Eventos Anais de eventos
ENCIT 2022
19th Brazilian Congress of Thermal Sciences and Engineering
Cooling of a metallic sheet during the impact of a water droplet measured by high-speed infrared thermography
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.CIT22-0016
Abstract
Many processes in thermal engineering involve droplets impacting heated surfaces at high temperatures. Some of these examples are found: in metallurgy, with spray cooling and jet impingement in steel production; in nuclear reactors, where a steam-droplets flow in 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. Understanding the fluid dynamics and the heat transfer processes during droplet impacts on heated walls is essential to be able to control the wall cooling and enhance or reduce it, depending on the application. Because the sequence of droplet impact-spread-splash (or bounce) lasts only a few milliseconds, a high-speed infrared camera becomes the best equipment to evaluate the wall cooling with fine spatial and temporal resolution. In this study, back-surface infrared imaging is used to evaluate the temperature evolution of a metallic sheet before, during and after a water-droplet impact. While the droplet characteristics were fixed (diameter and release height), test results for three wall temperatures are presented: 150, 195 and 235 ºC. Wall rewetting was observed in all the experiments, but the rate of cooling increased with the increase in the initial wall temperature. A 1D inverse method was used to estimate the dissipated heat flux at the center of the droplet impact zone to compare the heat dissipation performances. 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 infrared thermography.
Keywords
cooling, Heat transfer, Droplet, Spray
