[ flow control ]
Cutaway view of a vacuum-jacketed pipe
global motor-fuel pool . To that end , enterprising companies are looking for ways to optimize LH 2 dispensing in terms of efficiency , reliability , and – most importantly – safety through the development of innovative dispensing technologies , all while attempting to make the refueling process for the consumer as similar and familiar to that of the traditional service station as possible .
The challenge
While LH 2 can theoretically be used to power all motor vehicles , its capabilities are beginning to make it a top choice as a reliable and efficient fuel for use in long-haul vehicles such as transport trucks , planes , and ships . However , getting the fuel from Point A to Point B in the massive amounts required can be problematic .
So , while LH 2 possesses great potential for growth as an energy source , buoyed by its carbon-neutral status and environmentally sensitive emissions of water during consumption , its volatile nature can make it challenging to harvest , refine , transport , dispense , and consume . This makes ensuring safety for both the handler and the environment the top priority along its production and supply chain , regardless of the amount handled or dispensed .
Most notably , LH 2 possesses a working temperature of −423 ° F ( −253 ° C ), which is close to absolute zero , or −460 ° F ( −273 ° C ), making LH 2 one of the most challenging cryogenic gases . This means the equipment used to dispense LH 2 must contain massive amounts of thermal insulation in the dispensing nozzle to prevent significant ambient losses in volume due to evaporation as the fuel is dispensed .
Another phenomenon that developers of LH 2 nozzles must be aware of is the prevention of hydrogen embrittlement . It ’ s a physical fact that all metals will be detrimentally affected at some level by hydrogen , with the level of exposure helping to determine if any embrittlement will occur . If a metal does experience hydrogen embrittlement , it can result in noteworthy losses in tensile strength , ductility , and fracture toughness , along with accelerated fatigue-crack growth . When embrittlement reaches a critical point , it can result in catastrophic failure of LH 2
- containing components .
To reduce the risk of hydrogen embrittlement in an LH 2
-dispensing nozzle , metals that are more resistant to hydrogen embrittlement , such as high-quality stainless steel grades , should be used . Sealing on moving parts is another area where precision in material selection and engineering must be optimized to ensure a safe refueling solution .
Many common elastomers are not suitable for use with cryogenic substances . In this case , the recommended seal type is one made from polychlorotrifluoroethylene ( PCTFE ). PCTFE stands out in cryogenic service because of its high tensile strength and good thermal characteristics . This combination of exceptional physical characteristics and stability at ultra-low temperatures makes PCTFE an ideal choice for equipment used in LH 2 dispensing .
Hydrogen Tech World | Issue 18 | October 2024 35