## Properties of dry air at atmospheric pressure

°C
kg m-3
Pa s
m2 s-1
W m-1 K-1
J kg-1 K-1
m2 s-1
-

#### Notes

This calculator gathers several correlations to estimate the thermodynamic and transport properties of dry air at atmospheric pressure, for the range 200 - 400 K. All correlations deviate by less than 0.15 % from tabulated values.

Density follows a simple inverse relationship (ideal gas) with a small correction term:

$\rho \: \mathrm{[kg \: m^{-3}]} = \frac{351.99}{T} + \frac{344.88}{T^2}$

Viscosity and thermal conductivity can be estimated using Sutherland’s equation:

$\mu \: \mathrm{[10^{-6} Pa \: s]} = \frac{1.4592 T^{1.5}}{109.10 + T}$

$\nu \: \mathrm{[m^2 s^{-1}]} = \frac{\mu}{\rho}$

$k \: \mathrm{[W m^{-1} K^{-1}]} = \frac{2.3340 \times 10^{-3} T^{1.5}}{164.54 + T}$

Specific heat follows a quadratic relationship:

$C_p \: \mathrm{[J \: kg^{-1} K^{-1}]} = 1030.5 - 0.19975 T + 3.9734 \times 10^{-4} T^2$

Thermal diffusivity is calculated from the definition:

$\alpha \: \mathrm{[m^2 s^{-1}]} = \frac{k}{C_p \rho}$

Alternatively, it can be estimated by:

$\alpha \: \mathrm{[10^{-6} m^2 s^{-1}]} = -4.3274 + 4.1190 \times 10^{-2} T + 1.5556 \times 10^{-4} T^2$

Prandtl number is calculated by:

$Pr = \frac{C_p \mu}{k}$

#### References

B.E. Poling, J.M. Prausnitz, J.P. O'Connell. Properties of Gases and Liquids, 5th Edition, McGraw-Hill, 2001.