饱和多孔介质自然对流模型与实验

Model and experiment research of natural convection in saturated porous media

以饱和多孔介质内流体流动、流体和固体传热为研究对象,考虑流体密度随温度变化,局部热平衡,引入Brinkman-Forchheimer的扩展Darcy模型进行修正,建立固体随机堆积饱和多孔介质自然对流数值模型,采用有限体积法计算.利用自主研制的两侧恒温差立方体多孔介质实验台,对数值模型进行实验验证.综合数值计算和实验结果表明:腔体内最大流速随温差和瑞利数Ra增大而增大,且最大流速出现在高低温壁面附近;随着Ra增大,温度等值线由近似于平行于高低温壁面变为近似垂直于高低温壁面;高温壁面上Nu从上至下呈线性增加趋势;高温壁面Nu随Ra增大而增大,当Ra<102时,Nu维持在12以内;当102<Ra<106,Nu增加迅速,由11.4增加到276.4;当Ra>106,Nu增加速率很小.

Fluid flow and heat transfer between fluid and solid in saturated porous media is the object of this study. Considering the variation of fluid density with temperature and the local heat balance, this paper introduced the Brinkman-Forchheimer-extended Darcy model and established the numerical modal of natural convection in saturated porous media of solid piled up at random. Finite volume method is used and the independently developed experiment table of constant temperature difference at two sides is used to verify the numerical modal. Experiments and numerical computation shows that maximum flow velocity of cavity increases with temperature difference and Ra numbers increasing, maximum flow velocity appears near high and low temperature wall. With the increase of Ra, temperature contours becomes approximately perpendicular to high and low temperature wall from approximately parallel to high and low temperature wall; Nu numbers of high temperature wall are on the linearly rise; Nu^- of high temperature wall increases with Ra increasing, when Ra〈10^2, Nu^- maintains within 15; when 10^2〈Ra〈10^6, Nu^- increases rapidly from 11.4 to 276.4; when Ra〈10^6, Nu^- increases slowly.