title: A compact setup to study homogeneous nucleation and condensation.
abstract: An experiment is presented to study homogeneous nucleation and the subsequent droplet growth at high temperatures and high pressures in a compact setup that does not use moving parts. Nucleation and condensation are induced in an adiabatic, stationary expansion of the vapor and an inert carrier gas through a Laval nozzle. The adiabatic expansion is driven against atmospheric pressure by pressurized inert gas its mass flow carefully controlled. This allows us to avoid large pumps or vacuum storage tanks. Because we eventually want to study the homogeneous nucleation and condensation of zinc, the use of carefully chosen materials is required that can withstand pressures of up to 10(6) Pa resulting from mass flow rates of up to 600 l(N) min(-1) and temperatures up to 1200 K in the presence of highly corrosive zinc vapor. To observe the formation of droplets a laser beam propagates along the axis of the nozzle and the light scattered by the droplets is detected perpendicularly to the nozzle axis. An ICCD camera allows to record the scattered light through fused silica windows in the diverging part of the nozzle spatially resolved and to detect nucleation and condensation coherently in a single exposure. For the data analysis, a model is needed to describe the isentropic core part of the flow along the nozzle axis. The model must incorporate the laws of fluid dynamics, the nucleation and condensation process, and has to predict the size distribution of the particles created (PSD) at every position along the nozzle axis. Assuming Rayleigh scattering, the intensity of the scattered light can then be calculated from the second moment of the PSD.
authors.affiliation: High Temperature Solar Technology, Paul Scherrer Institute, 5232 Villigen PSI, Switzerland.
authors.forename: Mattias
authors.initials: M
authors.lastname: Karlsson
authors.forename: Ivo
authors.initials: I
authors.lastname: Alxneit
authors.forename: Frederik
authors.initials: F
authors.lastname: Rütten
authors.forename: Daniel
authors.initials: D
authors.lastname: Wuillemin
authors.forename: Hans Rudolf
authors.initials: HR
authors.lastname: Tschudi