Lattice Boltzmann Simulation Of Natural Convection Of Power-law Nanofluids In Partially Heated Square Enclosures

The natural convection problem in a closed enclosure is a classic convection heat transfer problem.It has very important and extensive applications in many fields,and has received much attention by many researchers.Adding nanoparticles in the liquid significantly increases the thermal conductivity of the fluid.Therefore,the heat flow of nanofluids is widely used in industrial applications such as refrigeration systems,electronic component heat dissipation,automobile manufacturing,and refrigerator manufacturing.In the past few decades,many scholars have extensive research on the flow of nanofluids.However,most studies use Newtonian fluids as the base fluid,ignoring the situation where the base fluid is a non-Newtonian fluid.In fact,nanofluids with large nanoparticle volume fractions and carbon nanotube nanofluids often exhibit non-Newtonian fluid properties.Therefore,research on non-Newtonian fluids is necessary.In this paper,the natural convection of power-law nanofluids in locally heated cavity is numerically simulated by the lattice Boltzmann method.And the nanofluid considered here is a water based nanofluid containing Cu nanoparticle.In order to determine the effect of different parameters on fluid flow and heat transfer,we performed a series of simulations.The range of the different parameters varies as follows: thermal Rayleigh number(64??1010 Ra),nanoparticle volume fraction(?? ?1.00),power-law index(??5.15.0 n),heat source length(??8.01.0 h),and heat source location(??75.025.0py).The results show that both the increase of the thermal Rayleigh number and the volume fraction of nanoparticles will increase the average Nusselt number and the heat transfer.Moreover,nanofluids with different power-law index also have significant effects on the heat conduction process.When the thermal Rayleigh number is larger,the heat transfer rate obtained for the shear-thinning fluid(n=5.0)is larger than other cases.In addition,the heat source length and position also affect the flow and heat transfer of the fluid.The heat transfer rate increases with the length of the heat source and is more conducive to heat transfer when the heat source is in the lower half of the cavity.