Numerical study of growing droplets dynamics in unsteady thermal convection flow

A mathematical model describing the unsteady thermal convection flow and deposition of growing droplets in an expansion-type Kelvin spectrometer is developed. The model includes the Navier–Stokes equations to describe the gas dynamic processes and a droplet growth model accounting for vapor depletion due to condensation. The evolution of gas temperature and velocities and growing droplet dynamics inside the spectrometer chamber are studied using CFD (computational fluid dynamics) code Fluent. The relative droplet concentrations and mass densities of condensed vapor on all droplets as a time function are investigated. In so doing it has been taking into account the droplet growth by condensation, sedimentation, heat conduction, thermal convection, droplet evaporation. It is shown that the droplet life time in the measuring chamber is limited by two processes: deposition on the walls and evaporation. The relative contribution of evaporation and sedimentation depends on the initial saturation.