carlo.stenali

HEM MODEL
HEM (Homogeneous Equilibrium Model) is based on two assumptions (Homogeneous flow)
1) velocity of gas an liquid phases are equal
2) vapor and liquid phase are in thermodynamic equilibrium
this is a general purpose model which gives good results for a broad range of problems

HNE MODEL
in HNE model (Homogeneous Non-Equilibrium Model) the vapor and liquid phases are not in thermodynamic equilibrium,
HNE has found (Fauske, Schmidt ...) to describe well the behaviour of subcooled fluids which reach two-phase equilibria in a nozzle, pipe

etc. for example the fluid residence time could be too short for a significant vaporisation.

SOME APPLICATIONS WITH PRODE PROPERTIES

Isentropic Nozzle model
this method alows to design/rate safety/relief devices as PSV etc. for critical and two-phase flow.
The Isentropic Nozzle model allows to define
1) HEM Homogeneous Equilibrium (Solution of Mass Flux integral)
2) HNE Homogeneous Non-equilibrium (HEM with Boling Delay and Gas-Liquid Slip Contributes)
3) HNE-DS , Homogeneous Non-equilibrium
4) NHNE Non-homogeneous Non-equilibrium

PIPE
this method allows to simulate single phase, two-phases, multiphase flow on circular pipes,
for multiphase flow different models are available including HEM (Homogeneous Equilibrium)

Speed of Sound
the methods StrMSS(), EStrMSS() in Prode Properties allow to calculate the speed of sound for gas, liquid and gas+liquid (mixed phases) with

HEM model

A TEST CASE
Prode Properties allows to compare HEM (Homogeneous Equilibrium Model) against different models as HNE (Homogeneous Non-Equilibrium Model)

and NHNE (Non-Homogeneous Non-Equilibrium Model),
this allows to select the most suitable pressure relief valve for a specific application

for additional information
'http://www.egpet.net/vb/threads/27092-Excel-library-for-process-calc-s-including-distillation'