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Second Thermal and Fluids Engineering  Conference

ISSN: 2379-1748
ISBN: 978-1-56700-430-4

EFFECTS OF ACOUSTICS ON INDUCED DROPLET SHEDDING FOR DROPWISE CONDENSATION

Jose Eduardo Mejia
Texas A&M University, College Station, TX, 77843, USA

Jorge L. Alvarado
Texas A&M University, College Station, TX, 77843, USA

Chun-Wei Yao
Lamar University, Beaumont, TX, 77710, USA

Abstract

In the area of condensation, dropwise condensation has been found to be more efficient than film condensation. However, droplet shedding is one of the limiting steps in the overall dropwise condensation process even when using engineered surfaces. Moreover, engineered surfaces can lead to undesirable contact angle hysteresis in droplets, which limits condensation rates. Therefore, external stimuli should be considered to promote adequate droplet shedding during condensation. To that end, an acoustic system has been developed to induce droplet shedding via substrate-droplet resonance. In order to understand the relationship between droplet sliding angle and body forces such as a gravity and acoustic streaming, a mathematical model has been postulated capable of predicting the critical sliding angle of droplets. Specifically, the theoretical model can be used to determine the rolling angle in terms of contact angle hysteresis, droplet volume and other characteristics of the droplets. The model has been validated experimentally with and without imposing acoustic stimuli under the influence of gravity. The model can be used to evaluate independently the effects of capillary, gravitational, vibrational and viscous forces on liquid droplets. Experimental data to date show that the model can be used effectively to relate imposed resonance frequency to critical rolling angle of droplets.

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