Temperature and Pressure
The density of dry air can be calculated using the ideal gas law, expressed as a function of temperature and pressure:
where ρ is the air density, p is absolute pressure, Rspecific is the specific gas constant for dry air, and T is absolute temperature.
The specific gas constant for dry air is 287.058 J/(kg·K) in SI units, and 53.35 (ft·lbf)/(lbm·R) in United States customary and Imperial units.
Therefore:
- At IUPAC standard temperature and pressure (0 °C and 100 kPa), dry air has a density of 1.2754 kg/m3.
- At 20 °C and 101.325 kPa, dry air has a density of 1.2041 kg/m3.
- At 70 °F and 14.696 psi, dry air has a density of 0.074887lbm/ft3.
The following table illustrates the air density–temperature relationship at 1 atm or 101.325 kPa:
| Temperature | Speed of sound | Density of air | Acoustic impedance |
|---|---|---|---|
| in °C | c in m·s−1 | ρ in kg·m−3 | Z in N·s·m−3 |
| +35 | 351.88 | 1.1455 | 403.2 |
| +30 | 349.02 | 1.1644 | 406.5 |
| +25 | 346.13 | 1.1839 | 409.4 |
| +20 | 343.21 | 1.2041 | 413.3 |
| +15 | 340.27 | 1.2250 | 416.9 |
| +10 | 337.31 | 1.2466 | 420.5 |
| +5 | 334.32 | 1.2690 | 424.3 |
| 0 | 331.30 | 1.2922 | 428.0 |
| −5 | 328.25 | 1.3163 | 432.1 |
| −10 | 325.18 | 1.3413 | 436.1 |
| −15 | 322.07 | 1.3673 | 440.3 |
| −20 | 318.94 | 1.3943 | 444.6 |
| −25 | 315.77 | 1.4224 | 449.1 |
Read more about this topic: Density Of Air
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