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