| Parameter
| Value
| Unit
|
| Molecular weight
| 2.01594
| g/mol
|
| Stoichiometric fraction in air
| 29.53
| vol%
|
| Boiling point (BP)
| 20.369
| K
|
| Melting point (MP)
| 14.01
| K
|
| Triple point (TP)
|
|
|
| temperature
| 13.08
| K
|
| pressure
| 7.2
| kPa
|
| Critical point
|
|
|
| temperature
| 33.145
| K
|
| pressure
| 1.2964
| kPa
|
| density
| 31.263
| kg/m3
|
| Electro-negativity
| 2.20
| Pauling scale
|
| Density
|
|
|
| gas @ NTP
| 0.08376
| g/mol
|
| gas @ STP
| 0.08990
| kg/m3
|
| gas @ BP
| 1.338
| kg/m3
|
| para liquid @ BP
| 70.78
| kg/m3
|
| normal liquid @ BP
| 70.96
| kg/m3
|
| slush with 50 wt% solid @ TP
| 81.48
| kg/m3
|
| para solid @ MP
| 86.50
| kg/m3
|
| solid @ 4K
| 88.0
| kg/m3
|
| Expansion ratio liquid/ambient
| 845
| -
|
| Diffusion coefficient @ NTP
| 0.61*104
| m2/s
|
| Diffusion velocity @ NTP
| < 0.02
| m/s
|
| Buoyant velocity
| 1.2 - 9.1
| m/s
|
| Gas constant
| 4124.3
| J/(kg K)
|
| Specific heat (constant p)
|
|
|
| gas @ NTP(2)
| 14.85
| kJ/(kg K)
|
| gas @ STP(1)
| 14.304
| kJ/(kg K)
|
| gas @ BP
| 12.15
| kJ/(kg K)
|
| liquid @ BP
| 9.66
| kJ/(kg K)
|
| Thermal conductivity
|
|
|
| gas @ NTP(2)
| 0.187
| W/(m K)
|
| gas @ BP
| 0.01694
| W/(m K)
|
| liquid @ BP
| 0.09892
| W/(m K)
|
| Visocity
|
|
|
| gas @ NTP(2)
| 89.48
| μPoise
|
| gas @ BP
| 11.28
| μPoise
|
| liquid @ BP
| 132.0
| μPoise
|
| Surface tension @ BP
| 1.93*10-3
| N/m
|
| Vapour pressure @
|
|
|
| Heat of conversion from para to ortho
| 708.8
| kJ/kg
|
| Heat of melting (fusion) @ MP
| 58.8
| kJ/kg
|
| Heat of vaporization @ BP
| 445.6
| kJ/kg
|
| Vaporization index(3)
| 8.9
| K cm3/J
|
| Vaporization rate of LH2 pool
| 4.2 - 8.3
| mm/s
|
| Heat of sublimation
| 379.6
| kJ/kg
|
| Speed of sound
|
|
|
| gas @ NTP(2)
| 1294
| m/s
|
| gas @ BP
| 355
| m/s
|
| liquid @ BP
| 1093
| m/s
|
| stoichiometric H2-air mixture
| 404
| m/s
|
| Inversion temperature
| 193
| K
|
| Flammability limits in air
| 4.0 - 75.0(4)
| vol%
|
| Detonability limits in air
| 13 - 70(5)
| vol%
|
| Minimum ignition energy
|
|
|
| for deflagration
| 1.9*105
| J
|
| for detonation
| ~ 10,000
| J
|
| Auto-ignition temperature in air
| 793 - 1023 (858)
| K
|
| Hot air jet ignition temperature
| 943
| K
|
| Gross heat of combustion (HHV) @ 15°C
| 286.1
| kJ/mol
|
| Net heat of combustion (LHV) @ 15°C
| 241.7
| kJ/mol
|
| Adiabatic flame temperature
| 2318
| K
|
| Burning rate of LH2 pool
| 0.5 - 1.1
| mm/s
|
| Laminar burning velocity in air
| 2.65 - 3.25
| m/s
|
| Visible laminar flame speed
| 18.6
| m/s
|
| Deflagration pressure ratio
| 8.15
| -
|
| Quenching distance @ NTP(2)
| 0.64
| mm
|
| Maximum experimental safe gap @ NTP(2)
| 0.08
| mm
|
| Detonation velocity
| 1480 - 2150
| m/s
|
| Chapman-Jouguet (CJ) velocity
| 1968
| m/s
|
| CJ detonation pressure ratio pCJ/po
| 15.6
| -
|
| Energy release
| 2.82
| MJ/kg of mixture
|
| Detonation cell size
| 15
| mm
|
| Critical tube diameter
| 0.2
| m
|
| Detonation initiation energy
| 1.1
| g tetryl
|
| Detonation induction distance @ NTP(2) length/diameter
| ~ 100
| -
|
| TNT equivalent
|
|
|
|
| 26.5
| kg TNT/kg of H2
|
|
| 2.22
| kg TNT/Nm3 of H2
|
(1) STP (Standard temperature and pressure): 273 K, 101325 Pa.
(2) NTP (Normal temperature and pressure): 293 K, 101325 Pa.
(3) Indicates the relative ease of a substance to vaporize.
(4) LFL is valid for upward propagation of flame. For downward propagation, LFL values is 5.3 vol%.
(5) Valid for weak ignition. For a high-energy igniter, a range of 11.6 - 74.9 was quoted.
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