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Constants
Every physical and engineering constant the engine reasons with, stored canonically in SI and quoted in English units wherever a textbook does. Looking for units and conversions instead? Units.
25 constants
Conversion
| Constant | Symbol | SI value | English value | Dimension | Notes |
|---|---|---|---|---|---|
| Ton of refrigeration | 1 ton | 3516.853 W | 12000 Btu/h | M·L²·T⁻³ | Standard refrigeration capacity unitCh. 11 |
Electromagnetism
| Constant | Symbol | SI value | English value | Dimension | Notes |
|---|---|---|---|---|---|
| Elementary charge | e | 1.60217663 × 10⁻¹⁹ C | — | T·I | Exact (SI definition)CODATA |
| Faraday constant | F | 9.64853321 × 10⁷ C/kmol | — | T·N⁻¹·I | 96485.33212 C/molCODATA |
| Vacuum permeability | mu₀ | 1.25663706 × 10⁻⁶ H/m | — | M·L·T⁻²·I⁻² | Magnetic couplingCODATA |
| Vacuum permittivity | eps₀ | 8.85418781 × 10⁻¹² F/m | — | M⁻¹·L⁻³·T⁴·I² | Electrostatic and MEMS couplingCODATA |
Heat transfer
| Constant | Symbol | SI value | English value | Dimension | Notes |
|---|---|---|---|---|---|
| Stefan-Boltzmann constant | sigma | 5.67037442 × 10⁻⁸ W/m²·K⁴ | 1.714 × 10⁻⁹ Btu/h·ft²·R⁴ | M·T⁻³·K⁻⁴ | Blackbody emissive powerCh. 12 |
Mechanics
| Constant | Symbol | SI value | English value | Dimension | Notes |
|---|---|---|---|---|---|
| Gravitational conversion constant | g_c | 1 kg·m/N·s² | 32.174 lbm·ft/lbf·s² | dimensionless | Unity in SI; needed in English engineering unitsSec. 1.6 |
| Standard gravitational acceleration | g | 9.80665 m/s² | 32.174 ft/s² | L·T⁻² | Standard sea-level valueStandard reference |
Thermodynamics
| Constant | Symbol | SI value | English value | Dimension | Notes |
|---|---|---|---|---|---|
| Constant-volume specific heat of air at 300 K | cᵥ | 718 J/kg·K | 0.171 Btu/lbm·R | L²·T⁻²·K⁻¹ | Cold-air-standard valueTable A-2 |
| Density of liquid water at 4 °C | rho | 1000 kg/m³ | 62.43 lbm/ft³ | M·L⁻³ | Reference densityTable A-3 |
| Gas constant of air | Rₐᵢᵣ | 287 J/kg·K | 0.06855 Btu/lbm·R | L²·T⁻²·K⁻¹ | R_u / M_air, M_air = 28.97 kg/kmolTable A-20 |
| Gas constant of water vapor | Rᵥ | 461.5 J/kg·K | 0.1102 Btu/lbm·R | L²·T⁻²·K⁻¹ | M = 18.015 kg/kmolTable A-1 |
| Ice point | T₀ | 273.15 K | 491.67 R | K | 0 °C = 32 °FCh. 1 |
| Latent heat of vaporization of water at 100 °C | h_fg | 2.257 × 10⁶ J/kg | 970.1 Btu/lbm | L²·T⁻² | At 101.325 kPaTable A-2 |
| Molar mass of air | Mₐᵢᵣ | 28.97 kg/kmol | 28.97 lbm/lbmol | M·N⁻¹ | Dry airTable A-1 |
| Specific heat of air at 300 K | cₚ | 1005 J/kg·K | 0.24 Btu/lbm·R | L²·T⁻²·K⁻¹ | Cold-air-standard valueTable A-2 |
| Specific heat ratio of air | k | 1.4 - | — | dimensionless | c_p/c_v at 300 KTable A-2 |
| Standard atmospheric pressure | Pₐₜₘ | 101325 Pa | 14.696 psia | M·L⁻¹·T⁻² | 1 atm = 1.01325 bar = 760 mmHgStandard reference |
| Standard reference temperature | T_ref | 298.15 K | 536.67 R | K | 25 °C = 77 °F, reference state for formation enthalpiesCh. 13 |
| Triple-point temperature of water | Tₜₚ | 273.16 K | 491.688 R | K | At 0.6117 kPaTable A-2 |
| Universal gas constant | Rᵤ | 8314.46262 J/kmol·K | 1.98588 Btu/lbmol·R | M·L²·T⁻²·K⁻¹·N⁻¹ | 8.314462618 kJ/kmol·K = 1545.37 ft·lbf/lbmol·RTable A-1 |
Universal
| Constant | Symbol | SI value | English value | Dimension | Notes |
|---|---|---|---|---|---|
| Avogadro constant | N_A | 6.02214076 × 10²⁶ 1/kmol | — | N⁻¹ | 6.02214076e23 1/mol, exactCODATA |
| Boltzmann constant | k_B | 1.380649 × 10⁻²³ J/K | — | M·L²·T⁻²·K⁻¹ | Exact (SI definition)CODATA |
| Planck constant | h | 6.62607015 × 10⁻³⁴ J·s | — | M·L²·T⁻¹ | Exact (SI definition)CODATA |
| Speed of light in vacuum | c | 2.99792458 × 10⁸ m/s | — | L·T⁻¹ | Exact (SI definition)CODATA |