Dear Gentlemen,
Please let me introduce myself, I am a mechanical Engineer, with experience in Rotating Equipment.
I am trying to understand the procedure for Centrifugal compressor performance assessment.
In the process I came across one message in this site as follows:
"..... For engineering applications related to gas compression and expansion the useful engineering entity is specific heat ratio (k) also known as isentropic expansion coefficient and is defined as:
k = Cp/Cv
Specific heat at constant pressure (Cp) of pure gases is readily available from a wide source available in physics, chemistry or thermodynamics textbooks and even on the internet as a free resource. One such free, recognized and reliable resource can be found as below:
http://webbook.nist.gov/chemistry/
If you are dealing with a gas mixture then the Cp of the gas mixture can be found out by the law of proportion based on the mole fraction of the individual pure components of the gas. The Cp of the gas mixture of say A,B & C components thus would be:
mole fraction of A*Cp of A + mole fraction of B*Cp of B + mole fraction of C*Cp of C"
The NIST webbook requires two inputs - Pressure & Temperature
My question is for a total gas pressure 200 psia, and 115 F, do I need to use partial pressure of gas A, B and C to obtain Cp values from NIST webbook or the full pressure (200 psia in this case)?
Please advise.
Regards,
Ramesh