Leidenfrost Temperature on Trapezoidal Grooved Surface

Abstract

In this study, we reported experimental results of a water droplet falling on trapezoidal grooved surfaces of heated silicon wafers with the groove width varied from 20 μm to 640 μm and the depth from 20 μm to 40 μm. Based on the observation of droplet dynamics captured by high-speed camera, we found that on the denser grooved surface, the maximum spreading diameter of the droplet perpendicular to the groove direction was smaller than that on the sparser grooved surface with the same groove depth. The residence time of the droplet on the denser grooved surface was shorter than that on the sparser grooved surface. The Leidenfrost point increased 50 °C with the groove width varied from 20 μm to 640 μm and decreased 10 °C when the depth was changed from 20 μm to 40 μm, which were higher than that on the smooth surface. Due to the deformation of the droplet during the droplet dynamics, it was difficult to calculate the heat transfer by measuring the droplet volume reduction rate. Based on the convective heat transfer from the grooved surface to the droplet, a Leidenfrost point model was developed. The results calculated by the model are in agreement with the experimental data.

Keywords

• Leidenfrost temperature
• trapezoidal grooved surface
• convective heat transfer
• capillary pressure
• vapor convection