dynamic and cinematic viscosity to vary in p and t

[Frank88]

Good morning to all,
I am dimensionalizing a pneumatic circuit where compressed air flows from a 10 bar lung tank and 295k, after which a pressure regulator is tested at 7 bar, considering an adiabatic transformation, the air temperature after the regulator should be about 266k. for calculating the load losses distributed in the downstream ducts of the pressure regulator, I need to calculate the number of reynolds, function of the dynamic viscosity of the fluid. I find the values of the cinematic viscosity and dynamics tabled for air to atmospheric p and to the variations of t.
in my case the dynamic and cinematic viscosity varies according to p and t? If yes, how do they calculate?
Thank you.

 

[DoctorBomber90]

ciao @frank88.
the number of reynold can be described as:

• r =[math](rho) u d/ (mu)[/math];
• r =[math]u d/(ni)[/math].

rho=density of fluid [Kg/m^3];
u= fluid speed [m/s];
mu = dynamic viscosity [N*s/m^2] (opture [Kg/(m*s)]);
d=internal diameter of conduct [m];
ni= cinematic viscosity of fluid [m^2/s].

on the internet you can find polynomial formulas where, depending on the temperature (expressed in celsius or kelvin degrees), the cinematic viscosity change (look at wikipedia or any other trusted source).
The dynamic viscosity is described in function of both pressure and temperature because:[math]mu= (rho) x (ni)[/math]Consider that you are treating the air that is a gas, so the temperature and pressure change. if you treat a liquid, then it is slightly affected by temperature change (except for cases where you have extremely low or high temperatures).
Because you have air, you could use the perfect gas law:[math]pressure/density=(air gas content=287j/(kg*k))*temperature[/math]other thing, consider that the air is influenced so much by what is inside (mainly by nitrogen about 78%, oxygen for 21% and the remaining 1% from other gas like argon,etc... )

 

[Frank88]

Okay, thanks.

 

[paulpaul]

I also recommend the properties of gases and liquids (poling and others) where you find formulas for determining the transport properties of liquids and gases according to the composition, pressure and temperature. for the air, as he said to you @enzobeltrandi90, find approximate formulas around.

 

[DoctorBomber90]

ciao @frank88.
the number of reynold can be described as:

• r =[math](rho) u d/ (mu)[/math];
• r =[math]u d/(ni)[/math].

rho=density of fluid [Kg/m^3];
u= fluid speed [m/s];
mu = dynamic viscosity [N*s/m^2] (opture [Kg/(m*s)]);
d=internal diameter of conduct [m];
ni= cinematic viscosity of fluid [m^2/s].

on the internet you can find polynomial formulas where, depending on the temperature (expressed in celsius or kelvin degrees), the cinematic viscosity change (look at wikipedia or any other trusted source).
The dynamic viscosity is described in function of both pressure and temperature because:[math]mu= (rho) x (ni)[/math]Consider that you are treating the air that is a gas, so the temperature and pressure change. if you treat a liquid, then it is slightly affected by temperature change (except for cases where you have extremely low or high temperatures).
Because you have air, you could use the perfect gas law:[math]pressure/density=(air gas content=287j/(kg*k))*temperature[/math]other thing, consider that the air is influenced so much by what is inside (mainly by nitrogen about 78%, oxygen for 21% and the remaining 1% from other gas like argon,etc... )

I admit that I wrote bad formulas and adopt Greek letters. I don't know how to write them on cad3d. For example, better write a report like the number of reynolds.

 

[biz]

I admit that I wrote bad formulas and adopt Greek letters. I don't know how to write them on cad3d. For example, better write a report like the number of reynolds.

You have to use latex. You can help yourself This is, for example, if you are not familiar.

 

[DoctorBomber90]

You have to use latex. You can help yourself This is, for example, if you are not familiar.

Thank you very much News.

I admit that I wrote bad formulas and non so adopt Greek letters. I don't know how to write them on cad3d. For example, better write a report like the number of reynolds.