Modeling of the very low pressure helium flow in the LHC cryogenic distribution line after a quench

This paper presents a dynamic model of the helium flow in the cryogenic distribution line (QRL) used in the Large Hadron Collider (LHC) at CERN. The study is focused on the return pumping line, which transports gaseous helium at low pressure and temperature (1.6kPa/3K) over 3.3km. Our aim is to propose a new real-time model of the QRL while taking into account the non-homogeneous transport phenomena. The flow model is based on 1D Euler equations and considers convection heat transfers, hydrostatic pressure and friction pressure drops. These equations are discretized using a finite difference method based on an upwind scheme. A specific model for the interconnection cells is also proposed. The corresponding simulation results are compared with experimental measurements of a heat wave along the line that results from a quench of a superconducting magnet. Different hypotheses are presented and the influence of specific parameters is discussed.