Sizing Needle Valves
Sizing Needle Valves
(OP)
I am trying to size a needle valve to make sure that it can allow the required flow rate at the fully open position (0.025 m^3/s). For a given Cv you should be able to calculate the maximum flow rate through the needle valve provided that you know the temperature of the gas and the pressure drop across the valve, but my problem is that I do not know what the outlet pressure of the needle valve is going to be ahead of time. Wouldn't P2 (outlet pressure) be dependent upon the needle valve itself? I seem to be confused on this point which is preventing me to get the correct size for the valve.
The flow conditions are:
Medium: Air
Upstream Pressure: 2 atm
Maximum flow rate required: 0.025 m^3/s
T = 300 K
Any help would be highly appreciated.
The flow conditions are:
Medium: Air
Upstream Pressure: 2 atm
Maximum flow rate required: 0.025 m^3/s
T = 300 K
Any help would be highly appreciated.





RE: Sizing Needle Valves
Good luck,
Latexman
Technically, the glass is always full - 1/2 air and 1/2 water.
RE: Sizing Needle Valves
RE: Sizing Needle Valves
In that case you need to model the entire fluid circuit in order to calculate the Cv you can tolerate for just the needle valve.
Mike Halloran
Pembroke Pines, FL, USA
RE: Sizing Needle Valves
RE: Sizing Needle Valves
Good luck,
Latexman
Technically, the glass is always full - 1/2 air and 1/2 water.
RE: Sizing Needle Valves
RE: Sizing Needle Valves
Good luck,
Latexman
Technically, the glass is always full - 1/2 air and 1/2 water.
RE: Sizing Needle Valves
dP = z*0.5*rho*V^2 (where z is resistance coefficient)
z = (899*d^4)/Cv^2 (where d is the orifice diameter in inches)