Calculation of the pressure rise in the Fermilab 19000 L helium dewar

This chapter describes the PD5000 computer program which was written to calculate the pressure rise in the liquid helium dewar of the Fermilab Central Helium Liquefier. The aim of the calculation is to verify that the pressure in the inner vessel will not rise above a safe level in a catastrophic venting situation. Computer runs of the program were made using various values of vent pipe diameter and the Darcy friction coefficient. The main program (MAIN) reads in the initial dewar conditions, step sizes, vent pipe diameter, length, the assumed Darcy friction factor for the gas flow in the vent pipe, and a stop time used to terminate the execution. At each step in the time development, MAIN calls subroutines FLUX and PIPE to calculate the heat flux to the inner vessel and the flow in the vent pipe respectively. The results of the calculation indicate that the 11.1 cm diameter vent stack installed in the dewar limits the pressure rise to a safe level