2-D microflow generation on superhydrophilic nanoporous substrates using epoxy spots for pool boiling enhancement

Abstract

Abstract We conduct an experimental investigation on the pool boiling enhancement in DI water on nanoporous surfaces. The surfaces are modified by anodic oxidation, and cavities with 2 mm diameter and pitches between 2.5 and 5 mm applied on them using EDM method filled with a two-part epoxy with low thermal conductivity properties. The capillary wicking action of the superhydrophilic nanoporous oxide layer enhances the rewetting and spreading of the liquid to dry-spots during boiling. The epoxy disks remain wet and prevent merging bubbles during the pool boiling experiment and a 2-D microflow is induced toward dried regions with synergic effects of nanoporous surface absorption, create a considerable delay in the formation of a vapor blanket. The results indicate that the anodized surface enhances the critical heat flux (CHF) by 33% and the heat transfer coefficient increases by 48% at the CHF compared to the non-coated substrate. It has been shown that for anodized samples with 3 and 4 mm epoxy spot pitches the CHF equals to 144 and 133 W/cm2, respectively, considerably higher than the coated surface without epoxy parts 125 W/cm2.