Density of Air - Temperature and Pressure

Temperature and Pressure

The density of dry air can be calculated using the ideal gas law, expressed as a function of temperature and pressure:

\rho = \frac{p}{R_{\rm specific} T}

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:

Effect of temperature
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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