Dynamic wetting and heat transfer characteristics of a liquid droplet impinging on heated textured surfaces

다국어 초록 (Multilingual Abstract)

<P><B>Abstract</B></P> <P>This article reports the dynamic wetting behavior during spreading and receding phases and the heat transfer characteristics for impinging droplets on heated textured surfaces. In particular, the present study suggests newly the modified equations of the total thermal energy absorbed by droplet and the cooling effectiveness for textured surfaces with consideration of three different wetting states: non-wetting, partial-wetting and total-wetting states. Captured images by using the high-speed cameras were analyzed to examine the influence of impact Weber number, surface temperature, and texture area fraction. It was found that for the textured surfaces, the maximum contact diameter of impinged droplet decreased owing to decrease in the surface energy. At increased surface temperatures, the maximum contact diameters slightly increased and the maximum recoil diameters decreased because of change in liquid viscosity. For the textured surfaces, the cooling effectiveness increased with the Weber number and its change substantially depended on the wetting state. In case of the total-wetting state, the cooling effectiveness increased with the texture area fraction, because of change in liquid–solid interface area. It shows that the control of wetting state would be important in heat transfer of an impinging droplet on solid surface.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Spreading and receding behaviors were observed for impinging droplets on heated textured surface. </LI> <LI> The effect of texture area fraction, surface temperature, and Weber number were examined. </LI> <LI> In the receding regime, droplets receded faster with the increase in surface temperature. </LI> <LI> A cooling effectiveness model for a textured surface was suggested by considering wetting states. </LI> <LI> The cooling effectiveness decreased with the increase in hydrophobicity. </LI> </UL> </P>