Hierarchical High Flux Evaporative Cooling

High power density electronics are severely limited by current thermal management solutions which are unable to dissipate the necessary heat flux while maintaining safe junction temperatures for reliable operation. Further, a wide range of industrial systems requires using low surface tension liquids where heat transfer enhancement has proved challenging for boiling and evaporation. Here, we enable a new paradigm of phase change heat transfer, which favors high volatility, low surface tension liquids rather than water. We achieved ultrahigh heat fluxes a nanoporous membrane of about 600 nm thickness and less than 140 nm pore diameters supported on efficient liquid supply architectures, decoupling capillary pumping from viscous loss. Proof-of-concept devices were microfabricated and tested in a custom-built environmental chamber. R245fa, pentane, methanol, isopropyl alcohol, and water were used as working fluids. We then compared pore-level heat transfer of different fluids, where R245fa showed approximately 10 times the performance of water under the same working conditions. Finally, we illustrate the usefulness of a figure of merit extracted from kinetic theory for evaporation. The current work provides fundamental insights into evaporation of low surface tension liquids, which can impact various applications such as refrigeration and air conditioning, petroleum and solvent distillation, and on-chip electronics cooling.

Related Articles: ACS Appl. Mater. Interfaces 2020, Microsystems & Nanoengineering 2018, IEEE Trans. Compon. Packag. Manuf. Technol. 2016