缩放管强化传热机理分析

应用数值模拟方法对光滑圆管与缩放管内的空气湍流对流传热在相同条件下进行了计算，对缩放管与光滑圆管内的对流传热系数、速度模量分布、径向速度分布、湍流强度的对比表明：缩放管内空气对流传热系数的提高，是近壁区域流体扰动增强产生了较大的流动径向速度与湍流强度的结果。表面传热系数、近壁区径向速度、近壁区湍流强度三者沿流向周期性变化的规律一致。缩放管强化传热的机理分析指出，强化气体传热的粗糙高度应位于流动过渡区。

Mechanism of Heat Transfer Enhancement for Converging-diverging Tube

The turbulent air flow and heat transfer in converging-diverging tube were numerically simulated with constant properties, periodically developed flow and uniform wall temperature considered, as well as for smooth tube under the same condition. The compare of heat transfer coefficient distribution, velocity magnitude distribution, radial velocity distribution and turbulent intensity distribution between converging-diverging tube and smooth tube was conducted. The Results showed that the augmentation of airflow heat transfer in converging-diverglng tube was due to disturb to the near wall fluid, intensified radial velocity and turbulent intensity. The periodically variation of heat transfer coefficient along flow direction was in exactly accordance with that of radial velocity and turbulent intensity in near wall region. The optimum roughness height was stressed to be in flow buffer region to achieve better air flow hydraulic and thermal characteristics.