Effect of wall adsorption on the nano-droplet evaporation in a nano-channel: A molecular dynamics investigation

Molecular dynamics method is used to study evaporation of an argon droplet without or with a macroscopic velocity in a platinum nano-channel. The droplet and its surrounding vapor initially in equilibrium are placed in a vacuum nano-channel and heated by the channel wall with a constant temperature. The effects of the channel size (25.2 × 25.2 × 34.0 nm3 and 50.4 × 50.4 × 34.0 nm3), wall temperature (120, 143.76, and 180 K), and droplet velocity (0, 0.08, 0.16, and 0.24 nm ps−1) on the temperatures of the droplet and vapor as well as on the evaporation rate are analyzed. Due to much strong adsorption effect of argon atoms in the vapor on the wall, the evaporation in the nano-channel differs significantly from that in the infinite space. The differences are as follows: (1) The evaporation rate in the nano-channel is much higher at the beginning of evaporation than that in the infinite space, then the rate rapidly reduces, which leads to that the droplet cannot evaporate completely, even the condensation occurs in final evaporating stage. (2) With the same channel size, the droplet evaporates faster at low wall temperature than that at high wall temperature. The results above demonstrate that the adsorption effect is more dominant than the heat transfer effect when droplet and its surrounding vapor are placed in a vacuum nano-channel.