Experimental studies on the heat transfer characteristics of silver water nanofluid

Abstract

The design of thermal energy systems has crossed many barriers in the past few decades leading to substantial improvements in performance parameters. Miniaturization is one of the most sought after feature in the quest for excellence in design. Although various techniques are applied to enhance heat transfer rate, there is still scope for improving the performance and compactness of the heat transfer devices. Reliable correlations and prognostic methods will overlay the means to capitalize on the advantages of nanofluids in appliance design. Initially, the thermo-physical properties, such as thermal conductivity and viscosity of nanofluids are experimentally measured. Silver nanoparticles dispersed in water with percentage volume concentrations of 0.3, 0.4, 0.6, 0.8, 0.9 and 1.2 are considered in the present study. The results have shown an increase in the measured thermal conductivity and viscosity of nanofluids as the particle concentrations increase. Further, the forced convective heat transfer coefficient and pressure drop characteristics of silver/water nanofluid with 0.3, 0.6 and 0.9% volume concentrations in a smooth horizontal tube are experimentally studied. The experimental results indicate that the use of silver nanoparticles in the base fluid enhances the heat transfer coefficients by 28.7% for 0.3% and 81.2% for 0.9% volume concentrations respectively. With the experimental results a new correlation for calculating the convective heat transfer coefficient of nanofluids is developed by modifying the exponents and coefficients of familiar correlations to fit in with the present experimental results. This new correlation includes the effect of the volume concentration and temperature to predict the heat transfer coefficient with a mean deviation of ± 10%. The outcome of the work is quite significant in understanding the convective heat transfer and pressure drop characteristics of silver/water nanofluids. The findings will be useful for better and optimal design of heat exchanger. newline newline newline