Wall rewetting during single and multiple droplet impact on a heated surface: theoretical and experimental investigation

• Grant number: 23/15397-5
• Support Opportunities: Scholarships in Brazil - Doctorate (Direct)
• Start date: January 01, 2024
• Status: Discontinued
• Field of knowledge: Engineering - Mechanical Engineering - Transport Phenomena
• Principal Investigator: Arthur Vieira da Silva Oliveira
• Grantee: Alvaro Felipe Campos Araya
• 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
• Associated scholarship(s): 24/17883-7 - Comprehensive experimental study of droplet impact on heated sapphire substrates in the Leidenfrost and the transition boiling regimes., BE.EP.DD

Abstract

Droplet impact on heated walls is still largely studied in the literature because of its many applications in the industry, like metallurgy, nuclear energy, automotive, electronics, and others. Even though much has advanced in the past decades, few investigations used combined optical techniques to measure all the thermal and fluid dynamics processes before, during, and after the droplet impact. Moreover, studies with multiple droplets impact are almost non-existent because of the phenomenon's complexity and time-consuming experiments. Nevertheless, studying the heat transfer with multiple droplets impacting onto a heated wall is an important step to better understand spray cooling and to develop a physics-based model. The present direct doctoral student will perform exhaustive experiments of single and multiple droplets impact onto a heated wall in the Leidenfrost regime. The main objectives are: understand better how multiple droplets affect the impact regime and the heat dissipation of a heated wall; extract the dissipated heat by single and multiple droplet impact, as well as the heat transfer coefficient, and the Leidenfrost temperature; develop models for the heat transfer coefficient and Leidenfrost temperature for multiple droplets impact and compare with experimental results. The doctoral student will use optical techniques to characterize different parameters, namely Shadowgraph (SDG) for the droplet size, shape, and velocity, Planar Laser-Induced Fluorescence (PLIF) for the droplet temperature, Total Internal Reflection (TIR) for the droplet-wall contact, and Infrared Thermography (IRT) for the wall temperature. While the activities held at EESC/USP will be supervised by Arthur Oliveira, the doctoral student will spend one year of his project at the LEMTA, at the Université de Lorraine, to perform complementary experiments under the supervision of Prof. Michel Gradeck, which will enrich the experimental campaign and model validations. (AU)