Effect of nanoparticle shapes on nanofluid mixed forced and thermocapillary convection in minichannel

Abstract

To reveal the influence of nanoparticle shapes on thermal transport performance of nanofluid convective boiling flow in minichannel, nanofluid forced flow coupled with gas bubble thermocapillary convection in minichannel is numerically investigated by two-phase mixture model. Firstly, the flow characteristics and heat transfer enhancement mechanism of mixed forced and thermocapillary convection in minichannel with different shaped nanoparticles (sphere, brick, blade, cylinder and platelet shaped particles) is disclosed. Secondly, the contribution of thermocapillary and forced flow to heat transfer is analyzed, and the relation of Nusselt number and total entropy production with nanoparticle concentration are given. Finally, the heat transfer performance of nanofluid flow with different shaped nanoparticles in minichannel is evaluated. The results show that, nanoparticle shape can effectively influence thermocapillary jet structure, and then affect the thermal transport at the vicinity of bubble. For nanofluid with spherical nanoparticle the thermocapillary jet structure is the largest, which is followed by brick, blade, cylinder and platelet shaped nanoparticles. The thermal transport performance of nanofluid with blade-shaped nanoparticle is the best, and the average Nusselt number is improved by 8.3% compared with that of nanofluid with spherical nanoaprticle as nanoparticle volume fraction is 0.05.