Enhanced pool boiling of Novec-7100 using nano/micro structured surfaces

Abstract

Fluorinated dielectric liquids (e.g., Novec-7100) are critical for electronics cooling applications, for which engineered surface textures can dramatically improve pool boiling performance. This study presents a systematic comparison between two distinct surface engineering approaches: (1) nanostructured surfaces created via chemical vapor deposition and (2) microstructured surfaces fabricated using porous copper foam and copper mesh. Through controlled pool boiling experiments, the results showed that the introduction of micro and nanostructured surfaces effectively reduced the wall superheat at the onset of nucleate boiling due to the coupling between surface structure and bubble evolution, with microstructured surfaces improving heat transfer coefficient and critical heat flux by 61.9 % and 65.23 %, respectively, which is superior to the nanostructured surfaces due to the improvement in the liquid replenishment. The three-dimensional interconnected pore structure of copper foam provides optimal cavity sizes for bubble nucleation while simultaneously enhancing liquid replenishment through capillary action. High-speed visualization reveals that copper mesh surfaces exhibit 2-fold higher bubble departure frequency than plain surfaces, directly correlating microstructural features with enhanced bubble dynamics. These findings establish porous metallic structures with multiscale porosity as the optimal solution for maximizing both heat transfer coefficient and critical heat flux in dielectric fluid boiling applications. The study advances fundamental understanding of structure-performance relationships in phase-change heat transfer and offers practical surface engineering solutions for next-generation electronics cooling systems.