source: trunk/eml/pressure_changers/valve.mso @ 616

#*-------------------------------------------------------------------
* 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: Estefane Horn, Núbia do Carmo Ferreira
*$Id: valve.mso 372 2007-09-21 22:17:36Z arge $                                                                 
*-------------------------------------------------------------------*#

using "streams";
        

Model valve
        ATTRIBUTES
        Pallete         = true;
        Icon            = "icon/Valve"; 
        Brief           = "Model of a valve.";
        Info            =
"== Model of valves ==
* Linear;
* Parabolic;
* Equal;
* Quick;
* Hyperbolic.
        
== Assumptions ==
* Steady State;
* Liquid;
* Isentalpic.
        
== Specify ==
* the valve type;
* the inlet stream;
* the Volumetric Flow (Qv);
* the Valve Coefficient (cv);
* the opening (x).
";
                
        PARAMETERS
        valve_type as Switcher (Valid = ["linear", "parabolic", "equal", "quick", "hyperbolic"], Default = "linear");
outer PP                as Plugin       (Brief = "External Physical Properties", Type = "PP");
outer NComp     as Integer      (Brief = "Number of chemical components", Lower = 1);
        rho60F  as dens_mass;

        VARIABLES
        Pratio  as positive                     (Brief = "Pressure Ratio", Symbol ="P_{ratio}");        
        Pdrop   as press_delta          (Brief = "Pressure Drop", DisplayUnit = 'kPa', Symbol ="\Delta P");
        Qv              as flow_vol                     (Brief = "Volumetric Flow");
        fc              as positive                     (Brief = "Opening Function");
        cv              as positive                     (Brief = "Valve Coefficient", Unit = 'm^3/h/kPa^0.5');
        Gf              as positive                     (Brief = "Specific Gravity");
        rho     as dens_mass;   
        vm              as vol_mol                      (Brief = "Mixture Molar Volume");       
        x               as fraction             (Brief = "Opening");
in      Inlet   as stream                       (Brief = "Inlet stream", PosX=0, PosY=0.7365, Symbol="_{in}");
out     Outlet  as streamPH                     (Brief = "Outlet stream", PosX=1, PosY=0.7365, Symbol="_{out}");
        
        SET
        rho60F = 999.02 * 'kg/m^3';
        
        EQUATIONS
        "Pressure Drop"
        Outlet.P  = Inlet.P - Pdrop;

        "Pressure Ratio"
        Outlet.P = Inlet.P * Pratio;
        
        "Enthalpy Balance"
        Outlet.h = Inlet.h;
        
        "Molar Balance"
        Outlet.F = Inlet.F;
        
        "Calculate Outlet Composition"
        Outlet.z = Inlet.z;

        if Pdrop > 0 then
                "Valve Equation - Flow"
                Qv = fc*cv*sqrt(Pdrop/Gf);      
        else
                "Valve Equation - Closed"
                Qv = 0 * 'm^3/h';
        end
        
        "Calculate Gf"
        Gf = rho/rho60F;
        
        "Calculate Specific Mass"
        rho = PP.LiquidDensity(Inlet.T,Inlet.P,Inlet.z);
        
        "Calculate Mass Flow"
        Qv = Inlet.F*vm;        
        
        "Calculate Liquid Molar Volume"
        vm = PP.LiquidVolume(Inlet.T,Inlet.P,Inlet.z);
        
        switch valve_type
        case "linear":

                "Opening Equation"
                fc = x;

        case "parabolic":

                "Opening Equation"
                fc = x^2;

        case "equal":

                "Opening Equation"
                fc = x^2/(2-x^4)^(1/2);

        case "quick":
        
                "Opening Equation"
                fc = 10*x/sqrt(1+99*x^2);

        case "hyperbolic":

                "Opening Equation"
                fc = 0.1*x/sqrt(1-0.99*x^2);

        end
end

#*-------------------------------------------------------------------
* Model of a valve (simplified)
*-------------------------------------------------------------------- 
*
* Author: Paula B. Staudt
*--------------------------------------------------------------------*#
Model valve_simplified
        ATTRIBUTES
        Pallete         = true;
        Icon            = "icon/Valve"; 
        Brief           = "Model of a very simple valve - used in distillation column models.";
        Info            =
"== Assumptions ==
* no flashing liquid in the valve;
* the flow in the valve is adiabatic;
* dynamics in the valve are neglected;
* linear flow type.
        
== Specify ==
* the inlet stream
* the plug position (x) OR outlet temperature (Outlet.T) OR outlet pressure (Outlet.P) 
        
        OR              
        
* the inlet stream excluding its flow (Inlet.F)
* the outlet pressure (Outlet.P) OR outlet flow (Outlet.F)
* the plug position (x)
";

        PARAMETERS
outer PP as Plugin(Type="PP");
outer NComp as Integer;
        
        VARIABLES
in      Inlet   as stream       (Brief = "Inlet stream", PosX=0, PosY=0.7365, Symbol="_{in}");
out     Outlet  as streamPH     (Brief = "Outlet stream", PosX=1, PosY=0.7365, Symbol="_{out}");
        x as fraction (Brief="Plug Position");
        rho as dens_mass (Brief="Fluid Density", Default=1e3);
        v as vol_mol (Brief="Specific volume", Default=1e3);
        Pdrop     as press_delta (Brief = "Pressure Drop", DisplayUnit = 'kPa', Symbol ="\Delta P");
        Pratio  as positive     (Brief = "Pressure Ratio", Symbol ="P_{ratio}");        

        PARAMETERS
        rho_ref as dens_mass (Brief="Reference Density", Default=1e4);
        k as Real (Brief="Valve Constant", Unit='gal/min/psi^0.5');

        EQUATIONS
        "Overall Molar Balance"
        Inlet.F = Outlet.F;
        
        "Componente Molar Balance"
        Inlet.z = Outlet.z;
        
        "Energy Balance"
        Inlet.h = Outlet.h;

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

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

        "Density"
        rho = Inlet.v*PP.VapourDensity((Inlet.T+Outlet.T)/2, (Inlet.P+Outlet.P)/2, Outlet.z) +
                (1-Inlet.v)*PP.LiquidDensity((Inlet.T+Outlet.T)/2, (Inlet.P+Outlet.P)/2, Outlet.z);

        "Volume"
        v = Inlet.v*PP.VapourVolume((Inlet.T+Outlet.T)/2, (Inlet.P+Outlet.P)/2, Outlet.z) +
                (1-Inlet.v)*PP.LiquidVolume((Inlet.T+Outlet.T)/2, (Inlet.P+Outlet.P)/2, Outlet.z);

        if Pdrop > 0 then
                "Flow"
                Outlet.F * v = k*x*sqrt(Pdrop * rho_ref / rho ) ;
        else
                "Closed"
                Outlet.F = 0 * 'kmol/h';
        end
end