source: mso/eml/stage_separators/flashPH.mso @ 101

#*-------------------------------------------------------------------
* 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 static PH flash
*-------------------------------------------------------------------- 
*       - Streams
*               * a liquid outlet stream
*               * a vapour outlet stream
*               * a feed stream
*
*       - Assumptions
*               * both phases are perfectly mixed
*
*       - Specify:
*               * the feed stream;
*               * the heat duty
*       * the outlet pressure
*
*----------------------------------------------------------------------
* Author: Rafael de P. Soares and Paula B. Staudt
* $Id: flashPH.mso 101 2007-01-09 15:59:59Z rafael $
*--------------------------------------------------------------------*#

using "streams";

Model FlashPHSteady
        PARAMETERS
ext PP as CalcObject;
ext NComp as Integer;
        B as Real(Default=1000, Brief="Regularization Factor");
        
        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(Brief="Real vaporization fraction");
        vsat as Real(Lower=-5, Upper=5, Brief="Vaporization fraction if saturated");
        Tsat as temperature(Lower=173, Upper=473, Brief="Temperature if saturated");
        xsat(NComp) as Real(Lower=-5, Upper=5, Brief="Liquid composition if saturated");
        ysat(NComp) as Real(Lower=-5, Upper=5, Brief="Vapour composition if saturated");
        
        zero_one as fraction(Brief="Regularization Variable");
        one_zero as fraction(Brief="Regularization Variable");

        EQUATIONS
        "Chemical equilibrium"
        PP.LiquidFugacityCoefficient(Tsat, OutletL.P, xsat)*xsat = 
                PP.VapourFugacityCoefficient(Tsat, OutletV.P, ysat)*ysat;

        "Global Molar Balance"
        Inlet.F = OutletV.F + OutletL.F;
        OutletV.F = Inlet.F * vfrac;

        "Component Molar Balance"
        Inlet.F*Inlet.z = OutletL.F*xsat + OutletV.F*ysat;
        sum(xsat) = sum(ysat);

        "Energy Balance if saturated"
        Inlet.F*Inlet.h  + Q =
                Inlet.F*(1-vsat)*PP.LiquidEnthalpy(Tsat, OutletL.P, xsat) +
                Inlet.F*vsat*PP.VapourEnthalpy(Tsat, OutletV.P, ysat);

        "Real Energy Balance"
        Inlet.F*Inlet.h  + Q =
                Inlet.F*(1-vfrac)*OutletL.h + Inlet.F*vfrac*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;
        
        # regularization functions
        zero_one = (1 + tanh(B * vsat))/2;
        one_zero = (1 - tanh(B * (vsat - 1)))/2;
        
        vfrac = zero_one * one_zero * vsat + 1 - one_zero;
        OutletL.z = zero_one*one_zero*xsat + (1-zero_one*one_zero)*Inlet.z;
        OutletV.z = zero_one*one_zero*ysat + (1-zero_one*one_zero)*Inlet.z;
end