Pool boiling of micro-/nanoparticles modified aluminum surface

Abstract

The purpose is to investigate the boiling heat transfer affected by different wettability aluminum surfaces. The hydrophobic and hydrophilic surfaces were modified from regular surfaces by sol-gel method. The water contact angles of sample surfaces are 150, 75, and 5 degrees. All the samples were tested by a carefully designed thermal system. The experimental results revealed that, at the same wall superheat condition, the hydrophilic surface had higher boiling heat flux and hydrophobic surface possessed the lowest. The boiling bubble generation images suggested that bubble formation rate and shape strongly affected the values of heat flux. The lower contact angle surface generated fewer bubbles at high heat flux state such that liquid could contact with larger part of solid interface and transfer more heat than other kinds of surfaces. For the high contact angle surface, at very high heat flux condition, the bubbles even collapsed into vapor film. Part of heat transferred to liquid was blocked by the film and caused the wall superheat to increase dramatically and finally damaged the sample. This heat flux limitation was called critical heat flux. The hydrophilic surface that possessed higher critical heat flux was also measured in this study. © 2013 Chin-Ting Yang and Chia-Cheng Yu.