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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