(329f) Implications of Multiscale Graphene Interfaces on “Reverse” or “Inversed” Boiling

Phase change heat transfer is crucial to various engineering applications. Some prominent examples include distillation reboiler, desalination, steam generators, high-powered electronic systems, and refrigeration. Boiling is a well-known process and has been studied extensively for decades. It is accompanied by phase change from liquid to vapor, subsequently, pool boiling involves the boiling of a stagnant liquid over a heated surface. It is desirable to enhance the boiling performance to enable higher heat dissipation to reduce equipment cost through surface engineering. For various manifestations, the pool boiling performance of a surface is dictated by higher critical heat fluxes and heat transfer coefficients with an increase in wall superheat. However, our graphene based surfaces have demonstrated an anomaly in the boiling curves with a decrease in wall superheat at higher critical heat fluxes which is reported as reverse boiling or “boiling inversion”. We attribute this to various physical mechanisms such as the temperature gradients, separate vapor-liquid pathways, and impinging liquid jets that arise within the multiscale surface morphologies. This talk aims to summarizes various experimental and physical mechanisms of boiling inversion observed with multiscale graphene coatings. First, several combined powder metallurgy and additive manufacturing methods to form composite copper/graphene coatings will be presented along with their pool boiling performance. The second part of the talk will focus on correlating the tunable surface properties such as roughness, porosity, hydrophilicity, wickability and wicking rates, and with the boiling inversion mechanisms. This fundamental study will aid in overall thermal management of various high temperature equipment and devices.