Numerical Study Of Natural Convection In Wavy Enclosures Filled With Porous Medium Saturated With Nanofluid

Natural convection heat transfer in porous medium widely exists in solar energy utilization,oil extraction,safe storage of nuclear waste,and cooling of electronic equipment.Due to the low thermal conductivity of the working fluid in porous medium,this limits the enhancement of natural convection in porous medium.By adding nanoparticles to the base fluid,heat transfer can be enhanced.In recent years,some scholars have studied natural convection in porous medium filled with nanofluids and some valuable results have been obtained.However,research works on natural convection in porous medium filled with nanofluids are relatively scarce.Therefore,in this paper natural convection in wavy-walled porous enclosures saturated by nanofluids is studied numerically with the local thermal equilibrium(LTE)model or local thermal non-equilibrium(LTNE)model.The contents and conclusions are as follows:(1)Natural convection heat transfer of Cu-water nanofluid in a wavy porous enclosure is studied numerically using Darcy-Brinkman model and LTE model.The central part of the right vertical sidewall of the enclosure is kept at a constant high temperature,and the left wavy sidewall is cooled at a constant low temperature while the rest part of the right sidewall and horizontal walls are adiabatic.The effects of the dimensionless heated length C of the right wall,the dimensionless amplitude of the wavy wall b,Rayleigh number Ra,nanoparticles volume fraction ?,Darcy number Da on natural convection are analyzed.The results show that the average Nusselt number decreases with the increase of C and increases with the increase of b.The average Nusselt number increases with increasing Ra,Da,and ?.(2)Natural convection heat transfer of Cu-water nanofluid in a wavy porous enclosure with two wavy walls is investigated numerically using LTE model.The right wavy curved wall is maintained at a constant high temperature,the left wavy curved wall is cooled at a constant low temperature,and the other walls are adiabatic.Darcy-Brinkman-Forchheimer model is used to describe the fluid flow in porous medium.The effects of the wavy number ? of the wavy curved wall,the dimensionless amplitude of the wavy curved wall b,Rayleigh number Ra,nanoparticles volume fraction ?,Darcy number Da,and porosity ? on natural convection are analyzed.The results show that the average Nusselt number decreases with the increase of ?.When Da is from 10-2 to 10-3,the average Nusselt number decreases with the increase of b.When Da is from 10-4 to 10-5,the average Nusselt number reduces slightly at first,and then slightly increases.When b is 0.1,the average Nusselt number reaches to the minimum value.The average Nu number increases with the increase of Ra,?,and Da.Meanwhile the average Nu number decreases slightly with the increase of ?.(3)Natural convection of Cu-water nanofluid in a wavy porous enclosure is studied numerically using LTNE model.The right wavy wall is maintained at a constant high temperature,the left wavy wall is cooled at a constant low temperature,and the other walls are adiabatic.The Darcy model is used for describing the fluid flow in porous medium.The effects of the dimensionless amplitude of the wave wall ?,the dimensionless volumetric heat transfer coefficient Nhs,nanoparticles volume fraction ? on natural convection are analyzed.The results show that the average Nusselt number Nu decreases with the increase of ?.The average Nusselt number of nanofluid Nunf decreases with Nhs increasing.The average Nusselt number of solid matrix Nus increases with an increase in Nhs.When Nhs is low,the influence of local thermal non-equilibrium is obvious.As ? increases,both Nunf and Nus increases.