Characterization and Modeling of the Heat Transfer Performance of Nanostructured Cu Micropost Wicks

Abstract

Micro heat pipes incorporating advanced wicks are promising for the thermal management of power electronics. We report the heat transfer performance of superhydrophilic Cu micropost wicks fabricated on thin silicon substrates using electrochemical deposition and controlled chemical oxidation. For a fixed post diameter, the interpost spacing and hence solid fraction is found to be a main design factor affecting the effective heat transfer coefficient and critical heat flux. The effective heat transfer coefficient >10 W/cm(2) K and the critical heat flux >500 W/cm(2) over 2 mm x 2 mm heating areas are demonstrated. Copper oxide nanostructures formed on the micropost surfaces significantly enhance the critical heat flux without compromising the effective heat transfer coefficient. An approximate numerical model is developed to help interpret the experimental data. A surface energy minimization algorithm is used to predict the static equilibrium shape of a liquid meniscus, which is then imported into a finite element model to predict the effective heat transfer coefficient. The advanced wick structures and experimental and modeling approaches developed in this work will help develop thin and lightweight thermal management solutions for high-power-density semiconductor devices. [DOI: 10.1115/1.4004168]