Characterization of secondary droplets and mass lost during droplet impact on heated walls.

• Grant number: 24/08409-0
• Support Opportunities: Scholarships in Brazil - Scientific Initiation
• Start date: October 01, 2024
• End date: September 30, 2025
• Field of knowledge: Engineering - Mechanical Engineering - Transport Phenomena
• Principal Investigator: Arthur Vieira da Silva Oliveira
• Grantee: Mariana Laviera Bezerro
• Host Institution: Escola de Engenharia de São Carlos (EESC). Universidade de São Paulo (USP). São Carlos , SP, Brazil
• Associated research grant: 21/01897-0 - Experimental study of droplets impact onto heated walls using combined optical techniques: single droplets, multiple droplets and sprays, AP.JP

Abstract

The use of sprays is common in several industrial areas: in the metallurgical sector, for the cooling of metal parts, in the manufacture of sponges, for the application of abrasives for surface coating, or in the manufacture of foods, such as powdered milk. Therefore, it is common for scientific studies in this area to use previously defined average parameters, such as the average droplet diameter and the average wall temperature, to analyze the impact of sprays, which compromises the verification of exclusive characteristics of certain drop impact regimes. Thus, this difficulty can be softened through the study and investigations into single drop phenomena, which can be controlled locally in the laboratory. Until nowadays, there are several studies in the literature that address techniques for observing and measuring the impact of single drops. However, it is necessary to develop new scientific work that favors a broader view of the process: portion adhered to the heated wall, formation of secondary drops, heat transfer and estimation of mass loss on impact. Seeking to contribute to this more deeper analysis, this Scientific Initiation work proposes the analysis of single droplet impacts, more specifically regarding the formation, characterization and quantification of secondary drops, using data previously collected by the group - with visualization using the Shadowgraph technique - in addition to the PTV (Particle Tracking Velocimetry) technique. The objective is to estimate and characterize the secondary droplets that are expelled during impacts in different scenarios - such as in the boiling regime, in which droplets are splashed by the formation of bubbles, or in thermal atomization, with droplet breakage and spreading. Finally, it is expected to estimate the mass lost due to the ejection of secondary drops, this parameter being essential to complete the mass balance and - in the future with thermal tests - the energy balance.