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ENCIT 2022
19th Brazilian Congress of Thermal Sciences and Engineering
Regimes and dynamics of a droplet impacting a heated wall by high-speed shadowgraphy
Submission Author:
Arthur Vieira da Silva Oliveira , SP
Co-Authors:
Arthur Vieira da Silva Oliveira
Presenter: Arthur Vieira da Silva Oliveira
doi://10.26678/ABCM.ENCIT2022.CIT22-0017
Abstract
Many processes in thermal engineering involve droplets impacting on heated surfaces: in metallurgy, where spray cooling is used to produce steel plates and bars; in nuclear reactors, where a steam-droplets flow is created during a hypothetical loss-of-coolant accident, and these droplets contribute to the cooling of the fuel assembly; in internal combustion engines, where the injected fuel impinges on the cylinder wall and the piston head. The fluid dynamics process during the droplet impact can play an important role, as it can deposit, splash or bounce on the surface, which affects directly the heat dissipated from the heated wall. The droplet contact time is very short, usually lasting a few micro or milliseconds, which requests high-speed imaging to evaluate correctly its dynamics. In this study, droplet dynamics before, during and after impacting a heated wall were evaluated by high-speed shadowgraphy. The effects of the droplet velocity and wall temperature were analyzed; more precisely, tests were performed for three different impact velocities and three different wall temperatures. The impact regime was identified and the evolutions in the droplet spread diameter and contact angle were measured for each experiment. This study is in the context of a FAPESP Young Investigator research project, in which droplet impact heat transfer and spray cooling will be investigated using several optical techniques, including high-speed shadowgraphy as used herein.
Keywords
cooling, Leidenfrost, Spread, bounce
