Should we use cp/cv or cp/cp-R for control valve sizing equations?
I'm calculating a gas breakthrough through a control valve and calculating Fk = k / 1.4.
Since the ideal cp/cv is used for PSV sizing I presume I should use the ideal Cp/Cp-R for calculating the gas breakthrough?
API states that the ideal k value should be used, however I cannot find a similar quote in any control valve sizing literature.
Appreciate any help
Thanks