平板过冷流体降膜流动传热特性的数值研究

本文采用电容探针和高速摄像对沿大平板垂直下降液膜的表面波进行了实验测量。根据实验数据对两种典型的波形建立模型。数值计算假设降膜表面波形状不变，且忽略空气对降膜表面的剪应力，对过冷降膜表面波内部的流动和传热特性进行了计算。研究表明：表面波内部液膜的二次涡流对过冷降膜的换热有重要影响。而大波幅的表面波对于换热的增强主要由两方面的效应构成：表面波内部的对流和二次涡流；二次涡流携带大量质能，从而对等效膜厚的减小作用。

Numerical Simulation on Heat-Transfer Character of Subcooled Falling Film on Flat Plate

In this paper, the capacitance probe and high speed camera were adopted to study the wave structure of the falling film on the flat plate experimentally. Two typical shape waves were studied numerically based on the experimental data. The wave shape kept invariant and the shear stress by the air was neglected in the numerical calculation. The numerical calculation was carried out to investigate the flow behaviour and heat transfer characteristic inside the surface wave. The results show that the vortices inside the surface wave have great effect on the heat transfer for sub-cooled falling film. The enhancement of the heat transfer induced by the large amplitude wave consists of two parts: Convection effect and vortices inside the surface wave which reduce the equivalent film thickness by carrying large mass and momentum