source: trunk/eml/stage_separators/tray.mso @ 680

#*-------------------------------------------------------------------
* 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: tray.mso 522 2008-05-21 23:21:12Z arge $
*--------------------------------------------------------------------*#

using "streams";

Model trayBasic
        ATTRIBUTES
        Pallete         = false;
        Icon            = "icon/Tray"; 
        Brief           = "Basic equations of a tray column model.";
        Info            =
"This model contains only the main equations of a column tray equilibrium model without
the hidraulic equations.
        
== Assumptions ==
* both phases (liquid and vapour) exists all the time;
* thermodymanic equilibrium with Murphree plate efficiency;
* no entrainment of liquid or vapour phase;
* no weeping;
* the dymanics in the downcomer are neglected.
";
        
        PARAMETERS
outer PP as Plugin(Brief = "External Physical Properties", Type="PP");
outer NComp as Integer;
        V as volume(Brief="Total Volume of the tray");
        Q as heat_rate (Brief="Rate of heat supply"); 
        Ap as area (Brief="Plate area = Atray - Adowncomer");
        
        VARIABLES
in      Inlet as stream (Brief="Feed stream", PosX=0, PosY=0.4932, Symbol="_{in}");
in      InletL as stream (Brief="Inlet liquid stream", PosX=0.5195, PosY=0, Symbol="_{inL}");
in      InletV as stream (Brief="Inlet vapour stream", PosX=0.4994, PosY=1, Symbol="_{inV}");
out     OutletL as liquid_stream (Brief="Outlet liquid stream", PosX=0.8277, PosY=1, Symbol="_{outL}");
out     OutletV as vapour_stream (Brief="Outlet vapour stream", PosX=0.8043, PosY=0, Symbol="_{outV}");

        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="Height of clear liquid on plate");
        yideal(NComp) as fraction;
        Emv as Real (Brief = "Murphree efficiency");
        
        EQUATIONS
        "Component Molar Balance"
        diff(M)=Inlet.F*Inlet.z + InletL.F*InletL.z + InletV.F*InletV.z
                - OutletL.F*OutletL.z - OutletV.F*OutletV.z;
        
        "Energy Balance"
        diff(E) = ( Inlet.F*Inlet.h + InletL.F*InletL.h + InletV.F*InletV.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;
        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, yideal)*yideal;

        "Murphree Efficiency"
        OutletV.z = Emv * (yideal - InletV.z) + InletV.z;
        
        "Thermal Equilibrium"
        OutletV.T = OutletL.T;
        
        "Mechanical Equilibrium"
        OutletV.P = OutletL.P;
        
        "Geometry Constraint"
        V = ML* vL + MV*vV;
        
        "Level of clear liquid over the weir"
        Level = ML*vL/Ap;
end

Model tray as trayBasic
        ATTRIBUTES
        Pallete         = false;
        Icon            = "icon/Tray"; 
        Brief           = "Complete model of a column tray.";
        Info            =
"== Specify ==
* the Feed stream
* the Liquid inlet stream
* the Vapour inlet stream
* the Vapour outlet flow (OutletV.F)
        
== Initial ==
* the plate temperature (OutletL.T)
* the liquid height (Level) OR the liquid flow OutletL.F
* (NoComps - 1) OutletL compositions

== Options ==
You can choose the equation for the liquid outlet flow and the vapour
inlet flow calculation through the VapourFlowModel and LiquidFlowModel
switchers.

== References ==
* ELGUE, S.; PRAT, L.; CABASSUD, M.; LANN, J. L.; CéZERAC, J. Dynamic models for start-up operations of batch distillation columns with experimental validation. Computers and Chemical Engineering, v. 28, p. 2735-2747, 2004.
* FEEHERY, W. F. Dynamic Optimization with Path Constraints. Tese (Doutorado) - Massachusetts Institute of Technology, June 1998.
* KLINGBERG, A. Modeling and Optimization of Batch Distillation. Dissertação (Mestrado) - Department of Automatic Control, Lund Institute of Technology, Lund, Sweden, fev. 2000.
* OLSEN, I.; ENDRESTOL, G. O.; SIRA, T. A rigorous and efficient distillation column model for engineering and training simulators. Computers and Chemical Engineering,v. 21, n. Suppl, p. S193-S198, 1997.
* REEPMEYER, F.; REPKE, J.-U.; WOZNY, G. Analysis of the start-up process for reactive distillation. Chemical Engineering Technology, v. 26, p. 81-86, 2003.
* ROFFEL, B.; BETLEM, B.; RUIJTER, J. de. First principles dynamic modeling and multivariable control of a cryogenic distillation column process. Computers and Chemical Engineering, v. 24, p. 111-123, 2000.
* WANG, L.; LI, P.; WOZNY, G.; WANG, S. A start-up model for simulation of batch distillation starting from a cold state. Computers and Chemical Engineering, v. 27, p.1485-1497, 2003.
";      

        PARAMETERS
        Ah as area (Brief="Total holes area");
        lw as length (Brief="Weir length");
        g as acceleration (Default=9.81);
        hw as length (Brief="Weir height");
        beta as fraction (Brief="Aeration fraction");
        alfa as fraction (Brief="Dry pressure drop coefficient");
        w as Real (Brief="Feehery's correlation coefficient", Unit='1/m^4', Default=1);
        btray as Real (Brief="Elgue's correlation coefficient", Unit='kg/m/mol^2', Default=1);
        fw as Real      (Brief = "Olsen's correlation coefficient", Default=1);
        Np as Real      (Brief = "Number of liquid passes in the tray", Default=1);
        Mw(NComp)       as molweight    (Brief = "Component Mol Weight");
        
        VapourFlow as Switcher(Valid = ["on", "off"], Default = "on");
        LiquidFlow as Switcher(Valid = ["on", "off"], Default = "on");
        VapourFlowModel as Switcher(Valid = ["Reepmeyer", "Feehery_Fv", "Roffel_Fv", "Klingberg", "Wang_Fv", "Elgue"], Default = "Reepmeyer");
        LiquidFlowModel as Switcher(Valid = ["default", "Wang_Fl", "Olsen", "Feehery_Fl", "Roffel_Fl"], Default = "default");

        SET
        Mw = PP.MolecularWeight();
        
        VARIABLES
        rhoL as dens_mass;
        rhoV as dens_mass;

        btemp as Real (Brief="Temporary variable of Roffel's liquid flow equation");
        
        EQUATIONS
        "Liquid Density"
        rhoL = PP.LiquidDensity(OutletL.T, OutletL.P, OutletL.z);
        "Vapour Density"
        rhoV = PP.VapourDensity(InletV.T, InletV.P, InletV.z);

        switch LiquidFlow
                case "on":
                        switch LiquidFlowModel
                                case "default":
                                "Francis Equation"
                                OutletL.F*vL = 1.84*'1/s'*lw*((Level-(beta*hw))/(beta))^2;
                        
                                case "Wang_Fl":
                                OutletL.F*vL = 1.84*'m^0.5/s'*lw*((Level-(beta*hw))/(beta))^1.5;
                        
                                case "Olsen":
                                OutletL.F / 'mol/s'= lw*Np*rhoL/sum(Mw*OutletV.z)/(0.665*fw)^1.5 * ((ML*sum(Mw*OutletL.z)/rhoL/Ap)-hw)^1.5 * 'm^0.5/mol';
                        
                                case "Feehery_Fl":
                                OutletL.F = lw*rhoL/sum(Mw*OutletL.z) * ((Level-hw)/750/'mm')^1.5 * 'm^2/s';
                        
                                case "Roffel_Fl":
                                OutletL.F = 2/3*sqrt(2*g)*rhoL/sum(Mw*OutletL.z)*lw*(2*btemp-1)*(ML*sum(Mw*OutletL.z)/(Ap*1.3)/rhoL/(2*btemp-1))^1.5;
                        end
                when Level < (beta * hw) switchto "off";
                
                case "off":
                "Low level"
                OutletL.F = 0 * 'mol/h';
                when Level > (beta * hw) + 1e-6*'m' switchto "on";
        end
        
        btemp = 1 - 0.3593/'Pa^0.0888545'*(OutletV.F*sum(Mw*OutletV.z)/(Ap*1.3)/sqrt(rhoV))^0.177709; #/'(kg/m)^0.0888545/s^0.177709';

        switch VapourFlow
                case "on":
                        switch VapourFlowModel
                                case "Reepmeyer":
                                InletV.F*vV = sqrt((InletV.P - OutletV.P)/(rhoV*alfa))*Ah;
                        
                                case "Feehery_Fv":
                                InletV.F = rhoV/Ap/w/sum(Mw*OutletV.z) * sqrt(((InletV.P - OutletV.P)-(rhoV*g*ML*vL/Ap))/rhoV);
                        
                                case "Roffel_Fv":
                                InletV.F^1.08 * 0.0013 * 'kg/m/mol^1.08/s^0.92*1e5' = (InletV.P - OutletV.P)*1e5 - (beta*sum(M*Mw)/(Ap*1.3)*g*1e5) * (rhoV*Ah/sum(Mw*OutletV.z))^1.08 * 'm^1.08/mol^1.08';
                        
                                case "Klingberg":
                                InletV.F * vV = Ap * sqrt(((InletV.P - OutletV.P)-rhoL*g*Level)/rhoV);
                        
                                case "Wang_Fv":
                                InletV.F * vV = Ap * sqrt(((InletV.P - OutletV.P)-rhoL*g*Level)/rhoV*alfa);
                                
                                case "Elgue":
                                InletV.F  = sqrt((InletV.P - OutletV.P)/btray);
                        end
                when InletV.F < 1e-6 * 'kmol/h' switchto "off";
                
                case "off":
                InletV.F = 0 * 'mol/s';
                when InletV.P > OutletV.P + Level*g*rhoL + 1e-1 * 'atm' switchto "on";
        end

end

#*-------------------------------------------------------------------
* Model of a tray with reaction
*-------------------------------------------------------------------*#
Model trayReact
        ATTRIBUTES
        Pallete         = false;
        Icon            = "icon/Tray"; 
        Brief           = "Model of a tray with reaction.";
        Info            =
"== Assumptions ==
* both phases (liquid and vapour) exists all the time;
* thermodymanic equilibrium with Murphree plate efficiency;
* no entrainment of liquid or vapour phase;
* no weeping;
* the dymanics in the downcomer are neglected.
        
== Specify ==
* the Feed stream;
* the Liquid inlet stream;
* the Vapour inlet stream;
* the Vapour outlet flow (OutletV.F);
* the reaction related variables.
        
== Initial ==
* the plate temperature (OutletL.T)
* the liquid height (Level) OR the liquid flow OutletL.F
* (NoComps - 1) OutletL compositions
";

        PARAMETERS
        outer PP as Plugin(Type="PP");
        outer NComp as Integer;
        V as volume(Brief="Total Volume of the tray");
        Q as power (Brief="Rate of heat supply"); 
        Ap as area (Brief="Plate area = Atray - Adowncomer");
        
        Ah as area (Brief="Total holes area");
        lw as length (Brief="Weir length");
        g as acceleration (Default=9.81);
        hw as length (Brief="Weir height");
        beta as fraction (Brief="Aeration fraction");
        alfa as fraction (Brief="Dry pressure drop coefficient");

        stoic(NComp) as Real(Brief="Stoichiometric matrix");
        Hr as energy_mol;
        Pstartup as pressure;
        
        VapourFlow as Switcher(Valid = ["on", "off"], Default = "off");
        LiquidFlow as Switcher(Valid = ["on", "off"], Default = "off");
        
        VARIABLES
in      Inlet as stream (Brief="Feed stream", PosX=0, PosY=0.4932, Symbol="_{in}");
in      InletL as stream (Brief="Inlet liquid stream", PosX=0.5195, PosY=0, Symbol="_{inL}");
in      InletV as stream (Brief="Inlet vapour stream", PosX=0.4994, PosY=1, Symbol="_{inV}");
out     OutletL as liquid_stream (Brief="Outlet liquid stream", PosX=0.8277, PosY=1, Symbol="_{outL}");
out     OutletV as vapour_stream (Brief="Outlet vapour stream", PosX=0.8043, PosY=0, Symbol="_{outV}");

        yideal(NComp) as fraction;
        Emv as Real (Brief = "Murphree efficiency");

        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="Height of clear liquid on plate");
        Vol as volume;
        
        rhoL as dens_mass;
        rhoV as dens_mass;
        r3 as reaction_mol (Brief = "Reaction resulting ethyl acetate", DisplayUnit = 'mol/l/s');
        C(NComp) as conc_mol (Brief = "Molar concentration", Lower = -1); #, Unit = "mol/l");
        
        EQUATIONS
        "Molar Concentration"
        OutletL.z = vL * C;
        
        "Reaction"
        r3 = exp(-7150*'K'/OutletL.T)*(4.85e4*C(1)*C(2) - 1.23e4*C(3)*C(4))*'l/mol/s';
        
        "Component Molar Balance"
        diff(M)=Inlet.F*Inlet.z + InletL.F*InletL.z + InletV.F*InletV.z
                - OutletL.F*OutletL.z - OutletV.F*OutletV.z + stoic*r3*ML*vL;
        
        "Energy Balance"
        diff(E) = ( Inlet.F*Inlet.h + InletL.F*InletL.h + InletV.F*InletV.h
                - OutletL.F*OutletL.h - OutletV.F*OutletV.h + Q ) + Hr * r3 * vL*ML;
        
        "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;
        
        "Liquid Volume"
        vL = PP.LiquidVolume(OutletL.T, OutletL.P, OutletL.z);
        "Vapour Volume"
        vV = PP.VapourVolume(OutletV.T, OutletV.P, OutletV.z);

        "Thermal Equilibrium"
        OutletV.T = OutletL.T;
        
        "Mechanical Equilibrium"
        OutletV.P = OutletL.P;
        
        "Level of clear liquid over the weir"
        Level = ML*vL/Ap;

        Vol = ML*vL;
        
        "Liquid Density"
        rhoL = PP.LiquidDensity(OutletL.T, OutletL.P, OutletL.z);
        "Vapour Density"
        rhoV = PP.VapourDensity(InletV.T, InletV.P, InletV.z);

        switch LiquidFlow
                case "on":
                "Francis Equation"
                OutletL.F*vL = 1.84*'1/s'*lw*((Level-(beta*hw)+1e-6*'m')/(beta))^2;
                when Level < (beta * hw) switchto "off";
                
                case "off":
                "Low level"
                OutletL.F = 0 * 'mol/h';
                when Level > (beta * hw) + 1e-6*'m' switchto "on";
        end

        switch VapourFlow
                case "on":
                #InletV.P = OutletV.P + Level*g*rhoL + rhoV*alfa*(InletV.F*vV/Ah)^2;
                InletV.F*vV = sqrt((InletV.P - OutletV.P - Level*g*rhoL + 1e-8 * 'atm')/(rhoV*alfa))*Ah;
                when InletV.P < OutletV.P + Level*g*rhoL switchto "off";
                
                case "off":
                InletV.F = 0 * 'mol/s';
                when InletV.P > OutletV.P + Level*g*rhoL + 3e-2 * 'atm' switchto "on";
                #when InletV.P > OutletV.P + Level*beta*g*rhoL + 1e-2 * 'atm' switchto "on";
        end

        "Chemical Equilibrium"
        PP.LiquidFugacityCoefficient(OutletL.T, OutletL.P, OutletL.z)*OutletL.z = 
                PP.VapourFugacityCoefficient(OutletV.T, OutletV.P, yideal)*yideal;
        
        OutletV.z = Emv * (yideal - InletV.z) + InletV.z;
        
        sum(OutletL.z)= sum(OutletV.z);
        
        "Geometry Constraint"
        V = ML* vL + MV*vV;
end

#*-------------------------------------
* Model of a packed column stage
-------------------------------------*#
Model packedStage
        ATTRIBUTES
        Pallete         = false;
        Icon            = "icon/PackedStage"; 
        Brief           = "Complete model of a packed column stage.";
        Info            =
"== Specify ==
* the Feed stream
* the Liquid inlet stream
* the Vapour inlet stream
* the stage pressure drop (deltaP)
        
== Initial ==
* the plate temperature (OutletL.T)
* the liquid molar holdup ML
* (NoComps - 1) OutletL compositions
";      
        
        PARAMETERS
outer PP as Plugin(Brief = "External Physical Properties", Type="PP");
outer NComp as Integer;
        PPwater as Plugin(Brief="Physical Properties",
                Type="PP",
                Components = [ "water" ],
                LiquidModel = "PR",
                VapourModel = "PR"
        );

        V as volume(Brief="Total Volume of the tray");
        Q as heat_rate (Brief="Rate of heat supply"); 
        d as length (Brief="Column diameter");  

        a as Real (Brief="surface area per packing volume", Unit='m^2/m^3');
        g as acceleration;
        e as Real (Brief="Void fraction of packing, m^3/m^3");
        Cpo as Real (Brief="Constant for resitance equation"); # Billet and Schultes, 1999.
        Mw(NComp)       as molweight    (Brief = "Component Mol Weight");
        hs as length (Brief="Height of the packing stage");
        Qsil as positive (Brief="Resistance coefficient on the liquid load", Default=1);

        VARIABLES
in      Inlet as stream (Brief="Feed stream", PosX=0, PosY=0.4932, Symbol="_{in}");
in      InletL as stream (Brief="Inlet liquid stream", PosX=0.5195, PosY=0, Symbol="_{inL}");
in      InletV as stream (Brief="Inlet vapour stream", PosX=0.4994, PosY=1, Symbol="_{inV}");
out     OutletL as liquid_stream (Brief="Outlet liquid stream", PosX=0.8277, PosY=1, Symbol="_{outL}");
out     OutletV as vapour_stream (Brief="Outlet vapour stream", PosX=0.8043, PosY=0, Symbol="_{outV}");

        M(NComp) as mol (Brief="Molar Holdup in the tray", Default=0.01, Lower=0, Upper=100);
        ML as mol (Brief="Molar liquid holdup", Default=0.01, Lower=0, Upper=100);
        MV as mol (Brief="Molar vapour holdup", Default=0.01, Lower=0, Upper=100);
        E as energy (Brief="Total Energy Holdup on tray", Default=-500);
        vL as volume_mol (Brief="Liquid Molar Volume");
        vV as volume_mol (Brief="Vapour Molar volume");
        
        miL as viscosity (Brief="Liquid dynamic viscosity", DisplayUnit='kg/m/s');
        miV as viscosity (Brief="Vapor dynamic viscosity", DisplayUnit='kg/m/s');
        rhoL as dens_mass;
        rhoV as dens_mass;
        
        deltaP as pressure;
        
        uL as velocity (Brief="volume flow rate of liquid, m^3/m^2/s", Lower=-10, Upper=100);
        uV as velocity (Brief="volume flow rate of vapor, m^3/m^2/s", Lower=-10, Upper=100);
        dp as length (Brief="Particle diameter", Default=1e-3, Lower=0, Upper=10);
        invK as positive (Brief="Wall factor", Default=1, Upper=10);
        Rev as Real (Brief="Reynolds number of the vapor stream", Default=4000);
        Al as area (Brief="Area occupied by the liquid", Default=0.001, Upper=1);
        hl as positive (Brief="Column holdup", Unit='m^3/m^3', Default=0.01,Upper=10);

        SET
        Mw = PP.MolecularWeight();

        EQUATIONS
        "Component Molar Balance"
        diff(M)=Inlet.F*Inlet.z + InletL.F*InletL.z + InletV.F*InletV.z
                - OutletL.F*OutletL.z - OutletV.F*OutletV.z;

        "Energy Balance"
        diff(E) = ( Inlet.F*Inlet.h + InletL.F*InletL.h + InletV.F*InletV.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;
        
        "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"
        OutletL.P = OutletV.P;
        
        "Geometry Constraint"
        V*e = ML*vL + MV*vV;
        
        "Liquid Density"
        rhoL = PP.LiquidDensity(OutletL.T, OutletL.P, OutletL.z);
        "Vapour Density"
        rhoV = PP.VapourDensity(InletV.T, InletV.P, InletV.z);
        "Liquid viscosity"
        miL = PP.LiquidViscosity(OutletL.T, OutletL.P, OutletL.z);
        "Vapour viscosity"
        miV = PP.VapourViscosity(InletV.T, InletV.P, InletV.z);

        "Area occupied by the liquid"
        Al = ML*vL/hs;

        "Volume flow rate of liquid, m^3/m^2/s"
        uL * Al = OutletL.F * vL;
        "Volume flow rate of vapor, m^3/m^2/s"
        uV * ((d^2*3.14159/4)*e - Al) = OutletV.F * vV;
        
        "Liquid holdup"
        hl = ML*vL/V/e;
        
        "Particle diameter"
        dp = 6 * (1-e)/a;
        
        "Wall Factor"
        invK = (1 + (2*dp/(3*d*(1-e))));
        
        "Reynolds number of the vapor stream"
        Rev*invK = dp*uV*rhoV / (miV*(1-e));
        
        deltaP = InletV.P - OutletV.P;
        
        "Pressure drop and Vapor flow"
        deltaP/hs  = Qsil*a*uV^2*rhoV*invK / (2*(e-hl)^3);

        "Liquid holdup"
        hl = (12*miL*a^2*uL/rhoL/g)^1/3;
end

#*-------------------------------------
* Nonequilibrium Model
-------------------------------------*#
Model interface
        
        ATTRIBUTES
        Pallete         = false;
        Icon            = "icon/Tray"; 
        Brief           = "Descrition of variables of the equilibrium interface.";
        Info            =
"This model contains only the variables of the equilibrium interface.";

        PARAMETERS
outer PP as Plugin(Brief = "External Physical Properties", Type="PP");
outer NComp as Integer;
outer NC1 as Integer;
        
        VARIABLES
        NL(NComp) as flow_mol_delta     (Brief = "Stream Molar Rate on Liquid Phase");
        NV(NComp) as flow_mol_delta     (Brief = "Stream Molar Rate on Vapour Phase");
        T as temperature                (Brief = "Stream Temperature");
        P as pressure                   (Brief = "Stream Pressure");
        x(NComp) as fraction    (Brief = "Stream Molar Fraction on Liquid Phase");
        y(NComp) as fraction    (Brief = "Stream Molar Fraction on Vapour Phase");
        a as area                           (Brief = "Interface Area");
        htL as heat_trans_coeff (Brief = "Heat Transference Coefficient on Liquid Phase");
        htV as heat_trans_coeff (Brief = "Heat Transference Coefficient on Vapour Phase");      
        E_liq as heat_rate      (Brief = "Liquid Energy Rate at interface");
    E_vap as heat_rate      (Brief = "Vapour Energy Rate at interface");        
        hL as enth_mol          (Brief = "Liquid Molar Enthalpy");
        hV as enth_mol          (Brief = "Vapour Molar Enthalpy");
        kL(NC1,NC1) as velocity (Brief = "Mass Transfer Coefficients");
        kV(NC1,NC1) as velocity (Brief = "Mass Transfer Coefficients");
        
        EQUATIONS
        "Liquid Enthalpy"
        hL = PP.LiquidEnthalpy(T, P, x);
        
        "Vapour Enthalpy"
        hV = PP.VapourEnthalpy(T, P, y);

end

Model trayRateBasic
        ATTRIBUTES
        Pallete         = false;
        Icon            = "icon/Tray"; 
        Brief           = "Basic equations of a tray rate column model.";
        Info            =
"This model contains only the main equations of a column tray nonequilibrium model without
the hidraulic equations.
        
== Assumptions ==
* both phases (liquid and vapour) exists all the time;
* no entrainment of liquid or vapour phase;
* no weeping;
* the dymanics in the downcomer are neglected.
";
        
        PARAMETERS
outer PP as Plugin(Brief = "External Physical Properties", Type="PP");
outer NComp as Integer;
    NC1 as Integer;
        V as volume(Brief="Total Volume of the tray");
        Q as heat_rate (Brief="Rate of heat supply"); 
        Ap as area (Brief="Plate area = Atray - Adowncomer");
        
        VARIABLES
in      Inlet as stream (Brief="Feed stream", PosX=0, PosY=0.4932, Symbol="_{in}");
in      InletFV as stream (Brief="Feed stream", PosX=0, PosY=0.4932, Symbol="_{in}");
in      InletL as stream (Brief="Inlet liquid stream", PosX=0.5195, PosY=0, Symbol="_{inL}");
in      InletV as stream (Brief="Inlet vapour stream", PosX=0.4994, PosY=1, Symbol="_{inV}");
out     OutletL as liquid_stream (Brief="Outlet liquid stream", PosX=0.8277, PosY=1, Symbol="_{outL}");
out     OutletV as vapour_stream (Brief="Outlet vapour stream", PosX=0.8043, PosY=0, Symbol="_{outV}");

        M_liq(NComp) as mol (Brief="Liquid Molar Holdup in the tray");
        M_vap(NComp) as mol (Brief="Vapour Molar Holdup in the tray");
        ML as mol (Brief="Molar liquid holdup");
        MV as mol (Brief="Molar vapour holdup");
        E_liq as energy (Brief="Total Liquid Energy Holdup on tray");
        E_vap as energy (Brief="Total Vapour Energy Holdup on tray");
        vL as volume_mol (Brief="Liquid Molar Volume");
        vV as volume_mol (Brief="Vapour Molar volume");
        Level as length (Brief="Height of clear liquid on plate");
        interf as interface;    

        SET   
        NC1=NComp-1;

        EQUATIONS
        "Component Molar Balance"
        diff(M_liq)=Inlet.F*Inlet.z + InletL.F*InletL.z 
        - OutletL.F*OutletL.z + interf.NL;
        
        diff(M_vap)=InletFV.F*InletFV.z + InletV.F*InletV.z 
        - OutletV.F*OutletV.z - interf.NV;
        
        "Energy Balance"
        diff(E_liq) = Inlet.F*Inlet.h + InletL.F*InletL.h
                - OutletL.F*OutletL.h  + Q + interf.E_liq;
        
        diff(E_vap) = InletFV.F*InletFV.h + InletV.F*InletV.h
                - OutletV.F*OutletV.h  - interf.E_vap;
        
        "Molar Holdup"
        M_liq = ML*OutletL.z;
        
        M_vap = MV*OutletV.z;
        
        "Energy Holdup"
        E_liq = ML*(OutletL.h - OutletL.P*vL);
        
        E_vap = MV*(OutletV.h - OutletV.P*vV);
        
        "Energy Rate through the interface"
        interf.E_liq = interf.htL*interf.a*(interf.T-OutletL.T)+sum(interf.NL)*interf.hL;       
        
        interf.E_vap = interf.htV*interf.a*(OutletV.T-interf.T)+sum(interf.NV)*interf.hV;
        
        "Mass Conservation"
        interf.NL = interf.NV;
        
        "Energy Conservation"
        interf.E_liq = interf.E_vap;
        
        "Mol fraction normalisation"
        sum(OutletL.z)= 1.0;
        sum(OutletL.z)= sum(OutletV.z);
        sum(interf.x)=1.0;
        sum(interf.x)=sum(interf.y);
        
        "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(interf.T, interf.P, interf.x)*interf.x = 
                PP.VapourFugacityCoefficient(interf.T, interf.P, interf.y)*interf.y;

        "Geometry Constraint"
        V = ML*vL + MV*vV;
        
        "Level of clear liquid over the weir"
        Level = ML*vL/Ap;

        "Total Mass Transfer Rates"
        interf.NL(1:NC1)=interf.a*sumt(interf.kL*(interf.x(1:NC1)-OutletL.z(1:NC1)))/vL+
                OutletL.z(1:NC1)*sum(interf.NL);

#       interf.NL(1:NC1)=0.01*'kmol/s';
        
        interf.NV(1:NC1)=interf.a*sumt(interf.kV*(OutletV.z(1:NC1)-interf.y(1:NC1)))/vV+
                OutletV.z(1:NC1)*sum(interf.NV);

        "Mechanical Equilibrium"
        OutletV.P = OutletL.P;
        interf.P=OutletL.P;
end

Model trayRate as trayRateBasic
        ATTRIBUTES
        Pallete         = false;
        Icon            = "icon/Tray"; 
        Brief           = "Complete rate model of a column tray.";
        Info            =
"== Specify ==
* the Feed stream
* the Liquid inlet stream
* the Vapour inlet stream
* the Vapour outlet flow (OutletV.F)
        
== Initial ==
* the plate temperature of both phases (OutletL.T and OutletV.T)
* the liquid height (Level) OR the liquid flow holdup (ML)
* the vapor holdup (MV)
* (NoComps - 1) OutletL compositions
";

        PARAMETERS
        Ah as area (Brief="Total holes area");
        lw as length (Brief="Weir length");
        g as acceleration (Default=9.81);
        hw as length (Brief="Weir height");
        beta as fraction (Brief="Aeration fraction");
        alfa as fraction (Brief="Dry pressure drop coefficient");
        
        VapourFlow as Switcher(Valid = ["on", "off"], Default = "on");
        LiquidFlow as Switcher(Valid = ["on", "off"], Default = "on");
        
        VARIABLES
        rhoL as dens_mass;
        rhoV as dens_mass;

        EQUATIONS
        "Liquid Density"
        rhoL = PP.LiquidDensity(OutletL.T, OutletL.P, OutletL.z);
        "Vapour Density"
        rhoV = PP.VapourDensity(InletV.T, InletV.P, InletV.z);

        switch LiquidFlow
                case "on":
                "Francis Equation"
#               OutletL.F*vL = 1.84*'m^0.5/s'*lw*((Level-(beta*hw))/(beta))^1.5;
                OutletL.F*vL = 1.84*'1/s'*lw*((Level-(beta*hw))/(beta))^2;
                when Level < (beta * hw) switchto "off";
                
                case "off":
                "Low level"
                OutletL.F = 0 * 'mol/h';
                when Level > (beta * hw) + 1e-6*'m' switchto "on";
        end

        switch VapourFlow
                case "on":
                InletV.F*vV = sqrt((InletV.P - OutletV.P)/(rhoV*alfa))*Ah;
                when InletV.F < 1e-6 * 'kmol/h' switchto "off";
                
                case "off":
                InletV.F = 0 * 'mol/s';
                when InletV.P > OutletV.P + Level*g*rhoL + 1e-1 * 'atm' switchto "on";
        end     
end