May somebody tell me where I can get the air properties like density-viscosity- thermal conductivity under vacuum conditions (i.e. in pressures less than atmospheric pressure) ?
Thank you
Viscosity in gases arises principally from the molecular diffusion that transports momentum between layers of flow. An elementary calculation can be found on the Wikipedia page
https://en.wikipedia.org/wiki/Viscosity#Gases
Air density for reduced pressure can be calculated from the "ideal gas equation". The thermal conductivity may be a little harder to find. I'll come back when I find something.
At very low pressure, the theory for continuous gases might not be applicable, as we should discuss individual molecules instead.
Numbers for thermal conductivity of air at various pressures (less than ambient) can be found here:
https://en.wikipedia.org/wiki/List_of_thermal_conductivities
Thanks a lot Dr. Ingo for the reply. I want the other properties like specific heat at constant pressure (Cp).
Thank you
Something like this?
https://www.engineeringtoolbox.com/air-specific-heat-various-pressures-d_1535.html
The first graph includes pressure down to 1% of atmpspheric pressure.
Thanks again. I look through this site but the problem most of the Cp values are at just 20 oC the problem I want it at 100 oC?
Probably it's too late, but I had a similar question.
I did however find the following work of Lemmon & Jacobsen (2004): Article Viscosity and Thermal Conductivity Equations for Nitrogen, O...
Although their equations do not hold for very low pressures, they do provide a thorough list of references with pressure and temperature ranges.
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