High-speed dynamics and temperature variation during drop impact on a heated surface

Drop impact on heated surfaces plays a vital role in numerous applications, such as spraying, cooling, and combustion. In addition to impact dynamics, we investigate both droplet and surface temperature changes using a high-speed infrared (IR) camera and thermocouples when a Milli-Q water droplet impacts on a heated surface under various Weber numbers (1 .6 <= We <= 129 , which compares the drop kinetic to surface energy) and initial surface temperature (100 degrees C <= T-s(i) <= 445 degrees C ). Theoretical models of droplet and surface temperature changes are deduced using the energy conservation principle. Both theoretical and experimental results show that temperature variations are dramatically influenced by impact dynamics, which shows spreading, spreading/splashing atomization, or complete rebound depending on We and T-s(i). For non-Leidenfrost droplets, the experimental results show that the mean droplet temperature change (Delta T-d) is increased with increasing We and T-s(i) and scales with Delta T-d similar to t(3/2) and Delta T-d similar to t in the initial spreading and later-time sticking stages, respectively. The experimental results of solid surface temperature change, Delta T-s(c) equivalent to Delta T-s (z = 0) , show that Delta T-s(c) alters sharply with We for We < 30 , whereas insignificantly for We > 30 with an identical T-s(i) . Under the same We , Delta T-s(c) increases first for 100 degrees C less than or similar to T-s(i) less than or similar to 300 degrees C and then reduces when 300 degrees C less than or similar to T-s(i) less than or similar to 445 degrees C because of enhanced atomization at elevated temperatures. Finally, a negligible Delta T-d and a nearly constant Delta T-s(c) (less than or similar to 4 degrees C ) are observed for Leidenfrost droplets due to the formation of an insulating vapor layer formed underneath the bouncing droplet. (C) 2022 The Authors. Published by Elsevier Ltd.

Automated summary

The impact of droplets on heated surfaces is crucial in various applications. Temperature variations during impact are significantly influenced by dynamics, with different behaviors observed at different Weber numbers and initial surface temperatures. Temperature changes in both droplets and surfaces are related to the energy conservation principle.