A new approach for the analysis of the nanoparticles effects on Cu-water nanofluid mixed convection heat transfer and required power in a lid-driven cavity

Abstract

In this paper, a new approach is used for numerical analysis of the sole effects of nanoparticles volume fraction of Cu-water nanofluid on laminar mixed and natural convection heat transfer in a 2D cavity. Horizontal walls are insulated and fixed, and vertical walls are maintained at constant temperature. Vertical walls are considered for both fixed and moving conditions. Some researchers have studied flow and heat transfer of nanofluid in a lid-driven cavity, keeping fixed both Ri and Gr. They found that by the increase of nanoparticles volume fraction, Nu number increases, then from this result they concluded the total heat transfer increases from the walls. It is shown that total heat transfer obtained from the Nu number by the mentioned approach results from not only the nanoparticles volume fraction increase but also temperature difference and walls velocity increases. Thus, this approach is not appropriate to study the sole effects of nanoparticles volume fractions on the mixed convection heat transfer. Using the new approach, it is shown that in order to have specific heat transfer rate from the walls, base fluid (water) needs less power for moving the wall than cu-nanofluid. Therefore, the usage of Cu-water nanofluid is not recommended to increase mixed convection heat transfer in a lid-driven cavity. Moreover, using this new approach, it is shown that the increase of nanoparticles volume fraction reduces natural convection heat transfer, which is contradictory to the previous studies. Thus, its usage is not recommended for this case as well.