| 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 714 2009-02-16 20:23:57Z bicca $ |
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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."; |
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| 27 | Info = |
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| 28 | "== Assumptions == |
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| 29 | * Both phases are perfectly mixed. |
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| 30 | |
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| 31 | == Specify == |
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| 32 | * The feed stream; |
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| 33 | * The outlet flows: OutletVapour.F and OutletLiquid.F. |
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| 34 | |
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| 35 | == Initial Conditions == |
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| 36 | * The flash initial temperature (Temperature_Initial); |
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| 37 | * The flash initial level (Levelpercent_Initial); |
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| 38 | *The Outlet Liquid Composition (Composition_Initial). |
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| 39 | "; |
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| 40 | |
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| 41 | PARAMETERS |
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| 42 | |
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| 43 | outer PP as Plugin (Brief = "External Physical Properties", Type="PP"); |
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| 44 | outer NComp as Integer (Brief = "Number of chemical components", Lower = 1); |
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| 45 | |
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| 46 | VesselVolume as volume (Brief="Total Volume of the flash"); |
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| 47 | Mw(NComp) as molweight (Hidden=true); |
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| 48 | Orientation as Switcher (Valid=["vertical","horizontal"],Default="vertical"); |
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| 49 | Diameter as length (Brief="Vessel diameter"); |
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| 50 | |
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| 51 | Levelpercent_Initial as positive (Brief="Initial liquid height in Percent", Default = 0.70); |
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| 52 | Temperature_Initial as temperature (Brief="Initial Liquid Temperature", Default = 330); |
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| 53 | Composition_Initial(NComp) as fraction (Brief="Initial Composition", Default = 0.10); |
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| 54 | |
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| 55 | SET |
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| 56 | |
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| 57 | Mw=PP.MolecularWeight(); |
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| 58 | |
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| 59 | VARIABLES |
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| 60 | |
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| 61 | in Inlet as stream (Brief="Feed Stream", PosX=0, PosY=0.5421, Symbol="_{in}"); |
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| 62 | out OutletLiquid as liquid_stream (Brief="Liquid outlet stream", PosX=0.4790, PosY=1, Symbol="_{outL}"); |
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| 63 | out OutletVapour as vapour_stream (Brief="Vapour outlet stream", PosX=0.4877, PosY=0, Symbol="_{outV}"); |
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| 64 | in InletQ as power (Brief="Rate of heat supply", PosX=1, PosY=0.7559, Protected =true,Symbol="_{in}"); |
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| 65 | |
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| 66 | TotalHoldup(NComp) as mol (Brief="Molar Holdup in the Vessel", Protected=true); |
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| 67 | LiquidHoldup as mol (Brief="Molar liquid holdup", Protected=true); |
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| 68 | VapourHoldup as mol (Brief="Molar vapour holdup", Protected=true); |
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| 69 | |
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| 70 | E as energy (Brief="Total Energy Holdup in the Vessel", Protected=true); |
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| 71 | vL as volume_mol (Brief="Liquid Molar Volume", Protected=true); |
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| 72 | vV as volume_mol (Brief="Vapour Molar volume", Protected=true); |
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| 73 | Level as length (Brief="liquid height", Protected=true); |
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| 74 | Across as area (Brief="Flash Cross section area", Protected=true); |
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| 75 | vfrac as positive (Brief="Vapourization fraction", Symbol="\phi", Protected=true); |
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| 76 | Pratio as positive (Brief = "Pressure Ratio", Symbol ="P_{ratio}", Protected=true); |
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| 77 | Pdrop as press_delta (Brief = "Pressure Drop", DisplayUnit = 'kPa', Symbol ="\Delta P", Protected=true); |
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| 78 | |
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| 79 | out TI as control_signal (Brief="Temperature Indicator", PosX=1, PosY=0.2, Protected=true); |
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| 80 | out PI as control_signal (Brief="Pressure Indicator", PosX=1, PosY=0.3, Protected=true); |
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| 81 | out LI as control_signal (Brief="Level Indicator", PosX=1, PosY=0.4, Protected=true); |
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| 82 | |
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| 83 | INITIAL |
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| 84 | |
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| 85 | # Initial level Percent |
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| 86 | LI = Levelpercent_Initial; |
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| 87 | |
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| 88 | # Initial Outlet Liquid Temperature |
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| 89 | OutletLiquid.T = Temperature_Initial; |
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| 90 | |
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| 91 | # Initial Outlet Liquid Composition Normalized |
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| 92 | OutletLiquid.z(1:NComp - 1) = Composition_Initial(1:NComp - 1)/sum(Composition_Initial); |
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| 93 | |
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| 94 | EQUATIONS |
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| 95 | |
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| 96 | "Component Molar Balance" |
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| 97 | diff(TotalHoldup)=Inlet.F*Inlet.z - OutletLiquid.F*OutletLiquid.z - OutletVapour.F*OutletVapour.z; |
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| 98 | |
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| 99 | "Energy Balance" |
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| 100 | diff(E) = Inlet.F*Inlet.h - OutletLiquid.F*OutletLiquid.h - OutletVapour.F*OutletVapour.h + InletQ; |
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| 101 | |
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| 102 | "Molar Holdup" |
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| 103 | TotalHoldup = LiquidHoldup*OutletLiquid.z + VapourHoldup*OutletVapour.z; |
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| 104 | |
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| 105 | "Energy Holdup" |
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| 106 | E = LiquidHoldup*OutletLiquid.h + VapourHoldup*OutletVapour.h - OutletLiquid.P*VesselVolume; |
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| 107 | |
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| 108 | "Mol fraction normalisation" |
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| 109 | sum(OutletLiquid.z)=1.0; |
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| 110 | |
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| 111 | "Mol fraction normalisation" |
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| 112 | sum(OutletLiquid.z)=sum(OutletVapour.z); |
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| 113 | |
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| 114 | "Vaporization Fraction" |
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| 115 | OutletVapour.F = Inlet.F * vfrac; |
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| 116 | |
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| 117 | "Liquid Volume" |
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| 118 | vL = PP.LiquidVolume(OutletLiquid.T, OutletLiquid.P, OutletLiquid.z); |
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| 119 | |
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| 120 | "Vapour Volume" |
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| 121 | vV = PP.VapourVolume(OutletVapour.T, OutletVapour.P, OutletVapour.z); |
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| 122 | |
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| 123 | "Chemical Equilibrium" |
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| 124 | PP.LiquidFugacityCoefficient(OutletLiquid.T, OutletLiquid.P, OutletLiquid.z)*OutletLiquid.z = |
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| 125 | PP.VapourFugacityCoefficient(OutletVapour.T, OutletVapour.P, OutletVapour.z)*OutletVapour.z; |
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| 126 | |
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| 127 | "Thermal Equilibrium" |
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| 128 | OutletVapour.T = OutletLiquid.T; |
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| 129 | |
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| 130 | "Mechanical Equilibrium" |
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| 131 | OutletVapour.P = OutletLiquid.P; |
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| 132 | |
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| 133 | "Pressure Drop" |
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| 134 | OutletLiquid.P = Inlet.P - Pdrop; |
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| 135 | |
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| 136 | "Pressure Ratio" |
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| 137 | OutletLiquid.P = Inlet.P * Pratio; |
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| 138 | |
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| 139 | "Geometry Constraint" |
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| 140 | VesselVolume = LiquidHoldup * vL + VapourHoldup * vV; |
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| 141 | |
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| 142 | "Temperature indicator in Celsius Degree" |
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| 143 | TI * 'K' = OutletLiquid.T - 273.15*'K'; |
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| 144 | |
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| 145 | "Pressure indicator" |
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| 146 | PI * 'atm' = OutletLiquid.P; |
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| 147 | |
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| 148 | "Level indicator" |
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| 149 | LI*VesselVolume= Level*Across; |
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| 150 | |
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| 151 | switch Orientation |
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| 152 | case "vertical": |
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| 153 | "Cross Section Area" |
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| 154 | Across = 0.5 * asin(1) * Diameter^2; |
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| 155 | |
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| 156 | "Liquid Level" |
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| 157 | LiquidHoldup * vL = Across * Level; |
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| 158 | |
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| 159 | case "horizontal": |
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| 160 | "Cylindrical Side Area" |
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| 161 | Across = 0.25*Diameter^2 * (asin(1) - asin((Diameter - 2*Level)/Diameter)) + |
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| 162 | (Level - 0.5*Diameter)*sqrt(Level*(Diameter - Level)); |
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| 163 | |
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| 164 | "Liquid Level" |
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| 165 | 0.5 * asin(1) * Diameter^2 * LiquidHoldup* vL = Across * VesselVolume; |
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| 166 | end |
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| 167 | |
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| 168 | end |
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| 169 | |
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| 170 | #*---------------------------------------------------------------------- |
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| 171 | * Model of a steady-state flash. |
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| 172 | *---------------------------------------------------------------------*# |
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| 173 | Model flash_steady |
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| 174 | |
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| 175 | ATTRIBUTES |
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| 176 | Pallete = true; |
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| 177 | Icon = "icon/Flash"; |
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| 178 | Brief = "Model of a static PH flash."; |
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| 179 | Info = |
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| 180 | "This model is for using the flashPH routine available on VRTherm. |
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| 181 | |
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| 182 | == Assumptions == |
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| 183 | * perfect mixing of both phases; |
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| 184 | |
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| 185 | == Specify == |
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| 186 | * The feed stream; |
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| 187 | * The heat duty; |
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| 188 | * The outlet pressure. |
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| 189 | "; |
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| 190 | |
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| 191 | PARAMETERS |
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| 192 | |
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| 193 | outer PP as Plugin(Brief = "External Physical Properties", Type="PP"); |
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| 194 | outer NComp as Integer; |
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| 195 | |
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| 196 | VARIABLES |
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| 197 | |
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| 198 | in Inlet as stream (Brief="Feed Stream", PosX=0, PosY=0.5421, Symbol="_{in}"); |
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| 199 | out OutletLiquid as liquid_stream (Brief="Liquid outlet stream", PosX=0.4790, PosY=1, Symbol="_{outL}"); |
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| 200 | out OutletVapour as vapour_stream (Brief="Vapour outlet stream", PosX=0.4877, PosY=0, Symbol="_{outV}"); |
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| 201 | in InletQ as power (Brief="Rate of heat supply", PosX=1, PosY=0.7559, Symbol="_{in}"); |
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| 202 | |
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| 203 | vfrac as fraction (Brief="Vaporization fraction", Symbol="\phi"); |
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| 204 | h as enth_mol (Brief="Mixture enthalpy"); |
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| 205 | Pratio as positive (Brief = "Pressure Ratio", Symbol ="P_{ratio}"); |
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| 206 | Pdrop as press_delta (Brief = "Pressure Drop", DisplayUnit = 'kPa', Symbol ="\Delta P"); |
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| 207 | |
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| 208 | EQUATIONS |
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| 209 | |
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| 210 | if vfrac > 0 and vfrac <1 |
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| 211 | |
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| 212 | then |
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| 213 | "The flash calculation" |
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| 214 | [vfrac, OutletLiquid.z, OutletVapour.z] = PP.Flash(OutletVapour.T, OutletVapour.P, Inlet.z); |
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| 215 | |
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| 216 | else |
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| 217 | "Chemical equilibrium" |
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| 218 | [vfrac,OutletLiquid.z,OutletVapour.z]=PP.FlashPH(OutletLiquid.P,h,Inlet.z); |
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| 219 | |
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| 220 | end |
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| 221 | |
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| 222 | "Global Molar Balance" |
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| 223 | Inlet.F = OutletVapour.F + OutletLiquid.F; |
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| 224 | |
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| 225 | "Vapour Fraction" |
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| 226 | OutletVapour.F = Inlet.F * vfrac; |
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| 227 | |
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| 228 | "Energy Balance" |
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| 229 | Inlet.F*(h - Inlet.h) = InletQ; |
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| 230 | Inlet.F*h = Inlet.F*(1-vfrac)*OutletLiquid.h + Inlet.F*vfrac*OutletVapour.h; |
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| 231 | |
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| 232 | "Thermal Equilibrium" |
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| 233 | OutletVapour.T = OutletLiquid.T; |
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| 234 | |
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| 235 | "Mechanical Equilibrium" |
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| 236 | OutletVapour.P = OutletLiquid.P; |
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| 237 | |
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| 238 | "Pressure Drop" |
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| 239 | OutletLiquid.P = Inlet.P - Pdrop; |
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| 240 | |
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| 241 | "Pressure Ratio" |
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| 242 | OutletLiquid.P = Inlet.P * Pratio; |
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| 243 | |
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| 244 | end |
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| 245 | |
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| 246 | #*---------------------------------------------------------------------- |
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| 247 | * Another model of a steady-state PH flash. |
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| 248 | * It is recommended to use [v,x,y]=PP.FlashPH(P,h,z) instead of. |
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| 249 | *---------------------------------------------------------------------*# |
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| 250 | Model FlashPHSteady |
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| 251 | ATTRIBUTES |
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| 252 | Pallete = true; |
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| 253 | Icon = "icon/Flash"; |
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| 254 | Brief = "Another model of a static PH flash."; |
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| 255 | Info = |
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| 256 | "This model shows how to model a pressure enthalpy flash |
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| 257 | directly with the EMSO modeling language. |
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| 258 | |
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| 259 | This model is for demonstration purposes only, the flashPH |
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| 260 | routine available on VRTherm is much more robust. |
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| 261 | |
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| 262 | == Assumptions == |
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| 263 | * perfect mixing of both phases; |
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| 264 | |
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| 265 | == Specify == |
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| 266 | * the feed stream; |
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| 267 | * the heat duty; |
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| 268 | * the outlet pressure. |
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| 269 | "; |
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| 270 | |
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| 271 | PARAMETERS |
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| 272 | outer PP as Plugin(Brief = "External Physical Properties", Type="PP"); |
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| 273 | outer NComp as Integer; |
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| 274 | B as Real(Default=1000, Brief="Regularization Factor"); |
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| 275 | |
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| 276 | VARIABLES |
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| 277 | in Inlet as stream(Brief="Feed Stream", PosX=0, PosY=0.5421, Symbol="_{in}"); |
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| 278 | out OutletL as liquid_stream(Brief="Liquid outlet stream", PosX=0.4790, PosY=1, Symbol="_{outL}"); |
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| 279 | out OutletV as vapour_stream(Brief="Vapour outlet stream", PosX=0.4877, PosY=0, Symbol="_{outV}"); |
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| 280 | in InletQ as power (Brief="Rate of heat supply", PosX=1, PosY=0.7559, Symbol="_{in}"); |
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| 281 | vfrac as fraction(Brief="Vaporization fraction", Symbol="\phi"); |
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| 282 | vsat as Real(Lower=-0.1, Upper=1.1, Brief="Vaporization fraction if saturated", Symbol="\phi_{sat}"); |
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| 283 | Tsat as temperature(Lower=173, Upper=1473, Brief="Temperature if saturated"); |
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| 284 | xsat(NComp) as Real(Lower=0, Upper=1, Brief="Liquid composition if saturated"); |
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| 285 | ysat(NComp) as Real(Lower=0, Upper=1, Brief="Vapour composition if saturated"); |
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| 286 | Pratio as positive (Brief = "Pressure Ratio", Symbol ="P_{ratio}"); |
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| 287 | Pdrop as press_delta (Brief = "Pressure Drop", DisplayUnit = 'kPa', Symbol ="\Delta P"); |
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| 288 | |
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| 289 | zero_one as fraction(Brief="Regularization Variable"); |
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| 290 | one_zero as fraction(Brief="Regularization Variable"); |
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| 291 | |
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| 292 | EQUATIONS |
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| 293 | "Chemical equilibrium" |
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| 294 | PP.LiquidFugacityCoefficient(Tsat, OutletL.P, xsat)*xsat = |
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| 295 | PP.VapourFugacityCoefficient(Tsat, OutletV.P, ysat)*ysat; |
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| 296 | |
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| 297 | "Global Molar Balance" |
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| 298 | Inlet.F = OutletV.F + OutletL.F; |
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| 299 | OutletV.F = Inlet.F * vfrac; |
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| 300 | |
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| 301 | "Component Molar Balance" |
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| 302 | Inlet.F*Inlet.z = OutletL.F*xsat + OutletV.F*ysat; |
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| 303 | sum(xsat) = sum(ysat); |
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| 304 | |
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| 305 | "Energy Balance if saturated" |
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| 306 | Inlet.F*Inlet.h + InletQ = |
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| 307 | Inlet.F*(1-vsat)*PP.LiquidEnthalpy(Tsat, OutletL.P, xsat) + |
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| 308 | Inlet.F*vsat*PP.VapourEnthalpy(Tsat, OutletV.P, ysat); |
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| 309 | |
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| 310 | "Real Energy Balance" |
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| 311 | Inlet.F*Inlet.h + InletQ = |
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| 312 | Inlet.F*(1-vfrac)*OutletL.h + Inlet.F*vfrac*OutletV.h; |
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| 313 | |
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| 314 | "Thermal Equilibrium" |
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| 315 | OutletV.T = OutletL.T; |
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| 316 | |
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| 317 | "Mechanical Equilibrium" |
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| 318 | OutletV.P = OutletL.P; |
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| 319 | |
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| 320 | "Pressure Drop" |
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| 321 | OutletL.P = Inlet.P - Pdrop; |
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| 322 | |
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| 323 | "Pressure Ratio" |
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| 324 | OutletL.P = Inlet.P * Pratio; |
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| 325 | |
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| 326 | # regularization functions |
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| 327 | zero_one = (1 + tanh(B * vsat))/2; |
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| 328 | one_zero = (1 - tanh(B * (vsat - 1)))/2; |
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| 329 | |
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| 330 | vfrac = zero_one * one_zero * vsat + 1 - one_zero; |
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| 331 | OutletL.z = zero_one*one_zero*xsat + (1-zero_one*one_zero)*Inlet.z; |
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| 332 | OutletV.z = zero_one*one_zero*ysat + (1-zero_one*one_zero)*Inlet.z; |
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| 333 | end |
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