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Air - Thermal Diffusivity

Figures and tables showing dry air thermal diffusivity at varying temperarure and pressure, SI and Imperial units

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Thermal diffusivity is the rate of transfer of heat of a material from the hot side to the cold side. It can be calculated by taking the thermal conductivity divided by density and specific heat capacity at constant pressure.

Thermal diffusivity has the SI derived unit of [m²/s], and is usually denoted α but a, κ, K, and D are also used. The formula is:

α =k /(ρ CP)            [1]

where
k = is thermal conductivity [W/(m·K)]
ρ = density [kg/m³]
CP = specific heat capacity [J/(kg·K)]

Below, thermal diffusivity for air at varying temperatures and pressures are given in figures and tables.

See also other properties of Air at varying temperature and pressure: Density and specific weight at varying temperature, Density at varying pressure, Diffusion Coefficients for Gases in Air, Prandtl Number, Specific heat at varying temperature and Specific heat at varying pressureThermal Conductivity, Properties at gas-liquid equilibrium conditions and Air thermophysical properties at standard conditions and Composition and molecular weight,
as well as thermal diffusivity of nitrogen, propane and water.

Air thermal diffusivity at 1 bara pressure, temperature given as °C or °F:
Air thermal diffusivity C

Air thermal diffusivity F

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Air thermal diffusivity at varying temperatures and constant pressures, SI and Imperial units:
Air thermal diffusivity pressure C

Air thermal diffusivity pressure F

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Air thermal diffusivity at atmospheric pressure, given in SI and Imperial units:

Temperature Thermal diffusivity Temperature Thermal diffusivity
[K] [°C] [x10-6 m2/s] [m2/h] [K] [°F] [x10-5 ft2/s] [ ft2/h]
173.2 -100 7.88 0.02837 172.0 -150 8.371 0.3014
223.2 -50 13.02 0.04686 213.7 -75 12.89 0.4640
243.2 -30 15.33 0.05518 227.6 -50 14.55 0.5238
253.2 -20 16.54 0.05953 241.5 -25 16.29 0.5863
263.2 -10 17.78 0.06401 249.8 -10 17.36 0.6251
268.2 -5 18.41 0.06629 255.4 0 18.09 0.6514
273.2 0 19.06 0.06860 260.9 10 18.84 0.6782
278.2 5 19.71 0.07094 266.5 20 19.59 0.7053
283.2 10 20.36 0.07331 283.2 50 21.92 0.7891
293.2 20 21.70 0.07813 297.0 75 23.93 0.8615
298.2 25 22.39 0.08059 310.9 100 26.01 0.9363
303.2 30 23.07 0.08307 324.8 125 28.15 1.013
323.2 50 25.91 0.09327 338.7 150 30.34 1.092
348.2 75 29.61 0.1066 366.5 200 34.92 1.257
373.2 100 33.49 0.1206 394.3 250 39.71 1.430
398.2 125 37.53 0.1351 422.0 300 44.71 1.610
423.2 150 41.73 0.1502 449.8 350 49.91 1.797
448.2 175 46.07 0.1659 477.6 400 55.30 1.991
473.2 200 50.56 0.1820 505.4 450 60.86 2.191
523.2 250 59.93 0.2157 533.2 500 66.59 2.397
573.2 300 69.79 0.2512 588.7 600 78.52 2.827

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Air thermal diffusivity at given temperatures and 1, 5 10 and 20 bara presure:

Temperature Thermal diffusivity at given pressures [x10-6 m2/s ]
[K] [°C] [°F] 1 bara,
14.5 psia
5 bara,
72.5 psia
10 bara,
145 psia
20 bara,
145 psia
60 -213 -352 0.0941 0.0942 0.0944 0.0947
80 -193 -316 1.59 0.0823 0.0826 0.0834
100 -173 -280 2.56 0.408 0.0643 0.0659
120 -153 -244 3.79 0.684 0.293 0.0814
140 -133 -208 5.21 0.983 0.455 0.189
180 -93.2 -136 8.58 1.68 0.815 0.385
200 -73.2 -99.7 10.5 2.07 1.02 0.490
220 -53.2 -63.7 12.6 2.50 1.23 0.602
240 -33.2 -27.7 14.9 2.96 1.46 0.721
260 -13.2 8.3 17.3 3.44 1.67 0.847
273.2 0.0 32.0 19.0 3.78 1.86 0.940
280 6.9 44.3 19.9 3.96 1.97 0.979
288.7 15.6 60.0 21.0 4.20 2.10 1.05
300 26.9 80.3 22.6 4.50 2.25 1.12
320 46.9 116 25.4 5.07 2.53 1.26
340 66.9 152 28.3 5.67 2.83 1.41
360 86.9 188 31.4 6.28 3.14 1.57
380 107 224 34.6 6.92 3.46 1.73
400 127 260 37.9 7.58 3.79 1.90
500 227 440 55.7 11.2 5.59 2.80
600 327 620 75.4 15.1 7.57 3.80
700 427 800 96.8 19.4 9.71 4.88
800 527 980 119.7 24.0 12.0 6.03
900 627 1160 144.2 28.9 14.5 7.26
1000 727 1340 169.6 34.1 17.1 8.57
1100 827 1520 198.1 19.9
1500 1227 2240 326.7 32.7
1900 1627 2960 483.7 48.5



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