Prode Properties includes a procedure to design/rate pressure safety valves with critical or two-phase flow with the most accurate models
-HEM (Homogeneous Equilibrium Model)
-HNE (Homogeneous Non-Equilibrium) with boiling delay and gas-liquid split contributes
-HNE-DS (Homogeneous Non-Equilibrium)
-NHNE (Non-Homogeneous Non-Equilibrium)

With Prode Properties you can size / rate a PSV directly in Excel (see the following application example)

 

 

typical applications are vaporizing/flashing fluids, critical, supercritical conditions,
in addition the rigorous thermodynamic models included in Prode Properties allow an accurate evaluation of all the thermophysical properties required.
The image shows a typical application in Microsoft Excel for a quick and accurate design and rating.

For additional information see

http://www.prode.com/docs/pppman.pdf