source: branches/newlanguage/eml/stage_separators/flash.mso @ 115

#*-------------------------------------------------------------------
* EMSO Model Library (EML) Copyright (C) 2004 - 2007 ALSOC.
*
* This LIBRARY is free software; you can distribute it and/or modify
* it under the therms of the ALSOC FREE LICENSE as available at
* http://www.enq.ufrgs.br/alsoc.
*
* EMSO Copyright (C) 2004 - 2007 ALSOC, original code
* from http://www.rps.eng.br Copyright (C) 2002-2004.
* All rights reserved.
*
* EMSO is distributed under the therms of the ALSOC LICENSE as
* available at http://www.enq.ufrgs.br/alsoc.
*
*-------------------------------------------------------------------
* Model of a dynamic flash
*-------------------------------------------------------------------- 
*       - Streams
*               * a liquid outlet stream
*               * a vapour outlet stream
*               * a feed stream
*
*       - Assumptions
*               * both phases are perfectly mixed
*
*       - Specify:
*               * the feed stream;
*               * the outlet flows: OutletV.F and OutletL.F
*
*       - Initial:
*               * the flash initial temperature (OutletL.T)
*               * the flash initial liquid level (Ll)
*               * (NoComps - 1) OutletL (OR OutletV) compositions
*----------------------------------------------------------------------
* Author: Paula B. Staudt
* $Id: flash.mso 72 2006-12-08 18:29:10Z paula $
*--------------------------------------------------------------------*#

using "streams";

Model flash
        PARAMETERS
ext PP as CalcObject;
ext NComp as Integer;
        V as volume(Brief="Total Volume of the flash");
        Mw(NComp) as molweight;
        Across as area  (Brief="Flash Cross section area");
        
        SET
        Mw=PP.MolecularWeight();
        
        VARIABLES
in      Inlet as stream; #(Brief="Feed Stream");
out     OutletL as stream_therm; #(Brief="Liquid outlet stream");
out     OutletV as stream_therm; #(Brief="Vapour outlet stream");
in      Q as heat_rate (Brief="Rate of heat supply"); 

        M(NComp) as mol (Brief="Molar Holdup in the tray");
        ML as mol (Brief="Molar liquid holdup");
        MV as mol (Brief="Molar vapour holdup");
        E as energy (Brief="Total Energy Holdup on tray");
        vL as volume_mol (Brief="Liquid Molar Volume");
        vV as volume_mol (Brief="Vapour Molar volume");
        Level as length (Brief="liquid height");
        
        EQUATIONS
        "Component Molar Balance"
        diff(M)=Inlet.F*Inlet.z - OutletL.F*OutletL.z - OutletV.F*OutletV.z;
        
        "Energy Balance"
        diff(E) = Inlet.F*Inlet.h - OutletL.F*OutletL.h - OutletV.F*OutletV.h + Q;
        
        "Molar Holdup"
        M = ML*OutletL.z + MV*OutletV.z; 
        
        "Energy Holdup"
        E = ML*OutletL.h + MV*OutletV.h - OutletL.P*V;
        
        "Mol fraction normalisation"
        sum(OutletL.z)=1.0;
        "Mol fraction normalisation"
        sum(OutletL.z)=sum(OutletV.z);
        
        "Liquid Volume"
        vL = PP.LiquidVolume(OutletL.T, OutletL.P, OutletL.z);
        "Vapour Volume"
        vV = PP.VapourVolume(OutletV.T, OutletV.P, OutletV.z);
        
        "Chemical Equilibrium"
        PP.LiquidFugacityCoefficient(OutletL.T, OutletL.P, OutletL.z)*OutletL.z = 
                PP.VapourFugacityCoefficient(OutletV.T, OutletV.P, OutletV.z)*OutletV.z;
        
        "Thermal Equilibrium"
        OutletV.T = OutletL.T;
        
        "Mechanical Equilibrium"
        OutletV.P = OutletL.P;
        
        "Geometry Constraint"
        V = ML* vL + MV*vV;
        "Liquid Level"
        ML* vL = Across * Level;
        
        "vaporization fraction "
        OutletV.v = 1.0;
        "vaporization fraction "
        OutletL.v = 0.0;

end

#*----------------------------------------------------------------------
* Model of a  Steady State flash
*---------------------------------------------------------------------*# 
Model flash_Steady
        PARAMETERS
ext PP as CalcObject;
ext NComp as Integer;
        
        VARIABLES
in      Inlet as stream; #(Brief="Feed Stream");
out     OutletL as stream_therm; #(Brief="Liquid outlet stream");
out     OutletV as stream_therm; #(Brief="Vapour outlet stream");
in      Q as heat_rate (Brief="Rate of heat supply"); 
        vfrac as fraction;

        EQUATIONS
        "The flash calculation"
        [vfrac, OutletL.z, OutletV.z] = PP.Flash(OutletV.T, OutletV.P, Inlet.z);
        
        "Global Molar Balance"
        Inlet.F = OutletV.F + OutletL.F;
        OutletV.F = Inlet.F * vfrac;
                
        "Energy Balance"
        Inlet.F*Inlet.h  + Q = OutletL.F*OutletL.h + OutletV.F*OutletV.h;
        
        "Thermal Equilibrium"
        OutletV.T = OutletL.T;
        
        "Mechanical Equilibrium"
        OutletV.P = OutletL.P;
        
        "vaporization fraction "
        OutletV.v = 1.0;
        "vaporization fraction "
        OutletL.v = 0.0;
end