source: mso/eml/stage_separators/tank.mso @ 42

#*-------------------------------------------------------------------
* Model of tanks
*-------------------------------------------------------------------- 
*       Streams:
*               * an inlet stream
*               * an outlet stream
*
*       Specify:
*               * the Inlet stream
*               * the Outlet flow
*               * the tank Q
*
*       Initial:
*               * the tank temperature (OutletL.T)
*               * the tank level (h)
*               * (NoComps - 1) Outlet compositions
*----------------------------------------------------------------------
* Author: Paula B. Staudt
* $Id: tank.mso 42 2006-10-26 19:44:05Z paula $
*--------------------------------------------------------------------*#

using "streams";

Model tank

        PARAMETERS
ext PP as CalcObject;
ext NComp as Integer;
        Across as area (Brief="Tank cross section area", Default=2);
        
        VARIABLES
in      Inlet as stream;
out     Outlet as stream_therm;

in      Q as heat_rate (Brief="Rate of heat supply"); 
        Level    as length(Brief="Tank level");
        M(NComp) as mol (Brief="Molar Holdup in the tank");
        E as energy (Brief="Total Energy Holdup on tank");
        vL as volume_mol (Brief="Liquid Molar Volume");

        EQUATIONS
        "Mass balance"
        diff(M) = Inlet.F*Inlet.z - Outlet.F*Outlet.z;
        
        "Energy balance"
        diff(E) = Inlet.F*Inlet.h - Outlet.F*Outlet.h + Q;

        "Energy Holdup"
        E = sum(M)*Outlet.h;

        "Mechanical Equilibrium"
        Inlet.P = Outlet.P;
        
        "Liquid Volume"
        vL = PP.LiquidVolume(Outlet.T, Outlet.P, Outlet.z);
        
        "Composition"
        M = Outlet.z*sum(M);
        
        "Level of liquid phase"
        Level = sum(M)*vL/Across;
        
        "Vapourisation Fraction"
        Outlet.v = Inlet.v;
end

Model tank_cylindrical

        PARAMETERS
ext PP as CalcObject;
ext NComp as Integer;
        radius as length(Brief="Tank radius");
        L as length(Brief="Tank length");
        
        VARIABLES
in      Inlet as stream;
out     Outlet as stream_therm;

in      Q as heat_rate (Brief="Rate of heat supply"); 
        Level    as length(Brief="Tank level");
        Across as area (Brief="Tank cross section area", Default=2);
        M(NComp) as mol (Brief="Molar Holdup in the tank");
        E as energy (Brief="Total Energy Holdup on tank");
        vL as volume_mol (Brief="Liquid Molar Volume");

        EQUATIONS
        "Mass balance"
        diff(M) = Inlet.F*Inlet.z - Outlet.F*Outlet.z;
        
        "Energy balance"
        diff(E) = Inlet.F*Inlet.h - Outlet.F*Outlet.h + Q;

        "Energy Holdup"
        E = sum(M)*Outlet.h;
        
        "Mechanical Equilibrium"
        Inlet.P = Outlet.P;
        
        "Liquid Volume"
        vL = PP.LiquidVolume(Outlet.T, Outlet.P, Outlet.z);
        
        "Composition"
        M = Outlet.z*sum(M);
        
        "Cylindrical Area"
        Across = radius^2 * (asin(1) - asin((radius-Level)/radius) ) + 
                                (Level-radius)*sqrt(Level*(2*radius - Level));

        "Level of liquid phase"
        Level = sum(M)*vL/Across;
        
        "Vapourisation Fraction"
        Outlet.v = Inlet.v;
end

Model tank_simplified
        PARAMETERS
        k as Real (Brief="Valve Constant", Unit = "m^2.5/h", Default=4);
        A as area (Brief="Tank area", Default=2);

        VARIABLES
        h    as length(Brief="Tank level");
in      Fin  as flow_vol(Brief="Input flow");
out     Fout as flow_vol(Brief="Output flow");

        EQUATIONS
        "Mass balance"
        diff(A*h) = Fin - Fout;
        
        "Valve equation"
        Fout = k*sqrt(h);               
end