Experimental investigation on thermophysical properties of Therminol® 55 based hybrid nanofluids with alumina and graphene nanoplatelets for medium temperature applications

Abstract

In light of the stable physical and thermal properties over a wide range of temperatures, Therminol®55 (TH55) have long been used as heat transfer fluids in medium temperature applications. In addressing the demerit of low performance of thermal systems, enhancing the thermal conductivity of TH55 is one of the promising routes to improve the performance of TH55 based systems. It has been postulated that nanofluids have provided more efficient heat transfer than conventional fluids. This study aims to experimentally investigate the effect of dispersing graphene nanoplatelets (GNP) and alumina (Al2O3) nanoparticlesin TH55 on thermophysical properties such as thermal conductivity, viscosity and specific heat. It is found that the use of hybrid nanofluid resulted in an increase in the thermal conductivity of 10.28% and 3.03% as compared with TH55-Al2O3 and TH55-GNP mono-nanofluid, respectively at a temperature of 65 °C. Initially, the viscosity of hybrid nanofluid is found to be increased by 66.99% at 20 °C as compared to the base fluid, and the viscosity decreases significantly as the temperature rises from 20 °C to 90 °C. Due to the lower specific heat of nanoparticles, the specific heat capacity of TH55 based nanofluids decreases with the addition of nanoparticles. Empirical correlations have been developed using the non-linear least square method for thermal conductivity, viscosity and specific heat of the hybrid nanofluids. Results show that the TH55-GNP/Al2O3 hybrid nanofluids can be used as a suitable replacement for the conventional fluids in medium temperature applications.