It is critical that liquid hydrogen pumps are hermetic sealed and leak only very small trace amounts hydrogen to the outside environment. And because liquid hydrogen temperatures are typically close to 20 K, it is also critical that heat input is minimized. Barber-Nichols' liuqid hydrogen pumps meet both of these critical requirements and more by incorporating the following features:
- No dynamic seals are used and the pump is hermetically sealed to meet the most stringent helium leak rate requirements.
- Anti-convection/radiation heat shields minimize heat input to the cryogenic fluid by disrupting natural convection currents and creating barriers to radiated heat.
- A long, thin-walled pump shaft and and an outer vacuum housing minimizes heat conduction into the cryogen.
- High-speed operation and the use of variable frequency drives increase hydraulic efficiency and minimizes generated heat.
- Vacuum housings allow pumps to be removed from a system for regular maintenance without breaking the cold box vacuum. This reduces time and preserves the system integrity during routine maintenance.
For aerospace applications, it often makes sense to utilize submersible liquid hydrogen pumps. BNI developed pumps for liquid helium destratification and recirculation for space application. 400 Hz AC induction and brushless DC motor options are both available.
|Model BNHP-08-000 In-Line
Cryogenic Hydrogen Pump
Slush Hydrogen Pump
The pump shown at left was used for cryogenic supercritical hydrogen service at Oak Ridge National Laboratory's Spallation Neutron Source. This pump rotates at speeds up to 60,000 rpm with no contacting parts as the magnetic bearings levitate the shaft. It is made for service at 20 K and pressures up to 20 bar (g).
As part of innovative development on a NASA SBIR, BNI designed, produced, and tested a liquid hydrogen pump utilizing composite materials. Composite materials which have extremely low heat transfer coefficients are being used in place of stainless steel on select components, further reducing conductive heat leak. Because the conducted heat transfer is negligible, the pump shaft can be shortened and a shorter pump shaft has greater rotordynamic stability and can therefore operate at higher speeds. As a result, hydraulic efficiency is increased and the heating of the cryogenic fluid is further minimized. Finally, as composite material usage increases, evidence suggests the manufacturing cost benefits will bypass that of stainless steel.
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