Using the HELIOS facility for assessment of bundle-jacket thermal coupling in a CICC

The mock-up was manufactured and tested in spring 2015. Bundle-jacket heat transfer coefficient was found in the range 300-500 W m−2 K−1. Results analysis suggests that the order of magnitude of convective heat transfer coefficient inside bundle is closer to Colburn-Reynolds analogy than to Dittus-Boelter correlation, and that bundle-jacket thermal coupling is mainly limited by thermal resistance due to wrappings. A model based on an equivalent layer of stagnant helium between wraps and jacket was proposed and showed a good consistency with the experiment, with relevant values for the helium layer thickness.