轻介质传输中辐射热传导近似成立的判别因子

Satisfied qualification of radiative heat conduction approximation when radiation transferred in light media

从辐射输运方程出发，通过递推的方法，推导并得到了包含高级修正的辐射能流表达式。利用这个表达式，分析了辐射在轻介质中传输时，辐射热传导近似的成立条件。热传导近似的成立条件总是要求温度空间变化尺度与自由程之比远大于某个值，该值即判别因子，它表征热传导近似条件满足的苛刻程度，其值越大，热传导近似就越难满足。讨论得出；当同时考虑轫致和散射过程时，这一判别因子的值在3～60之间。并进一步分析了密度的空间变化以及1维球坐标下的半径对判别因子的影响。

Based on the radiation transfer equation, the radiation energy density flux with higher terms was obtained using iteratire method. Using the formula, the satisfied qualification of the radiative heat conduction approximation was analyzed when radiation transferred in light media. The approximation always required the quotient between varying scale of temperature and Rosseland mean free path to be far larger than some value, as called citerion η, it indicated the hardness of satisfaction of the approximation： as the criterion increased, the approximation will be hardly satisfied. The results indicated that the criterion is between 3 and 60 when the bremsstrahlung and scattering process are both concerned. And the influence of two factors, the changing scale of density in space and the radius in one sphere dimension, on the criterion was analyzed.