CFD Modeling of Wall Steam Condensation: Two‐Phase Flow Approach versus Homogeneous Flow Approach

S Mimouni,A Foissac,M Ouraou,N Mechitoua,M Hassanaly

doi:10.1155/2011/941239

S Mimouni, A Foissac + Show 3 more

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https://doi.org/10.1155/2011/941239

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Abstract

The present work is focused on the condensation heat transfer that plays a dominant role in many accident scenarios postulated to occur in the containment of nuclear reactors. The study compares a general multiphase approach implemented in NEPTUNE_CFD with a homogeneous model, of widespread use for engineering studies, implemented in Code_Saturne. The model implemented in NEPTUNE_CFD assumes that liquid droplets form along the wall within nucleation sites. Vapor condensation on droplets makes them grow. Once the droplet diameter reaches a critical value, gravitational forces compensate surface tension force and then droplets slide over the wall and form a liquid film. This approach allows taking into account simultaneously the mechanical drift between the droplet and the gas, the heat and mass transfer on droplets in the core of the flow and the condensation/evaporation phenomena on the walls. As concern the homogeneous approach, the motion of the liquid film due to the gravitational forces is neglected, as well as the volume occupied by the liquid. Both condensation models and compressible procedures are validated and compared to experimental data provided by the TOSQAN ISP47 experiment (IRSN Saclay). Computational results compare favorably with experimental data, particularly for the Helium and steam volume fractions.

Highlights

Condensation heat transfer in the presence of noncondensable gases is a relevant phenomenon in many industrial applications, including nuclear reactors.In particular, during the course of a hypothetical severe accident in a nuclear pressurized water reactor (PWR), hydrogen may be produced by the reactor core oxidation and distributed into the reactor containment according to convective flows, water steam wall condensation, and interaction with the spraying droplets
During the course of a hypothetical severe accident in a nuclear pressurized water reactor (PWR), hydrogen may be produced by the reactor core oxidation and distributed into the reactor containment according to convective flows, water steam wall condensation, and interaction with the spraying droplets
A large amount of steam and hydrogen gas is expected to be released within the dry containment of a pressurized water reactor (PWR), after the hypothetical beginning of a severe accident leading to the melting of the core

Summary

Introduction

Condensation heat transfer in the presence of noncondensable gases is a relevant phenomenon in many industrial applications, including nuclear reactors. During the course of a hypothetical severe accident in a nuclear pressurized water reactor (PWR), hydrogen may be produced by the reactor core oxidation and distributed into the reactor containment according to convective flows, water steam wall condensation, and interaction with the spraying droplets. The TOSQAN experimental programme [1] has been created to simulate typical accidental thermal hydraulic flow conditions of the reactor containment. The heat and mass exchanges between the spray droplets and the gas with thermal hydraulic conditions representative of this hypothetical severe accident have been studied in [2]. The aim of this work is, to focus on wall condensation

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