Kv calculation for depressurization valve

[andreeeea]

Hello,

I'm having some trouble with this problem. Does anybody can help me, please?

Request:
Calculate Kv (range) of a valve that has to be used to have a constant depressurization of a vessel with supercritical Co2 inside. The vent is in atmosphere.

Hypothesis:
Initial Pressure: 120 bar

Temperature: 40 °C constant (heater)

Volume vessel: 10 liters = 0.01 m^3


- What Kv formula should I use for supercritical fluid?

- If I would obtain a constant depressurization (e.g. 4 bar/min), is volumetric flow constant in all the process, right?

depressurization time = 120 bar/(4bar/min) = 30 min = 0.5 h

volumetric flow = volume (constant)/time = 0.01/0.5 = 0.02 m^3/h


- Does mass flow change because pressure change so density change, isn't it?

 

[MarcTroy]

assuming pout << 0.5 * Pin the formula is that for critical flow,
yes, mass flow depends from density with (probably) a initial high value.

 

[MortenA]

sounds like school work