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ISSN Online: 2377-424X

ISBN Print: 0-85295-345-3

International Heat Transfer Conference 10
August, 14-18, 1994, Brighton, UK

THE MODELLING OF BUOYANT PLUMES ABOVE AGR FUEL USING CFD METHODS

Get access (open in a dialog) DOI: 10.1615/IHTC10.2620
pages 227-232

Resumo

The paper describes experimental and analytical work investigating the flow and temperature fields generated by heat sources at the bottom of a long, sealed enclosure with cooled walls which is filled with pressurised Nitrogen or Carbon Dioxide. An electrically heated dummy AGR (Advanced Gas-cooled Reactor) fuel element was placed at the bottom of a pressure vessel, similar to a fuel disposal facility. Temperature, velocity and turbulence measurements were made within the gaseous space above the fuel or in the annular gap between the fuel element and the vessel wall. The experiment has been modelled by an axisymmetric finite element mesh, where the fuel region is represented by a porous volume. The Reynolds averaged Navier Stokes equations were solved using the Nuclear Electric code FEAT. The turbulence closure equations made use of the standard k,ε model, or of a slightly different formulation of that model, known as the q,f model. The turbulence equations were not, in general, solved right to the wall; instead, the effect of the solid boundaries on the main flow field was modelled using wall functions.
The experimental results show that a recirculatory flow is formed, with the axial velocity, turbulence intensity and gas temperature decaying with vertical displacement above the heat source. The results from the CFD work show similar behaviour but agreement is best when the q,f formulation is used, together with turbulent Prandtl numbers in excess of 1.