On turbulence and interfacial momentum transfer in dispersed gas-liquid flows: contribution of bubbly flow experiments under microgravity conditions

2021 ◽  
pp. 103903
Author(s):  
Mariem Rezig ◽  
Ghazi Bellakhal ◽  
Jamel Chahed
Keyword(s):  
Momentum Transfer ◽  
Bubbly Flow ◽  
Microgravity Conditions ◽  
Liquid Flows ◽  
Flow Experiments

Two-Phase Flow in Liquid Filled Vessels During the Depressurization by Periodic Venting

2003 ◽  
Author(s):  
Dieter Mewes ◽  
Dirk Schmitz
Keyword(s):  
Single Phase ◽  
Two Phase Flow ◽  
Bubbly Flow ◽  
Exothermic Reaction ◽  
Liquid Mixtures ◽  
Phase Flow ◽  
Two Phase ◽  
Pressure Losses ◽  
Short Period ◽  
Liquid Flows

Pressurized chemical reactors or storage vessels are often partly filled with liquid mixtures of reacting components. In case of an unexpected and uncontrolled exothermic reaction the temperature might increase. By this the pressure follows and would exceed a critical maximum value if there would be no mechanism to decrease the pressure and the temperature in a very short period of time. A sudden venting by the opening of a safety valve or a rupture disc causes a rapid vaporization of the reacting liquid mixture. A two-phase flow will pass the ventline. Since two-phase gas-liquid flows cause high pressure losses and give rise to limited mass flows leaving the reactor, single-phase gas flows are preferred. This is emphasized by a periodic venting mechanism of the pressurized vessel. Each time the two-phase flow from the bubbling-up liquid inside the vessel reaches a certain cross-section close the entrance of the ventline. The outlet-valve is closed. Inside the vessel the increasing pressure stops the two-phase flow and only single phase flow is leaving the vessel. The two-phase bubbly flow inside the vessel is detected by a tomographic measurement device during the venting process. Experimental results for local and time dependant phase void fractions as well as pressures are compared with those obtained by numerical calculations of the instationary bubble swarm behavior inside the vessel.

scholarly journals Behaviour and Stability of the Two-Fluid Model for Fine-Scale Simulations of Bubbly Flow in Nuclear Reactors

2015 ◽  
Vol 13 (4) ◽  
pp. 449-459 ◽  
Author(s):  
Henrik Ström ◽  
Srdjan Sasic ◽  
Klas Jareteg ◽  
Christophe Demazière
Keyword(s):  
Volume Fraction ◽  
Nuclear Reactors ◽  
Fluid Model ◽  
Bubbly Flow ◽  
Domain Size ◽  
Fuel Assemblies ◽  
Two Fluid Model ◽  
Liquid Flows ◽  
Two Fluid ◽  
Meso Scale

Abstract In the present work, we formulate a simplistic two-fluid model for bubbly steam-water flow existing between fuel pins in nuclear fuel assemblies. Numerical simulations are performed in periodic 2D domains of varying sizes. The appearance of a non-uniform volume fraction field in the form of meso-scales is investigated and shown to be varying with the bubble loading and the domain size, as well as with the numerical algorithm employed. These findings highlight the difficulties involved in interpreting the occurrence of instabilities in two-fluid simulations of gas-liquid flows, where physical and unphysical instabilities are prone to be confounded. The results obtained in this work therefore contribute to a rigorous foundation in on-going efforts to derive a consistent meso-scale formulation of the traditional two-fluid model for multiphase flows in nuclear reactors.

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