Eventos Anais de eventos
ENCIT 2016
16th Brazilian Congress of Thermal Sciences and Engineering
SURFACE ROUGHNESS AND NANOFLUID CONCENTRATION EFFECTS ON THE SURFACE WETTABILITY AND NANOFLUID BOILING HEAT TRANSFER
Submission Author:
Leonardo Manetti , MS
Co-Authors:
Alex Cunha, Igor Seicho Kiyomura, Marcos Antônio de Souza Peloso Junior, Elaine Maria Cardoso
Presenter: Leonardo Manetti
doi://10.26678/ABCM.ENCIT2016.CIT2016-0242
Abstract
The fluid/surface interaction has an important influence on pool boiling phenomena and can be large affected by changing the surface roughness or the working fluid properties. This paper mainly focuses on the effect of surface roughness and nanofluid concentration on the wettability and also, on the heat transfer coefficient (HTC). In order to analyze the interaction between the surface roughness and nanoparticles deposited on the heating surface, the tests were performed on copper heating surfaces with different roughness values. The nanostructured surfaces were produced by maghemite and alumina nanoparticle deposition, for different mass concentration, via nanofluid boiling process. All surfaces were submitted to metallographic, roughness and wettability analysis. The roughness of nanocoated surface is a function of the boiled nanofluid concentration. As the nanofluid concentration increases the surface roughness increases and the contact angle decreases, characterizing a hydrophilic behavior. Concerning the heat transfer coefficient, it was observed that the smooth surface has the lowest values compared to the other samples. The porous nanolayer formed on the rough surfaces increases the thermal resistance of the surface, degrading the heat transfer; for smooth surfaces, the nanoparticle deposition increases the microcavities, increasing the boiling heat transfer. However, this enhancement only occurred for low nanofluid concentrations, for which the thermal conductivity of the nanofluid overcomes the thermal resistance of the nanolayer formed on the surface.
Keywords
Nanofluid, Wettability, Heat transfer coefficient, pool boiling
