Scale formation and subcooled flow boiling heat transfer of CuO–water nanofluid inside the vertical annulus

Abstract

The forced convective and subcooled flow-boiling heat transfer of CuO/water nanofluid as well as fouling rate of nanofluid are experimentally quantified for different dilute concentrations of CuO nanoparticles in water over a range of mass fluxes (353kg/m2s<G<1059kg/m2s). Stabilization of nanofluid was also carried out using pH control method and examined using time-spend experiment. In the best case of stabilization (about 216h), experimental results demonstrate that two discrete regions of heat transfer are seen namely force convective and nucleate boiling. Results also show that when concentration of nanofluid increases, heat transfer coefficient in both regions significantly decreases in comparison to pure water. Beside, results reveal that increase of heat and mass flux significantly increases the heat transfer coefficient in both heat transfer mechanisms. In the range of these experiments; nanoparticles have an insignificant effect on the flow pressure drop with the CuO/water nanofluid. Beside, Influence of some operating conditions on flow boiling heat transfer coefficient and fouling rate is discussed.