Boiling Heat Transfer Performance of Pure Water on Binary Oxide-Based Nanoparticles Coatings

Abstract

Pool boiling heat transfer performance has been evaluated on a binary oxide based nanoparticles coated surface. Electrophoretic deposition techniques were used for TiO2 and Al2O3 nanoparticles coatings on polished copper substrates. Four different surfaces have been prepared by varying the deposition time 2.5, 5, 10, and 15 min which are referred to in the text as coated surface (CS)#1, CS#2, CS#3, and CS#4, respectively. The surface characteristics like surface roughness, morphology, and wettability have changed after the coating. It has been observed that all the deposited surfaces are hydrophobic, whereas polished copper surfaces are hydrophilic by nature. The boiling heat transfer performance of surface CS#2 is superior to the other three surfaces, while CS#4 is the worst. The highest enhancement in boiling heat transfer coefficient (BHTC) observed for CS#2 is 62.3%, corresponding to a heat flux of ∼220 kW/m2. The coating layer thickness was also observed to be an important parameter, apart from surface roughness, wettability, and morphology, which may be a cause for heat transfer deterioration, if it crosses a limiting value. In this study the limiting value of coating layer thickness discovered ∼15 μm experimentally.