| 1 | #*------------------------------------------------------------------- |
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| 2 | * Model of a dynamic flash |
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| 3 | *-------------------------------------------------------------------- |
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| 4 | * - Streams |
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| 5 | * * a liquid outlet stream |
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| 6 | * * a vapour outlet stream |
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| 7 | * * a feed stream |
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| 8 | * |
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| 9 | * - Assumptions |
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| 10 | * * both phases are perfectly mixed |
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| 11 | * |
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| 12 | * - Specify: |
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| 13 | * * the feed stream; |
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| 14 | * * the outlet flows: OutletV.F and OutletL.F |
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| 15 | * |
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| 16 | * - Initial: |
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| 17 | * * the flash initial temperature (OutletL.T) |
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| 18 | * * the flash initial liquid level (Ll) |
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| 19 | * * (NoComps - 1) OutletL (OR OutletV) compositions |
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| 20 | *---------------------------------------------------------------------- |
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| 21 | * Author: Paula B. Staudt |
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| 22 | * $Id: flash.mso 55 2006-11-12 20:27:35Z arge $ |
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| 23 | *--------------------------------------------------------------------*# |
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| 24 | |
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| 25 | using "streams"; |
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| 26 | |
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| 27 | Model flash |
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| 28 | PARAMETERS |
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| 29 | ext PP as CalcObject; |
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| 30 | ext NComp as Integer; |
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| 31 | V as volume(Brief="Total Volume of the flash"); |
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| 32 | Mw(NComp) as molweight; |
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| 33 | Across as area (Brief="Flash Cross section area"); |
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| 34 | |
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| 35 | SET |
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| 36 | Mw=PP.MolecularWeight(); |
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| 37 | |
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| 38 | VARIABLES |
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| 39 | in Inlet as stream; #(Brief="Feed Stream"); |
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| 40 | out OutletL as stream_therm; #(Brief="Liquid outlet stream"); |
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| 41 | out OutletV as stream_therm; #(Brief="Vapour outlet stream"); |
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| 42 | in Q as heat_rate (Brief="Rate of heat supply"); |
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| 43 | |
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| 44 | M(NComp) as mol (Brief="Molar Holdup in the tray"); |
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| 45 | ML as mol (Brief="Molar liquid holdup"); |
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| 46 | MV as mol (Brief="Molar vapour holdup"); |
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| 47 | E as energy (Brief="Total Energy Holdup on tray"); |
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| 48 | vL as volume_mol (Brief="Liquid Molar Volume"); |
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| 49 | vV as volume_mol (Brief="Vapour Molar volume"); |
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| 50 | Level as length (Brief="liquid height"); |
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| 51 | |
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| 52 | EQUATIONS |
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| 53 | "Component Molar Balance" |
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| 54 | diff(M)=Inlet.F*Inlet.z - OutletL.F*OutletL.z - OutletV.F*OutletV.z; |
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| 55 | |
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| 56 | "Energy Balance" |
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| 57 | diff(E) = Inlet.F*Inlet.h - OutletL.F*OutletL.h - OutletV.F*OutletV.h + Q; |
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| 58 | |
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| 59 | "Molar Holdup" |
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| 60 | M = ML*OutletL.z + MV*OutletV.z; |
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| 61 | |
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| 62 | "Energy Holdup" |
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| 63 | E = ML*OutletL.h + MV*OutletV.h - OutletL.P*V; |
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| 64 | |
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| 65 | "Mol fraction normalisation" |
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| 66 | sum(OutletL.z)=1.0; |
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| 67 | "Mol fraction normalisation" |
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| 68 | sum(OutletL.z)=sum(OutletV.z); |
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| 69 | |
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| 70 | "Liquid Volume" |
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| 71 | vL = PP.LiquidVolume(OutletL.T, OutletL.P, OutletL.z); |
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| 72 | "Vapour Volume" |
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| 73 | vV = PP.VapourVolume(OutletV.T, OutletV.P, OutletV.z); |
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| 74 | |
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| 75 | "Chemical Equilibrium" |
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| 76 | PP.LiquidFugacityCoefficient(OutletL.T, OutletL.P, OutletL.z)*OutletL.z = |
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| 77 | PP.VapourFugacityCoefficient(OutletV.T, OutletV.P, OutletV.z)*OutletV.z; |
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| 78 | |
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| 79 | "Thermal Equilibrium" |
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| 80 | OutletV.T = OutletL.T; |
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| 81 | |
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| 82 | "Mechanical Equilibrium" |
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| 83 | OutletV.P = OutletL.P; |
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| 84 | |
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| 85 | "Geometry Constraint" |
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| 86 | V = ML* vL + MV*vV; |
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| 87 | "Liquid Level" |
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| 88 | ML* vL = Across * Level; |
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| 89 | |
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| 90 | "vaporization fraction " |
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| 91 | OutletV.v = 1.0; |
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| 92 | "vaporization fraction " |
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| 93 | OutletL.v = 0.0; |
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| 94 | |
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| 95 | end |
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| 96 | |
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| 97 | #*---------------------------------------------------------------------- |
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| 98 | * Model of a Steady State flash |
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| 99 | *---------------------------------------------------------------------*# |
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| 100 | Model flash_Steady |
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| 101 | PARAMETERS |
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| 102 | ext PP as CalcObject; |
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| 103 | ext NComp as Integer; |
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| 104 | |
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| 105 | VARIABLES |
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| 106 | in Inlet as stream; #(Brief="Feed Stream"); |
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| 107 | out OutletL as stream_therm; #(Brief="Liquid outlet stream"); |
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| 108 | out OutletV as stream_therm; #(Brief="Vapour outlet stream"); |
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| 109 | in Q as heat_rate (Brief="Rate of heat supply"); |
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| 110 | vfrac as fraction; |
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| 111 | |
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| 112 | EQUATIONS |
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| 113 | "The flash calculation" |
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| 114 | [vfrac, OutletL.z, OutletV.z] = PP.Flash(OutletV.T, OutletV.P, Inlet.z); |
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| 115 | |
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| 116 | "Global Molar Balance" |
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| 117 | Inlet.F = OutletV.F + OutletL.F; |
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| 118 | OutletV.F = Inlet.F * vfrac; |
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| 119 | |
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| 120 | "Energy Balance" |
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| 121 | Inlet.F*Inlet.h + Q = OutletL.F*OutletL.h + OutletV.F*OutletV.h; |
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| 122 | |
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| 123 | "Thermal Equilibrium" |
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| 124 | OutletV.T = OutletL.T; |
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| 125 | |
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| 126 | "Mechanical Equilibrium" |
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| 127 | OutletV.P = OutletL.P; |
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| 128 | |
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| 129 | "vaporization fraction " |
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| 130 | OutletV.v = 1.0; |
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| 131 | "vaporization fraction " |
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| 132 | OutletL.v = 0.0; |
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| 133 | end |
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| 134 | |
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