Energy Reports (Nov 2022)
Forced convection heat transfer of nanofluids in turbulent flow in a flat tube of an automobile radiator
Abstract
Nanofluids are fluids that can be applied in devices to obtain better performances (i.e. energy, heat transfer and others). Latest up to date literatures on nanofluids show that they can be used in engine cooling systems, solar water heating, cooling of electronics, to improving diesel generator efficiency, to improve heat transfer efficiency of chillers, in nuclear reactor and defense and space.This paper focuses on the numerical study of the performance of two nanofluids (Al2O3-water and TiO2-water) in heat transfer by forced convection in a flat tube of an automobile radiator In the computational simulations it was considered that the nanofluids have a constant velocity and a temperature of 363.15 K at the entrance of the tube. The tube wall is at a constant temperature of 303.15 K. This study is restricted to turbulent flows with Reynolds numbers equal to 5000, 10000, 15000 and 20000. The 3D computer simulations were performed using the Fluent software. The characteristic parameters of heat transfer from nanofluids subjected to forced convection were obtained for nanoparticle concentrations up to 10% and were compared with the base fluid (water). The numerical results were validated, comparing the friction coefficient and the Nusselt number with empirical correlations for the turbulent regime, available in the literature. The results for the heat transfer coefficient and the heat flux along the tube, for the studied conditions, are presented. Average values of some parameters associated with heat transfer and fluid flow were also determined, such as heat transfer coefficient, heat flux, Nusselt number, Prandtl number, wall shear stress, pressure drop, density, viscosity, thermal conductivity and specific heat, all of which were found to increase with the concentration of nanoparticles. The heat transfer enhancement with the nanoparticles concentrations up to 10% was also investigated. Furthermore, both nanofluids show the same behavior, for instance, for Re = 5000 the heat transfer enhancement rise 32.7% whereas for Re = 20000 the growth drops slightly to 31.3% with the concentration of Al2O3.
