The Study On Natural Convective Heat And Mass Transfer In Square Composite Porous/Fluid Cavity

Natural convection heat and mass transfer in composite porous/fluid domain widespreadly exist in the natural phenomenon, life phenomenon and many areas of production, its applications include:drying process, solar collector tubes, building energy conservation, electronic components cooling and geothermal useing, etc, so the study of natural convection heat and mass transfer in composite porous/fluid domain is very significant. Due to the flow and heat and mass transfer mechanism is more complex in composite porous/fluid domain, research relatively less.this paper mainly through studying the laws of natural convection heat and mass transfer in square composite porous-fluid cavity to provide necessary theoretical guidance for engineering practice.The flow field, temperature field and concentration field coexist to form a multi-physics. In multi-physical, flow field, temperature field and concentration field influence each other, this is called cross-coupling diffusive effect. At the fluid/porous interface, there are stress slip and temperature slip which obviously effect on fluid flow and heat transfer in cavity. According to the principle of irreversible thermodynamics, natural convection heat and mass transfer unsteady mathematical model is established by two regional model. The influence of the cross-coupling diffusive effects and interface slip effects on heat and mass transfer are taken into the mathematical model. Finite element method is used to solve mathematical model. This paper numerically simulate the changing of flow field, temperature and concentration field over time, reveal natural convection heat and mass transfer rule in the square composite porous/fluid cavity, discuss the effect of porous medium thickness d, darcy number Da, buoyancy ratio N, lewis number Le, rayleigh number Ra, cross-coupling effect coefficient STC and DCT on steady and unsteady natural convection heat and mass transfer in cavity, analyse the effect of interface slip coefficients on natural convection heat and mass transfer.The results show,1) porous medium thickness d and darcy number Da have significant effect on the intensity of heat and mass transfer, the thicker, the weaker heat and mass transfer intensity, the smaller Da can significantly weaken the intensity of mass transfer; 2) buoyancy ratio N decide flowing direction, N=-1,the intensity of heat and mass transfer is the weakest, the longest time is required to reach steady state, rayleigh number Ra decide the size of the natural convection strength, the changeing of flow field, temperature field and concentration field with time are markedly different when Ra is different, lewis number Le decide the relative size of the intensity and the transmission rate of thermal diffusion and mass diffusion; 3) in different moment, the law of cross coupling diffusion effect on heat and mass transfer is different.4) using different interface stress slip conditions, the speed curve of 1/2 highly place at interface area is different, the interface slip coefficientβ1 andβ2 have important influence on flow field at interface area, but temperature field is less affected.5) temperature slip coefficientβ3 has a certain influence on flow field and temperature field.