CATHARE modelling of the HELIOS loop for the study of heat transfer to supercritical helium flowing in pipes following loss of insulating vacuum

Abstract

The loss of insulating vacuum is a major accidental situation for cryogenic facilities. The sizing of pressure relief devices requires the knowledge of the heat flux transmitted to the fluid. Up to now, heat flux measurements with supercritical helium have been only carried out for tanks. However, to ensure a reliable sizing of pressure relief systems, heat flux measurements have also to be performed for supercritical helium flowing in pipes. In this context, an experimental set up called HELIOS will be modified at CEA Grenoble to perform controlled loss of insulating vacuum around a cryoline and measure the heat flux received by the forced flow. The new design of the HELIOS loop was investigated with the thermal hydraulic system code CATHARE. A former experiment carried out with HELIOS was previously modelled to verify the ability of the code to predict properly the thermal hydraulic behaviour of a forced flow supercritical helium loop thermally coupled to a saturated helium bath. The results are compared with experimental data and discussed in the article. The predictive results computed by CATHARE for the new experimental set-up are then presented. The new sizing of the HELIOS device is validated on a loss of vacuum scenario. The modelling work also supports the assessment of the methodology to quantify the heat flux received by supercritical helium resulting from vacuum break.