# Precise estimation of air properties as a function of temperature at 1 atm

Are there any tables with empirical equations to calculate properties of air as a function of a temperature at 1 atm?

For example, NIST provides such equations for a large number of gases, but I was not able to find such solution for air, where I would specifically like to obtain:

• Dynamic viscosity,
• Specific heat,
• Prandtl number,
• Thermal conductivity,
• Thermal diffusivity.

It would be best, if I could put these calculation in MS Excel, because I need to change these values with respect to temperature in multiple equations.

• Properties of air are not precise. Jan 20, 2021 at 22:45
• As @Mithoron states, "air" varies, particularly as to water vapor. This was a problem for carburetors, the design of which often ignored that, leading to icing of the venturi. Jan 21, 2021 at 1:03

Here are some links that look like they might be useful, there seems to be promising information on some engineering resource sites:

The point that has been made about water vapor fluctuations is valid, but most calculations of air properties assume dry air with constant composition.

• I have a similar table for air properties at 1 atm. I also found some other calculators, but calculating every values in a calculator is not very productive for my purposes, however, the "Appendix B" looks very promising - I will have to try the differences for values computed as a temperature function to those in the chart, if the correlation is satisfying, I'm all settled :). Jan 21, 2021 at 7:58

A lot can be found at engineeringtoolbox , like air-prandtl-number-viscosity-heat-capacity-thermal-conductivity.

The data are ( at least mostly ) presented as combination of an online calculator, tabelated numerical values and charts, instead of specific empirical formulas. But it should not be a big deal to invent some interpolation or approximation formulas for those tabelated numerical values.

Air - Composition and Molecular Weight
Air - Density at varying pressure and constant temperatures
Air - Density, Specific Weight and Thermal Expansion Coefficient at Varying Temperature and Constant Pressures
Air - Diffusion Coefficients of Gases in Excess of Air
Air - Dynamic and Kinematic Viscosity
Air - Molecular Weight and Composition - Dry air
Air - Properties at Gas-Liquid Equilibrium Conditions
Air - Specific Heat at Constant Temperature and Varying Pressure
Air - Thermal Conductivity
Air - Thermal Diffusivity
Air - Thermophysical Properties

• Thanks, as matter of fact, the engineeringtoolbox was the first thing I found, however, when I had to always fill out their calculator (which is great for its purpose), I realized that I need to put calculations to MS Excel, because it was very slow. Jan 21, 2021 at 7:52
• But putting a table to Excel and processing some numerical analysis.... E.g. the obvious and trivial least square method for a polynomial or rational function via Excel Solver..... At least you know this is the last resort option if you do not find anything better. Jan 21, 2021 at 7:57
• I know... it won't be horrible. In general, I was just very curious whether I missed any empirical equations, which would solve my problem most efficiently. Jan 21, 2021 at 8:24