Electrical discharge surface texturing for enhanced pool boiling heat transfer

Abstract

This research pertains to pool boiling heat transfer characteristics of Aluminum 6061 alloy surfaces that were textured using sink electrical discharge machining (EDM). Prior related work elsewhere utilized EDM as an essential means to roughen a surface or fabricate geometric features such as microchannels and micropillars to investigate boiling. As opposed to this, the present work systematically examined the effect of EDM process parameters viz., the discharge current and the discharge duration to enhance/benchmark boiling performance in the natural convection and nucleate boiling regimes, and comprehend underlying mechanisms. A process-related factor that limits boiling was found to be the growth of a superficial layer on the machined surface, the formation of which is facilitated by the hydrocarbon dielectric fluid used in EDM. This notwithstanding, the highest heat transfer coefficient obtained in this work was roughly five times as that of a reference polished surface. The Data Dependent Systems methodology was adopted to mathematically extract characteristic crater geometry from EDM-textured surface profiles, which highlighted the significance of parameters that are physically relevant such as the crater diameter and the crater volume in correlating boiling performance.