Investigation of Mixed Convection in an Enclosure Filled with Nanofluids of Al_2O_3-Water and Graphene-Ethylene Glycol

摘要

In this research work, heat transfer enhancement of mixed convection in an enclosure is investigated with a moving top wall. Numerical simulations based on an Al_2O_3-water nanofluid are conducted by using variable thermophysical properties. Flow fields and temperature distributions are analyzed by considering effects of two partially heated walls. Moreover, water-ethylene glycol mixed with graphene nanoplatelets (GnP-WEG) is also considered to analyze effects of the heating procedure, Reynolds number, Rayleigh number and volume fraction of the nanoparticles, as well as on the heat transfer enhancement. It is found that there is a velocity difference between the pure water and the Al_2O_3-water nanofluid due to the increase of the fluid viscosity by an injection of Al_2O_3 nanoparticles into the water. Moreover, flow patterns are significantly affected by the Reynolds number and the Rayleigh number. The heat transfer in the enclosure is enhanced by the increase of the top wall moving velocity. Although heat transfer enhancement for most cases are obtained by increasing the volume fraction of graphene nanoplatelets, a mixture of 0.25% graphene nanoplatelets and the water-ethylene glycol (the base fluid) provides the largest enhancement of heat transfer at low Reynolds number (Re = 1).