管内耦合换热的辐射热流特征及抽样模式比较

RADIATIVE HEAT FLUX CHARACTERISTICS OF COUPLED HEAT TRANSFER IN TUBES AND COMPARISON OF RANDOM SAMPLING MODES

通过数值模拟,研究了圆管层流入口段辐射与对流祸合换热中的辐射热流分布特征,提出并比较了采用蒙特卡罗法计算辐射换热的两种抽样模式。结果表明,在圆管入口段的耦合换热中,同一截面的径向辐射热流密度与轴向辐射热流密度数量级相当,世分布形态差别很大。用蒙特卡罗方法计算辐射换热时,采取等权能束的抽样模式,可消除因抽样能束的能量不同而造成的计算误差、降低计算量、提高计算精度。

By numerical simulation, the radiative heat flux characteristics of coupled radiation and convection heat transfer in tube is investigated, and the random sampling modes for the Monte Carlo calculation of radiative heat transfer are compared. A laminar developing flow of high temperature gray medium in tube is considered in the investigation. The results show that, within a cross section of the tube, the magnitude of the radial radiative heat flux is equivalent to that of the axial radiative heat flux, but their distribution shapes are quite different. For a radiative heat transfer calculation by the Monte Carlo method, the use of the random sampling mode of weight-equivalent energy beams can eliminate the calculating error caused by a random sampling of different energy beams. And thus, by this random sampling, the calculating efficiency and precision can be improved obviously.