Dependence of pressure on viscosity of air
Dependence of pressure on viscosity of air
(OP)
Hi all,
I'm looking for a formula, graph or explanation which describes the viscosity of air depending on the pressure (1 atm until vacuum). Can anyone join this information?
With kind regards,
ME
I'm looking for a formula, graph or explanation which describes the viscosity of air depending on the pressure (1 atm until vacuum). Can anyone join this information?
With kind regards,
ME





RE: Dependence of pressure on viscosity of air
RE: Dependence of pressure on viscosity of air
RE: Dependence of pressure on viscosity of air
At these low pressures http://webbook.nist.gov/chemistry/ gives for nitrogen an oxygen at 25 deg C, 17.8 and 20.4 μPa, respectively.
Besides, your conversion from mBar to psi has an error by a factor of 10.
RE: Dependence of pressure on viscosity of air
RE: Dependence of pressure on viscosity of air
P (psia) Viscosity (lb/ft-hr
1.5E-08 0.04410
0.001 0.04410
1 0.04411
3 0.04412
5 0.04412
10 0.04414
20 0.04417
50 0.04425
100 0.04438
200 0.04467
500 0.04567
1000 0.04771
2000 0.05287
3000 0.05901
5000 0.07238
8000 0.09182
RE: Dependence of pressure on viscosity of air
I should have written μPa.s. The link I gave above gives the viscosities for nitrogen and oxygen over the full range of pressures and temperatures.
As indicated by iainuts, it appears that -at constant temperature- the required high vacuum diminishes the dynamic viscosity at atmospheric pressure by about 1%.
RE: Dependence of pressure on viscosity of air
The kinematic viscosity, on the other hand, being the ratio of the dynamic viscosity (kg/m.s) to density (kg/m3), and expressed in m2/s (or cSt), changes a lot with pressure.