Flow simulation- Inlet and outlet boundary condition

[Jezovuk]

Hello!
I have a problem defining inlet and outlet boundary rules for "gas pressure regulator" flow simulation of methane gas.

My inlet conditions are: - Inlet pressure= 1 bar (relative pressure)
- Inlet speed= 55 m/s

My outlet condition is: - Outlet pressure= 0.1 bar

I would like to know volume flow rate through the volume of reguulator show on picture attached.

At inlet surface i go to "Flow boundary condition" and pick "inlet flow" as type, "velocity" as magnitude mode and hit apply, and do that again using "pressure rise" magnitude mode.

At outlet surface i just define "pressure rise".

I can't get any result because an error arrives every time i try to solve.

I use NX 8.0.

 

[Jezovuk]

When i apply such conditions on a simple model and get results i can't get data on flow rate through the volume, just speed, pressure, etc.

 

[BlasMolero]

Hello!,
You need to define FLOW BOUNDARY CONDITIONs, at the surface inlet you need to select the option INLET FLOW, but at the outlet you need to select OPENING, and EXTERNAL CONDITIONS = AMBIENT. You can define the Temperature and ABSOLUTE pressure at the ambient conditions card in the properties of the study, or specify an external absolute pressure in the above command.

Forgot al all to use command FLOW BOUNDARY CONTION > OUTLET FLOW, because at the outlet opening the flow velocity & pressure are the "unknows" of the analysis.

Also, if your target is to compute the PRESSURE DROP use command FLOW BOUNDARY CONTION > REPORT > 3D FLOW DATA > Pressure Drop.

Best regards,
Blas.

~~~~~~~~~~~~~~~~~~~~~~
Blas Molero Hidalgo
Ingeniero Industrial
Director

IBERISA
48011 BILBAO (SPAIN)
WEB:

http://www.iberisa.com

Blog de FEMAP & NX Nastran:

http://iberisa.wordpress.com/

 

[Jezovuk]

Thank You BlasMolero! Your answer was very helpful concerning flow boundary conditions. However, I still can get the output I want.

I need VOLUME FLOW as outlet (final) value. Volume flow depends of inlet and outlet pressure and nozzle diameter.

When we test our gas pressure regulators in our laboratory, all we have as known variables are inlet and outlet pressure and diameter of the nozzle.

Than we measure the volume flow on gas flow meters.

I would like to get some results before we go to the lab, because that takes time and it is expensive.

 

[Jezovuk]

Can someone help me?

I need to test one gas pressure regulator to determine it's capacity (volume flow).