The effect of water absorption on critical heat flux enhancement during pool boiling

A pool-boiling critical heat flux (CHF) correlation that can reflect the effect of capillary wicking on micro- and nano-structured surfaces was developed based on Kandlikar's CHF correlation dealing with wettability. Capillary wicking tests were performed to examine the significant pool-boiling CHF enhancement on a zirconium surface due to anodic oxidation modification. The amount of water absorption was measured using a capillary tube. Compared with a bare or wettable surface, the micro- and nano-structured surfaces showed much higher absorption ability. The behavior was different for each surface. The amount of water absorption indicated the effective capillary wicking on the surface and was used to explain the CHF enhancement provided by the zirconium surfaces. The tendency toward water absorption, depending on the surface, agreed with the experimental CHF data. A simple and additional contribution to Kandlikar's CHF correlation was proposed to account for the effect of capillary wicking. This modified correlation was in good agreement with CHF results from experiments. (C) 2012 Elsevier Inc. All rights reserved.