Annular Air Leaks in a liquid hydrogen storage tank

• Published in: IOP conference series. Materials Science and Engineering Vol. 278; no. 1; pp. 12065 - 12072
• Main Authors: Krenn, AG, Youngquist, RC, Starr, SO
• Format: Journal Article
• Language: English
• Published: Bristol IOP Publishing 01.12.2017
• Subjects: Damage accumulation; Drainage; Ductility tests; Failure analysis; Hydrogen storage; Liquid air; Liquid hydrogen; Low temperature; Mean time to failure; Nitrogen; Perlite; Storage tanks; Tank geometry; Thermal analysis; Thermal conductivity; Void fraction
• ISSN: 1757-8981; 1757-899X
• DOI: 10.1088/1757-899X/278/1/012065

Large liquid hydrogen (LH2) storage tanks are vital infrastructure for NASA, the DOD, and industrial users. Over time, air may leak into the evacuated, perlite filled annular region of these tanks. Once inside, the extremely low temperatures will cause most of the air to freeze. If a significant mass of air is allowed to accumulate, severe damage can result from nominal draining operations. Collection of liquid air on the outer shell may chill it below its ductility range, resulting in fracture. Testing and analysis to quantify the thermal conductivity of perlite that has nitrogen frozen into its interstitial spaces and to determine the void fraction of frozen nitrogen within a perlite/frozen nitrogen mixture is presented. General equations to evaluate methods for removing frozen air, while avoiding fracture, are developed. A hypothetical leak is imposed on an existing tank geometry and a full analysis of that leak is detailed. This analysis includes a thermal model of the tank and a time-to-failure calculation. Approaches to safely remove the frozen air are analyzed, leading to the conclusion that the most feasible approach is to allow the frozen air to melt and to use a water stream to prevent the outer shell from chilling.