Tripartite Mass Transfer Model: Development, Implementation in DYVRO, Verification and Validation
NURETH-14 - 2011 September 25-30


Presented at:
NURETH-14
2011 September 25-30
Location:
Toronto, Canada
Session Title:
B12-1 Minisymposium on Pressure Surges in Nuclear Power Plants

Authors:
Thorsten Neuhaus (TUEV NORD SysTec GmbH & Co. KG)
Andreas Schaffrath (TUEV NORD SysTec GmbH & Co. KG)
  

Abstract



The calculation of condensation induced water hammer (CIWH) resulting from the contact of steam and sub-cooled water, is still a sophisticated challenge because of time-dependent condensation, highly transient flow phenomena and the change of flow pattern. In this paper a tripartite mass transfer (TMT) model that accounts for vaporization due to flashing, condensation due to isentropic decompression and direct contact condensation at the phase interface is presented. The TMT model shall be considered as a frame for sub-models which may be arranged for the above phenomena. For contact condensation a simplified approach has been applied taking into account a constant heat transfer coefficient and a basic approach for the calculation of the interface area. The TMT model has been implemented in the one-dimensional two-phase pressure surge code DYVRO mod 3. A verification and validation procedure was performed based on experiments at test facilities in Oberhausen (PPP), Rossendorf (CWHTF) and Budapest (PMK-2). The computational results of the column rejoining experiments at PPP and CWHTF show better agreement to experimental data in comparison to the application of an equilibrium model. Especially the relatively gentle pressure and temperature increase, when the steam bubble collapses respectively when the steam bubble is compressed, can be captured better. Concerning the condensation induced water hammer experiments after steam/water counter-flow in a horizontal pipe, which was examined at PMK-2, a parameter study was performed with DYVRO. As initial conditions stratified flow conditions are defined. The phenomenology and the maximum pressure increase could be satisfactorily approximated by DYVRO in combination with the TMT model. In future the direct contact condensation model shall be improved using flow velocity dependent heat transfer coefficients.

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