Experimental investigation of the effect of nanoparticle size on thermal conductivity of in-situ prepared silica–ethanol nanofluid

In this study the effects of particle size, temperature and volume fraction of SiO2 nanoparticles on thermal conductivity of nanofluid were investigated. Silica nanoparticles were prepared by the Stöber method. The results of experiments showed that with the increase of particle size, temperature and volume fraction the thermal conductivity of silica–ethanol nanofluid increased. Effect of particle size on thermal conductivity of nanofluid was attributed to high surface hydrophilicity of silica nanoparticles resulting decrease in interfacial thermal resistance with the increase of particle size. Also an empirical equation incorporating particle size, volume fraction and temperature was proposed for estimation of thermal conductivity of nanofluid. Comparison between this correlation and measurements showed that the deviation of calculated data from experimental results is within − 9.5% to 5.4%. The literature results agree well with the predictions by correlation proposed.