Approaching the limits of two-phase boiling heat transfer: High heat flux and low superheat

We demonstrate capillary fed porous copper structures capable of dissipating over 1200Wcm(-2) in boiling with water as the working fluid. Demonstrated superheats for this structure are dramatically lower than those previously reported at these high heat fluxes and are extremely insensitive to heat input. We show superheats of less than 10K at maximum dissipation and varying less than 5K over input heat flux ranges of 1000Wcm(-2). Fabrication of the porous copper layers using electrodeposition around a sacrificial template allows fine control of both microstructure and bulk geometry, producing structures less than 40 mu m thick with active region lateral dimensions of 2 mm x 0.3 mm. The active region is volumetrically Joule heated by passing an electric current through the porous copper bulk material. We analyze the heat transfer performance of the structures and suggest a strong influence of pore size on superheat. We compare performance of the current structure to existing wick structures. (C) 2015 AIP Publishing LLC.