剪切层流蒸发液膜的传热特性

为克服理论分析中气液界面对流换热难以计算的问题,基于气相传热模型,建立了在同向或反向切应力作用下层流饱和蒸发液膜的传热模型,推导出无量纲液膜厚度和壁面对流换热系数与流动长度、界面切应力和初始雷诺数间的理论关系式.研究表明,受液膜蒸发的影响,液膜厚度沿流动长度不断减小,换热传热系数不断增加;同向切应力具有减薄液膜厚度和增大传热系数的作用;反向切应力则具有相反的作用,其影响更为明显.这一理论模型可以反映层流饱和蒸发液膜的传热特性.

Heat Transfer Characteristics of Evaporating Laminar Liquid Flow Films with Interfacial Shear

In order to overcome the difficult problem,of accurately calculating convective heat transfer along liquid-vapor interfaces,in theoretical analysis work,a heat transfer model,based on the vapor-phase heat transfer model,has been formulated for saturated evaporating liquid laminar flow films acted upon by co-current or counter-current interfacial shear.The theoretical relationship formula between the non-dimensional film thickness,including the wall's heat transfer coefficient,and the flow distance,the interfacial shear and the initial Reynolds number,has been derived.Study results indicate that,under the effect of film evaporation,the film thickness continuously decreases and the heat transfer coefficient continuously increases along the flow path.On the other hand, co-current shear stress causes the film to get thinner and the heat transfer coefficient to increase,while counter-current shear stress exerts a reverse effect.The theoretical model can perfectly reflect the heat transfer characteristics of saturated evaporating laminar liquid flow films.