Numerical Study of the Final Cooldown from 4.5 K to 1.9 K of the Large Hadron Collider

To simulate and analyze the final cooldown process of a LHC standard cell (106.9 m length) including the filling operation at 4.5 K and the cooldown from 4.5 K to 1.9 K, a mathematical model is proposed and validated by experimental data. In this model, the mass equations for liquid and vapor, the momentum equation for liquid and the general equation for mixed flow are taken into account for the different filling and cooldown phases. As a result of the simulation, the temperature profiles of the cold mass of the cell as well as the evolution of the helium void fractions, filling ratio and HeII position are obtained. The filling and cooldown times have also been estimated, and some characteristics of heat transfer of the HeII bayonet heat exchanger have been presented.