(574c) Copper-Carbon Nanomaterial Composite Coatings for Dramatic Improvements in Phase Change Heat Transfer

Phase change heat transfer is crucial to various engineering applications. Some prominent examples include distillation reboiler, nuclear reactor, high-powered electronic systems, and refrigeration. Boiling is a heat transfer process accompanied by phase change from liquid to vapor, subsequently, pool boiling involves the boiling of a stagnant liquid over a heated surface. This talk aims to examine the physical mechanisms of boiling heat transfer that are of prime importance to quantify the efficacy of the process. For various manifestations, the pool boiling performance of a surface is dictated by higher critical heat fluxes (CHF) and heat transfer coefficients.

This talk will examine various strategies to create multiscale surface-active engineered surfaces with tunable properties essentially roughness, porosity, hydrophilicity, wickability and wicking rates and their influence on the heat transfer properties. These surfaces were developed as benchmark studies, to produce a new class of hierarchical porous coatings to improve critical heat fluxes and heat transfer coefficients while facilitating morphology-induced mechanisms such as: wettability, contact angle hysteresis, roughness, and capillary wicking. In addition, the aging characteristics such as surface chemistry and morphology variablity resulting from repetitive chaotic boiling tests will also be discussed. High thermal conductivity along with improved hydrophilicity and wickability of the copper/carbon nanomaterial composites are attributed for the enhanced CHF. High-speed images revealed reduced bubble departure diameters and micro-size pores on the electrodeposited surface serving as nucleation sites. The increase in the bubble frequency and delayed formation of vapor blanket resulted in enhanced heat transfer properties.