Numerical investigation on forced hybrid nanofluid flow and heat transfer inside a three-dimensional annulus equipped with hot and cold rods: Using symmetry simulation

Abstract

A 3D computational fluid dynamics method is used in the current study to investigate the hybrid nanofluid (HNF) flow and heat transfer in an annulus with hot and cold rods. The chief goal of the current study is to examine the influences of dissimilar Reynolds numbers, emissivity coefficients, and dissimilar volume fractions of nanoparticles on hydraulic and thermal characteristics of the studied annulus. In this way, the geometry is modeled using a symmetry scheme. The heat transfer fluid is a water, ethylene–glycol, or water/ethylene–glycol mixture-based Cu-Al2 O3 HNF, which is a Newtonian NF. According to the findings for the model at Re = 3000 and φ1 = 0.05, all studied cases with different base fluids have similar behavior. φ1 and φ2 are the volume concentration of Al2 O3 and Cu nanoparticles, respectively. For all studied cases, the total average Nusselt number (Nuave ) reduces firstly by an increment of the volume concentrations of Cu nanoparticles until φ2 = 0.01 or 0.02 and then, the total Nuave rises by an increment of the volume concentrations of Cu nanoparticles. Additionally, for the case with water as the base fluid, the total Nuave at φ2 = 0.05 is higher than the values at φ2 = 0.00. On the other hand, for the other cases, the total Nuave at φ2 = 0.05 is lower than the values at φ2 = 0.00. For all studied cases, the case with water as the base fluid has the maximum Nuave . Plus, for the model at Re = 4000 and φ1 = 0.05, all studied cases with different base fluids have similar behavior. For all studied cases, the total Nuave reduces firstly by an increment of the volume concentrations of Cu nanoparticles until φ2 = 0.01 and then, the total Nuave rises by an increment of the volume concentrations of Cu nanoparticles. The Nuave augments are found by an increment of Reynolds numbers. Higher emissivity values should lead to higher radiation heat transfer, but the portion of radiative heat transfer in the studied annulus is low and therefore, has no observable increment in HNF flow and heat transfer.