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

• Subcooled flow boiling heat transfer to CuO/water nanofluid is conducted.
• Effect of operating condition on scale formation and HTC is discussed.
• Heat flux and mass flux increase the HTC and fouling resistance.
• A comparison between experimental data and Chen type model is carried out.
• Deterioration of HTC of nanofluid is reported when vol.% of nanofluid increases.

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 (353 kg/m2 s < G < 1059 kg/m2 s). Stabilization of nanofluid was also carried out using pH control method and examined using time-spend experiment. In the best case of stabilization (about 216 h), 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.

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