的非线性关系式。研究表明：随初始雷诺数的增大，液膜厚度增加，传热系数减小；同向切应力具有减薄液膜厚度和增大传热系数的作用；反向切应力则起相反的作用，而且切应力的影响在反向情形下相对显著；界面对流换热强度的增强使得液膜厚度增加，传热系数减小，但与切应力相比，其影响相对较弱。

Heat Transfer of Laminar Saturated Falling Films Under Interfacial Shear

The laminar flow of saturated falling films under interfacial shear is one of most important two-phase flows, and the characteristics of heat and mass transfer is extremely different from that of condensing liquid film investigated by present literatures.. Base on the force balance and energy balance, the physical model of heat transfer was established for the laminar saturated falling films under countercurrent and cocurrent interfacial shear, and the theoretical equations of the film thickness and heat transfer coefficient on streamwise direction were presented. The present models include the effects of the interfacial shear, the intensity of interfacial convection heat transfer and Reynolds number. The investigation shows that the film thickness increases and heat transfer coefficient decreases with initial Reynolds number. The cocurrent shear plays the roles on thinning film thickness and enhancing heat transfer, and the countercurrent shear has inverse effect. And the effect of countercurrent is more remarkable than that of cocurrent shear. The intensity of interfacial convection heat transfer has influence on increasing film thickness and impeding heat transfer, and the effect is less notable than that of interfacial shear.