New Model for Liquid Evaporation and Vapor Transport in Nanopores Covering the Entire Knudsen Regime and Arbitrary Pore Length.

Abstract

Liquid evaporation and the associated vapor transport in micro/nanopores are ubiquitous in nature and play an important role in industrial applications. Accurate modeling of the liquid evaporation process in nanopores is critical to achieving a better design of devices for enhanced evaporation. Although having high impact on evaporation rate, vapor transport resistance in micro/nanopores remains incompletely understood. In this study, we proposed a new model which, for the first time, considered vapor transport in finite-length pores under various Knudsen regimes and then coupled the transport resistance to liquid evaporation. Direct Simulation Monte Carlo and laboratory experiments were conducted to provide validation for our model. The model successfully predicts the variation of pore transmissivity with Knudsen number and nanopore size, which cannot be revealed by prior theories. The relative error of model-predicted evaporation rate was within 1% in L/r = 0 cases and within 3.5% in L/r > 0 cases. Our model is featured by its applicability under the entire range of Knudsen numbers. The evaporation of various types of liquids in arbitrarily sized pores can be modeled using a universal relation.