Effect of particle migration on flow and heat transfer characteristics of magnetic nanoparticle suspensions

Flow and heat transfer characteristics of the suspensions containing Fe3O4 magnetic nanoparticles have been evaluated in turbulent flow regime. The effects of particle migration which lead to non-uniform concentration distribution have been considered in the simulation. For this purpose, the effects of Brownian motion, shear rate and viscosity gradient have been taken into account on diffusion of the particles. By applying the effects of particle migration, the amount of concentration at the wall vicinity will be lower than that at the tube center. Non-uniformity of the concentration distribution is more significant for the coarser particles. Meanwhile, this non-uniformity intensifies by increasing mean concentration and Reynolds number. Thermophysical properties of the suspension also demonstrate a non-uniform distribution. Nusselt number increases by raising the Reynolds number and mean concentration. The effect of concentration on Nusselt number reduces at higher Reynolds numbers. The increase of the concentration will raise the friction coefficient, which has an almost similar trend at various Reynolds numbers. The results obtained are properly consistent with the experimental results.