These tables summarize the thermophysical properties of air in the liquid and gaseous states as calculated from the pseudo-pure fluid equation of state of Lemmon et al. (Ref. 1). Table 1 refers to liquid and gaseous air at equilibrium as a function of temperature. The tabulated properties are the bubble-point pressure; the dew-point pressure; density; enthalpy; entropy; isochoric heat capacity; isobaric heat capacity; speed of sound; viscosity; and thermal conductivity. The normal boiling point of air, i.e., the temperature at which the bubble-point pressure reaches 1 standard atmosphere (1.01325 bar), is 78.90 K (-194.25 °C). Column definitions for Tables 1 and 2 are as follows.
Column heading | Definition |
T | Temperature, in K |
P | Bubble-point pressure or dew-point pressure, in MPa [Not relevant for Table 2] |
ρ | Density, in kg m-3 |
H | Enthalpy, in units kJ kg-1 |
S | Entropy, in units kJ kg-1 K-1 |
Cv | Isochoric heat capacity, in units kJ kg-1 K-1 |
Cp | Isobaric heat capacity, in units kJ kg-1 K-1 |
μ | Speed of sound, in units m s-1 |
η | Viscosity, in units μPa s |
λ | Thermal conductivity, in units mW m-1 K-1 |
In Table 1, the first line of identical temperatures is the bubble-point pressure, i.e., the pressure at which boiling begins as the pressure of the liquid is lowered; the second line is the dew-point pressure, i.e., the pressure at which condensation begins as the pressure of the gas is raised.
Table 2 gives the properties of air along various isobars. An entry with non-integer temperatures in the isobar section indicates a phase transition (liquid–vapor) at these temperatures; property values are then given for both phases. These are identified by the high densities in the liquid and the low densities in the vapor. Additional calculations at state points not listed below can be obtained by using the NIST program REFPROP <http://www.nist.gov/srd/nist23.cfm>.
In the range from the solidification point to 873 K at pressures to 70 MPa, the estimated uncertainty of density values calculated with the equation of state is 0.1%. The estimated uncertainty of calculated speed-of-sound values is 0.2%, and that for calculated heat capacities is 1%. At temperatures above 873 K and 70 MPa, the estimated uncertainty of calculated density values is 0.5%, increasing to 1.0% at 2000 K and 2000 MPa.
Substance | T/ K | P/ MPa | ρ/ kg m–3 | H/ kJ kg–1 | S/ kJ kg–1 K–1 | Cv/ kJ kg–1 K–1 | Cp/ kJ kg–1 K–1 | u/ m s–1 | η/ µPa s | λ/ mW m–1 K–1 |
Continued on next page... | ||||||||||
Air | 59.75 | 0.005265 | 957.6 | -36.66 | -0.5306 | 1.174 | 1.901 | 1030 | 376.6 | 171.4 |
Air | 59.75 | 0.002432 | 0.1421 | 185.5 | 3.340 | 0.7184 | 1.009 | 154.8 | 4.220 | 5.294 |
Air | 60 | 0.005546 | 956.5 | -36.19 | -0.5226 | 1.173 | 1.901 | 1028 | 371.9 | 171.0 |
Air | 60 | 0.002584 | 0.1504 | 185.8 | 3.326 | 0.7186 | 1.009 | 155.1 | 4.238 | 5.320 |
Air | 62 | 0.008270 | 948.2 | -32.38 | -0.4603 | 1.157 | 1.901 | 1012 | 336.9 | 167.8 |
Air | 62 | 0.004111 | 0.2318 | 187.7 | 3.225 | 0.7198 | 1.012 | 157.6 | 4.386 | 5.529 |
Air | 64 | 0.01200 | 939.9 | -28.58 | -0.3999 | 1.143 | 1.902 | 995.8 | 306.3 | 164.5 |
Air | 64 | 0.006325 | 0.3460 | 189.6 | 3.132 | 0.7212 | 1.015 | 160.0 | 4.532 | 5.739 |
Air | 66 | 0.01699 | 931.5 | -24.77 | -0.3414 | 1.129 | 1.903 | 979.1 | 279.4 | 161.3 |
Air | 66 | 0.009442 | 0.5018 | 191.5 | 3.047 | 0.7230 | 1.019 | 162.3 | 4.679 | 5.950 |
Air | 68 | 0.02352 | 923.0 | -20.95 | -0.2846 | 1.115 | 1.906 | 962.2 | 255.7 | 158.0 |
Air | 68 | 0.01371 | 0.7089 | 193.4 | 2.968 | 0.7252 | 1.024 | 164.5 | 4.825 | 6.162 |
Air | 70 | 0.03191 | 914.4 | -17.13 | -0.2293 | 1.102 | 1.908 | 945.1 | 234.8 | 154.7 |
Air | 70 | 0.01943 | 0.9785 | 195.2 | 2.896 | 0.7277 | 1.030 | 166.7 | 4.970 | 6.376 |
Air | 72 | 0.04250 | 905.7 | -13.31 | -0.1756 | 1.090 | 1.912 | 927.7 | 216.3 | 151.4 |
Air | 72 | 0.02692 | 1.322 | 197.0 | 2.828 | 0.7305 | 1.037 | 168.7 | 5.115 | 6.592 |
Air | 74 | 0.05566 | 897.0 | -9.468 | -0.1232 | 1.078 | 1.917 | 910.0 | 199.9 | 148.1 |
Air | 74 | 0.03655 | 1.753 | 198.7 | 2.766 | 0.7338 | 1.046 | 170.6 | 5.260 | 6.810 |
Air | 76 | 0.07179 | 888.1 | -5.617 | -0.07209 | 1.067 | 1.923 | 892.1 | 185.2 | 144.8 |