Nanoscale droplet vaporisation by molecular dynamics

Abstract

Nanoscale droplet vaporisation was studied by molecular dynamics, which allows the calculation of properties for droplets statistically without considering the discontinuous interface between a liquid droplet and surrounding gas. An argon droplet was created and immersed inside its vapour. After equilibration, the periphery of the system was heated by a carrier gas to vaporise the droplet. Replications were conducted to check the variation in the phenomenon. Thermodynamic properties such as the density, pressure and temperature profiles were sampled for each interval. The evolution of the surface tension of the droplet undergoing vaporisation was investigated. Moreover, the vaporisation rate of nanodroplets was compared with the kinetic theory-based Hertz–Knudsen–Langmuir equation and two diffusion-based models, which are the D² evaporation law and Kincaid and Longley model [Kincaid DC, Longley TS. A water droplet evaporation and temperature model. Trans ASAE. 1989; 32(2):457–463]. The kinetic model underestimates the vaporisation rate by one order of magnitude whereas the two diffusion-based models overestimate the rate by one order of magnitude.

Keywords::

• vaporisation
• molecular dynamics
• nanoscale droplet