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 321 2007-07-20 14:30:53Z arge $ |
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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 | ATTRIBUTES |
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23 | Pallete = true; |
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24 | Icon = "icon/Flash"; |
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25 | Brief = "Model of a dynamic flash."; |
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26 | Info = |
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27 | "Assumptions: |
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28 | * both phases are perfectly mixed. |
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29 | |
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30 | Specify: |
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31 | * the feed stream; |
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32 | * the outlet flows: OutletV.F and OutletL.F. |
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33 | |
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34 | Initial Conditions: |
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35 | * the flash initial temperature (OutletL.T); |
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36 | * the flash initial level (Level); |
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37 | * (NoComps - 1) OutletL (OR OutletV) compositions. |
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38 | "; |
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39 | |
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40 | PARAMETERS |
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41 | outer PP as Plugin (Brief = "External Physical Properties", Type="PP"); |
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42 | outer NComp as Integer (Brief = "Number of chemical components", Lower = 1); |
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43 | V as volume (Brief="Total Volume of the flash"); |
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44 | Mw(NComp) as molweight; |
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45 | orientation as Switcher (Valid=["vertical","horizontal"],Default="vertical"); |
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46 | diameter as length (Brief="Vessel diameter"); |
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47 | |
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48 | SET |
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49 | Mw=PP.MolecularWeight(); |
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50 | |
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51 | VARIABLES |
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52 | in Inlet as stream(Brief="Feed Stream"); |
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53 | out OutletL as liquid_stream(Brief="Liquid outlet stream"); |
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54 | out OutletV as vapour_stream(Brief="Vapour outlet stream"); |
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55 | in InletQ as energy_stream (Brief="Rate of heat supply"); |
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56 | |
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57 | M(NComp) as mol (Brief="Molar Holdup in the tray"); |
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58 | ML as mol (Brief="Molar liquid holdup"); |
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59 | MV as mol (Brief="Molar vapour holdup"); |
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60 | E as energy (Brief="Total Energy Holdup on tray"); |
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61 | vL as volume_mol (Brief="Liquid Molar Volume"); |
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62 | vV as volume_mol (Brief="Vapour Molar volume"); |
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63 | Level as length (Brief="liquid height"); |
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64 | Across as area (Brief="Flash Cross section area"); |
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65 | |
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66 | EQUATIONS |
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67 | "Component Molar Balance" |
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68 | diff(M)=Inlet.F*Inlet.z - OutletL.F*OutletL.z - OutletV.F*OutletV.z; |
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69 | |
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70 | "Energy Balance" |
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71 | diff(E) = Inlet.F*Inlet.h - OutletL.F*OutletL.h - OutletV.F*OutletV.h + InletQ.Q; |
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72 | |
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73 | "Molar Holdup" |
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74 | M = ML*OutletL.z + MV*OutletV.z; |
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75 | |
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76 | "Energy Holdup" |
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77 | E = ML*OutletL.h + MV*OutletV.h - OutletL.P*V; |
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78 | |
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79 | "Mol fraction normalisation" |
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80 | sum(OutletL.z)=1.0; |
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81 | "Mol fraction normalisation" |
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82 | sum(OutletL.z)=sum(OutletV.z); |
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83 | |
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84 | "Liquid Volume" |
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85 | vL = PP.LiquidVolume(OutletL.T, OutletL.P, OutletL.z); |
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86 | "Vapour Volume" |
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87 | vV = PP.VapourVolume(OutletV.T, OutletV.P, OutletV.z); |
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88 | |
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89 | "Chemical Equilibrium" |
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90 | PP.LiquidFugacityCoefficient(OutletL.T, OutletL.P, OutletL.z)*OutletL.z = |
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91 | PP.VapourFugacityCoefficient(OutletV.T, OutletV.P, OutletV.z)*OutletV.z; |
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92 | |
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93 | "Thermal Equilibrium" |
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94 | OutletV.T = OutletL.T; |
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95 | |
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96 | "Mechanical Equilibrium" |
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97 | OutletV.P = OutletL.P; |
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98 | |
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99 | "Geometry Constraint" |
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100 | V = ML * vL + MV * vV; |
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101 | |
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102 | switch orientation |
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103 | case "vertical": |
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104 | "Cross Section Area" |
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105 | Across = 0.5 * asin(1) * diameter^2; |
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106 | |
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107 | "Liquid Level" |
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108 | ML * vL = Across * Level; |
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109 | |
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110 | case "horizontal": |
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111 | "Cylindrical Side Area" |
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112 | Across = 0.25*diameter^2 * (asin(1) - asin((diameter - 2*Level)/diameter)) + |
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113 | (Level - 0.5*diameter)*sqrt(Level*(diameter - Level)); |
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114 | |
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115 | "Liquid Level" |
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116 | 0.5 * asin(1) * diameter^2 * ML* vL = Across * V; |
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117 | end |
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118 | end |
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119 | |
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120 | #*---------------------------------------------------------------------- |
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121 | * Model of a Steady State flash |
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122 | *---------------------------------------------------------------------*# |
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123 | Model flash_steady |
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124 | ATTRIBUTES |
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125 | Pallete = true; |
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126 | Icon = "icon/Flash"; |
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127 | Brief = "Model of a Steady State flash."; |
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128 | Info = |
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129 | "Assumptions: |
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130 | * both phases are perfectly mixed. |
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131 | |
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132 | Specify: |
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133 | * the feed stream; |
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134 | * the outlet pressure (OutletV.P); |
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135 | * the outlet temperature OR the heat supplied. |
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136 | "; |
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137 | |
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138 | PARAMETERS |
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139 | outer PP as Plugin(Brief = "External Physical Properties", Type="PP"); |
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140 | |
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141 | VARIABLES |
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142 | in Inlet as stream(Brief="Feed Stream"); |
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143 | out OutletL as liquid_stream(Brief="Liquid outlet stream"); |
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144 | out OutletV as vapour_stream(Brief="Vapour outlet stream"); |
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145 | in InletQ as energy_stream (Brief="Rate of heat supply"); |
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146 | vfrac as fraction; |
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147 | |
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148 | EQUATIONS |
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149 | "The flash calculation" |
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150 | [vfrac, OutletL.z, OutletV.z] = PP.Flash(OutletV.T, OutletV.P, Inlet.z); |
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151 | |
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152 | "Global Molar Balance" |
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153 | Inlet.F = OutletV.F + OutletL.F; |
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154 | "Vaporisation Fraction" |
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155 | OutletV.F = Inlet.F * vfrac; |
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156 | |
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157 | "Energy Balance" |
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158 | Inlet.F*Inlet.h + InletQ.Q = OutletL.F*OutletL.h + OutletV.F*OutletV.h; |
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159 | |
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160 | "Thermal Equilibrium" |
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161 | OutletV.T = OutletL.T; |
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162 | |
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163 | "Mechanical Equilibrium" |
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164 | OutletV.P = OutletL.P; |
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165 | end |
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166 | |
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167 | #*---------------------------------------------------------------------- |
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168 | * Model of a steady-state PH flash. |
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169 | *---------------------------------------------------------------------*# |
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170 | Model FlashPHSteady |
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171 | ATTRIBUTES |
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172 | Pallete = true; |
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173 | Icon = "icon/Flash"; |
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174 | Brief = "Model of a static PH flash."; |
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175 | Info = " |
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176 | This model is for using the flashPH |
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177 | routine available on VRTherm. |
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178 | |
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179 | Assumptions: |
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180 | * perfect mixing of both phases; |
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181 | |
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182 | Specify: |
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183 | * the feed stream; |
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184 | * the heat duty; |
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185 | * the outlet pressure. |
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186 | "; |
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187 | |
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188 | PARAMETERS |
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189 | outer PP as Plugin(Brief = "External Physical Properties", Type="PP"); |
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190 | outer NComp as Integer; |
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191 | |
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192 | VARIABLES |
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193 | in Inlet as stream (Brief="Feed Stream"); |
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194 | out OutletL as liquid_stream (Brief="Liquid outlet stream"); |
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195 | out OutletV as vapour_stream (Brief="Vapour outlet stream"); |
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196 | in InletQ as energy_stream (Brief="Rate of heat supply"); |
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197 | vfrac as fraction(Brief="Real vaporization fraction"); |
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198 | h as enth_mol(Brief="Mixture enthalpy"); |
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199 | |
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200 | EQUATIONS |
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201 | |
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202 | "Chemical equilibrium" |
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203 | [vfrac,OutletL.z,OutletV.z]=PP.FlashPH(OutletL.P,h,Inlet.z); |
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204 | |
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205 | "Global Molar Balance" |
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206 | Inlet.F = OutletV.F + OutletL.F; |
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207 | OutletV.F = Inlet.F * vfrac; |
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208 | |
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209 | "Energy Balance" |
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210 | Inlet.F*(h - Inlet.h) = InletQ.Q; |
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211 | Inlet.F*h = Inlet.F*(1-vfrac)*OutletL.h + Inlet.F*vfrac*OutletV.h; |
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212 | |
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213 | "Thermal Equilibrium" |
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214 | OutletV.T = OutletL.T; |
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215 | |
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216 | "Mechanical Equilibrium" |
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217 | OutletV.P = OutletL.P; |
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218 | end |
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219 | |
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220 | #*---------------------------------------------------------------------- |
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221 | * Another model of a steady-state PH flash. |
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222 | * It is recommended to use [v,x,y]=PP.FlashPH(P,h,z) instead of. |
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223 | *---------------------------------------------------------------------*# |
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224 | Model FlashPHSteadyA |
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225 | ATTRIBUTES |
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226 | Pallete = true; |
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227 | Icon = "icon/Flash"; |
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228 | Brief = "Another model of a static PH flash."; |
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229 | Info = " |
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230 | This model shows how to model a pressure enthalpy flash |
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231 | directly with the EMSO modeling language. |
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232 | |
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233 | This model is for demonstration purposes only, the flashPH |
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234 | routine available on VRTherm is much more robust. |
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235 | |
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236 | Assumptions: |
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237 | * perfect mixing of both phases; |
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238 | |
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239 | Specify: |
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240 | * the feed stream; |
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241 | * the heat duty; |
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242 | * the outlet pressure. |
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243 | "; |
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244 | |
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245 | PARAMETERS |
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246 | outer PP as Plugin(Brief = "External Physical Properties", Type="PP"); |
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247 | outer NComp as Integer; |
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248 | B as Real(Default=1000, Brief="Regularization Factor"); |
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249 | |
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250 | VARIABLES |
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251 | in Inlet as stream (Brief="Feed Stream"); |
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252 | out OutletL as liquid_stream (Brief="Liquid outlet stream"); |
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253 | out OutletV as vapour_stream (Brief="Vapour outlet stream"); |
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254 | in InletQ as energy_stream (Brief="Rate of heat supply"); |
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255 | vfrac as fraction(Brief="Real vaporization fraction"); |
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256 | vsat as Real(Lower=-0.1, Upper=1.1, Brief="Vaporization fraction if saturated"); |
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257 | Tsat as temperature(Lower=173, Upper=1473, Brief="Temperature if saturated"); |
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258 | xsat(NComp) as Real(Lower=0, Upper=1, Brief="Liquid composition if saturated"); |
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259 | ysat(NComp) as Real(Lower=0, Upper=1, Brief="Vapour composition if saturated"); |
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260 | |
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261 | zero_one as fraction(Brief="Regularization Variable"); |
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262 | one_zero as fraction(Brief="Regularization Variable"); |
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263 | |
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264 | EQUATIONS |
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265 | "Chemical equilibrium" |
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266 | PP.LiquidFugacityCoefficient(Tsat, OutletL.P, xsat)*xsat = |
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267 | PP.VapourFugacityCoefficient(Tsat, OutletV.P, ysat)*ysat; |
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268 | |
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269 | "Global Molar Balance" |
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270 | Inlet.F = OutletV.F + OutletL.F; |
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271 | OutletV.F = Inlet.F * vfrac; |
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272 | |
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273 | "Component Molar Balance" |
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274 | Inlet.F*Inlet.z = OutletL.F*xsat + OutletV.F*ysat; |
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275 | sum(xsat) = sum(ysat); |
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276 | |
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277 | "Energy Balance if saturated" |
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278 | Inlet.F*Inlet.h + InletQ.Q = |
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279 | Inlet.F*(1-vsat)*PP.LiquidEnthalpy(Tsat, OutletL.P, xsat) + |
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280 | Inlet.F*vsat*PP.VapourEnthalpy(Tsat, OutletV.P, ysat); |
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281 | |
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282 | "Real Energy Balance" |
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283 | Inlet.F*Inlet.h + InletQ.Q = |
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284 | Inlet.F*(1-vfrac)*OutletL.h + Inlet.F*vfrac*OutletV.h; |
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285 | |
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286 | "Thermal Equilibrium" |
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287 | OutletV.T = OutletL.T; |
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288 | |
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289 | "Mechanical Equilibrium" |
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290 | OutletV.P = OutletL.P; |
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291 | |
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292 | # regularization functions |
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293 | zero_one = (1 + tanh(B * vsat))/2; |
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294 | one_zero = (1 - tanh(B * (vsat - 1)))/2; |
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295 | |
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296 | vfrac = zero_one * one_zero * vsat + 1 - one_zero; |
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297 | OutletL.z = zero_one*one_zero*xsat + (1-zero_one*one_zero)*Inlet.z; |
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298 | OutletV.z = zero_one*one_zero*ysat + (1-zero_one*one_zero)*Inlet.z; |
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299 | end |
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