MRT-LB Numerical Simulation Research On Flow And Heat Transfer In Porous Media

The phenomenon of flow and heat transfer in porous media is widespread in nature and engineering technology,ranging from air movement and precipitation to small indoor space heat exchange,electronic components heat dissipation and solar receiver energy storage,etc.,which involve the flow of fluids.For heat transfer issues,it is particularly important to carry out research on the mechanism of fluid flow and heat transfer in a porous medium cavity.Lattice Boltzmann Method(LBM)is a mesoscopic numerical simulation method based on kinetics.It can deal with fluid flow and heat transfer issues concisely,and it is easy to construct complex geometric boundary structures with heterogeneity.Parallel computing and other characteristics have been widely used in simulating mesoscopic fluid flow and heat transfer problems in recent years.In this paper,the multi-relaxationtime Boltzmann method(MRT-LBM)is used to simulate and study the influence of wall heat source arrangement on the natural convection process and the flow and heat transfer process in a solar receiver with porous media.First,in view of the influence of wall heat source arrangement on the natural convection heat transfer of a square cavity containing porous media,the lattice Boltzmann method is used to study the heat and mass transfer of a two-dimensional square cavity containing porous media.Emphasizes the analysis of the thermal boundary layout(six layout models 1-6),porosity,Da number,Ra number,cavity inclination and other parameters on the influence of flow heat transfer.The research results show that the porosity has a great influence on the flow and heat transfer in the cavity.Under high Ra number and high Da number,the heat transfer effect of model 6 continuous thermal boundary condition increases significantly with the increase of porosity.Under low Ra and Da numbers,the inclination angle of the square cavity has almost no effect on the flow heat transfer,and under this condition,the angular heating method of Model 1 has better heat transfer characteristics.With the increase of Ra and Da numbers,the inclination angle of the square cavity has a great influence on the flow heat transfer.At high Ra and Da numbers,the thermal boundary conditions of Model 6 have better heat transfer characteristics.Secondly,the flow and heat transfer process in the solar receiver was explored,and the evolution process of the flow field temperature field under different inlet heat flow distribution and receiver porosity was compared.The average temperature of solid particles and the temperature characteristics of the inlet and outlet vary with time.transformation.When ε is 0.558,0.495,0.435 and 0.385,the maximum inlet temperature,the average temperature of solid particles and the average outlet temperature changes with time are explored respectively.The research results show that when the porosity continues to decrease,the area of the internal solid particles increases,the flow is blocked,and the heat accumulation at the entrance is difficult to diffuse to the exit,which causes the temperature of the entrance solid particles to rise faster After the same time of flow and heat transfer,the heat conducted to the outlet is relatively small.When the porosity is 0.495,the effect of flow heat transfer is better and the rate of inlet temperature rise is relatively better.At the same time,it is found that when the inlet particles are arranged in an axisymmetric manner,the Gaussian distribution heat flux in the case of a large co is likely to cause the local temperature of the inlet to be too large,which places higher requirements on the material of the solid particles,and with the increase of co Great,the rate and speed of the average temperature increase at the outlet have been significantly improved.