多孔介质通道发展传热的理论研究及数值分析

发布时间：2018-01-20 06:41

本文关键词： 多孔介质发展传热强迫对流局部热非平衡分离变量法　出处：《上海工程技术大学》2016年硕士论文　论文类型：学位论文

【摘要】：近年来,以多孔介质作为媒介进行强化传热的研究备受关注,主要是表现为在各类机械相关设备上的应用,如太阳能储能器设计、换热器、化学物质反应设备、干燥设备、电子设备冷却等等。本文以空气为工作介质通过理论和数值相结合的方法在局部热非平衡和常温边界条件下对多孔介质圆管和圆环通道进行了传热分析,所得结果为科学研究者和工业界提供了有价值的参考。首先,本文基于局部热非平衡条件下的圆管能量方程,对其进行无量纲化,忽略孔隙流体径向的热传导,运用数学物理方法中的分离变量法对能量方程进行求解,推导出固相和气相无量纲温度以及Nusselt数(Nu)的解析解。然后,利用多物理场耦合分析软件COMSOL Multiphysics对前面所得的无量纲温度以及Nusselt数进行验证。对比结果表明,COMSOL Multiphysics所得数值解和解析解十分吻合,从而证明了本文解析解的正确性。随后,对多孔介质圆管通道的无量纲温度和Nusselt数进行参数分析,分析固相和气相随着位置或者Peclet数(Pe)的变化规律,发现气固相的无量纲温度随着轴向坐标和径向坐标的增大而减小,随着Peclet数的增大而增大,最终都趋于零,并且固相的温度在减小到零之前始终小于相同位置下的气相温度;Nusselt数随着轴向位置坐标的增大而减小,而随着Peclet数的增大而增大,并在某一位置达到稳定值。最后,我们将多孔介质圆管通道的解析方法推广到多孔介质圆环通道,并推导出相应的解析解,并与相同条件下COMSOL Multiphysics所得数值解十分吻合。结果发现在多孔介质圆环通道中无量纲温度和Nusselt数随着坐标和Peclet数的变化趋势和圆管通道相同,并且圆环通道中的气固相温度低于相同位置下的圆管通道,而前者在入口处Nusselt数及其稳定值均高于后者。此外,对无量纲温度随圆管内径的变化进行了研究发现,内径愈大,无量纲温度愈低,Nusselt数愈高。借助COMSOL Multiphysics,考虑气相在径向方向上的热传导,并对相应的能量控制方程进行求解,所得结果表明,不论是多孔介质圆管通道还是圆环通道,无量纲温度和Nusselt数均小于不考虑气相径向热传导情况,但是变化趋势相同,结果相差不大。
[Abstract]:In recent years, the study of heat transfer enhancement with porous media has attracted much attention, mainly for the application of various mechanical related equipment, such as solar energy storage device design, heat exchanger, chemical reaction equipment. Drying equipment. In this paper, the heat transfer analysis of porous media tube and annular channel is carried out under the condition of local thermal non-equilibrium and normal temperature boundary condition by using air as the working medium through the combination of theory and numerical method. The results provide valuable reference for scientific researchers and industry. Firstly, based on the energy equation of circular tube under the condition of local thermal non-equilibrium, the dimensionless heat conduction of porous fluid is ignored. The energy equation is solved by using the method of separating variables in mathematical and physical methods. The analytical solutions of the dimensionless temperature of solid and gas phase and the Nusselt number are derived. The dimensionless temperature and Nusselt number obtained above are verified by multi-physical field coupling analysis software COMSOL Multiphysics. The numerical solution obtained by COMSOL Multiphysics is in good agreement with the analytical solution, which proves the correctness of the analytical solution in this paper. The dimensionless temperature and Nusselt number of porous media tube channel are analyzed, and the variation of solid and gas phase with position or Peclet number is analyzed. It is found that the dimensionless temperature decreases with the increase of axial and radial coordinates and increases with the increase of Peclet number. And the temperature of the solid phase is always lower than that of the gas phase at the same position before decreasing to zero. The Nusselt number decreases with the increase of the axial coordinates, but increases with the increase of the Peclet number, and reaches a stable value at a certain position. Finally. We extend the analytical method of porous media tube channel to the porous media circular channel and derive the corresponding analytical solution. And COMSOL under the same conditions. It is found that the dimensionless temperature and Nusselt number change with coordinate and Peclet number in porous media annular channel. Same channel. Moreover, the gas-solid temperature in the annular channel is lower than that in the same position, and the Nusselt number and its stability at the entrance of the former are higher than those in the latter. The variation of dimensionless temperature with the inner diameter of circular pipe is studied. It is found that the larger the inner diameter, the lower the dimensionless temperature is, and the higher the Nusselt number is, with the aid of COMSOL Multiphysics. The heat conduction in the radial direction of the gas phase is considered and the corresponding energy governing equation is solved. The results show that both the porous media tube channel and the circular channel are obtained. The dimensionless temperature and Nusselt number are smaller than those without considering the gas phase radial heat conduction, but the variation trend is the same and the result is not different.
【学位授予单位】：上海工程技术大学
【学位级别】：硕士
【学位授予年份】：2016
【分类号】：TK124

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