Coupling of Wall Boiling with Discrete Population Balance Model
NURETH-14 - 2011 September 25-30

Presented at:
2011 September 25-30
Toronto, Canada
Session Title:
A9-3 Interfacial Area Transport - Computational

Conxita Lifante (ANSYS Germany)
Florian Reiterer (ANSYS Germany)
Thomas Frank (ANSYS Germany)
Alan Burns (ANSYS UK Ltd.)


A coupling between a polydisperse population balance method (Multiple Size Group Model -

MUSIG) and the RPI wall boiling model for nucleate subcooled boiling has been implemented in

ANSYS CFX. It allows more accurate prediction of the interfacial area density for mass,

momentum and energy transfer between phases in comparison to the usual local-monodisperse

bubble size assumption and underlying bulk bubble diameter correlations as they are commonly

used in boiling flow applications like e.g. the prediction of subcooled nucleate boiling in rod

bundles and fuel assemblies of PWR. The paper outlines the methodology of the coupled CFD

model, which automatically avoids possible inconsistencies in the model formulation for the

heated wall, when the generated steam bubbles on the heater surface are injected exactly in the

bubble size class corresponding to the predicted bubble departure diameter.

The coupling of the RPI wall boiling model and the MUSIG model has been implemented for

both homogenous/inhomogeneous variants of the MUSIG model. The paper presents the

validation of the coupled modeling approach for the well known test case of nucleate subcooled

boiling of R113 refrigerant in a circular annulus with inner heated rod based on the experiments

of Roy et al. [1]. ANSYS CFX results with the newly implemented approach as well as

comparison to data and locally-monodisperse simulations are provided.

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