Research On Heat And Mass Transfer In Square Cavity Based On Lattice Boltzmann Method

The fluid flow and heat and mass transfer phenomena contained in double diffusive convection are common in various fields of nature and industry,such as air pollution transportation,crystal growth,nuclear waste storage,metal solidification process,etc.At present,many scholars use numerical methods to conduct a large number of simulation studies on it.As an efficient numerical method,the lattice Boltzmann method has the advantages of simple algorithm,easy parallelization and saving calculation time,so it has attracted much attention.In this paper,the lattice Boltzmann method is used to study the double diffusive natural convection in a square cavity.First,the lattice Boltzmann method was used to simulate the double-diffused natural convection of a composite cavity with a thermally conductive partition.The width of the heat conducting partition was considered.The effects of different Rayleigh numbers,thermal conductivity ratio,buoyancy ratio,and partition width on the heat and mass transfer characteristics in the cavity were analyzed.The streamline,isotherm,concentration line,local Nusselt number and local Sherwood number curve corresponding to different parameters are given.The simulation results show that the thermal conductivity ratio and the width of the partition have a great influence on the fluid flow pattern in the cavity.When w > 10,there are inflection points in the distribution curve of the local Nusselt number and Sherwood number.In addition,the absolute value of the buoyancy ratio and Rayleigh The increase of the number can effectively enhance the heat and mass transfer efficiency in the cavity.Second,the effect of magnetic field on double diffusive natural convection in an enclosure with heat conducting partition is studied.Constant temperatures and concentrations are imposed along the left and right walls,and horizontal walls are insulated.The Lattice Boltzmann method is used to solve the dimensionless governing equations.Streamlines,isotherms,isoconcentrations,average Nusselt and Sherwood number for various values of thermal Rayleigh number,Hartmann number,partition length,magnetic field angle and buoyancy ratio are obtained.The results indicate that the heat and mass transfer mechanisms are influenced by Hartmann number.The flow patterns are significantly depend on the magnetic field angle.In addition,there is an optimal magnetic field angle of 90° at which the stable and maximum heat and mass transfer rates is obtained.Moreover,the correlations of theaverage Nusselt and Sherwood number are also fitted.Third,numerical simulation of double diffusive natural convection of nanofluids in an enclosure with heat conducting partitions vertically attached to the horizontal walls has been considered.Sinusoidal boundary conditions are applied to the right side wall of the enclosure filled with Cu-water nanofluid.The Maxwell-Garnett model are used in the governing equation to modify the fluid properties affected by Cu nanoparticles.Solution of governing equation was performed via the lattice Boltzmann method.The effect of thermal Rayleigh number,nanoparticle volume fraction,phase deviation,thermal conductivity ratio was investigated.The results indicate that the position of partitions is a major factor in controlling the heat and mass transfer rate of nanofluids,and the average Nusselt and Sherwood numbers are linearly related to the change of nanoparticle volume fraction.In addition,there is an optimal phase deviation value ? = ?/4 at which the maximum heat and mass transfer enhancement is obtained.Moreover,increasing in the thermal conductivity ratio results to the heat and mass transfer enhancement by properly setting the position of the partitions.The research in this article can provide a useful reference for the study of double diffusive convection in an enclosure with heat conducting partition.