Study of thermal stratification and mixing using PIV

B. Yamaji, R. Szijártó, A. Aszódi, Budapest University of Technology and Economics, Hungary

20th Symposium of AER on VVER Reactor Physics and Reactor Safety (2010, Hanasaari, Espoo, Finland)
Nuclear applications of three-dimensional thermal hydraulics


Paks Nuclear Power Plant uses the REMIX code for the calculation of the coolant mixing in
case of the use of high pressure injection system while stagnating flow is present. The use of
the code for Russian type WWER-440 reactors needs strict conservative approach, and in
several cases the accuracy and the reserves to safety margins cannot be determined now. In
order to quantify and improve these characteristics experimental validation of the code is
An experimental program has been launched at the Institute of Nuclear Techniques with the
aim of investigating thermal stratification processes and the mixing of plumes in simple
geometries. With the comparison and evaluation of measurement data and computational fluid
dynamics (CFD) results computational models can be validated.
For the experiments a simple hexahedral plexiglas tank (250×500×100 mm ? HxLxD) was
fabricated with five nozzles attached, which can be set up as inlets or outlets. With different
inlet and outlet setups and temperature differences thermal stratification, plume mixing may
be investigated using Particle Image Velocimetry (PIV).
In the paper comparison of PIV measurements carried out on the plexigas tank and the results
of simulations will be presented. For the calculations the ANSYS CFX three-dimensional
CFD code was used.

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