U型圆管内混合对流换热特性数值研究

本文通过三维数值模拟的方法研究了混合对流作用下U型管管内的换热特性,分析了管内截面自然对流对管内层流换热的影响及主流速度、壁面热流密度和U型管倾角等参数对管内混合对流换热特性的影响.结果表明：与纯强制对流相比混合对流作用下其管内换热系数显著增大;在混合对流作用下,随壁面热流密度增大,管内换热增强,但随进口流速或U型管倾角的增大时,管内换热减弱.

Numerical Study on the Characteristics of Heat Transfer in a U-Tube with Mixed Convection

In this paper, the characteristics of heat transfer in a U-tube with mixed convection are studied by three-dimensional numerical simulation method. The influence of natural convection in cross section of U-Tube on the heat transfer is investigated, and the influences of streamwise mean velocity, heat flux on the tube wall and the incline angle between the U-tube and horizontal plane on the mixed convection heat transfer are analyzed. Results show that the heat transfer coefficient increase remarkably in the U-tube duo to the effect of mixed convection compared with the case of forced convection. The heat transfer increases with increase of wall heat flux for the mixed convection in the U-tube, but it decreases with increase of streamwise mean velocity and the incline angle.