Numerical Simulation Of Flow And Heat Transfer By SiO₂-water Nanofluid For Natural Convection In A Square Cavity

The nanofluid is a new particular fluid and many researchers have studied it for many years. They reported that the nanofluid has a significant impact on the heat transfer. In this paper, we study numerically the fluid flow and heat transfer of nanofluid for natural convection in a square cavity with a thermal column. The feature about the fluid flow and heat transfer of nanofluid in single phase and multiphase model has been studied. Also, the local entropy and total entropy of nanofluid have been studied in single phase.Firstly, The effects of some parameters on the fluid flow and heat transfer of SiO₂-water nanofluid in single model have been investigated. The parameters are Rayleigh number?ranging from 103 to 106?, volume fraction of nanoparticles?varying from 0.01 to 0.04?, the temperature of the thermal column?T=0, 0.5, 1, 1.5?, respectively. It is found that different temperature of thermal column contributes to different flow and temperature fields. At Ra=103, the heat conduct dominates the cavity and at Ra=106, the means of heat transfer is heat convection. Also, with increasing the volume fraction, the flow and tempeature field show no considerable changes and the mean Nusselt number increases.Secondly, the heat transfer and fluid flow have been studied in multiphase model. It is found that with the increase of volume fraction, the average Nusselt number increases. And when Ra=103, T=1.5 and Ra=106, the volume fraction has remarkable effects on the fluid flow and heat transfer of nanofluid.Lastly, the local entropy generation and total entropy generation of SiO₂-water nanofluid for natural convection in a square cavity in single phase model have been investigated. It is found that differernt temperature of thermal column leads to different local entropy generation. When T?0.5, the total entropy generation decreases with the increase of the temperature. However, when T?1, increasing temperature brings about the aguement of total entropy generation. In addition, for Ra=103, T=0.5, the total entropy generation is minimum and for Ra=106, T=1.5, it is maximum. It is also found that the heat transfer mechanism is the main parameter affecting the growth in the total entropy generation.