Air - Thermal Diffusivity vs. Temperature and Pressure
Thermal diffusivity is the rate of transfer of heat of a material from the hot side to the cold side - a measure of how quickly a material can absorb heat from its surroundings. 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 pressure , Thermal 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 at varying temperatures and constant pressures, SI and Imperial units:
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 | |
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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