[manojkv]

Hello Everyone,

I would like to know if we can calculate/extrapolate effective area or flow rate at a different inlet pressure for a given pressure ratio, valve position at both upstream and downstream of the valve.

Please note: i am looking for a calculation using excel/hand calculations and not using any other CFD solver.

[duri]

Is the flow compressible? Is pressure ratio total-static or static-static?

[manojkv]

Yes, its compressible. And pressure ratio is total-static and fluid is air.

Is there a way to find using hand calculation?

[duri]

Calculate valve downstream total pressure and temperature using upstream values and valve loss.
Use downstream total pressure/static pressure ratio with isentropic relations to find Mach number at downstream.
Use compressible mass flow rate equation given in below link to find mass flow rate.
https://www.grc.nasa.gov/WWW/k-12/Vi...ne/mflchk.html

Use this same relation at upstream and find the upstream mach number. This is not straight forward. You may need to interpolate or iterate which ever is comfortable.
Use isentropic relation to find upstream static pressure using upstream mach number.

For given total to static pressure ratio and fixed area you would get only one mass flow rate. You may need to change total pressure or area or downstream static pressure to get different mass flow rate. Probably valve is doing that job.

[manojkv]

Thanks for the information above.

I am familiar with the link provided above and can understand i can calculate mass flow rate and in turn the effective area based on the given pressure ratios.

However, my concern is at the downstream, where the fluid flows past the valve. Since the flow behaviou changes after the fluid flows past the valve, i am unable to calculate downstream mass flow rate or effective area.

I do understand this is not straight forward procedure, and therefore can you share any example to illustrate the same, if any?