Pool boiling heat transfer on hierarchically nanostructured surfaces

• Grant number: 17/04276-1
• Support type: Scholarships in Brazil - Scientific Initiation
• Effective date (Start): April 01, 2017
• Effective date (End): September 30, 2018
• Field of knowledge: Engineering - Mechanical Engineering - Transport Phenomena
• Principal researcher: Elaine Maria Cardoso
• Grantee: Isabela Ignácio da Silva
• Home Institution: Faculdade de Engenharia (FEIS). Universidade Estadual Paulista (UNESP). Campus de Ilha Solteira. Ilha Solteira , SP, Brazil
• Associated research grant: 13/15431-7 - Application of nanotechnology in thermal processes and energy conversion, AP.JP

Abstract

This project deals with the study of pool boiling on hierarchically structured surfaces. This research involves the design of an experimental apparatus and the results analysis. The aim of this study is to analyze the influence of the surface characteristics on the heat transfer coefficient, taking into account the geometric parameters of the micro-structured surfaces, and also, the parameters related to the nanoparticles deposition such as: surface roughness, nanofluid concentration and wettability before and after the nanocoating process. Aspects concerning the height, diameter and center-to-center spacing for micropillars are thoroughly studied by analysis of the experimental data. This study will also involve the characterization of the surfaces tested, through the techniques of scanning electron microscopy (SEM) and wettability test, before and after the boiling tests. The tests will be performed for deionized water as working fluids (at atmospheric pressure and at saturation temperature) and, for heating surfaces of copper with micropillars and also, nanostructured micropillars (hierarchically structured surfaces). The nanocoated surfaces will be obtained by the boiling process of Al2O3-water based nanofluid, for two different nanofluid concentrations, 0.05 g/l (corresponding to low nanofluid concentration) and of 0.5 g/l (corresponding to high nanofluid concentration). The contribution of this work is to obtain results of interest to the industry for new refrigeration system components, air conditioning and cooling of electronic components for thermal control of machines, where the heat fluxes to be removed are higher than those provided by single-phase systems. Moreover, to improve the knowledge on the mechanism responsible for the enhancement/degradation of the pool boiling heat transfer on hierarchically nanostructured surfaces. (AU)