Enhanced nucleate boiling on copper micro-porous surfaces

Saturation boiling of PF-5060 dielectric liquid on Cu micro-porous surface layers (95, 139, 171, 197 and 220-mu m thick) is investigated. These layers are deposited on 10 x 10 mm Cu substrates using two-stage electrochemical process. The basic micro-structure, obtained in the first stage using current density of 3 A/cm(2) for 15-44 s, depending on thickness, is strengthened by continuing electrochemical deposition using much lower current density for 10's of minutes. For conditioned surface layers, after a few successive boiling tests, the pool boiling curves are reproducible and the temperature excursion prior to boiling incipience is either eliminated or reduced <7 K. Present nucleate boiling results are markedly better than those reported for dielectric liquids on micro- and macro-structured surfaces. Present values of CHF (22.7-27.8 W/cm(2)) and h(MNB) (2.05-13.5 W/cm(2) K) are similar to 40-70% higher than and >17 times those reported on plane surfaces (<16 W/cm(2) and similar to 0.8 W/cm(2) K). Best results are those of the 171-mu m thick layer: CHF of 27.8 W/cm(2) occurs at Delta T-sat of only 2.1 K and h(MNB) of 13.5 W/cm(2) K occurs at Delta T-sat = 2.0 K. (C) 2010 Elsevier Ltd. All rights reserved.