高温下加热/冷却管内参与性介质的辐射与对流耦合换热研究

本文通过数值模拟方法研究了高温下加热 /冷却管内层流充分发展流动的参与性介质热起始段的辐射与对流耦合换热。采用离散坐标法求解圆柱坐标系下的非线性积分微分辐射传递方程 ,采用有限差分法求解辐射与对流的耦合换热能量方程。通过计算 ,分析了不同壁温及入口温度下 ,介质导热系数、壁面发射率、介质散射反照率及散射相函数等因素对局部努谢尔数、壁面热流密度及有效加热 /冷却长度的影响 ,并同时采用努谢尔数和壁面热流密度评价了耦合换热中辐射对对流换热的影响。

Coupled Radiation and Convection Heat Transfer in High Temperature Heated/Cooled Tubes with Inside Participating Medium Flowing

The coupled radiation and convection heat transfer in high temperature heated/cooled tubes with inside participating medium flowing is investigated by numerical simulation.The laminar flow is developed with a Poiseuille velocity distribution but thermal status is developing.By the discrete ordinate method,the nonlinear integrodifferential radiative transfer equation in cylindrical coordinate system is solved to obtain the radiative source term in the energy equation.And the energy equation for the coupled heat transfer is discretized by the finite difference approximation.The local Nusselt number and wall heat flux for convection and the total wall heat flux for coupled heat transfer are used to evaluate the influence of radiation on convection.The effects of the medium thermal conductivity,scattering albedo and phase function as well as the wall emissivity are discussed based on the calculated results.The analysis shows that the effect of radiation weakens convection heat transfer,but compared with the simplex convection,the coupled heat transfer accelerates the development of temperature field and significantly shortens the tube length with obvious heated/cooled effect.Difference appears between the two cases of coupled heat transfer in heated/cooled tubes even though the medium property parameters keep constant.The wall emissivity,the medium thermal conductivity and scattering albedo have great influences on the coupled heat transfer,while the effect of the medium scattering phase function is small.