倾斜管内热进口段自然强制复合对流传热

COMBINED FREE AND FORCED CONVECTION INTHERMAL ENTRANCE REGION OF INCLINED PIPES

用数值分析方法研究了倾斜管内热进口段自然强制同向复合对流传热 ,分析了浮力、倾斜角及轴向导热对流动和传热特性的影响 ,得到了速度、温度、壁面剪切应力、局部及平均Nusselt数的分布和变化 研究结果显示Pe=71时平均Nusselt数的最大值位于 2 5°～ 45°之间 ,Pe=2 5时则在 90°处出现 .

Numerical analyses are conducted for combined free and forced laminar convection in the thermal entrance region of inclined pipes with buoyancy-aided flow. The effects of buoyancy force, pipe inclination angle and axial conduction on the hydrodynamic and heat transfer characteristics are investigated, and numerical res-ults of velocity and temperature profiles, distributions of the Nusselt numbers and wall shear stress are obtained. The velocity and temperature profiles are distorted and become asymmetric, and a reverse flow occurs near the pipe top as the buoyancy effect becomes significant. The wall shear stress varies from minimum at the top pipe wall to maximum at the bottom pipe wall. The axial conduction effect becomes significant at low Pe number. The circumferential average Nusselt number reaches a maximum at an inclination angle between 25° and 45° for Pe=71 but the maximum appears at α=90° for Pe=2.5.