Study On The Flow And Heat Transfer Of Viscoelastic Fluid And Nanofluid

Nowadays,the problem of energy shortage is getting worse.In the industrial field,fluid transportation and convective heat transfer will consume a lot of energy.Therefore,fluid drag reduction technology and enhanced convective heat transfer technology have important research value.Viscoelastic fluids can play a role in drag reduction and nanofluids can promote convective heat transfer,therefore,this article starts with these two fluids and uses ANSYS FLUENT software to study the flow and heat transfer of viscoelastic fluids,nanofluids and viscoelastic fluid-based nanofluids under different models.Firstly,study the flow of Newtonian fluid and viscoelastic fluid in the reverse driving of the upper and lower walls of the isosceles trapezoidal cavity.In this paper,the Oldroyd-B model which ignores shear thinning is adopted,and the constitutive equation of viscoelastic fluid is programmed in C language through UDF and imported into ANSYS FLUENT to couple with the Navier-Stokes equation.The effects of Re,Wi,and β on fluids are studied by numerical simulation methods,and it is found that with the increase of Re,the changing trends of Newtonian fluid and viscoelastic fluid are consistent.In the viscoelastic fluid condition,with the increase of β,the vortex center moves to the left,and the peak value of the sub-velocity v/U becomes larger.When Wi increases to 0.04,as the elasticity increases to a certain extent,at the bottom right corner of the isosceles trapezoidal cavity,the secondary vortex structure starts to rotate counterclockwise,and then as Wi increases,the area around the flow gradually increases.When Wi>0.8,the streamline gradually changes from a single-vortex structure to a multi-vortex structure.Secondly,study the natural convection heat transfer of Cu-oil nanofluid in the right-angle trapezoidal cavity,choose the single-phase model,select the Boussinesq hypothesis for density,and keep the rest of the physical properties unchanged.Through numerical simulation methods,the effects of Ra,low-temperature wall position,bottom surface inclination,nanoparticle volume fraction,and heat flux length on the convective heat transfer in the right-angle trapezoidal cavity are studied.The study found that when the low-temperature wall is located in the upper half of the inclined wall,the convective heat transfer effect is the best.At the same time,it is found that within a certain range,the change of the inclination angle can promote the convective heat transfer better than adding a certain volume fraction of nanoparticles to the engine oil.Finally,the two fluids are combined together to study the effects of Re,β,Wi and nanoparticle volume fraction on the flow and convective heat transfer of viscoelastic fluid-based nanofluids in circular pipes.The research results show that under laminar flow,the viscoelastic fluid can neither reduce the drag but also inhibit the convective heat transfer,while the viscoelastic fluid-based nanofluid can improve the convective heat transfer,but the resistance increases significantly,while the increase of Re can not only reduce friction resistance coefficient,and can promote convective heat transfer.The size of β and Wi has no effect on heat transfer.With the increase of β and Wi,the rent reduction rate is basically stable at-16.7%,which does not play a role in drag reduction.