水平方管层流混合对流的三维数值模拟

NUMERICAL SIMULATIONS OF 3D-FLOW FOR LAMINAR MIXED CONVECTION IN HORIZONTAL RECTANGULAR TUBES

本文建立了水平矩形通道三维层流混合对流的数学模型，提出了壁面导热与流动耦合的简化计算方法，采用SIMPLER算法对其流动和换热过程进行了数值模拟。计算结果表明由于浮升力的作用使水平通道内出现二次流现象，加热面的上下顶端周向导热热流密度存在极大值，下底面的局部Nusselt数最大，上底面最小。混合对流平均Nusselt数随Re和Gr^＊的增大而增大；但当Re较大时，平均Nusselt数随Gr^8变化而近似不变。

A mathematical model was established to simulate the three-dimensional laminar mixed convection in a horizontal rectangular duct. The program was developed based on SIMPLER algorithm and the coupled convection and conduction heat transfer was simulated by the thermal balance method. The results showed that the secondary flow in the horizontal tube appeared due to the buoyancy force, and the conduction heat flux across the circumferential direction of duct walls reached different maximum values at the bottom and top corners related to the heated plate. The local Nusselt numbers related to the bottom wall were larger than those related to other walls, and the local Nusselt numbers related to the top wall were smaller than those related to other walls. The mean Nusselt numbers increased with the increase of Re and Gr^＊, but when Re was larger than 1500 the mean Nusselt numbers were almost independent of Gr^＊.