| Mixed convection heat transfer in porous open cavity with a heat source widely exists in many engineering applications such as electronic equipment cooling,material drying,chemical accumulation reaction bed and air conditioning surface cooler.Meanwhile,compared with conventional fluids,nanofluids have higher heat transfer performance.Nanofluids are considered to have great potential for heat transfer enhancement.Therefore,numerical study of mixed convection heat transfer characteristics of conventional working fluid and nanofluids in a porous open cavity with a heat source has been conducted.The effects of the shape of the heated source,type of heat transfer medium and the opening position on mixed convection are analyzed.The main research contents and conclusions are as below:（1）Mixed convective heat transfer of water in a porous open cavity with different heat sources shapes is numerically studied.Three shapes of heated cylinder,circle cross section,square cross section and triangle cross section are considered.In the numerical research,the finite volume method is used to discretize the dimensionless equations describing the problem,and the SIMPLEC algorithm is used to solve the discretizede equations.The influence of Richardson number,Darcy number and Rayleigh number on mixed convective heat transfer is analyzed.The results show that when the shape of the heat source is circular,the average Nusselt number on the surface of the heat source is the largest,and the mixed convection heat transfer effect is the best.The average Nusselt number on the surface of the heat source increases with the decrease of Richardson number and Darcy number,and increases with the increase of Rayleigh number.（2）Mixed convection of different nanofluids in porous open cavity with a heat source is numerically investigated.Three different types of nanofluids（Cu-water,Al2O3-water,and Ti O2-water nanofluids）are considered.The effects of Richardson number,nanoparticles volume fractionφ,Darcy number,and Rayleigh number on mixed convection are analyzed.The results show that the addition of nanoparticles significantly improves the mixed convection heat transfer in the cavity,and when Cu-water nanofluid is used as the working medium,the average Nusselt number on the surface of the heat source is the largest,and the mixed convection heat transfer effect is the best.The average Nusselt number on the surface of the heat source increases with the increase of the nanoparticle volume fractionφand Rayleigh number,and increases with the decrease of Richardson number and Darcy number.（3）Mixed convection heat transfer characteristics of Cu-water nanofluid in a porous open cavity with a circular heat source and different inlet and outlet positions is numerically studied.The effects of inlet and outlet dimensions and related non-dimensional parameters on mixed convection are mainly analyzed.The results show that mixed convection heat transfer rate in the cavity is larger when fluid enters into the cavity from the lower part of left wall and flows out of the upper part of right wall.The average Nusselt number on the surface of the heat source is directly proportional to the change of d and nanoparticle volume fractionφ,and it is inversely proportional to the change of the Richardson number.（4）Using Cu-water nanofluid as working fluid,the average Nusselt number on the surface of heat source is the largest at d=0.5 when fluid enters into the cavity from the lower part of left wall and flows out of the upper part of right wall. |
