Characterization of the freezing process of droplets on cold surfaces using optical techniques.

• Grant number: 23/09775-7
• Support Opportunities: Scholarships in Brazil - Scientific Initiation
• Start date: September 01, 2023
• End date: August 03, 2025
• Field of knowledge: Engineering - Mechanical Engineering - Thermal Engineering
• Principal Investigator: Arthur Vieira da Silva Oliveira
• Grantee: Murillo Augusto Correa Masculi
• 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): 24/18585-0 - Surface Functionalization for Studies of Icing of Impacting Droplet, BE.EP.IC

Abstract

Droplet freezing is present in many different areas of industry. In aeronautics, for example, water droplets can freeze on aircraft in full cruise flight, which poses a risk during the flight, since there is the possibility of obstruction and breakage of essential equipment for the flight, such as the pitot tube, flaps, turbine blades and others. This droplet freezing phenomenon is also present in refrigeration cycle evaporators, which have their efficiency compromised due to ice accumulation. Studies of droplet freezing and its impact on cooled surfaces aim to propose solutions to avoid problems such as those mentioned above. There are many studies in the literature addressing the impact of droplets on frozen surfaces, but most have been limited to simplified visualization and measurement methodologies. Therefore, there is a need for new works that use combinations of advanced temperature field measurement and image analysis techniques, enabling a more detailed view of the phenomenon. Given this context, this Scientific Initiation research proposes to perform droplet impact tests on cold surfaces, using Shadowgraph and LIF (Laser Induced Fluorescence) techniques. The objective is to initiate the study of droplet freezing during impact on cold surfaces using optical techniques developed by the Young Researcher Aid research group. For this, some parameters will be varied, such as: i) droplet impact velocity; ii) wall temperature and iii) initial fluid temperature. A bench with a controlled environment is proposed to perform the tests, but also an open bench could be used to improve the optical access to the test section, thus allowing the use of the LIF technique for the characterization of the freezing front. This Scientific Initiation will open doors for the research group to explore new applications of droplet impact studies beyond the cooling of heated surfaces.