Evaporation-driven liquid flow through nanochannels

JC Fan and HA Wu and FC Wang, PHYSICS OF FLUIDS, 32, 012001 (2020).

DOI: 10.1063/1.5137803

Evaporation-driven liquid flow through nanochannels has attracted extensive attention over recent years due to its applications in mass and heat transfer as well as energy harvesting. A more comprehensive understanding is still expected to reveal the underlying mechanisms and quantitatively elucidate the transport characteristics of this phenomenon. In this study, we investigated evaporation-driven liquid flow through nanochannels using molecular dynamics simulations. The evaporation flux from the solid-liquid interface was higher than that from the middle region of the channel or the liquid-vapor interface. This finding may explain why experimental observations of evaporation flux through nanochannels exceed the limits predicted by the classical Hertz-Knudsen equation. Upon increasing the interaction strength between liquid atoms, the liquid exhibited enhanced solid-liquid interfacial evaporation and higher surface tension, albeit with reduced total flux. We also found that lyophilic channels exhibited higher evaporation fluxes than lyophobic channels, which can be interpreted by a Gibbs free energy analysis. The energy conversion analysis indicated that the effective pressure gradient exerted on a liquid flow by evaporation depends on the channel length. This was consistent with our simulations. Evaporation-driven liquid flow through nanochannels could be modeled quantitatively using this knowledge. Published under license by AIP Publishing.

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