Saturated pool boiling heat transfer of acetone and HFE-7200 on modified surfaces by electrophoretic and electrochemical deposition
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Boiling heat transfer intensification is of big relevance to energy conversion and conservation, materials and resources saving, and electronics cooling. This work aims to enhance saturated pool boiling of well-wetting liquids, i.e., acetone and HFE-7200 on nanoparticles-deposited surfaces by electrophoretic deposition and on microporous foam surfaces by electrochemical deposition. The electrophoretic-deposited surfaces enhance the heat transfer coefficient of acetone and HFE-7200 by up to 70% and 190%, respectively. However, the critical heat flux is not improved on electrophoretic-deposited surfaces. The electrochemical-deposited surfaces increase the boiling heat transfer coefficient by up to 370% and the critical heat flux by more than 30%. Bubble dynamics were visualized simultaneously. The bubble departure diameter from experiments can be predicted by a dynamic force balance model within a ±20% error band. A mechanistic heat transfer model was proposed for modified porous surfaces, including not only the heat fluxes from microlayer evaporation and transient conduction but also the heat flux from micro-convection due to liquid agitation and entrainment by growing and departing bubbles. The mechanistic heat transfer model can predict experimental pool boiling curves of acetone and HFE-7200 on electrophoretic-deposited and electrochemical-deposited surfaces relatively well, especially for the isolated bubble regime where most bubbles are isolated and bubble coalescence is not intensive. Besides, the critical heat flux of a modified surface can be estimated if the initial (maximum) wicked volume flux on the structured surface relative to the smooth surface is considered.