Hydrodynamics of Similar Gases in Vortex Mixers: Effect of Physical Properties on the Onset of Instability

Abstract

The effect of physical properties of gases on the flow hydrodynamics and on the onset of instability was studied to acquire information on how to design fast mixers specific for relevant operations where complete and improved gas mixing is important. To assess the effect of physical properties on the gas flow dynamics in vortex mixers, three gases hydrogen, nitrogen, and argon were chosen because of the viscosity and density differences they provide. Using flow visualization and PIV flow-field characterization techniques, critical Reynolds numbers of flow regime changes were identified from segregated to engulfment flow regimes for three pairs of gases. It was shown that the first critical point of the flow, where the gases have a full rotation in the chamber, depends on the inertial force in terms of dynamic pressure. While hydrogen having the highest kinematic viscosity had a full rotation at Re = 40, nitrogen and argon gases had their full rotation at Re = 70. After these points, a steady rotational flow as a consequence of the balance between the centrifugal and centripetal forces was observed. Similarly, the onset of the engulfment regime was observed earlier for hydrogen, at Re = 150, while it was at Re = 200 for nitrogen and Re = 220 for argon. The present study shows that the gas properties are effective parameters not only on the critical points but also on the shape of the swirling flow pattern formed in the mixer.

Optimization Analysis of Pretreatment Device Structural Parameters for Low-Concentration CBM Utilization

“…The Reynolds number Re is used to measure the change of internal flow of the gas mixing unit. Its physical meaning is the ratio of inertial force and viscous force of the fluid in the flow field [29], which is calculated according to the following formula:…”