Enhancement of pool boiling heat transfer in water on aluminum surface with high temperature conductive microporous coating

• Published in: International journal of heat and mass transfer Vol. 132; pp. 772 - 781
• Main Authors: Godinez, Juan C., Fadda, Dani, Lee, Jungho, You, Seung M.
• Format: Journal Article
• Language: English
• Published: Oxford Elsevier Ltd 01.04.2019; Elsevier BV
• Subjects: Aluminum; Boehmite; Boehmite nano layer; Coating effects; Coefficients; Contact angle; Critical Heat Flux (CHF); Distilled water; Heat; Heat flux; Heat transfer; Heat transfer coefficient; High temperature; Microporous coating; Nucleate boiling; Oxidation; Particle size; Pool boiling; Thickness; Boehmite nano layer; Critical Heat Flux (CHF); Contact angle; Heat transfer coefficient; Pool boiling; Microporous coating
• ISSN: 0017-9310; 1879-2189
• DOI: 10.1016/j.ijheatmasstransfer.2018.11.166

•Study of the effects of an aluminum high temperature conductive microporous coating on pool boiling.•Aluminum microporous coating (Al-HTCMC) fabricated using different aluminum powder particle sizes.•Coating thickness optimized to yield highest nucleate boiling heat transfer coefficients.•Boehmite treatment applied to aluminum surface with the microporous coating. The effects of an aluminum high temperature conductive microporous coating (Al-HTCMC) on the nucleate boiling heat transfer (NBHT) coefficient and critical heat flux (CHF) are studied in saturated distilled water at 1 atm. Aluminum powders with three different mean particle diameters (dm = 11, 24, and 66 µm) are used in the fabrication of the Al-HTCMC. For each mean particle diameter, an optimal coating thickness to yield the highest NBHT coefficient is determined. The optimized Al-HTCMC thickness is found to result in comparable NBHT coefficients regardless of the particle diameter. Pool boiling tests with a plain aluminum surface are used for comparison. The coated and plain aluminum surfaces are treated equally before the pool boiling tests to establish a Boehmite oxidation nano layer on the aluminum surfaces. Following the Boehmite treatment, the contact angle is unmeasurable (∼0°) with the Al-HTCMC surface and 12° with a plain aluminum surface. Then, pool boiling tests are performed and reveal comparable CHF (1725–1850 kW/m2) values with or without the Al-HTCMC. However, the Al-HTCMC is shown experimentally to improve the NBHT coefficient by a factor of five as the wall superheat is reduced by from 31 K to 6 K just before CHF. The results obtained are also compared to similar work using an HTCMC layer on a copper surface to demonstrate the performance of the Al-HTCMC.