Acronyms, notations and symbols

Hydrogen liquefaction

Figure 1 - Installation of a super-insulated cold box (Air Liquide document, photo credit © Laurent Lelong)

Figure 2 - Isenthalpic curves for a pure body in a (T, P) diagram

Figure 3 - Joule-Thomson inversion curves for hydrogen and nitrogen as a function of pressure and temperature (source: NASA Technical Note D-6807 [3])

Figure 4 - Diagram of ortho- and para-hydrogen forms

Figure 5 - Evolution of the mole fraction of para-hydrogen at thermodynamic equilibrium as a function of temperature (curve taken from NBS Monograph, 168 [1]).

Figure 6 - Mass enthalpy of conversion of ortho-hydrogen to para-hydrogen as a function of temperature (curve taken from NBS Monograph, 168 [1])

Figure 7 - Natural kinetics for converting ortho-hydrogen into para-hydrogen (Air Liquide document)

Figure 8 - Evolution of the liquid level in a liquid hydrogen storage tank by natural conversion of ortho-hydrogen to para-hydrogen (Air Liquide document)

Figure 9 - Phase diagram of normal hydrogen (source: Gas Encyclopedia, Air Liquide [2])

Figure 10 - Temperature-entropy diagram of n-hydrogen in the range 180-300 K (curve taken from NBS Monograph, 168 [1])

Figure 11 - Temperature-entropy diagram of n-hydrogen in the range 90 to 220 K (curve taken from NBS Monograph, 168 [1])

Figure 12 - Temperature-entropy diagram of n-hydrogen in the range 0 to 100 K (curve taken from NBS Monograph, 168 [1])

Figure 13 - Simplified diagram of the liquefaction process

Figure 14 - Helium liquefaction cycle

Figure 15 - Hydrogen liquefaction cycle

Figure 16 - Nevada site combining hydrogen production and liquefaction (Air Liquide document)

Figure 17 - Steam methane reforming furnace (Air Liquide document)

Figure 18 - PSA for hydrogen purification (Air Liquide document)

Figure 19 - 3D model of hydrogen liquefaction equipment

Figure 20 - Spherical storage at the Nevada site (Air Liquide document)