垂直窄缝通道内环状流沸腾传热特性

Heat Transfer Characteristics of Annular Flow in Vertical Narrow Rectangular Channel

本研究基于液膜和蒸汽的质量、动量和能量方程,建立了均匀热流垂直窄缝通道内环状流沸腾传热模型,通过相关文献估算环状流起始点处液膜厚度,利用有限差分法对环状流模型方程组进行数值求解,得到沿流道环状流区域的液膜厚度,并进一步预测了局部沸腾传热系数,结果表明:环状流区域的局部沸腾传热系数随质量流量和干度的增加而增加,与Kenning关联式对比,模型预测沸腾传热系数较关联式计算值偏低。将不同工况下的226组两相环状流实验数据与模型预测结果进行对比,平均绝对误差为18.2%。

A model of annular and saturated flow boiling in vertical narrow rectangular channel subjected to a uniform heat flux has been developed based on mass,momentum and energy equations of the liquid film and the vapor. The initial value of liquid film at the onset of annular flow is evaluated by employing the proper correlations available in literature. A finite difference technique is used to solve the model equations numerically,and then the liquid film thickness of annular flow region along the channel is obtained and used to further predict the local boiling heat transfer coefficient. The presented model shows that the heat transfer coefficient increases with the mass flux and the vapor quality. Predicted heat transfer coefficient by proposed model is lower than calculated values by Kenning correlations. The presented model has been compared with 226 experimental data points of two-phase annular flow at different operating conditions,and it shows that the mean absolute error of the model prediction is 18. 2%.