Enhancement mechanism of convective heat transfer via nanofluid: An analysis by means of synchrotron radiation imaging

The enhancement mechanism on the heat transfer coefficient of SiO(2 )nanofluid compared to the ethylene glycol/water solvent was investigated by means of synchrotron x-ray radiographic imaging at 300.15 K. The experimental results showed a low concentration of local particles near the wall in the channel cross-section. This anomalous particle distribution alters the flow velocity distribution. Based on the law of conservation of momentum, the thickness of the thermal boundary layer becomes thin in the nanofluid, consequently enhancing the convective heat transfer. The thickness of the thermal boundary layer in the nanofluid based on the particle distribution visualized from x-ray imaging depends on the particle diameter, and its dependency is consistent with the magnitude relation of the heat transfer coefficient. (C) 2020 Elsevier Ltd. All rights reserved.