ISSN Online: 2377-424X
ISBN Print: 978-1-56700-421-2
International Heat Transfer Conference 15
Evaporation Dynamics of Microdroplets
Аннотация
We carried out a series of molecular dynamics simulations in order to explore microscale evaporating process from a tiny droplet into vacuum. Two systems were investigated. System 1: Monatomic simple fluid with the Lennard-Jones (LJ) interatomic potential. After thermally equilibrating a droplet of size ? 10 nm, we started the evaporation into vacuum by cintaneously removing vaporized particles. As free evaporation proceeds, we monitored the change of droplet size, the local temperature, and the structure inside. The temperature and the density were found to be almost uniform in spite of the fast evaporative cooling. The time evolution of the evaporating droplet was successfully explained with a simple one-dimensional liquid-vapor model. After sufficiently long runs (? 4 ns), we found that supercooled droplets crystalize into FCC structure in several cases. Detailed structural analyses indicate that the crystallization is a stochastic nucleation process. System 2: Water model with the TIP4P model potential. In contrast to the LJ case, the evaporation cooling is a very slow process. The temperature of the droplets reaches ? 250K after 20 ns, and still the molecular structure inside is similar to that of normal liquid with no indication of crystallization.