ISSN Online: 2377-424X
ISBN Print: 0-85295-345-3
International Heat Transfer Conference 10
THE MODELLING OF BUOYANT PLUMES ABOVE AGR FUEL USING CFD METHODS
要約
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.
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.