Synergetic effect of magnetic field location, strength and orientation on heat transfer characteristics of brine-based hybrid nanofluid in rectangular confinement

Abstract

The hybrid nanofluid emergence is presently receiving untold research attention as an improved cooling medium. This paper presents an investigation into the free convection thermal transport performance of brine (ethylene glycol-deionized water (60:40 vol%)-based hybrid ferrofluid (Fe2O3-Al2O3) (BBHF) in a rectangular cavity under steady-state conditions with and without magnetic inducement. The synergetic effect of different magnetic field orientations and intensities imposed on the various walls of the confinement and their influence on the heat transfer characteristics of BBHF was examined. At volume concentrations of 0.05–0.40 %, the BBHF was formulated and characterised for its viscosity, stability, morphology, and thermal conductivity. Without a magnetic stimulus, the average Nusselt number, heat transfer rate, and coefficient of heat transfer of 0.05–0.2 vol% BBHF samples were improved relative to the brine. At a cavity temperature gradient of 35 °C using 0.05 vol% BBHF, a peak thermal transport enhancement of 10.09 % was observed when compared with the brine. With 0.05 vol% BBHF, the vertical positioning of the magnetic stimulus on the cavity side wall was noticed to yield maximum improvement of heat transfer (4.3 %). An increment in the strength of the magnetic stimulus from 4.89 mT to 13.00 mT enhanced thermal transport by >15 %, which subsequently deteriorated when increased to 21.95 mT for all the studied magnetic stimulus arrangements. In addition, correlations were proposed to predict the Nusselt number, thermal conductivity, and viscosity of the BBHFs. The employment of hybrid nanoparticles, magnetic stimulus, and different arrangements of the magnetic stimulus was observed to amplify the heat transfer of BBHFs in the cavity which is of practical and engineering benefit.