Helium Conservation through Diffusion Restricted Purging of Liquid Hydrogen Tanks – NASA
This newsletter is from the 2024 Technical Replace.
The NASA Engineering and Protection Heart (NESC) has evolved an analytical style that predicts diffusion between two gases all over piston purging of liquid hydrogen (LH2) tanks. This style is helping provide an explanation for dramatic helium financial savings observed in a up to date Kennedy House Heart (KSC) purge, presentations that undesired turbulent blending passed off in House Travel Exterior Tank purges, and is acceptable to long term helium purges of the House Release Device Core Level LH2 tanks.
Background
In 2023, paintings was once finished on a brand new 1.3-million-gallon (174,000 usual cubic ft (scf)) liquid hydrogen tank at KSC in make stronger of the House Release Device[1], see Determine 1. Consistent with contract, the seller delivered this tank stuffed with gaseous nitrogen, leaving KSC floor operations the duty of changing the nitrogen with helium: a essential step previous to introducing liquid hydrogen, which might freeze the nitrogen. Prior helium/nitrogen purges at the Apollo/House Travel generation 850,000-gallon (114000 scf) LH2 tanks have been carried out through pumping
out the nitrogen, introducing helium, drawing samples, after which repeating if essential. Alternatively, the brand new tank didn’t have a vacuum port, so as a substitute, it was once determined to introduce the helium from the highest of the tank and push the nitrogen out of the ground. Two million scf of helium was once received and made able for worry the 2 gases would combine, leading to a protracted and dear purge. Unusually, this top-down, or piston purge, led to a fast substitute of the nitrogen with helium, the use of most effective 406,000 scf of helium, about 1.6 million scf not up to deliberate (at $1/scf it is a $1.6 million greenback financial savings). To higher perceive this outstanding outcome, the NESC was once requested to handle the questions; why did this paintings so smartly and will or not it’s stepped forward additional?
Upon understanding that the purge was once diffusion restricted and may well be modelled, permutations have been studied, main to 3 essential conclusions. The float price must be higher till the onset of turbulent blending; as soon as began, the purge must now not be stopped as a result of this permits further diffusion to happen; and seeking to enhance the purge through various temperature or power has little get advantages. Purging of the large LH2 spheres is uncommon, however purging of flight tanks is not unusual. In 2008, purge knowledge from 3 House Travel Exterior Tanks was once measured the use of a mass spectrometer and the NESC was once requested to use the diffusion style to this knowledge. Doing this confirmed
proof that turbulent blending passed off indicating that the float charges had to be lowered. Having this sort of style has supplied perception into using piston-type helium purges at KSC, with the function of saving helium and manpower. This paintings is now immediately acceptable to purging the LH2 tank at the House Release Device Core Level.
The Binary Gasoline Sensor
All through previous purges, fuel samples have been taken to a lab to suggest the standing of the purge however doing that for a piston purge would introduce time delays, permitting undesirable diffusion to happen. Happily, an unbiased NESC overview[4] was once comparing a binary fuel sensor, with a very good mixture of price, measurement, energy, and weight to put in force within the box, offering fast real-time tracking of the purge fuel ratio. The use of this sensor made the piston purging of the brand new LH2 tank a success.
References
- Fesmire, J.; Swanger, A.; Jacobson, J; and Notardonato, W.: “Power environment friendly
large-scale garage of liquid hydrogen,” In IOP Convention Collection: Fabrics
Science and Engineering, vol. 1240, no. 1, p. 012088. IOP Publishing, 2022. - Youngquist, R.; Arkin C.; Nurge, M.; Captain, J.; Johnson, R.; and Singh, U.:
Helium Conservation through Diffusion Restricted Purging of Liquid Hydrogen Tanks,
NASA/TM-20240007062, June 2024. - Singh, U.: Analysis and Trying out of Anaerobic Hydrogen Sensors for the
Exploration Floor Programs Program, NASA/TM-20240012664, Sept. 2024.
