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Application Area 3: Chemical & Process, Thermal Hydraulics & Nuclear Safety

Application Challenge AC3-11


This AC concerns turbulent downward flow in an annulus with a uniformly heated core and an adiabatic outer casing. An investigation is made on the influence of buoyancy on mixed convection flow, heat transfer and turbulence. The Reynolds number of the flows ranges from 1000 to 6000, and the Grashof number (based on heat flux) ranges from 1.1x108 to 1.4x109.

The experimental rig is housed in the Nuclear Engineering Department, School of Engineering, University of Manchester. The experimental data collected are temperatures, velocity and turbulence.

A representative set of CFD calculations have been undertaken at UMIST. The calculations undertaken at UMIST have employed the k-e turbulence model, with three different approaches to the modelling of near-wall turbulence.

Most of the computations of the flow were three-dimensional with the circumferential grid covering the entire 360o of the annulus cross-section. This was necessary in order to explore deviations from axi-symmetric conditions.

CFD calculations of this Application Challenge are currently being undertaken at UMIST and at British Energy.

This is a test case by which the competency of CFD for use in nuclear power stations can be judged. However, it only shows the validity for buoyancy influenced flows with vertical boundary layers. This AC is well understood due to the available experimental data. However, only a relatively small amount of CFD has been undertaken so far, and so a comprehensive set of CFD requirements are not yet available for this flow.

The assessment parameter used to judge the competency of CFD calculations is the variation of Nusselt number on the heated core.

Contributors: Mike Rabbitt - British Energy