Experimental Investigation on Thermophysical Properties of Nanofluids

Abstract

Heat transfer fluids have inherently low thermal conductivity that greatly limits the heat exchange efficiency. While the effectiveness of extending surfaces and redesigning heat exchange equipment to increase the heat transfer rate has reached a limit, many researchers made an attempt to improve the thermal transport properties of the fluids by adding more thermally conductive solids into liquids. Liquid dispersions of nanoparticles, which have been termed “nanofluids”, exhibit substantially higher thermal conductivities than those of the corresponding base fluids.

Various aspects of nanofluids including synthesis, potential applications, experimental and analytical studies on the thermal conductivity, viscosity and density, particle size analysis have been carried out. For nanofluids, nanoparticles of Alumina (Al2O3) and the base fluids, such as, distilled water, ethylene glycol, and a mixture of distilled water & ethylene glycol are used. The volume fractions of nanoparticles used are 0.1%, 0.25%, 0.50% and 1.0%. Thermal conductivity is measured by ‘KD2 pro thermal property analyzer’. Viscosity and density are measured by Ubbelohde viscometer and pycnometer, respectively. Particle size analysis of nanofluids is characterized by using Brookhaven particle size analyzer.

Results show that thermal conductivity increases with nanoparticles concentration as well as with the temperature. Whereas, viscosity and density decreases with temperature and increases with nanoparticles concentration. The particle size analysis shows that agglomeration increases with diluting the sample. It means, towards higher concentration, agglomeration decreases.

More theoretical and experimental studies are needed to understand the thermophysical properties and heat transfer characteristics of nanofluids and identify new applications of these fields.