Fluids Engineering and Design

Air Density Equation and proof.

Physical properties of air can be represented by the real gas equation, which is the modified version of ideal gas equation.

Dry air obeys the ideal gas law,

where:

ρ_d = density of dry air kg - m^-3
M_a = molecular weight of air (28.97 kg / mol)
P = barometric pressure (Pa)
R = universal gas constant 8.31432 × 10³  N·m·kmol^-1· K^-1
T = air temperature (K).

At standard temperature (T = T₀ = 273.15 K) and pressure (P = P₀ = 1013.25 mb), gives ρ_d0 = 1.2922 kg m^-3.

Therefore, our equation also gives:

where ρ_d is in kg m^-3 when P is in millibars and T is in kelvins.

Related:

Air Density and Specific weight equations and Calculations