Turbulent mass transfer of Al2O3 and TiO2 electrolyte nanofluids in circular tube

Abstract

Experimental study was performed to investigate turbulent mass transfer in straight circular tube. Electrochemical limiting diffusion current technique was used to measure the mass transfer coefficient in fully developed hydrodynamics and under developed mass transfer region. TiO2 and γ-Al2O3 nanoparticles were added into the electrolyte solution (ES) to make electrolyte nanofluids (ENF). Measurements revealed that enhancement in mass transfer reaches 10 % in a 0.01 vol% γ-Al2O3/electrolyte nanofluid while 18 % in a 0.015 vol% TiO2/electrolyte nanofluid relative to the base ES. Mass transfer coefficients increased with nanoparticles concentration up to an optimum concentration (0.01 % in γ-Al2O3/electrolyte nanofluid and 0.015 % in TiO2/electrolyte nanofluid) while decreased by increasing nanoparticles concentration further. Enhancement ratio which is the ratio of the mass transfer coefficient of nanofluid to that of the base fluid was a function of nanoparticle concentration and was independent of Reynolds number. The mechanisms of nanoparticles Brownian motion and nanoparticles clustering were used to describe the behavior of the enhancement ratio in ENF.