|
|
Investigation of droplet nucleation in CCS relevant systems – design and testing of the expansion chamber
Čenský, Miroslav ; Hrubý, Jan ; Vinš, Václav ; Hykl, Jiří ; Šmíd, Bohuslav
A unique in-house designed experimental apparatus for investigation of nucleation of droplets in CCS relevant systems is being developed by the present team. The apparatus allows simulating various processes relevant to CCS technologies. Gaseous mixtures with CO2 are prepared in a Mixture Preparation\nDevice (MPD) based on accurate adjustment of flow rates of individual components [EPJ Web of Conferences 143, 02140 (2017)]. The mixture then flows into an expansion chamber, where it undergoes a rapid adiabatic expansion. As a consequence of adiabatic cooling, the mixture becomes supersaturated and nucleation and simultaneous growth of droplets occurs. In this study, we describe the design and testing of the expansion part of the experimental setup. The rapid expansion was realized using two valve systems, one for low pressures (up to 0.7 MPa) and the other for high pressures (up to 10 MPa). A challenge for a proper design of the expansion system is avoiding acoustic oscillations. These can occur either in the mode of Helmholtz resonator, where the compressible gas in the chamber acts as a spring and the rapidly moving\ngas in the valve system as a mass, or in the “flute” mode, where acoustic waves are generated in a long outlet tubing.\n
|
|
|
Consistency of empirical corrections of the classical nucleation theory for nucleation in steam with nucleation experiments and molecular simulations
Hrubý, Jan ; Duška, Michal ; Němec, Tomáš ; Kolovratník, M.
We compare experimental nucleation rates for water vapour in various carrier gases, nucleation rates deduced from empirical adjustments of the classical nucleation theory (CNT) earlier developed to reproduce pressure and optical data for condensing steam flows in converging-diverging nozzles and turbine stages, and ucleation rates obtained from molecular simulations. Results of original molecular dynamic simulations for TIP4P/2005 force field in the NVE conditions are provided. New experimental nucleation rate data sets are generated based on empirical CNT corrections by Valha and Nedbal (1980) and by Petr and Kolovratník (2011). Correction of the CNT for non-isothermal nucleation conditions is applied to experimental, simulated and the derived experimental data. The derived experimental\nnucleation rate data follow a similar temperature trend as the nucleation rate data for water vapour in carrier gases at lower temperatures. The ratio of observed nucleation rates to CNT predictions decreases more steeply with temperature than the empirical correction by Wölk et al. (2002). Ratios of nucleation rates computed from molecular simulations to CNT predictions do not show a significant temperature trend.
|
host ::
RSS.