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sunilpatil April 14, 2014 02:36

joule thomson effect
Hello every one,
I am trying to simulate joule thomson effect by sending nitrogen vapor at high pressure (80 bar) in pipe with sudden expansion. for this which multiphase model i have to select in CFX (please see the attached image)

Thank you

JuPa April 14, 2014 06:16

Although not directly the same as what you're doing, Dr Thomas Frank from Ansys did the Edwards test for pressurised water (80 MPa) which suddenly decompressed to atmospheric pressure causing sudden flashing. Have a look at his papers to gauge how you'll get your problem to be numerically stable.

ghorrocks April 14, 2014 07:18

Why is this multiphase? Is the inlet Nitrogen a liquid at 80 bar?

sunilpatil April 15, 2014 10:23

joule thomson effect
No sir, at inlet nitrogen is in vapor state only due to sudden expansion it changes its phase

sunilpatil April 15, 2014 10:25

Thanks for providing material i will look into it

ghorrocks April 16, 2014 06:04

Have you seen the equilibrium phase change model? Look it up in the documentation.

Opaque April 16, 2014 23:39

ANSYS CFX uses very specific terminology to differentiate between material and phase modeling. When multiple materials are used within a single phase, it is termed "multicomponent material model", and "Eulerian multiphase" when multiple Eulerian phases are used. It is very important to understand the differences before selecting a modeling approach.

You seem to be trying to model the phase change of a single material from vapor to liquid under "thermodynamic equilibrium conditions". Theoretically, this is a process through the equation of state for the given material.

ANSYS CFX provides the "Homogeneous Binary Mixture" material to model the "thermodynamic phase change" of a pure substance modeled as a "single CFX Eulerian phase". This is the appropriate material to use "Equlibrium Phase Change" Glenn suggested.

Hope the above helps..

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