Analytical Analysis of Non-Boiling Heat Transfer During Droplet Impact on Heated Wall and the Effect of Thermophysical Properties

Droplet impact process exhibits excellent heat and mass transfer characteristics. Analytical study on droplet impact heat transfer is able to reveal the physical essence, however it is quite insufficient and limited to flow field analysis. In this paper, the analytical model of non-boiling heat transfer during droplet impact on heated wall was established. The analytical solutions of heat flux and temperature variation were obtained based on boundary layer theory and the similarity between thermal boundary layer and viscous boundary layer. The parameter analysis of thermophysical properties was conducted to explore the influencing mechanism of droplet and wall materials. The results showed that the analytical solutions have high accuracy at low impact velocity and low initial wall temperature. It was worth noting that copper wall with highest heat flux shows lower inner temperature drop than silicon wall. Parameter analysis showed that the effect trend of wall materials on heat flux and temperature drop is quite different. Heat flux was the single-valued function of wall thermal effusivity, while temperature drop was the coupling effect of thermal effusivity and thermal conductivity: thermal conductivity dominated at low thermal conductivity, while thermal effusivity dominated at high thermal conductivity. Different from the effect wall property, droplet properties had great and similar effect on heat flux and temperature distribution inside solid wall. Dropet thermal effusivity and Prandtl number were the decisive parameters. The importance of thermal effusivity was demonstrated and high thermal effusivity was preferred in thermal management