Conference Proceedings Paper
Turbulence Modelling of High-Pressure Convective Boiling Two-Phase Flows
NURETH-14 - 2011 September 25-30
Jil Gueguen (CEA/Grenoble/Division for Nuclear Energy)
Fabrice Francois (CEA/Grenoble/Division for Nuclear Energy)
Hervé Lemonnier (CEA/Grenoble/Division for Nuclear Energy)
This article is a contribution to the modelling of multidimensional high-pressure convective
boiling two-phase flows relative to PWR’s thermal hydraulics conditions.
Postulating that the turbulence is one possible physical mechanism for heat removal from the
wall towards the two-phase flow core, this work focuses on modelling turbulent transport terms
in the momentum and energy balance equations.
Using the pioneering work of Sato
, , the momentum and the energy balance
equations are derived for a two-phase mixture. Such a system can be expressed as a combination
of parameters, which include the local void fraction as well as the fluid velocity profile, the wall
shear stress and the eddy diffusivity. By specifying a closure relation for this last parameter, a
numerical solution can be obtained. As a preliminary step towards a numerical solution, the
turbulent structure of the two-phase flow is expressed as a linear superposition of an inherent
liquid turbulence and an additional one due to the bubble agitation. On the basis of this theory,
the mixture velocity and temperature profiles can be predicted provided that the local void
fraction and the wall shear stress are known.
The model is then tested against the experimental data bank DEBORA (Garnier
, ) which
is devoted to the study of high pressure boiling flows. The first results are encouraging for the
mechanical part but some discrepancies are observed on temperature profiles for boiling tests.
This work should be continued in order to (i) improve the model especially for the thermal
aspects and (ii) identify the key parameters responsible for the heat flux limitation (DNB).
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