Boiling Enhancement on Nanostructured Surfaces with Engineered Variations in Wettability and Thermal Conductivity

Abstract

This work provides fundamental insights into the underlying mechanisms of pool boiling enhancement using a variety of different engineered surface designs. Specifically, the effects of nanostructured coatings, surfaces with mixed wettability, and surfaces with in-plane variations in thermal conductivity are investigated. The positive and negative impacts of each design on the onset of nucleate boiling, heat transfer coefficient, bubble dynamics and the ebullition cycle, as well as critical heat flux have been characterized. It is seen that while several techniques enhance one element of the boiling process, they can degrade others. This analysis has led to the design, fabrication, and characterization of complex heterogeneous surfaces by combining multiple engineered surface techniques. Nanostructured surfaces with variations in substrate thermal conductivity have been shown to increase critical heat flux by a factor of 2.6× as compared to bare copper substrates. In addition, nanostructured surfaces with engineered variations in substrate conductivity as well as surface wettability have been shown to increase heat transfer coefficient by more than a factor of 10×.