Experimental study of the optimum size of silica nanoparticles on the pool boiling heat transfer coefficient of silicon oxide/deionized water nanofluid

Abstract

This research has experimentally investigated the effect of the size of silicon oxide nanoparticles in a base fluid of deionized water on the coefficient of pool boiling heat transfer on a copper surface at atmospheric pressure. Silicon oxide nanoparticles with concentrations of 0.01, 0.1, 0.5 and 1.0 vol% have been used. The sizes of silicon oxide nanoparticles have been determined by TEM tests. The test results indicate that these nanoparticles have a roughly spherical structure and their average sizes are 11, 50 and 70 nm. Moreover, the degree of nanofluid stability (lack of coagulation of nanoparticles) has been determined by the Zeta-Potential test. The boiling results of the pure water sample show that the curve of boiling heat transfer flux versus the excess temperature difference of surface is very close to the Rohsenow's curve. The results obtained for nanofluid boiling on copper surface indicates that, at all the considered concentrations and nanoparticle sizes (except nanoparticle size of 70 nm size and concentration of 0.1 vol%), the boiling heat transfer coefficient for the nanofluid sample is much smaller than that of the pure water sample. The findings show that by increasing the diameter of silica nanoparticles from 11 to 70 nm, the boiling heat transfer coefficient is increased. These results show that for all the considered nanoparticle sizes and concentrations, the highest boiling heat transfer coefficient is achieved by the silicon oxide/deionized water nanofluid with the concentration of 0.1 vol% and particle size of 70 nm.