Numerical analysis of 60° V-ribs for helium-cooled high heat flux loaded first wall, challenges and contributions

The HCPB (Helium Cooled Pebble Bed) blanket concept for EU DEMO fusion reactors employs high-pressure (8 MPa) helium gas as coolant for the plasma facing first wall (FW). Up-to-date estimates for the total maximum of heat flux go up to 0.73 MW/m². Higher short-term transient loads are possible. 60°-V-shaped ribs show high heat transfer and are thus the subject of the presented studies. Although Scale-Resolving Simulation (SRS) techniques such as LES (Large Eddy Simulation) are able to calculate heat transfer and pressure drop precisely, their application is limited to an individual ribs or a few mm channel segment due to the high required mesh count. Nevertheless, SRS techniques can be used to compare different ribs and to evaluate the performance of RANS (Reynolds-Averaged Navier-Stokes Simulations). Selected RANS models can be used to evaluate the development of secondary flow structures along the channel and compare complete channels with different rib configurations for thermohydraulic performance.
The objectives of the present paper are (i) to offer guidance on the range and limits of applicability of numerical methods when dealing with cooling flows in structured channels (sections 1–4) and (ii) to provide results on specific design features of surface structures (sections 5–7) that help designers in implementing thermal-hydraulic efficient yet fabrication friendly structured channels
... mehr
Challenges like long entrance length and high material properties gradients are shown. Strategies for ribs height reduction with increasing heat transfer and reduction of pressure drop resulting in higher Cooling Performance Numbers (CPN) are found. Thermohydraulic performance of fabrication friendly ribs is calculated along the channel.