An experimental study of dynamic capillary action in open-cell copper foams

With an increasing focus on data center development and innovation, high efficiency cooling systems are required to manage the ultra-high heat fluxes of advanced chip technologies. This study is motivated by a thermal management solution that leverages porous metal media to pump a coolant, via capillary action, to a liquid-vapor interface where evaporation facilitates heat dissipation from the chip. The maximum rate of evaporative heat transfer is governed by the capillary-driven fluid flow through the porous media. To explore performance limits, we experimentally investigated the effect of hydrophilic surface treatments of high porosity copper foam with varying thicknesses on the dynamics of capillary-driven wicking in the foam. For the experiments, copper foam samples were solvent-cleaned and treated with either oxygen or argon plasma to respectively promote either copper oxide formation or remove airborne contamination from the sample surfaces We measured capillary-driven imbibition time across the thickness of each sample via sessile droplet tests and wicking along the length of each sample via Washburn tests, all with water as the working fluid. We found that argon and oxygen plasma treatments were able to improve both imbibition time and fluid flow through the copper foams, compared to the untreated samples, and via comparing with an analytical model, we obtained foam sample permeability.