Numerical study of thermal performance and production of alumina nanofluid entropy in thermal wells

Abstract

In this study, using fluent software, entropy generation and heat transfer of alumina nanofluid flow (water-aluminum oxide) with four volumetric concentrations, inside a well with a circular channel, is investigated numerically. The thermophysical properties of nanofluid and base fluid (water) are considered based on classical and temperature-dependent models, and the nanofluid flow regime to the thermal well is also considered to be layered. The results show that by increasing the volumetric concentration of nanofluid, the heat transfer entropy generation rate and the total entropy generation rate decrease compared to the base fluid. Also, with increasing volume fraction, the frictional share of entropy generation rate increases and the hydrodynamic efficiency of the system decreases. An increase in Reynolds numbers has a significant effect on the rate of entropy generation and increases the irreversibility and rate of entropy generation caused by friction. Also, according to the results, the higher Reynolds number increases the cooling efficiency of the thermal well. An increase in the Reynolds number and an increase in the volume fraction of the nanoparticles have led to an increase in the average Naselt number, which can be due to the temperature dependence of the thermal conductivity and the Brownian motion of the nanoparticles. As the Reynolds number increases, the slope of the Naselt curve first increases and then decreases. As the volumetric concentration of nanofluid increases, the dissipation power increases due to the increase in nanofluid viscosity. The increase in the dissipation power is less than the increase in the number of naselts, which indicates the strong potential of the nanofluid for use in electronic chips and the cooling industry.