| 1 | #*------------------------------------------------------------------- |
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| 2 | * EMSO Model Library (EML) Copyright (C) 2004 - 2007 ALSOC. |
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| 3 | * |
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| 4 | * This LIBRARY is free software; you can distribute it and/or modify |
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| 5 | * it under the therms of the ALSOC FREE LICENSE as available at |
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| 6 | * http://www.enq.ufrgs.br/alsoc. |
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| 7 | * |
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| 8 | * EMSO Copyright (C) 2004 - 2007 ALSOC, original code |
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| 9 | * from http://www.rps.eng.br Copyright (C) 2002-2004. |
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| 10 | * All rights reserved. |
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| 11 | * |
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| 12 | * EMSO is distributed under the therms of the ALSOC LICENSE as |
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| 13 | * available at http://www.enq.ufrgs.br/alsoc. |
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| 14 | *---------------------------------------------------------------------- |
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| 15 | * Author: Paula B. Staudt |
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| 16 | * $Id: flash.mso 825 2009-08-12 13:43:17Z mamuller $ |
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| 17 | *--------------------------------------------------------------------*# |
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| 18 | |
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| 19 | using "streams"; |
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| 20 | |
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| 21 | Model flash |
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| 22 | |
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| 23 | ATTRIBUTES |
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| 24 | Pallete = true; |
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| 25 | Icon = "icon/Flash"; |
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| 26 | Brief = "Model of a Dynamic Flash Vessel."; |
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| 27 | Info = |
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| 28 | "== ASSUMPTIONS == |
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| 29 | * perfect mixing of both phases; |
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| 30 | * thermodynamics equilibrium. |
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| 31 | |
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| 32 | == SET == |
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| 33 | *Orientation: vessel position - vertical or horizontal; |
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| 34 | *Heads (bottom and top heads are identical) |
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| 35 | **elliptical: 2:1 elliptical heads (25% of vessel diameter); |
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| 36 | **hemispherical: hemispherical heads (50% of vessel diameter); |
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| 37 | **flat: flat heads (0% of vessel diameter); |
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| 38 | *Diameter: Vessel diameter; |
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| 39 | *Lenght: Side length of the cylinder shell; |
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| 40 | |
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| 41 | == SPECIFY == |
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| 42 | * the Inlet stream; |
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| 43 | * the outlet flows: OutletVapour.F and OutletLiquid.F; |
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| 44 | * the InletQ (the model requires an energy stream, also you can use a controller for setting the heat duty using the heat_flow model). |
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| 45 | |
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| 46 | == OPTIONAL == |
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| 47 | * the Flash model has three control ports |
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| 48 | ** TI OutletLiquid Temperature Indicator; |
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| 49 | ** PI OutletLiquid Pressure Indicator; |
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| 50 | ** LI Level Indicator; |
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| 51 | |
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| 52 | == INITIAL CONDITIONS == |
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| 53 | * Initial_Temperature : the Flash temperature (OutletLiquid.T); |
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| 54 | * Initial_Level : the Flash liquid level (Level); |
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| 55 | * Initial_Composition : (NoComps) OutletLiquid compositions. |
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| 56 | "; |
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| 57 | |
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| 58 | PARAMETERS |
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| 59 | outer PP as Plugin (Brief = "External Physical Properties", Type="PP"); |
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| 60 | outer NComp as Integer (Brief = "Number of components", Lower = 1); |
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| 61 | |
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| 62 | Mw(NComp) as molweight (Brief="Mol Weight", Hidden=true); |
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| 63 | pi as positive (Brief="Pi value", Default=3.141593,Hidden=true, Symbol="\pi"); |
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| 64 | g as acceleration (Brief="Gravity Acceleration",Default=9.81,Hidden=true); |
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| 65 | |
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| 66 | Orientation as Switcher (Valid=["vertical","horizontal"],Default="vertical"); |
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| 67 | Heads as Switcher (Valid=["elliptical","hemispherical","flat"],Default="flat"); |
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| 68 | Diameter as length (Brief="Vessel diameter", Symbol="D_{i}"); |
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| 69 | Lenght as length (Brief="Side length of the cylinder shell", Symbol="L_{vessel}"); |
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| 70 | |
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| 71 | Vhead_elliptical as volume (Brief="Elliptical Head Total Volume",Hidden=true, Symbol="V_{head}^{elliptical}"); |
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| 72 | Vhead_hemispherical as volume (Brief="Hemispherical Head Total Volume",Hidden=true, Symbol="V_{head}^{hemispherical}"); |
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| 73 | Vcylinder as volume (Brief="Cylinder Total Volume",Hidden=true, Symbol="V_{cylinder}"); |
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| 74 | radius as length (Brief="Vessel radius",Hidden=true, Symbol="R_{cylinder}"); |
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| 75 | |
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| 76 | Levelpercent_Initial as positive (Brief="Initial liquid height in Percent", Default = 0.70); |
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| 77 | Temperature_Initial as temperature (Brief="Initial Liquid Temperature", Default = 330); |
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| 78 | Composition_Initial(NComp) as fraction (Brief="Initial Composition", Default = 0.10); |
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| 79 | |
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| 80 | SET |
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| 81 | |
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| 82 | Mw=PP.MolecularWeight(); |
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| 83 | |
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| 84 | Vhead_elliptical = (pi*Diameter^3)/12; |
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| 85 | Vhead_hemispherical = (pi*Diameter^3)/6; |
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| 86 | Vcylinder = 0.25*(pi*Diameter^2)*Lenght; |
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| 87 | radius = 0.5*Diameter; |
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| 88 | g = 9.81 * 'm/(s^2)'; |
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| 89 | |
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| 90 | VARIABLES |
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| 91 | |
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| 92 | in Inlet as stream (Brief="Feed Stream", PosX=0, PosY=0.48, Symbol="_{in}"); |
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| 93 | out OutletLiquid as liquid_stream (Brief="Liquid outlet stream", PosX=0.43, PosY=1, Symbol="_{out}^{Liquid}"); |
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| 94 | out OutletVapour as vapour_stream (Brief="Vapour outlet stream", PosX=0.43, PosY=0, Symbol="_{out}^{Vapour}"); |
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| 95 | in InletQ as power (Brief="Heat Duty", PosX=1, PosY=0.81, Protected =true,Symbol="Q_{in}"); |
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| 96 | |
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| 97 | Vtotal as volume (Brief="Vessel total volume",Protected=true, Symbol="V_{total}"); |
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| 98 | Vfilled as volume (Brief="Vessel volume content",Protected=true, Symbol="V_{filled}"); |
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| 99 | |
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| 100 | TotalHoldup(NComp) as mol (Brief="Molar Holdup in the Vessel", Protected=true); |
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| 101 | LiquidHoldup as mol (Brief="Molar liquid holdup", Protected=true); |
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| 102 | VapourHoldup as mol (Brief="Molar vapour holdup", Protected=true); |
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| 103 | |
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| 104 | E as energy (Brief="Total Energy Holdup in the Vessel", Protected=true); |
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| 105 | vL as volume_mol (Brief="Liquid Molar Volume", Protected=true); |
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| 106 | vV as volume_mol (Brief="Vapour Molar volume", Protected=true); |
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| 107 | Level as length (Brief="liquid height", Protected=true); |
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| 108 | Across as area (Brief="Vessel cylinder shell Cross section area", Hidden=true, Symbol="A_{cross}"); |
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| 109 | vfrac as positive (Brief="Vapourization fraction", Symbol="\phi", Protected=true); |
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| 110 | Pratio as positive (Brief = "Pressure Ratio", Symbol ="P_{ratio}", Protected=true); |
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| 111 | Pdrop as press_delta (Brief = "Pressure Drop", DisplayUnit = 'kPa', Symbol ="\Delta P", Protected=true); |
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| 112 | |
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| 113 | Peq as pressure (Brief="Equilibrium pressure on the liquid surface", Protected=true, Symbol="\Delta P_{eq}"); |
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| 114 | Pstatic as pressure (Brief="Static head at the bottom of the tank", Protected = true, Symbol="P_{static}^{Liquid}"); |
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| 115 | |
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| 116 | out TI as control_signal (Brief="Temperature Indicator", PosX=1, PosY=0.39, Protected=true); |
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| 117 | out PI as control_signal (Brief="Pressure Indicator", PosX=1, PosY=0.21, Protected=true); |
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| 118 | out LI as control_signal (Brief="Level Indicator", PosX=1, PosY=0.59, Protected=true); |
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| 119 | |
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| 120 | INITIAL |
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| 121 | |
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| 122 | "Initial level Percent" |
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| 123 | LI = Levelpercent_Initial; |
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| 124 | |
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| 125 | "Initial Outlet Liquid Temperature" |
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| 126 | OutletLiquid.T = Temperature_Initial; |
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| 127 | |
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| 128 | "Initial Outlet Liquid Composition Normalized" |
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| 129 | OutletLiquid.z(1:NComp - 1) = Composition_Initial(1:NComp - 1)/sum(Composition_Initial); |
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| 130 | |
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| 131 | EQUATIONS |
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| 132 | |
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| 133 | switch Orientation |
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| 134 | |
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| 135 | case "vertical": |
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| 136 | |
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| 137 | "Vessel Cross Section Area" |
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| 138 | Across = 0.25*(pi*Diameter^2); |
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| 139 | |
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| 140 | switch Heads |
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| 141 | |
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| 142 | case "elliptical": |
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| 143 | |
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| 144 | "Vessel Total Volume" |
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| 145 | Vtotal = Vhead_elliptical + Vcylinder; |
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| 146 | |
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| 147 | if Level < 0.25*Diameter then |
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| 148 | |
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| 149 | "Vessel Filled Volume" |
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| 150 | Vfilled = 0.25*pi*(((Diameter*Level)/(0.25*Diameter))^2)*(0.25*Diameter-Level/3); |
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| 151 | |
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| 152 | else |
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| 153 | |
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| 154 | "Vessel Filled Volume" |
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| 155 | Vfilled = 0.25*pi*(Diameter^2)*(Level - 0.25*Diameter/3); |
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| 156 | |
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| 157 | end |
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| 158 | |
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| 159 | case "hemispherical": |
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| 160 | |
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| 161 | "Vessel Total Volume" |
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| 162 | Vtotal = Vhead_hemispherical + Vcylinder; |
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| 163 | |
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| 164 | if Level < 0.5*Diameter then |
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| 165 | |
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| 166 | "Vessel Filled Volume" |
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| 167 | Vfilled = 0.25*pi*(Level^2)*(2*Diameter-4*Level/3); |
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| 168 | |
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| 169 | else |
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| 170 | |
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| 171 | "Vessel Filled Volume" |
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| 172 | Vfilled = 0.25*pi*((2/3)*((0.5*Diameter)^3) - (0.25*(Diameter)^3) + Level*Diameter^2); |
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| 173 | |
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| 174 | end |
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| 175 | |
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| 176 | case "flat": |
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| 177 | |
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| 178 | "Vessel Total Volume" |
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| 179 | Vtotal = Vcylinder; |
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| 180 | |
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| 181 | "Vessel Filled Volume" |
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| 182 | Vfilled = Across*Level; |
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| 183 | |
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| 184 | end |
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| 185 | |
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| 186 | case "horizontal": |
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| 187 | |
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| 188 | "Vessel Cross Section Area" |
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| 189 | Across = (radius^2)*acos((radius-Level)/radius)-(radius-Level)*sqrt((2*radius*Level-Level^2)); |
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| 190 | |
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| 191 | switch Heads |
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| 192 | |
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| 193 | case "elliptical": |
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| 194 | |
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| 195 | "Vessel Total Volume" |
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| 196 | Vtotal = Vhead_elliptical + Vcylinder; |
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| 197 | |
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| 198 | "Vessel Filled Volume" |
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| 199 | Vfilled = 0.5236*Level^2*(1.5*Diameter-Level) + Across*Lenght; |
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| 200 | |
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| 201 | case "hemispherical": |
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| 202 | |
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| 203 | "Vessel Total Volume" |
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| 204 | Vtotal = Vhead_hemispherical + Vcylinder; |
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| 205 | |
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| 206 | "Vessel Filled Volume" |
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| 207 | Vfilled = 1.0472*Level^2*(1.5*Diameter-Level) + Across*Lenght; |
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| 208 | |
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| 209 | case "flat": |
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| 210 | |
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| 211 | "Vessel Total Volume" |
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| 212 | Vtotal = Vcylinder; |
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| 213 | |
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| 214 | "Vessel Filled Volume" |
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| 215 | Vfilled = Across*Lenght; |
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| 216 | |
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| 217 | end |
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| 218 | |
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| 219 | end |
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| 220 | |
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| 221 | "Component Molar Balance" |
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| 222 | diff(TotalHoldup)=Inlet.F*Inlet.z - OutletLiquid.F*OutletLiquid.z - OutletVapour.F*OutletVapour.z; |
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| 223 | |
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| 224 | "Energy Balance" |
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| 225 | diff(E) = Inlet.F*Inlet.h - OutletLiquid.F*OutletLiquid.h - OutletVapour.F*OutletVapour.h + InletQ; |
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| 226 | |
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| 227 | "Molar Holdup" |
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| 228 | TotalHoldup = LiquidHoldup*OutletLiquid.z + VapourHoldup*OutletVapour.z; |
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| 229 | |
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| 230 | "Energy Holdup" |
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| 231 | E = LiquidHoldup*OutletLiquid.h + VapourHoldup*OutletVapour.h - OutletLiquid.P*Vtotal; |
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| 232 | |
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| 233 | "Mol fraction normalisation" |
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| 234 | sum(OutletLiquid.z)=1.0; |
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| 235 | |
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| 236 | "Mol fraction normalisation" |
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| 237 | sum(OutletLiquid.z)=sum(OutletVapour.z); |
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| 238 | |
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| 239 | "Vaporization Fraction" |
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| 240 | OutletVapour.F = Inlet.F * vfrac; |
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| 241 | |
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| 242 | "Liquid Volume" |
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| 243 | vL = PP.LiquidVolume(OutletLiquid.T, Peq, OutletLiquid.z); |
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| 244 | |
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| 245 | "Vapour Volume" |
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| 246 | vV = PP.VapourVolume(OutletVapour.T, Peq, OutletVapour.z); |
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| 247 | |
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| 248 | "Chemical Equilibrium" |
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| 249 | PP.LiquidFugacityCoefficient(OutletLiquid.T, Peq, OutletLiquid.z)*OutletLiquid.z = |
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| 250 | PP.VapourFugacityCoefficient(OutletVapour.T, Peq, OutletVapour.z)*OutletVapour.z; |
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| 251 | |
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| 252 | "Thermal Equilibrium" |
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| 253 | OutletVapour.T = OutletLiquid.T; |
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| 254 | |
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| 255 | "Mechanical Equilibrium for the Vapour Phase" |
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| 256 | OutletVapour.P = Peq; |
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| 257 | |
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| 258 | "Static Head" |
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| 259 | Pstatic = PP.LiquidDensity(OutletLiquid.T, Peq, OutletLiquid.z) * g * Level; |
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| 260 | |
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| 261 | "Mechanical Equilibrium for the Liquid Phase" |
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| 262 | OutletLiquid.P = Peq + Pstatic; |
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| 263 | |
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| 264 | "Pressure Drop" |
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| 265 | OutletLiquid.P = Inlet.P - Pdrop; |
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| 266 | |
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| 267 | "Pressure Ratio" |
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| 268 | OutletLiquid.P = Inlet.P * Pratio; |
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| 269 | |
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| 270 | "Geometry Constraint" |
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| 271 | Vtotal = LiquidHoldup * vL + VapourHoldup * vV; |
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| 272 | |
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| 273 | "Temperature indicator" |
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| 274 | TI * 'K' = OutletLiquid.T; |
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| 275 | |
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| 276 | "Pressure indicator" |
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| 277 | PI * 'atm' = OutletLiquid.P; |
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| 278 | |
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| 279 | "Level indicator" |
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| 280 | LI*Vtotal= Vfilled; |
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| 281 | |
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| 282 | "Liquid Level" |
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| 283 | LiquidHoldup * vL = Vfilled; |
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| 284 | |
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| 285 | end |
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| 286 | |
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| 287 | Model flash_steady |
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| 288 | |
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| 289 | ATTRIBUTES |
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| 290 | Pallete = true; |
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| 291 | Icon = "icon/Flash"; |
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| 292 | Brief = "Model of a static PH flash."; |
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| 293 | Info = |
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| 294 | "This model is for using the flashPH routine available on VRTherm. |
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| 295 | |
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| 296 | == ASSUMPTIONS == |
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| 297 | * perfect mixing of both phases; |
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| 298 | * thermodynamics equilibrium. |
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| 299 | * static model. |
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| 300 | |
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| 301 | == SPECIFY == |
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| 302 | * The Inlet stream; |
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| 303 | * The heat duty; |
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| 304 | * The outlet pressure. |
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| 305 | "; |
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| 306 | |
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| 307 | PARAMETERS |
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| 308 | |
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| 309 | outer PP as Plugin(Brief = "External Physical Properties", Type="PP"); |
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| 310 | outer NComp as Integer; |
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| 311 | |
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| 312 | VARIABLES |
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| 313 | |
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| 314 | in Inlet as stream (Brief="Feed Stream", PosX=0, PosY=0.48, Symbol="_{in}"); |
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| 315 | out OutletLiquid as liquid_stream (Brief="Liquid outlet stream", PosX=0.43, PosY=1, Symbol="_{out}^{Liquid}"); |
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| 316 | out OutletVapour as vapour_stream (Brief="Vapour outlet stream", PosX=0.43, PosY=0, Symbol="_{out}^{Vapour}"); |
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| 317 | in InletQ as power (Brief="Heat Duty", PosX=1, PosY=0.81, Protected =true,Symbol="Q_{in}"); |
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| 318 | |
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| 319 | vfrac as fraction (Brief="Vaporization fraction", Symbol="\phi", Protected =true); |
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| 320 | h as enth_mol (Brief="Mixture enthalpy", Hidden =true); |
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| 321 | Pratio as positive (Brief = "Pressure Ratio", Symbol ="P_{ratio}", Protected =true); |
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| 322 | Pdrop as press_delta (Brief = "Pressure Drop", DisplayUnit = 'kPa', Symbol ="\Delta P", Protected =true); |
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| 323 | |
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| 324 | EQUATIONS |
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| 325 | |
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| 326 | if vfrac > 0 and vfrac <1 |
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| 327 | |
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| 328 | then |
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| 329 | "The flash calculation" |
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| 330 | [vfrac, OutletLiquid.z, OutletVapour.z] = PP.Flash(OutletVapour.T, OutletVapour.P, Inlet.z); |
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| 331 | |
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| 332 | else |
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| 333 | "Chemical equilibrium" |
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| 334 | [vfrac,OutletLiquid.z,OutletVapour.z]=PP.FlashPH(OutletLiquid.P,h,Inlet.z); |
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| 335 | |
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| 336 | end |
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| 337 | |
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| 338 | "Global Molar Balance" |
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| 339 | Inlet.F = OutletVapour.F + OutletLiquid.F; |
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| 340 | |
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| 341 | "Vapour Fraction" |
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| 342 | OutletVapour.F = Inlet.F * vfrac; |
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| 343 | |
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| 344 | "Energy Balance" |
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| 345 | Inlet.F*(h - Inlet.h) = InletQ; |
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| 346 | Inlet.F*h = Inlet.F*(1-vfrac)*OutletLiquid.h + Inlet.F*vfrac*OutletVapour.h; |
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| 347 | |
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| 348 | "Thermal Equilibrium" |
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| 349 | OutletVapour.T = OutletLiquid.T; |
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| 350 | |
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| 351 | "Mechanical Equilibrium" |
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| 352 | OutletVapour.P = OutletLiquid.P; |
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| 353 | |
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| 354 | "Pressure Drop" |
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| 355 | OutletLiquid.P = Inlet.P - Pdrop; |
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| 356 | |
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| 357 | "Pressure Ratio" |
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| 358 | OutletLiquid.P = Inlet.P * Pratio; |
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| 359 | |
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| 360 | end |
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| 361 | |
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| 362 | Model FlashPHSteady |
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| 363 | ATTRIBUTES |
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| 364 | Pallete = false; |
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| 365 | Icon = "icon/Flash"; |
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| 366 | Brief = "Another model of a static PH flash."; |
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| 367 | Info = |
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| 368 | "This model shows how to model a pressure enthalpy flash |
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| 369 | directly with the EMSO modeling language. |
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| 370 | |
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| 371 | This model is for demonstration purposes only, the flashPH |
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| 372 | routine available on VRTherm is much more robust. |
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| 373 | |
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| 374 | == Assumptions == |
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| 375 | * perfect mixing of both phases; |
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| 376 | |
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| 377 | == Specify == |
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| 378 | * the feed stream; |
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| 379 | * the heat duty; |
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| 380 | * the outlet pressure. |
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| 381 | "; |
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| 382 | |
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| 383 | PARAMETERS |
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| 384 | outer PP as Plugin(Brief = "External Physical Properties", Type="PP"); |
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| 385 | outer NComp as Integer; |
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| 386 | B as Real(Default=1000, Brief="Regularization Factor"); |
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| 387 | |
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| 388 | VARIABLES |
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| 389 | in Inlet as stream(Brief="Feed Stream", PosX=0, PosY=0.5421, Symbol="_{in}"); |
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| 390 | out OutletL as liquid_stream(Brief="Liquid outlet stream", PosX=0.4790, PosY=1, Symbol="_{outL}"); |
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| 391 | out OutletV as vapour_stream(Brief="Vapour outlet stream", PosX=0.4877, PosY=0, Symbol="_{outV}"); |
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| 392 | in InletQ as power (Brief="Rate of heat supply", PosX=1, PosY=0.7559, Symbol="_{in}"); |
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| 393 | vfrac as fraction(Brief="Vaporization fraction", Symbol="\phi"); |
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| 394 | vsat as Real(Lower=-0.1, Upper=1.1, Brief="Vaporization fraction if saturated", Symbol="\phi_{sat}"); |
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| 395 | Tsat as temperature(Lower=173, Upper=1473, Brief="Temperature if saturated"); |
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| 396 | xsat(NComp) as Real(Lower=0, Upper=1, Brief="Liquid composition if saturated"); |
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| 397 | ysat(NComp) as Real(Lower=0, Upper=1, Brief="Vapour composition if saturated"); |
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| 398 | Pratio as positive (Brief = "Pressure Ratio", Symbol ="P_{ratio}"); |
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| 399 | Pdrop as press_delta (Brief = "Pressure Drop", DisplayUnit = 'kPa', Symbol ="\Delta P"); |
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| 400 | |
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| 401 | zero_one as fraction(Brief="Regularization Variable"); |
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| 402 | one_zero as fraction(Brief="Regularization Variable"); |
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| 403 | |
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| 404 | EQUATIONS |
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| 405 | "Chemical equilibrium" |
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| 406 | PP.LiquidFugacityCoefficient(Tsat, OutletL.P, xsat)*xsat = |
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| 407 | PP.VapourFugacityCoefficient(Tsat, OutletV.P, ysat)*ysat; |
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| 408 | |
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| 409 | "Global Molar Balance" |
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| 410 | Inlet.F = OutletV.F + OutletL.F; |
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| 411 | OutletV.F = Inlet.F * vfrac; |
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| 412 | |
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| 413 | "Component Molar Balance" |
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| 414 | Inlet.F*Inlet.z = OutletL.F*xsat + OutletV.F*ysat; |
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| 415 | sum(xsat) = sum(ysat); |
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| 416 | |
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| 417 | "Energy Balance if saturated" |
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| 418 | Inlet.F*Inlet.h + InletQ = |
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| 419 | Inlet.F*(1-vsat)*PP.LiquidEnthalpy(Tsat, OutletL.P, xsat) + |
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| 420 | Inlet.F*vsat*PP.VapourEnthalpy(Tsat, OutletV.P, ysat); |
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| 421 | |
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| 422 | "Real Energy Balance" |
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| 423 | Inlet.F*Inlet.h + InletQ = |
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| 424 | Inlet.F*(1-vfrac)*OutletL.h + Inlet.F*vfrac*OutletV.h; |
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| 425 | |
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| 426 | "Thermal Equilibrium" |
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| 427 | OutletV.T = OutletL.T; |
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| 428 | |
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| 429 | "Mechanical Equilibrium" |
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| 430 | OutletV.P = OutletL.P; |
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| 431 | |
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| 432 | "Pressure Drop" |
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| 433 | OutletL.P = Inlet.P - Pdrop; |
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| 434 | |
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| 435 | "Pressure Ratio" |
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| 436 | OutletL.P = Inlet.P * Pratio; |
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| 437 | |
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| 438 | # regularization functions |
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| 439 | zero_one = (1 + tanh(B * vsat))/2; |
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| 440 | one_zero = (1 - tanh(B * (vsat - 1)))/2; |
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| 441 | |
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| 442 | vfrac = zero_one * one_zero * vsat + 1 - one_zero; |
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| 443 | OutletL.z = zero_one*one_zero*xsat + (1-zero_one*one_zero)*Inlet.z; |
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| 444 | OutletV.z = zero_one*one_zero*ysat + (1-zero_one*one_zero)*Inlet.z; |
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| 445 | end |
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