4 replies to this topic

[twell]

I have to design a PSV for discharging a natural gas mixture at conditions above critical point,

does the ISPF() Excel macro allowable in PRODE library allow to calculate a PSV above

critical point  where normal methods are not applicable, see API 520, appendix B ?

 

[marchem]

yes,

you can call the ISPF() macro directly in Excel

or load the predefined page nozzle.xls included in Prode Properties distribution files,

as far as I know there are no problems to solve with fluids

above critical point in dense phase, see the attached example

for a hydrocarbon's mixture (C1-C6) at 160 Bar 420 K

 

set HEM as model which can solve

 

gas (superheated)

vapor+liquid (two phases)

liquid (subcooled)

 

the procedure does that automatically :-)

Attached Files

•  PSVsupercritical.jpg   104.69KB   3 downloads

[_luis]

Try this in case it is applicable to your system:
http://people.clarks...gn/reliefv2.pdf

[twell]

Marchem,

thanks for the comment, I have verified values calculated by Prode against numerical integration proposed in API and they are close.

Does Prode adopt the same procedure ?

 

_luis,

thanks for the link, the author discusses the theoretical basis for calculating the required orifice area at document's end,
as I understand the procedure is similar to that proposed in API (numerical integration) which I comment above.

[PaoloPemi]

the macro ISPF() which is available in Excel with Prode Properties library,

solves directly the vena contracta condition,

it is fast and accurate being based on evaluation of critical condtions,

if you campare against API procedure based on numerical integration

make sure to adopt (with API method) a suitable number of steps in

order to limit final error.