提出了适合于在温差20～720K下层流自然对流计算的变物性流体模型。在不可压流体模型的基础上,该模型考虑了流体密度、粘度和热导率随温度的改变。开发了非均匀同位网格下的SIMPLEC修正算法。用该模型对20K和720K温差下和不同Ra数(103～105)下的方腔内自然对流问题进行了数值计算,得到速度场分布、温度场分布和热壁处平均Nu数。计算结果与基准解,以及与基于Boussi-nesq假设的不可压流体模型计算结果进行了比较,验证了该模型及算法是行之有效和简单的。 A variable fluid model suitable for natural convection calculation of laminar flow at temperature difference of 20 ~ 720K is proposed. Based on the model of incompressible fluid, this model considers the change of fluid density, viscosity and thermal conductivity with temperature. A SIMPLEC algorithm is developed for non-uniform parity grid. The model was used to calculate the natural convection problem in the cavity under 20K and 720K temperature difference and different Ra number (103 ~ 105). The velocity field distribution, temperature field distribution and average Nu number at the hot wall were obtained. Comparing the results with the baseline solution and with the results of the calculation of the incompressible fluid model based on Boussi-nesq assumption, the model and the algorithm are proved to be effective and simple.