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通过数值计算深入分析了超临界压力条件下水的强烈的物性变化及对流换热的边界条件对水平同心套管间自然对流换热的影响规律，并为高新技术的发展提供一定的理论基础。采用求解原始变量的有限差分法，并利用大型通用计算程序ＰＨＯＥＮＩＣＳ，对控制方程组进行了数值求解。分析了在内、外管表面均为等壁温边界条件或内管为常热流、外管为等壁温边界条件下，同心套管间的流场和温度场；研究了强烈的变物性、内外表面温差及内管壁面上的热流密度等对内、外管壁上自然对流换热系数的影响规律。结果发现：在内管表面热流密度相同的条件下，不同的外管表面温度所对应的内、外管表面温差及对流换热系数有比较大的差异；在某些条件下，随着热流密度的升高，尽管套管内自然对流流速增大，但是自然对流换热能力却下降。
The influence of the strong physical property change of water and the convection heat transfer boundary conditions on the natural convective heat transfer between horizontal concentric bushing were analyzed numerically. The theoretical basis for the development of high and new technology was provided. The finite difference method for solving the original variables is adopted, and the control equations are numerically solved by the large-scale generalized calculation program PHOENICS. The flow field and temperature field between concentric bushing under the conditions of isothermal wall temperature and inner tube being always heat flow and the outer tube being isothermal wall boundary were analyzed. The inner and outer surface temperature difference and the heat pipe density on the inner wall, the inner and outer wall of the natural convection heat transfer coefficient. The results show that under the same heat flux density of the inner tube surface, the temperature difference between the inner and outer tube surface and the convective heat transfer coefficient of the different outer tube surface temperature are quite different. Under certain conditions, with the increase of heat flux Of the increase, despite the natural convection tube flow rate increases, but the natural convection heat transfer capacity has declined.