High heat flux evaporation from nanoporous silicon membranes

We investigated the evaporative cooling performance of a nanoporous membrane based thermal management solution designed for ultra-high heat flux dissipation from high performance integrated circuits. The biporous evaporation device utilizes thermally-connected, mechanically-supported, high capillarity membranes that maximize thin film evaporation and high permeability liquid supply channels that minimize viscous pressure losses. The 600 nm thick membrane was created on a silicon on insulator (SOI) wafer, fusion-bonded to a separate wafer with larger liquid channels. Overall device performance arising from non-uniform heating and evaporation of methanol was captured experimentally. Heat fluxes up to 412 W/cm ² over an area of 0.4×5 mm, at a temperature rise of 24.1 K from the heated substrate to ambient vapor, were obtained. These results are in good agreement with a high-fidelity coupled fluid convection and solid conduction compact model that incorporates non-equilibrium and sub-continuum effects at the liquid-vapor interface. This work provides a proof-of-concept demonstration of our biporous evaporation device. Simulations of the validated model at optimized operating conditions and with improved working fluids, predict heat dissipation in excess of 1 kW/cm ² with a device temperature rise under 30 K, for this scalable cooling approach.