Convective Heat Transfer Characteristics Of Nanofluids In Metal Foams Based On Lattice Boltzmann Method

Researchers have been seeking new solutions for optimizing the heat transfer performance of heat exchangers.Recently,the dual heat transfer enhancement method using nanofluid and metal foam has attracted much attention.Nanofluid owns a thermal conductivity higher than conventional thermal transfer fluids,and metal foam can provide sufficient heat transfer area with its large specific surface area.This paper presents a lattice Boltzmann method to numerically study the convective heat transfer characteristics of a nanofluid in metal foams.Natural convective heat transfer of nanofluid is studied with single-phase lattice Boltzmann model.This model ignores the relative motion and heat transfer interaction between nanoparticle and base fluid.Results show that an increase in nanoparticle volume fraction and Rayleigh number can enhance the convective heat transfer.Simultaneously,the relative motion and heat transfer between nanoparticle and base fluid are studied with two-phase lattice Boltzmann model,and the distribution of nanoparticles and its effect on convective heat transfer are analyzed.Results show that the driving force of temperature difference is still the main force affecting the natural convective heat transfer.The Brown force and the interphase resistance are relatively large,which causes local micro convective flow and enhance convective heat transfer.The natural convective heat transfer and the forced convective heat transfer of nanofluid in metal foam are studied with the lattice Boltzmann method,and the local thermal equilibrium model and the local thermal non-equilibrium model are adopted respectively.According to the results,effects of various parameters on the convective heat transfer performance are analyzed.Results show that Nusselt number increases with an increase in Rayleigh number,Reynolds number,Darcy number,porosity and thermal conductivity of the nanoparticle and metal foam,and the effect of Rayleigh number,Reynolds number and Darcy number on flow and heat transfer is very notable.Finally,this paper presented an innovative research on multiphase flow and heat transfer coupling,and the three-phase lattice Boltzmann model of nanoparticle,base fluid and metal foam is established.This three-phase model is investigated with the convective heat transfer of nanofluid in metal foam.By comparing the single-phase model with the two-phase model,the influence of various parameters and forces on the results of the three-phase model is analyzed.By using the lattice Boltzmann method,the convective heat transfer of nanofluid in metal foams with different models,the research can play a guiding role for practical application.The three-phase model proposed in this paper laid the foundation for the further study of inter-phase forces,and heat transfer mechanisms between nanoparticles,base fluid and metal foam phases...