Prandtl number for air

The Prandtl number is a dimensionless number, defined as the ratio of kinematic viscosity (also called momentum diffusivity) to thermal diffusivity.

Values are taken from the engineering toolbox .

The formula is taken from IEC 60287-2-3 and is valid for atmospheric pressure.

Symbol

$\mathrm{Pr}_{air}$

Formulae

$0.715-2.5{\cdot}{10}^{-4} \theta_{at}$

Related

$\mathrm{Pr}_{gas}$

Prandtl number for gas

$\theta_{at}$

Air temperature under load [°C]

Used in

$C_{vair}$

Volumetric heat capacity of air [J/(K.m$^3$)]

$T_{at}$

Thermal resistance by convection, air to tunnel [K.m/W]

Choices

Gas	Pressure	220 K	240 K	260 K	273 K	300 K	320 K	340 K	360 K	380 K	400 K
Air	1 bar	0.721	0.717	0.713	0.711	0.709	0.705	0.703	0.701	0.7	0.699
Air	5 bar	0.728	0.722	0.718	0.715	0.711	0.708	0.705	0.703	0.702	0.701
Air	10 bar	0.736	0.729	0.723	0.72	0.714	0.711	0.708	0.706	0.704	0.703
Air	20 bar	0.754	0.742	0.734	0.729	0.722	0.717	0.714	0.711	0.709	0.706