Residual Ion Dump : CFD Analyses of the Cooling Chan nels in the High Heat Flux Panels

For the successful operation of the MITICA Electrostatic Residual Ion Dump ERID, a reliable cooling system has to be designed in order to avoid damages in its components. One of the critical features in its manufacturing is the possible presence of a step around the length center of the Beam Stopping Element (BSE) channel due to the double side drilling. The fluid will operate under subcooled boiling conditions, thus, a careful study of probable cavitation, fluid stagnation or low boiling margin at this zone was performed in order to assure its correct operation. This work presents the designed fluid operation conditions at the High Heat Flux (HHF) panels using analytical methods developed by RFX and a study of the critical zone using CFD analysis, this latest performed by KIT. CFD analyses are undertaken to investigate the thermohydraulic parameters related to the local phenomena in the double side drilled cooling channels. This investigation is articulated in the following paragraphs dealing with each parameter; a configuration for the cooling system and an answer to the FDR chit are proposed. As a result, an optimized twisted tape cross section was developed. This new twisted tape will reduce to the minimum the possible issues. As a conclusion, it was proved that under the designed cooling operation conditions and the designed HHF panel and twisted tape geometry, the system will operate without complications even if a worst case scenario appears due to the BSE channels manufacturing or during ERID operation conditions. This task is embedded in the Agreement on the Neutral Beam Test Facility between RFX and KIT in order to achieve a design and analyses status on the ERID, ready for the FDR. The studies at KIT were herewith a continuous activity throughout 2013 and 2014.