APS March Meeting 2022
Volume 67, Number 3
Monday–Friday, March 14–18, 2022;
Chicago
Session T00: Poster Session III (1pm- 4pm CST)
1:00 PM,
Thursday, March 17, 2022
Room: McCormick Place Exhibit Hall F1
Abstract: T00.00361 : Droplet evaporation on hot microstructured superhydrophobic surfaces: Analysis of evaporation from droplet cap and base surfaces*
Abstract
Presenter:
Jiangtao Cheng
(Virginia Tech)
Author:
Jiangtao Cheng
(Virginia Tech)
We experimentally and theoretically investigated evaporation of sessile water droplets on hot micro-structured superhydrophobic surfaces in this study. Water droplets of 4 μL were placed on micro-pillared silicon substrates with the substrate temperature heated up to 120 °C. A comprehensive thermal circuit model is developed to analyze the effects of substrate roughness and substrate temperature on the sessile droplet evaporation. For the first time, two components of heat and mass transfer, i.e., one from the droplet cap surface and the other from the droplet base surface, during droplet evaporation are distinguished and systematically studied. As such, the evaporation rates from both the droplet cap surface and the interstitial liquid-vapor interface between micropillars at the droplet base are calculated in various conditions. For droplet evaporation on the heated substrates in the range of 40 °C – 80 °C, the predicted droplet cap temperature matches well with the experimental results. During the constant contact radius mode of droplet evaporation, the decrease of evaporation rate from the droplet base contributes most to the continuously decreasing total evaporation rate, whereas the decrease of evaporation rate from the droplet cap surface is dominant in the constant contact angle mode. The influence of internal fluid flow is considered for droplet evaporation on substrates heated above 100 °C, and an effective thermal conductivity is adopted as a correction factor to account for the effect of convection heat transfer inside the droplet. Temperature differences between the droplet base and substrate surface are estimated to be ~ 2 °C, 5 °C, 8 °C, 12.5 °C and 18 °C for droplet evaporation on substrates heated at 40 °C, 60 °C, 80 °C, 100 °C, and 120 °C, respectively, which elucidates the delayed or depressed boiling of water droplets on a heated rough surface.
*NSF CBET under grant number 1550299, NSF ECCS under grant 1808931 and NSFC under grant number 52075071