Dual channel cable in conduit thermohydraulics: Influence of some design parameters

In the framework of the controlled nuclear fusion by magnetic confinement p rogramme, a particular design of a Cable-in-Conduit Conductor (CICC) is bei ng developed, including two parallel cooling channels. The central channel is separated from the strand channel by a spiral structure whose geometry c an substantially influence the overall pressure drop. The thermo-hydraulics of this so called dual channel CICC is not well known. Hence various exper iments with pressurised nitrogen at room temperature, on straight and curve d unit lengths from the ITER toroidal field model coil (TFMC) production, h ave been performed at both Ansaldo and CEA-Cadarache to characterise the fr iction factor of the two parallel cooling regions, in a range of representa tive Reynolds numbers. These experimental results are presented. It has been possible to character ise different kinds of spiral geometries used in the manufacture of the two model coils for ITER : the TFMC and the Central Solenoid Model Coil. A relative assessment of the most suitable spiral for the ITER magnets is p resented. This discussion includes: manufacturing aspects with the capability of the spiral to support the cabl ing process as a function of the geometry of the spiral and the compaction of the cable. pressure drop considerations, as a function of the spiral geometry which pl ays an important role in the cooling process and the required cold pump pow er. Conclusions and recommendations are drawn.