Article #701 - Basic Hydrogen Properties
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| Properties | Value | Units |
|---|---|---|
| Auto ignition temperature [a] | 585 | °C |
| 1085 | °F | |
| Boiling point (1 atm) [b] | -252.9 | °C |
| -423.2 | °F | |
| Density NTP [1,b] | 0.08375 | kg/m³ |
| 0.005229 | lb/ft³ | |
| Diffusion coefficient in air NTP [1, a] | 0.610 | cm²/s |
| 6.57 E-4 | ft²/s | |
| Enthalpy NTP [1, b] | 3858.1 | kJ/kg |
| 1659.8 | Btu/lb | |
| Entropy NTP [1, b] | 53.14 | J/g-K |
| 12.70 | Btu/lb-°R | |
| Flame temperature in air [a] | 2045 | °C |
| 3713 | °F | |
| Flammable range in air [1,a] | 4.0 - 75.0 | vol% |
| Ignition energy in air [c] | 2.0 E-5 | J |
| 1.9 E-8 | Btu | |
| Internal Energy NTP [1, 2, b] | 2648.3 | kJ/kg |
| 1139.3 | Btu/lb | |
| Molecular weight [b] | 2.02 | |
| Specific gravity (air = 1) NTP [1, c] | 0.0696 | |
| Specific volume NTP [1,b] | 11.94 | m³/kg |
| 191.26 | ft³/lb | |
| Specific heat at constant pressure , Cp NTP [1, b] | 14.29 | J/g-K |
| 191.3 | Btu/lb-°R | |
| Specific heat at constant volume, Cv NTP [1, b] | 10.16 | J/g-K |
| 2.428 | Btu/lb-°R | |
| Thermal conductivity NTP [1, b] | 0.1825 | W/m-K |
| 0.1054 | Btu/ft-h-°R | |
| Viscosity NTP [1,b] | 8.813 E-5 | g/cm-sec |
| 5.922 E-6 | lb/ft-sec |
Notes:
- NTP (normal temperature and pressure) = 20°C (68°F) and 1 atm
- Reference state: Internal Energy U=0 at 273.16 K for saturated liquid; Entropy S=0 at 273.16 K for saturated liquid.
Sources:
- [a]
National Aeronautical and Space Administration, Safety Standard for Hydrogen and Hydrogen Systems (NSS 1740.16) (PDF, 3.01 MB)
- [b]
NIST Chemistry WebBook
- [c]
"Hydrogen Fuel Cell Engines and Related Technologies. Module 1: Hydrogen Properties." U.S. DOE. 2001 (PDF, 1.33 MB)
Last Modified:
2007-10-26