Abstract:

A mathematical model of annular flow in vertical rectangular narrow channel was developed and experimental verification was performed in order to study flow and heat transfer characteristics of annular flow in vertical rectangular narrow channel. Through numerically solving the mathematical model, pressure gradient, boiling heat transfer and liquid film velocity profile in the annular flow region were obtained. The present model could well predict pressure gradient and boiling heat transfer. The liquid film velocity profile of annular flow in the normal direction was not linear, and liquid film velocity gradient was large in the laminar boundary layer. Rectangular narrow channel size and heat flux had significant effect on liquid film velocity profile. Liquid film velocity increased with increasing heat flux and decreased with increasing channel size. The effect of mass flow rate on liquid film velocity was smaller than the effect of heat flux and channel size, and liquid film velocity decreased with increasing mass flow rate.

Key words: rectangular narrow channel, liquid film velocity, annular flow, phase equilibrium, heat transfer, phase change

摘要：

为了研究竖直窄矩形通道内环状流的流动传热特性,建立了窄矩形通道内环状流的数学物理模型,并进行了实验验证。通过数值求解环状流的数学物理模型得到了环状流区域的压降梯度、沸腾传热系数和液膜内的速度分布。结果表明窄矩形通道内的环状流模型能够很好地预测环状流区域的压降梯度和沸腾传热系数,而且环状流液膜内速度在法向的分布是非线性的,在层流边界层区速度梯度较大。热通量和窄矩形通道的尺寸对液膜的流速有很大影响,随热通量的增加和窄矩形通道尺寸的减小液膜的流速逐渐增加,然而质量流速对液膜流速的影响较小,而且随质量流速的增加液膜的速度逐渐减小。

关键词: 窄矩形通道, 液膜流速, 环状流, 相平衡, 传热, 相变