source: branches/gui/eml/stage_separators/flash.mso @ 991

#*-------------------------------------------------------------------
* 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.
*----------------------------------------------------------------------
* Author: Paula B. Staudt
* $Id: flash.mso 918 2010-02-25 16:45:10Z rafael $
*--------------------------------------------------------------------*#

using "tank";

Model flash as VesselVolume

ATTRIBUTES
        Pallete         = true;
        Icon            = "icon/Flash"; 
        Brief           = "Model of a Dynamic Flash Vessel.";
        Info            =
"== ASSUMPTIONS ==
* perfect mixing of both phases;
* thermodynamics equilibrium.

== SET ==
*Orientation: vessel position - vertical or horizontal;
*Heads (bottom and top heads are identical)
**elliptical: 2:1 elliptical heads (25% of vessel diameter);
**hemispherical: hemispherical heads (50% of vessel diameter);
**flat: flat heads (0% of vessel diameter);
*Diameter: Vessel diameter;
*Lenght: Side length of the cylinder shell;
        
== SPECIFY ==
* the Inlet stream;
* the outlet flows: OutletVapour.F and OutletLiquid.F;
* the InletQ (the model requires an energy stream, also you can use a controller for setting the heat duty using the heat_flow model).

== OPTIONAL ==
* the Flash model has three control ports
** TI OutletLiquid Temperature Indicator;
** PI OutletLiquid Pressure Indicator;
** LI Level Indicator;

== INITIAL CONDITIONS ==
* Initial_Temperature :  the Flash temperature (OutletLiquid.T);
* Initial_Level : the Flash liquid level (Level);
* Initial_Composition : (NoComps) OutletLiquid compositions.
";
        
PARAMETERS
outer PP                as Plugin       (Brief = "External Physical Properties", Type="PP");
outer NComp     as Integer      (Brief = "Number of components", Lower = 1); 

        Mw(NComp)               as molweight    (Brief="Mol Weight", Hidden=true);
        
        Levelpercent_Initial                    as positive     (Brief="Initial liquid height in Percent", Default = 0.70);
        Temperature_Initial                             as temperature  (Brief="Initial Liquid Temperature", Default = 330);
        Composition_Initial(NComp)              as fraction             (Brief="Initial Composition", Default = 0.10);

SET

        Mw=PP.MolecularWeight();

VARIABLES

in      Inlet                   as stream                       (Brief="Feed Stream", PosX=0, PosY=0.48, Symbol="_{in}");
out     OutletLiquid    as liquid_stream        (Brief="Liquid outlet stream", PosX=0.43, PosY=1, Symbol="_{out}^{Liquid}");
out     OutletVapour    as vapour_stream        (Brief="Vapour outlet stream", PosX=0.43, PosY=0, Symbol="_{out}^{Vapour}");
in      InletQ                  as power                        (Brief="Heat Duty", PosX=1, PosY=0.81, Protected =true,Symbol="Q_{in}");

        TotalHoldup(NComp)              as mol  (Brief="Molar Holdup in the Vessel", Protected=true);
        LiquidHoldup                    as mol  (Brief="Molar liquid holdup", Protected=true);
        VapourHoldup                    as mol  (Brief="Molar vapour holdup", Protected=true);
        
        E                       as energy               (Brief="Total Energy Holdup in the Vessel", Protected=true);
        vL                      as volume_mol   (Brief="Liquid Molar Volume", Protected=true);
        vV                      as volume_mol   (Brief="Vapour Molar volume", Protected=true);
        vfrac           as positive     (Brief="Vapourization fraction", Symbol="\phi", Protected=true);
        Pratio          as positive             (Brief = "Pressure Ratio", Symbol ="P_{ratio}", Protected=true);        
        Pdrop           as press_delta  (Brief = "Pressure Drop", DisplayUnit = 'kPa', Symbol ="\Delta P", Protected=true);

        Peq             as pressure             (Brief="Equilibrium pressure on the liquid surface", Protected=true, Symbol="\Delta P_{eq}");
        Pstatic         as pressure             (Brief="Static head at the bottom of the tank", Protected = true, Symbol="P_{static}^{Liquid}");

out     TI as control_signal    (Brief="Temperature Indicator", PosX=1, PosY=0.39, Protected=true);
out     PI as control_signal    (Brief="Pressure Indicator", PosX=1, PosY=0.21, Protected=true);
out     LI as control_signal    (Brief="Level Indicator", PosX=1, PosY=0.59, Protected=true);

INITIAL

"Initial level Percent"
        LI = Levelpercent_Initial;
        
"Initial Outlet Liquid Temperature"
        OutletLiquid.T = Temperature_Initial;
        
"Initial Outlet Liquid Composition Normalized"
        OutletLiquid.z(1:NComp - 1) = Composition_Initial(1:NComp - 1)/sum(Composition_Initial);

EQUATIONS

"Component Molar Balance"
        diff(TotalHoldup)=Inlet.F*Inlet.z - OutletLiquid.F*OutletLiquid.z - OutletVapour.F*OutletVapour.z;
        
"Energy Balance"
        diff(E) = Inlet.F*Inlet.h - OutletLiquid.F*OutletLiquid.h - OutletVapour.F*OutletVapour.h + InletQ;
        
"Molar Holdup"
        TotalHoldup = LiquidHoldup*OutletLiquid.z + VapourHoldup*OutletVapour.z; 
        
"Energy Holdup"
        E = LiquidHoldup*OutletLiquid.h + VapourHoldup*OutletVapour.h - OutletLiquid.P*Vtotal;
        
"Mol fraction normalisation"
        sum(OutletLiquid.z)=1.0;

"Mol fraction normalisation"
        sum(OutletLiquid.z)=sum(OutletVapour.z);

"Vaporization Fraction"
        OutletVapour.F = Inlet.F * vfrac;

"Liquid Volume"
        vL = PP.LiquidVolume(OutletLiquid.T, Peq, OutletLiquid.z);

"Vapour Volume"
        vV = PP.VapourVolume(OutletVapour.T, Peq, OutletVapour.z);
        
"Chemical Equilibrium"
        PP.LiquidFugacityCoefficient(OutletLiquid.T, Peq, OutletLiquid.z)*OutletLiquid.z = 
                PP.VapourFugacityCoefficient(OutletVapour.T, Peq, OutletVapour.z)*OutletVapour.z;
        
"Thermal Equilibrium"
        OutletVapour.T = OutletLiquid.T;

"Mechanical Equilibrium for the Vapour Phase"
        OutletVapour.P = Peq;
        
"Static Head"   
        Pstatic = PP.LiquidDensity(OutletLiquid.T, Peq, OutletLiquid.z) * Gconst * Level;

"Mechanical Equilibrium for the Liquid Phase"
        OutletLiquid.P = Peq + Pstatic; 

"Pressure Drop"
        OutletLiquid.P  = Inlet.P - Pdrop;

"Pressure Ratio"
        OutletLiquid.P = Inlet.P * Pratio;

"Geometry Constraint"
        Vtotal = LiquidHoldup * vL + VapourHoldup * vV;

"Temperature indicator"
        TI * 'K' = OutletLiquid.T;

"Pressure indicator"
        PI * 'atm' = OutletLiquid.P;

"Level indicator"
        LI*Vtotal= Vfilled;

"Liquid Level"
        LiquidHoldup * vL = Vfilled;

end

Model flash_steady

ATTRIBUTES
        Pallete         = true;
        Icon            = "icon/Flash"; 
        Brief           = "Model of a static PH flash.";
        Info            =
"This model is for using the flashPH routine available on VRTherm.

== ASSUMPTIONS ==
* perfect mixing of both phases;
* thermodynamics equilibrium.
* static model.

== SPECIFY ==
* The Inlet stream;
* The heat duty;
* The outlet pressure.
";      

PARAMETERS

outer PP                as Plugin(Brief = "External Physical Properties", Type="PP");
outer NComp     as Integer;

VARIABLES

in      Inlet                   as stream                       (Brief="Feed Stream", PosX=0, PosY=0.48, Symbol="_{in}");
out     OutletLiquid    as liquid_stream        (Brief="Liquid outlet stream", PosX=0.43, PosY=1, Symbol="_{out}^{Liquid}");
out     OutletVapour    as vapour_stream        (Brief="Vapour outlet stream", PosX=0.43, PosY=0, Symbol="_{out}^{Vapour}");
in      InletQ                  as power                        (Brief="Heat Duty", PosX=1, PosY=0.81, Protected =true,Symbol="Q_{in}");

        vfrac           as fraction             (Brief="Vaporization fraction", Symbol="\phi", Protected =true);
        h                       as enth_mol             (Brief="Mixture enthalpy", Hidden =true);
        Pratio          as positive     (Brief = "Pressure Ratio", Symbol ="P_{ratio}", Protected =true);       
        Pdrop           as press_delta  (Brief = "Pressure Drop", DisplayUnit = 'kPa', Symbol ="\Delta P", Protected =true);

EQUATIONS

if vfrac > 0 and vfrac <1 

then
"The flash calculation"
        [vfrac, OutletLiquid.z, OutletVapour.z] = PP.Flash(OutletVapour.T, OutletVapour.P, Inlet.z);

else
"Chemical equilibrium"
        [vfrac,OutletLiquid.z,OutletVapour.z]=PP.FlashPH(OutletLiquid.P,h,Inlet.z);

end

"Global Molar Balance"
        Inlet.F = OutletVapour.F + OutletLiquid.F;

"Vapour Fraction"
        OutletVapour.F = Inlet.F * vfrac;

"Energy Balance"
        Inlet.F*(h - Inlet.h) = InletQ;
        Inlet.F*h = Inlet.F*(1-vfrac)*OutletLiquid.h + Inlet.F*vfrac*OutletVapour.h;

"Thermal Equilibrium"
        OutletVapour.T = OutletLiquid.T;
        
"Mechanical Equilibrium"
        OutletVapour.P = OutletLiquid.P;

"Pressure Drop"
        OutletLiquid.P  = Inlet.P - Pdrop;

"Pressure Ratio"
        OutletLiquid.P = Inlet.P * Pratio;

end

Model FlashPHSteady
        ATTRIBUTES
        Pallete         = false;
        Icon            = "icon/Flash"; 
        Brief           = "Another model of a static PH flash.";
        Info            =
"This model shows how to model a pressure enthalpy flash
directly with the EMSO modeling language.

This model is for demonstration purposes only, the flashPH
routine available on VRTherm is much more robust.

== Assumptions ==
* perfect mixing of both phases;

== Specify ==
* the feed stream;
* the heat duty;
* the outlet pressure.
";      
        
        PARAMETERS
outer PP as Plugin(Brief = "External Physical Properties", Type="PP");
outer NComp as Integer;
        B as Real(Default=1000, Brief="Regularization Factor");

        VARIABLES
in      Inlet as stream(Brief="Feed Stream", PosX=0, PosY=0.5421, Symbol="_{in}");
out     OutletL as liquid_stream(Brief="Liquid outlet stream", PosX=0.4790, PosY=1, Symbol="_{outL}");
out     OutletV as vapour_stream(Brief="Vapour outlet stream", PosX=0.4877, PosY=0, Symbol="_{outV}");
in      InletQ as power (Brief="Rate of heat supply", PosX=1, PosY=0.7559, Symbol="_{in}");
        vfrac as fraction(Brief="Vaporization fraction", Symbol="\phi");
        vsat as Real(Lower=-0.1, Upper=1.1, Brief="Vaporization fraction if saturated", Symbol="\phi_{sat}");
        Tsat as temperature(Lower=173, Upper=1473, Brief="Temperature if saturated");
        xsat(NComp) as Real(Lower=0, Upper=1, Brief="Liquid composition if saturated");
        ysat(NComp) as Real(Lower=0, Upper=1, Brief="Vapour composition if saturated");
        Pratio as positive (Brief = "Pressure Ratio", Symbol ="P_{ratio}");     
        Pdrop as press_delta (Brief = "Pressure Drop", DisplayUnit = 'kPa', Symbol ="\Delta P");
        
        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  + InletQ =
                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  + InletQ =
                Inlet.F*(1-vfrac)*OutletL.h + Inlet.F*vfrac*OutletV.h;

        "Thermal Equilibrium"
        OutletV.T = OutletL.T;
        
        "Mechanical Equilibrium"
        OutletV.P = OutletL.P;

        "Pressure Drop"
        OutletL.P  = Inlet.P - Pdrop;

        "Pressure Ratio"
        OutletL.P = Inlet.P * Pratio;

        # 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