Simulation of the Axial-Flow Centrifugal Bubble Separator for Liquid-Fueled Molten Salt Reactors Using Eulerian Two-Fluid Model

Abstract

The axial-flow centrifugal bubble separator designed for the gaseous fission product removal system in liquid-fueled molten salt reactors is simulated using the Eulerian two-fluid model coupled with the Adaptive Multiple Size Group method to account for the significant coalescence and breakup in the bubble separator. The behavior of the gas core in the bubble separator is mimicked by the symmetric interfacial area concentration model. The separator efficiency, local velocity, and pressure profiles at various conditions are compared with experimental data. Good agreement is found between the experiment and the simulation for the separator efficiency. With the coalescence and breakup being accounted for, the effect of the inlet void fraction on the separator efficiency is correctly captured. For the local pressure and velocity profiles, the agreement is only quantitative due to the simplifications on the geometry and potential limitations of the current computational fluid dynamics models. As good agreement is found for the separator efficiency, the sensitivity study is performed for various operational and design parameters with further simplified two-dimensional axisymmetric simulation.

Keywords:

• Bubble separator
• fission product removal
• two-phase flow
• computational fluid dynamics
• molten salt reactor

Acknowledgments

The information, data, or work presented herein was funded in part by the Advanced Research Projects Agency-Energy, U.S. Department of Energy, under award number DE-AR0000983. The views and opinions of authors expressed herein do not necessarily state or reflect those of the United States Government or any agency thereof. This research made use of Idaho National Laboratory computing resources, which are supported by the Office of Nuclear Energy of the U.S. Department of Energy and the Nuclear Science User Facilities under contract number DE-AC07-05ID14517.

Disclosure Statement

No potential conflict of interest was reported by the author(s).

Nomenclature

$a_i$ =	=	interfacial area concentration
$d$ =	=	bubble diameter
$d_{sm}$ =	=	Sauter mean diameter
$g$ =	=	gravity acceleration
$j_g$ =	=	superficial gas velocity
$j_l$ =	=	superficial liquid velocity
$k_v$ =	=	vane slope
$n_i$ =	=	number density of bubble group i
$p$ =	=	pressure
$\mathrm{R}\mathrm{e}=\frac{ud}{\nu }$ =	=	Reynolds number
$T$ =	=	temperature
$u_k$ =	=	velocity of phase k
$\nu$ =	=	kinematic viscosity

Greek

${\alpha }_k$ =	=	void fraction of k phase
$ϵ$ =	=	turbulent dissipation rate
$\mu$ =	=	dynamic viscosity
${\rho }_k$ =	=	density of phase k
$\sigma$ =	=	surface tension

Additional information

Funding

This work was supported by the Advanced Research Projects Agency-Energy [award number DE-AR0000983].