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Liquid Hydrogen Boil-off

  1. Jun 26, 2015 #1
    I've read a fews post about liquid hydrogen boil off, but could use a bit more clarification; insight on the following thought experiment would be really helpful: What happens if I take a 1 L steel vessel, put 1 L of liquid H2 into it, seal it off, and let it sit in a room at 25C?

    The density of LH2 is ~71 g / L, which at a molecular density of 2.016 g / mol works out to ~35.2 mols. At STP, this has a volume of ~ 790L, so solving for P = (nRT/V) gets me to a pressure of ~ 12,600 PSI at 25 C.

    So my question is, if my vessel can withstand, say, 15,000 PSI, the H2 just sits there as a gas under pressure, right? And maybe there is some negligible rate at which the H2 gas diffuses through the steel over long periods of time? Of course, if the vessel can't withstand at least 12,600 PSI, it blows up and kills me, which is very likely unless it's encased in carbon fiber.
  2. jcsd
  3. Jun 26, 2015 #2


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    Staff: Mentor

    I would think at that pressure the ideal gas law might break down. It would probably be better to look at a phase diagram.
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