方管内混合对流与管壁导热耦合换热的数值模拟

针对方管内空气混合对流时的流固耦合换热问题,提出将壁面导热作为边界条件进行处理的壁面导热与流动耦合简化计算方法,推导了计算公式,并采用SIMPLER算法进行了数值模拟.算法忽略壁面沿厚度方向的导热,假设管壁温度沿轴向一维分布,采用热量平衡法建立边界单元的能量守恒方程,将固体区域的导热简化为流体区域的边界条件,以提高计算的精度和可靠性.计算结果表明,受二次流影响,沿通道周向热量从加热面同时沿顺时针和逆时针方向迅速向两边传递,各壁面最大温差小于0.5℃,在轴向归一化长度为2～4时壁面轴向导热热流密度出现最值.平均Nusselt数Num随Reynolds数Re及方管倾斜角度θ的增大而增大,最优倾角在-30°和0°之间变化,但当Re＞1 500时,Num随θ的变化近似保持不变.计算结果与实验数据吻合良好,最大偏差小于±28.7％.

Numerical Investigation on Conjugated Heat Transfer of Conduction in Wall and Mixed Convection

The conjugated heat transfer of heat conduction in the wall and air mixed convection in tubes was numerically simulated with the SIMPLER algorithm and a new simplified method developed for dealing with conjugated problems.The results show that the circumferential conductive heat of the duct plate moves in both clockwise and anticlockwise directions,and the temperature difference of each plate is less than 0.5 ℃.In the axial direction,the maximum conductive heat flux occurs at the places where the axial non-dimensional length equals 2-4.The average Nusselt number increases with the Reynolds number and the inclination angle of the tube,and the optimum inclination angle is a variable value from-30° to 0°.However,the average Nusselt number is almost independent of the inclination angle when Re>1 500.The numerical results are in reasonably good agreement with the experimental data with the deviations within ±28.7%.