To quantify primary side aerosol retention, an Eulerian/Lagrangian approach was
used to investigate aerosol transport in a compressible, turbulent, adiabatic, internal,
wall-bounded flow. The ARTIST experimental project (Phase I) served as the physical
model replicated for numerical simulation. Realizable k-ε and standard k-ω turbulence
models were selected from the computational fluid dynamics (CFD) code, FLUENT, to
provide the Eulerian description of the gaseous phase.
Flow field simulation results exhibited: a) onset of weak secondary flow
accelerated at bend entrance towards the inner wall; b) flow separation zone
development on the convex wall that persisted from the point of onset; c) centrifugal
force concentrated high velocity flow in the direction of the concave wall; d) formation
of vortices throughout the flow domain resulted from rotational (Dean-type) flow; e)
weakened secondary flow assisted the formation of twin vortices in the outflow cross
section; and f) perturbations induced by the bend influenced flow recovery several pipe diameters upstream of the bend. These observations were consistent with those of
previous investigators.
The Lagrangian discrete random walk model, with and without turbulent
dispersion, simulated the dispersed phase behavior, incorrectly. Accurate deposition
predictions in wall-bounded flow require modification of the Eddy Impaction Model
(EIM). Thus, to circumvent shortcomings of the EIM, the Lagrangian time scale was
changed to a wall function and the root-mean-square (RMS) fluctuating velocities were
modified to account for the strong anisotropic nature of flow in the immediate vicinity of
the wall (boundary layer). Subsequent computed trajectories suggest a precision that
ranges from 0.1% to 0.7%, statistical sampling error. The aerodynamic mass median
diameter (AMMD) at the inlet (5.5 μm) was consistent with the ARTIST experimental
findings. The geometric standard deviation (GSD) varied depending on the scenario
evaluated but ranged from 1.61 to 3.2. At the outlet, the computed AMMD (1.9 μm) had
GSD between 1.12 and 2.76. Decontamination factors (DF), computed based on
deposition from trajectory calculations, were just over 3.5 for the bend and 4.4 at the
outlet. Computed DFs were consistent with expert elicitation cited in NUREG-1150 for
aerosol retention in steam generators.
| Identifer | oai:union.ndltd.org:tamu.edu/oai:repository.tamu.edu:1969.1/ETD-TAMU-1333 |
| Date | 15 May 2009 |
| Creators | Longmire, Pamela |
| Contributors | Hassan, Yassin A., Marlow, William H. |
| Source Sets | Texas A and M University |
| Language | en_US |
| Detected Language | English |
| Type | Book, Thesis, Electronic Dissertation, text |
| Format | electronic, application/pdf, born digital |
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