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 Tommaso June 24, 2003 12:04

Kinetic Theory

hi

In the ideal gas model using the kinetic theory for Cp and K, which are the values to insert in degrees of freedom...........

 BAK_FLOW July 25, 2003 15:53

Re: Kinetic Theory

Hi,

the number of translational and rotational modes are added up. For monatomic gasses this is 3 for diatomic this is 5 ie 3 translations and 2 rotations.

Cv=DOF/2*R/M Cp=(DOF+2)/2*R/M

R=universal Gas Constant 8.314[kJ/kg/K] M=mollecular Weight [kg/kmol]

So let us try this for Argon, DOF=3, M=39.94[kg/kmol]

Plug it in and get 0.527[kJ/kg/K]

compare to Reynold's and Perkins, "Engineering Thermodynamics" talbe B-6b 0.523[kJ/kg/K]

Similarly k=Cp/Cv=3/5=1.67

Try it out for nitrogen and oxygen and you will get pretty good comparison as well, ie k=1.4! So as a first approximation it works quite well for monatomic and diatomic gasses.

Regards,

BAK_FLOW

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