Thermal Conductivity Enhancement in Water-Based Nanofluids for Heat Transfer Applications

Abstract

ABSTRACT The performance of cooling and heat-exchange systems is limited by the modest thermal conductivity of conventional fluids such as water, and dispersing nanometre-sized solid particles to form a nanofluid is a promising way to raise it. The enhancement depends on the type and concentration of the nanoparticles. This paper reports an experimental study of the thermal conductivity enhancement of water-based nanofluids for heat transfer applications, comparing alumina and copper-oxide nanoparticles across a range of low volume fractions. Stable nanofluids were prepared by dispersing the nanoparticles in distilled water with a surfactant and ultrasonication, and their thermal conductivity was measured by the transient hot-wire method. The thermal conductivity rose steadily with volume fraction for both nanofluids, and the copper-oxide nanofluid enhanced conductivity more than the alumina one at every concentration, reaching about twenty-one percent enhancement at one percent volume fraction. The greater enhancement of the copper-oxide nanofluid reflects the higher intrinsic conductivity of its particles. The results confirm that nanofluids can substantially improve the thermal conductivity of water, with the choice of nanoparticle an important design variable for heat transfer.

KEYWORDS: nanofluid, thermal conductivity, heat transfer, nanoparticles, volume fraction, transient hot-wire