Air - Prandtl Number

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The Prandtl Number - Pr - is a dimensionless number approximating the ratio of momentum diffusivity (kinematic viscosity) to thermal diffusivity - and is often used in heat transfer and free and forced convection calculations.

The Prandtl number can for calculations be expressed as

Pr = μ c_p / k (1)

where
μ = absolute or dynamic viscosity [kg/(m s)], [lb_m /(ft h)]
c_p = specific heat [J/(kg K)], [Btu/(lb_m ^oF)]
k = thermal conductivity [W/(m K)], [Btu/(h ft²^oF/ft)]

Below, Prandtl numbers for air at varying temperatures and pressures are given in figures and tables .

Air Prandtl number at 1 bara pressure, temperature given as °C or °F:

Air Prandtl number at varying temperatures and constant pressures, SI and Imperial units:

Air Prandtl number at 1 bara pressure, temperature given as °C or °F:

Air - Prandtl Number at 1 bara Pressure
Temperature	Pr	Temperature	Pr
[°C]	[-]	[°F]	[-]
-100	0.734	-150	0.733
-50	0.720	-50	0.719
0	0.711	0	0.714
25	0.707	60	0.709
50	0.705	75	0.708
100	0.701	100	0.706
150	0.699	200	0.701
200	0.698	300	0.699
250	0.699	400	0.698
300	0.702	500	0.700

Air Prandtl number at given temperatures and 1, 5 10 and 20 bara pressure:

Air - Prandtl Number
Temperature			Prandtl number at given pressures
[K]	[°C]	[°F]	1 bara, 14.5 psia	5 bara, 72.5 psia	10 bara, 145 psia	20 bara, 725 psia
60	-213.2	-351.7	4.138	4.153	4.170	4.187
80	-193.2	-315.7	1.7	2.252	2.259	2.269
100	-173.2	-279.7	0.780	0.898	1.783	1.770
120	-153.2	-243.7	0.759	0.806	0.890	1.360
140	-133.2	-207.7	0.747	0.773	0.812	0.923
180	-93.2	-135.7	0.731	0.743	0.759	0.792
200	-73.2	-99.7	0.726	0.735	0.745	0.769
220	-53.2	-63.7	0.721	0.728	0.736	0.754
240	-33.2	-27.7	0.717	0.722	0.729	0.742
260	-13.2	8.3	0.713	0.718	0.723	0.734
273	0.0	32.0	0.711	0.715	0.720	0.729
280	6.9	44.3	0.710	0.714	0.718	0.727
289	15.6	60.0	0.709	0.713	0.716	0.723
300	26.9	80.3	0.707	0.711	0.714	0.722
320	46.9	116.3	0.705	0.708	0.711	0.717
340	66.9	152.3	0.703	0.705	0.708	0.714
360	86.9	188.3	0.701	0.703	0.706	0.711
380	106.9	224.3	0.700	0.702	0.704	0.709
400	126.9	260.3	0.699	0.701	0.703	0.706
500	226.9	440.3	0.698	0.700	0.701	0.703
600	326.9	620.3	0.703	0.704	0.704	0.706
700	426.9	800.3	0.710	0.710	0.711	0.712
800	526.9	980.3	0.717	0.718	0.718	0.719
900	626.9	1160.3	0.724	0.725	0.725	0.725
1000	726.9	1340.3	0.730	0.730	0.730	0.731
1100	826.9	1520.3	0.734		0.735
1500	1226.9	2240.3	0.743		0.743
1900	1626.9	2960.3	0.742		0.742

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