Numerical Study On Convection Heat Transfer Of Porous Materials

With the rapid development of economy and society, energy and environmental issues have become increasingly prominent. How to improve heat transfer efficiency is causing increasing interest in the study. Porous materials have showed attractive prospect because of the high efficiency and convenience in heat transfer process. To study the characteristics and laws that of gas flow and heat transfer in porous materials, in this thesis, flow and heat transfer process within high porosity porous materials used in solar-thermal conversion device are studied by numerical simulation. The main objective is to promote further theoretical research and practical application.In this thesis, the following aspects have been studied and explored.1.In this study,several turbulence models applied to some typical porous calculated structure have been studied. Turbulence in two-dimensional model structure was simulated with standard k ?εmodel and the RNG k ?εmodel,detailed distribution of turbulent kinetic energy and velocity was obtained. Besides, results in the literature were compared to verify the reasonableness of this calculation.2. In order to get closer to the calculation of the real porous material model, a dis-continuous film structure with pores model has been developed in this study. Detailed analyses of the calculated geometry of the structure are also presented. On this basis, the impact on heat transfer performance caused by the different aspects of the structural was been investigated. An approximated correlate equation for Nusselt number was also been asserted.Studies have shown that different turbulence model will cause different calculation results for two-dimensional model. At the same time, calculation results of the micro flow field show great influences of framework structure on turbulent characteristics. Dis-continuous film structure with pores in this paper and truss structure been studied in many literatures can both fit the real flow and heat transfer situation. Besides the Nusselt number calculated in this thesis is within the range of most literature, which can be used for designing porous heat-absorbing cavity.