source: trunk/eml/pressure_changers/expander.mso @ 996

#*-------------------------------------------------------------------
* 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: Marcos L. Alencastro,  Estefane S. Horn (Revised Gerson B. Bicca)
* $Id: expander.mso 687 2008-11-20 19:42:33Z bicca $
*--------------------------------------------------------------------*#

using "streams";

Model expander
        
ATTRIBUTES
        Pallete         = true;
        Icon            = "icon/expander"; 
        Brief           = "Model of an expander.";
        Info            =
"To be documented

== References ==

[1] GPSA, 1979, Engineering Data Book, Chapter 4, 5-9 - 5-10.

[2] Bloch, Heinz P., A Practical Guide to Compressor Technology, John Wiley & Sons, Incorporate, 2006.";
        
PARAMETERS

outer PP                                        as Plugin                       (Brief = "External Physical Properties", Type="PP");
outer NComp                     as Integer              (Brief = "Number of chemical components", Lower = 1);
        Rgas                                            as positive             (Brief = "Constant of Gases", Unit= 'kJ/kmol/K', Default = 8.31451,Hidden=true);
        Mw(NComp)                       as molweight    (Brief = "Molar Weight",Hidden=true);
MechanicalEff                   as positive     (Brief = "Mechanical efficiency",Lower=1E-3);
        IsentropicEff   as positive     (Brief = "Isentropic efficiency",Lower=1E-3);
VARIABLES

        Pratio          as positive             (Brief = "Pressure Ratio", Lower = 1E-6, Symbol ="P_{ratio}");  
        Pdrop           as press_delta  (Brief = "Pressure Drop", DisplayUnit = 'kPa', Symbol ="\Delta P");
        Pdecrease       as press_delta  (Brief = "Pressure Decrease", DisplayUnit = 'kPa', Symbol ="P_{incr}");
        PowerLoss       as power        (Brief = "Power Losses",Lower=0);
        Head                                    as energy_mass  (Brief = "Actual Head", Protected=true);
        HeadIsentropic  as energy_mass  (Brief = "Isentropic Head", Protected=true);
        
        FluidPower      as power        (Brief = "Fluid Power", Protected=true);
        BrakePower      as power        (Brief = "Brake Power", Protected=true);

        IseCoeff                        as positive     (Brief = "Isentropic Coefficient", Lower=0.2,Protected=true); 


        Tisentropic     as temperature          (Brief = "Isentropic Temperature",Protected=true);
        hise                    as enth_mol             (Brief = "Enthalpy at constant entropy",Hidden=true);
        Mwm                     as molweight            (Brief = "Mixture Molar Weight",Hidden=true);
        rho_in                  as dens_mass            (Brief = "Mass Density at inlet conditions", Lower = 1E-6, Protected=true);
        rho_out         as dens_mass            (Brief = "Mass Density at outlet conditions", Lower = 1E-6, Protected=true);
        Zfac_in                 as fraction             (Brief = "Compressibility factor at inlet", Lower = 1E-3, Protected=true);
        Zfac_out                as fraction             (Brief = "Compressibility factor at outlet", Lower = 1E-3, Protected=true);

in      Inlet           as stream       (Brief = "Inlet stream", PosX=0.14, PosY=0.0, Symbol="_{in}");
out     Outlet          as streamPH     (Brief = "Outlet stream", PosX=0.83, PosY=1, Symbol="_{out}");

out     WorkOut as power        (Brief = "Work Outlet", PosX=1, PosY=0.45, Protected=true);

SET

        Mw = PP.MolecularWeight();

        Rgas    = 8.31451*'kJ/kmol/K';

EQUATIONS

"Overall Molar Balance"
        Outlet.F = Inlet.F;

"Component Molar Balance"
        Outlet.z = Inlet.z;

"Average Molecular Weight"
        Mwm = sum(Mw*Inlet.z);

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

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

"Pressure Decrease"
        Outlet.P  = Inlet.P - Pdecrease;

"Mass Density at inlet conditions"
        rho_in = PP.VapourDensity(Inlet.T, Inlet.P, Inlet.z);

"Mass Density at outlet conditions"
        rho_out= PP.VapourDensity(Outlet.T, Outlet.P, Outlet.z);

"Enthalpy at isentropic conditions"
        hise = PP.VapourEnthalpy(Tisentropic, Outlet.P, Outlet.z);
        
"Compressibility factor at Inlet Conditions"
        Zfac_in = PP.VapourCompressibilityFactor(Inlet.T,Inlet.P,Inlet.z);

"Compressibility factor at Outlet Conditions"
        Zfac_out = PP.VapourCompressibilityFactor(Outlet.T,Outlet.P,Outlet.z);

"Actual Head"
        Head*Mwm = (Outlet.h-Inlet.h);

if IsentropicEff >= 1

        then
"Discharge Temperature"
        Outlet.T = Tisentropic;

        else

"Discharge Temperature"
        (Outlet.h-Inlet.h)= (hise-Inlet.h)*IsentropicEff;

end

"Isentropic Outlet Temperature"
        PP.VapourEntropy(Tisentropic, Outlet.P, Outlet.z) = PP.VapourEntropy(Inlet.T, Inlet.P, Inlet.z);

"Brake Power"
        BrakePower = WorkOut;

"Brake Power"
        BrakePower = FluidPower*MechanicalEff;

"Power Loss"
        PowerLoss = BrakePower - FluidPower;

"Fluid Power"
        FluidPower = HeadIsentropic*Mwm*Inlet.F*IsentropicEff;

"Isentropic Coefficient"
        HeadIsentropic*Mwm*((IseCoeff-1.001)/IseCoeff) = (0.5*Zfac_in+0.5*Zfac_out)*Rgas*Inlet.T*((Pratio)^((IseCoeff-1.001)/IseCoeff) - 1);

"Isentropic Head"
        HeadIsentropic*Mwm = (hise -Inlet.h);

end