Cooldown Flow Rate Limits Imposed by Thermal Stresses in Liquid Hydrogen or Nitrogen Pipelines

Abstract

Warm cryogenic pipelines are usually cooled to operating temperature by a small, steady flow of the liquid cryogen. If this cooldown flow rate is too high or too low, undesirable stresses will be produced. Lower flow rate limits based on avoidance of stratified two-phase flow have already been developed [1]. A previous study [2] developed a relationship between cooldown flow rate and thermal stress in AISI 304 stainless steel flanges cooled with liquid hydrogen, thus permitting the selection of upper liquid hydrogen flow rate limits to keep the thermal stresses in safe bounds in these flanges. The purpose of the present study is to extend the previous calculations to the cooldown of AISI 304 steel and 6061 aluminum flanges by liquid hydrogen or liquid nitrogen.