An overview on the role of wettability and wickability as a tool for enhancing pool boiling heat transfer

Abstract

The present chapter addresses the main recent contributions to the development of structured surfaces to enhance pool boiling heat transfer with modifications of apparent wettability and capillary wicking. First, a critical chronological description of some investigations regarding parametric effects that could be potentially relevant for pool boiling heat transfer augmentation is presented. Then, different methodologies applied to modifying surfaces are divided as follows: (i) surface roughening; (ii) porous surfaces; (iii) micro and nanostructured surfaces. In this context, employed manufacturing techniques and the role of fundamental heat transfer mechanisms associated to the surface modifications are described. Modifications of wettability and capillary wicking are highlighted as strategies that mostly impact heat transfer enhancement, due to engineered modifications of liquid/surface interactions over increased contact area. In addition, the creation of artificial microcavities to increase the active nucleate sites density is directly related to pool boiling performance, which has been predominantly covered by several experimental studies in the last few decades. Overall, these methodologies aim to achieve ameliorations of critical heat flux and heat transfer coefficient based on mechanistic approaches that guarantee a stable boiling regime, with continuous vapor removal and liquid supply, associated with modified surfaces that would be durable and stable over time.