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# Air - Prandtl Number

## Prandtl number for air vs. temperature and pressure.

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 cp / k                           (1)

where
μ = absolute or dynamic viscosity [kg/(m s)], [lbm/(ft h)]
cp = specific heat [J/(kg K)], [Btu/(lbm 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.

as well as Prandtl number of Ammonia, Methane, Nitrogen, Propane and Water.

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:

 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:

 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

## Related Topics

• Air Psychrometrics - Moist and humid air - psychrometric charts, Mollier diagrams, air-condition temperatures and absolute and relative humidity and moisture content.
• Fluid Mechanics - The study of fluids - liquids and gases. Involving velocity, pressure, density and temperature as functions of space and time.
• Gases and Compressed Air - Air, LNG, LPG and other common gas properties, pipeline capacities, sizing of relief valves.
• Material Properties - Material properties of gases, fluids and solids - densities, specific heats, viscosities and more.

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Temperature

oC
oF

Length

m
km
in
ft
yards
miles
naut miles

Area

m2
km2
in2
ft2
miles2
acres

Volume

m3
liters
in3
ft3
us gal

Weight

kgf
N
lbf

Velocity

m/s
km/h
ft/min
ft/s
mph
knots

Pressure

Pa (N/m2)
bar
mm H2O
kg/cm2
psi
inches H2O

Flow

m3/s
m3/h
US gpm
cfm

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