Pressure-Temperature Histories of Liquid Hydrogen under Pressurization and Venting Conditions

Abstract

Experience has shown that the pressure in a closed liquid-hydrogen tank may be considerably greater than the vapor pressure that corresponds to the average liquid temperature. This increase in pressure is due to a. surface layer of liquid hydrogen that is warmer than the bulk liquid. Previous experiments carried out at the Lewis Research Center with liquid nitrogen have shown that stirring the liquid tends to mix the warmer surface layer into the bulk liquid, causing a drop in pressure. These studies have been extended to include the effect of the pressurization and venting of liquid-hydrogen tanks on the temperature gradients established in the tank. Presented herein are some results of an experimental investigation involving the temperature stratification and pressure rise of liquid hydrogen contained in an aircraft-type tank exposed to atmospheric turbulence conditions during flight. The temperature of the fluid, both liquid and vapor, at various levels in the tank under both pressurization and venting periods is given. In addition, results of some calculations utilizing the temperature profile data to predict the variation in tank pressures during a venting period are presented.