中文摘要：

在大温差自然对流中物性随温度变化较大，针对定物性计算时存在的计算精度误差较大问题，采用两种不同物性参数处理方法对不同温差下的封闭腔体内自然对流进行数值计算，研究瑞利数Ra从10^3～10^6时，腔体内空气自然对流换热的规律，对比分析了采用多项式、考虑气体密度、动力粘度随温度变化情况下数值模拟的结果．计算结果表明：在小温差情况下密度采用Boussinesq、动力粘度采用定常系数方法可以一定程度上减小计算量，加速计算收敛速度，但在大温差为500K时这种方法将导致计算结果误差为7．40％．在计算大温差自然对流问题时建议考虑物性系数随温度的变化影响．

英文摘要：

Physical properties of the natural convection in the large range of temperature change drastically with temperature. According to larger problem of the calculation accuracy error for the given properties, natural convection in a closed square cavity was calculated by two different physical parameters approaches in the different range of temperatures with the Rayleigh Number in the range of 10^3 to 10^6. And at the same time, the polynomial method was used to analyze the numerical simulation results of density and dynamic viscosity changes with temperature under different in temperatures. The numerical results show that, in the small temperature difference, Boussinesq and constant approximation can reduce the computation work and accelerate the convergence, but it will bring 7.40% for 500K temperature difference. In the calculation of the large temperature difference natural convection, the changes of coefficient with the temperature is suggested to consider.