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API 520 sizing for 2-phase

API 520 sizing for 2-phase

API 520 sizing for 2-phase

(OP)
Why is it that API 520 section C.2.1.1.3 states that sucessive _isentropic_ flashes at lower pressure with the fixed entrphy equal to stagnation conditions shall be used for these calculations? I would have though that a valve is isenthalpic? Where does the "work" go when you keep the entrophy constant? Is it because its "worst case" (with regards to low temperature) or what?

Best regards

Morten

RE: API 520 sizing for 2-phase

MortenA, theoretically we need to do the following flashes:

- From inlet to nozzle thoat: Isentropic flash as work goes into accelerating the fluid (mostly).

- From inlet to outlet: Isenthalpic flash as most of the velocity is destroyed. This is the flash calc we are used to.

 

RE: API 520 sizing for 2-phase

(OP)
hmm - okay i think i can buy into this.

Thank you Kruger

Best regards

Morten

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