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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