An Ultrathin Nanoporous Membrane Evaporator

Abstract

Evaporation is a ubiquitous phenomenon found in nature and widely used in industry. Yet a fundamental understanding of interfacial transport during evaporation remains limited to date owing to the difficulty of characterizing the heat and mass transfer at the interface, especially at high heat fluxes (>100 W/cm²). In this work, we elucidated evaporation into an air ambient with an ultrathin (≈200 nm thick) nanoporous (≈130 nm pore diameter) membrane. With our evaporator design, we accurately monitored the temperature of the liquid–vapor interface, reduced the thermal–fluidic transport resistance, and mitigated the clogging risk associated with contamination. At a steady state, we demonstrated heat fluxes of ≈500 W/cm² across the interface over a total evaporation area of 0.20 mm². In the high flux regime, we showed the importance of convective transport caused by evaporation itself and that Fick’s first law of diffusion no longer applies. This work improves our fundamental understanding of evaporation and paves the way for high flux phase-change devices. Keywords: evaporation; high flux; Maxwell−Stefan equation; nanoporous; Ultrathin