Spray cooling: transient thermal modeling with the Monte Carlo method

• Grant number: 23/03243-3
• Support Opportunities: Scholarships in Brazil - Scientific Initiation
• Start date: May 01, 2023
• End date: May 06, 2024
• Field of knowledge: Engineering - Mechanical Engineering - Thermal Engineering
• Principal Investigator: Arthur Vieira da Silva Oliveira
• Grantee: Carlos Eduardo Brasil de Mendonça Rocha
• 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): 23/14469-2 - Comparison of experimental data of dissipated energy during a droplet impact on heated walls and spray cooling, BE.EP.IC

Abstract

Droplet impact on walls is a process found in many engineering applications, such as metallurgy, nuclear reactors, internal combustion engines, propulsion turbines, cooling of electronic components, among others. To better characterize the hydrodynamic and thermal processes during the impact of one or more drops on a heated surface, a FAPESP Young Research research project started at EESC/USP (São Carlos) in 2022, in which several optical techniques will be used to perform the necessary measurements. To date, some tests with the impact of only one droplet on the wall have been performed; however, we need to advance the work on the impact of several drops during the cooling of a metal plate, that is, spray cooling. This Undergraduate Research project proposes to perform transient three-dimensional heat conduction numerical simulations representing spray cooling of a metal plate. As a boundary condition of these simulations, we will use hydrodynamic and thermal mechanistic models of the droplet impact on heated walls that are available in the literature. Such models will be compared to experimental results obtained in the first Undergraduate Research made by Carlos Eduardo, the student of the present proposal, in order to use in the simulations the most representative model of the physical process. Then the Monte Carlo method will be used to "generate" droplets of different diameters - respecting the droplets' size distribution of the spray in study - and to determine the droplet impact location on the heated wall. Global spray parameters, such as mass flow rate and injection pressure, will allow setting other impact parameters, such as droplet velocity and rate of droplets impacting the wall. With the Monte Carlo method and the mechanistic model of heat exchange per droplet, dispersed spray cooling can be simulated. At this stage, some spray cooling experiments will be made to compare simulation results with experimental data. Finally, several simulations will be performed by varying spray parameters (such as average droplet size, injection pressure and spray distribution) to evaluate their impacts on plate cooling. It is worth mentioning that this Undergraduate Research project proposal is a continuity of the work that has been developed by the student in his first Undergraduate Research project, and both the material necessary for the experiment and the code of finite differences for the solution of the transient three-dimensional heat equation are already available.