Numerical investigation of heat transfer enhancement of a water/ethylene glycol mixture with Al2O3-TiO2 nanoparticles

This paper presents a numerical study of a four-component hybrid nanofluid consisting of binary nanoparticles, Al2O3 and TiO2, dispersed into a double base fluid mixture of water and ethylene glycol. The nanofluid were modeled as a single phase fluid with volume concentrations of 2.5% Al2O3-1.5% TiO2 and 5% Al2O3-3% TiO2 respectively. The nanoparticles are suspended in a double base fluid of water and ethylene glycol mixture with a 70:30 vol ratio. The simulations were conducted for turbulenct flow through a pipe at working temperatures of 293 K and varying Reynolds numbers (7800-2000). Constant heat flux of 129,983 W/m(2) heat flux was applied to the pipe wall. The thermal conductivity was enhanced by 24% and 11% at concentrations of 5-3% and 2.5-1.5%, respectively. While, viscosity of hybrid nanofluids was rising up to 70% and 67% at the same concentration. The avarage heat transfer coefficient of Al2O3-TiO2 hybrid nanofluids were enhanced with increase of temperature and volume concentration. It was noted that the maximum heat transfer enhancement is 52% higher than the base fluid for a volume concentration of 53%. There is a slight increase in the friction factor of Al2O3-TiO2 hybrid nanofluids with higher volume concentration. Crown Copyright (C) 2019 Published by Elsevier Inc. All rights reserved.