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 | *-------------------------------------------------------------------- |
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16 | * Author: Gerson Balbueno Bicca |
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17 | * $Id: Heatex.mso 733 2009-02-26 22:25:45Z bicca $ |
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18 | *--------------------------------------------------------------------*# |
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19 | |
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20 | using "heat_exchangers/HEX_Engine"; |
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21 | |
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22 | Model Heatex_Basic |
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23 | |
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24 | ATTRIBUTES |
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25 | Pallete = false; |
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26 | Brief = "Basic Model for Simplified Heat Exchangers"; |
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27 | Info = |
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28 | "Model of a simplified heat exchanger. |
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29 | This model perform only material and heat balance. |
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30 | |
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31 | == Assumptions == |
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32 | * Steady-State operation; |
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33 | * No heat loss to the surroundings. |
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34 | |
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35 | == Specify == |
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36 | * The Inlet streams: Hot and Cold; |
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37 | "; |
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38 | |
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39 | PARAMETERS |
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40 | outer PP as Plugin (Brief="External Physical Properties", Type="PP"); |
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41 | outer NComp as Integer (Brief="Number of Components"); |
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42 | |
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43 | M(NComp) as molweight (Brief="Component Mol Weight",Hidden=true); |
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44 | |
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45 | VARIABLES |
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46 | |
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47 | in InletHot as stream (Brief="Inlet Hot Stream", PosX=0, PosY=0.508, Symbol="^{inHot}"); |
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48 | out OutletHot as streamPH (Brief="Outlet Hot Stream", PosX=1, PosY=0.508, Symbol="^{outHot}"); |
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49 | in InletCold as stream (Brief="Inlet Cold Stream", PosX=0.50, PosY=1, Symbol="^{inCold}"); |
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50 | out OutletCold as streamPH (Brief="Outlet Cold Stream", PosX=0.50, PosY=0, Symbol="^{outCold}"); |
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51 | |
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52 | A as area (Brief="Exchange Surface Area"); |
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53 | Q as power (Brief="Duty", Default=7000, Lower=1e-6, Upper=1e10); |
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54 | U as heat_trans_coeff (Brief="Overall Heat Transfer Coefficient",Default=1,Lower=1e-6,Upper=1e10); |
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55 | |
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56 | PdropHotSide as press_delta (Brief="Pressure Drop Hot Side",Default=0.01, Lower=0,DisplayUnit='kPa' , Symbol ="\Delta P_{hot}"); |
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57 | PdropColdSide as press_delta (Brief="Pressure Drop Cold Side",Default=0.01, Lower=0,DisplayUnit='kPa' , Symbol ="\Delta P_{cold}"); |
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58 | |
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59 | SET |
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60 | |
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61 | #"Component Molecular Weight" |
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62 | M = PP.MolecularWeight(); |
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63 | |
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64 | EQUATIONS |
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65 | |
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66 | "Energy Balance Hot Stream" |
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67 | Q = InletHot.F*(InletHot.h-OutletHot.h); |
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68 | |
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69 | "Energy Balance Cold Stream" |
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70 | Q =-InletCold.F*(InletCold.h-OutletCold.h); |
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71 | |
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72 | "Molar Balance Hot Stream" |
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73 | InletHot.F = OutletHot.F; |
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74 | |
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75 | "Molar Balance Cold Stream" |
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76 | InletCold.F = OutletCold.F; |
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77 | |
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78 | "Hot Stream Molar Fraction Constraint" |
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79 | OutletHot.z = InletHot.z; |
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80 | |
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81 | "Cold Stream Molar Fraction Constraint" |
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82 | OutletCold.z = InletCold.z; |
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83 | |
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84 | "Pressure Drop Hot Stream" |
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85 | OutletHot.P = InletHot.P - PdropHotSide; |
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86 | |
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87 | "Pressure Drop Cold Stream" |
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88 | OutletCold.P = InletCold.P - PdropColdSide; |
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89 | |
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90 | end |
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91 | |
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92 | Model Heatex_LMTD as Heatex_Basic |
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93 | |
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94 | ATTRIBUTES |
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95 | Pallete = true; |
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96 | Icon = "icon/Heatex"; |
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97 | Brief = "Simplified model for Heat Exchangers"; |
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98 | Info = |
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99 | "This model perform material and heat balance using the Log Mean Temperature Difference Approach. |
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100 | This shortcut calculation does not require exchanger configuration or geometry data. |
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101 | |
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102 | == Assumptions == |
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103 | * Steady-State operation; |
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104 | * No heat loss to the surroundings. |
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105 | |
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106 | == Specify == |
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107 | * The Inlet streams: Hot and Cold. |
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108 | |
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109 | == References == |
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110 | [1] E.A.D. Saunders, Heat Exchangers: Selection, Design and |
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111 | Construction, Longman, Harlow, 1988. |
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112 | |
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113 | [2] Taborek, J., Shell-and-tube heat exchangers, in Heat Exchanger Design Handbook, Vol. 3 |
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114 | Hemisphere Publishing Corp., New York, 1988. |
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115 | |
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116 | [3] Fakheri, A. , Alternative approach for determining log mean temperature difference correction factor |
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117 | and number of shells of shell and tube heat exchangers, Journal of Enhanced Heat Transfer, v. 10, p. 407- 420, 2003. |
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118 | "; |
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119 | |
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120 | PARAMETERS |
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121 | |
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122 | ExchangerType as Switcher (Brief="Type of Heat Exchanger",Valid=["Counter Flow","Cocurrent Flow", "Shell and Tube"],Default="Cocurrent Flow"); |
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123 | LMTDcorrection as Switcher (Brief="LMTD Correction Factor Model",Valid=["Bowmann","Fakheri"],Default="Bowmann"); |
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124 | |
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125 | VARIABLES |
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126 | |
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127 | Method as LMTD_Basic (Brief="LMTD Method of Calculation", Symbol =" "); |
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128 | R as positive (Brief="Capacity Ratio for LMTD Correction Fator",Lower=1e-6,Hidden=true); |
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129 | P as positive (Brief="Non - Dimensional Variable for LMTD Correction Fator ",Lower=1e-6,Hidden=true); |
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130 | Rho as positive (Brief="Non - Dimensional Variable for LMTD Correction Fator in Fakheri Equation",Lower=1e-6,Hidden=true); |
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131 | Phi as positive (Brief="Non - Dimensional Variable for LMTD Correction Fator in Fakheri Equation",Lower=1e-6, Symbol ="\phi",Hidden=true); |
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132 | |
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133 | EQUATIONS |
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134 | |
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135 | "Duty" |
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136 | Q = U*A*Method.LMTD*Method.Fc; |
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137 | |
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138 | switch ExchangerType |
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139 | |
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140 | case "Cocurrent Flow": |
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141 | |
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142 | "Temperature Difference at Inlet" |
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143 | Method.DT0 = InletHot.T - InletCold.T; |
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144 | |
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145 | "Temperature Difference at Outlet" |
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146 | Method.DTL = OutletHot.T - OutletCold.T; |
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147 | |
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148 | "R: Capacity Ratio for LMTD Correction Fator" |
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149 | R=1; |
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150 | |
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151 | "P: Non - Dimensional Variable for LMTD Correction Fator" |
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152 | P=1; |
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153 | |
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154 | " Variable useless with this model" |
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155 | Phi = 1; |
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156 | |
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157 | " Variable useless with this model" |
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158 | Rho = 1; |
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159 | |
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160 | "LMTD Correction Factor in Cocurrent Flow" |
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161 | Method.Fc = 1; |
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162 | |
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163 | case "Counter Flow": |
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164 | |
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165 | "Temperature Difference at Inlet" |
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166 | Method.DT0 = InletHot.T - OutletCold.T; |
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167 | |
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168 | "Temperature Difference at Outlet" |
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169 | Method.DTL = OutletHot.T - InletCold.T; |
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170 | |
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171 | "R: Capacity Ratio for LMTD Correction Fator" |
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172 | R=1; |
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173 | |
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174 | "P: Non - Dimensional Variable for LMTD Correction Fator" |
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175 | P=1; |
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176 | |
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177 | " Variable useless with this model" |
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178 | Phi = 1; |
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179 | |
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180 | " Variable useless with this model" |
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181 | Rho = 1; |
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182 | |
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183 | "LMTD Correction Factor in Counter Flow" |
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184 | Method.Fc = 1; |
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185 | |
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186 | case "Shell and Tube": |
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187 | |
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188 | "Temperature Difference at Inlet" |
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189 | Method.DT0 = InletHot.T - OutletCold.T; |
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190 | |
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191 | "Temperature Difference at Outlet" |
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192 | Method.DTL = OutletHot.T - InletCold.T; |
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193 | |
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194 | switch LMTDcorrection |
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195 | |
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196 | case "Bowmann": |
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197 | |
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198 | " Variable not in use with Bowmann equation" |
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199 | Phi = 1; |
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200 | |
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201 | " Variable not in use with Bowmann equation" |
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202 | Rho = 1; |
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203 | |
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204 | "R: Capacity Ratio for LMTD Correction Fator when Shell and Tube" |
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205 | R*(OutletCold.T - InletCold.T ) = (InletHot.T-OutletHot.T); |
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206 | |
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207 | "P: Non - Dimensional Variable for LMTD Correction Fator when Shell and Tube" |
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208 | P*(InletHot.T- InletCold.T)= (OutletCold.T-InletCold.T); |
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209 | |
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210 | if R equal 1 |
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211 | |
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212 | then |
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213 | |
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214 | "LMTD Correction Fator when 1 Pass Shell Side" |
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215 | Method.Fc = (sqrt(2)*P)/((1-P)*ln( abs( ( 2-P*0.585786)/( 2-P*3.414214)))); |
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216 | |
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217 | else |
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218 | |
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219 | "LMTD Correction Fator when 1 Pass Shell Side" |
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220 | Method.Fc = sqrt(R*R+1)*ln(abs((1-P*R)/(1-P)))/((1-R)*ln( abs( ( 2-P*(R+1-sqrt(R*R+1)))/ ( 2-P*(R + 1 + sqrt(R*R+1)))))); |
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221 | |
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222 | end |
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223 | |
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224 | case "Fakheri": |
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225 | |
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226 | "R: Capacity Ratio for LMTD Correction Fator when Shell and Tube" |
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227 | R*(OutletCold.T - InletCold.T ) = (InletHot.T-OutletHot.T); |
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228 | |
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229 | "P: Non - Dimensional Variable for LMTD Correction Fator when Shell and Tube" |
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230 | P*(InletHot.T- InletCold.T)= (OutletCold.T-InletCold.T); |
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231 | |
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232 | "Non Dimensional Variable for LMTD Correction Fator in Fakheri Equation " |
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233 | Phi = (sqrt(((InletHot.T- OutletHot.T)*(InletHot.T- OutletHot.T))+((OutletCold.T - InletCold.T)*(OutletCold.T - InletCold.T))))/(2*((InletHot.T+ OutletHot.T)-(InletCold.T+ OutletCold.T))); |
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234 | |
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235 | "Non Dimensional Variable for LMTD Correction Fator in Fakheri Equation" |
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236 | Rho*(1-P*R) = (1-P); |
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237 | |
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238 | if Rho equal 1 |
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239 | |
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240 | then |
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241 | |
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242 | "LMTD Correction Fator when 1 Pass Shell Side" |
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243 | Method.Fc = (4*Phi)/(ln(abs((1+2*Phi)/(1-2*Phi)))); |
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244 | |
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245 | else |
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246 | |
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247 | "LMTD Correction Fator when 1 Pass Shell Side" |
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248 | Method.Fc = (2*Phi*(Rho+1)*ln(abs(Rho)))/( ln(abs((1+2*Phi)/(1-2*Phi)))*(Rho-1)); |
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249 | |
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250 | end |
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251 | |
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252 | end |
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253 | |
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254 | end |
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255 | |
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256 | end |
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257 | |
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258 | Model Heatex_NTU as Heatex_Basic |
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259 | |
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260 | ATTRIBUTES |
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261 | Pallete = true; |
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262 | Icon = "icon/Heatex"; |
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263 | Brief = "Simplified model for Heat Exchangers"; |
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264 | Info = |
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265 | "This model perform material and heat balance using the NTU-Effectiveness Approach. |
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266 | This shortcut calculation does not require exchanger configuration or geometry data. |
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267 | |
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268 | == Assumptions == |
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269 | * Steady-State operation; |
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270 | * No heat loss to the surroundings. |
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271 | |
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272 | == Specify == |
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273 | * The Inlet streams: Hot and Cold. |
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274 | |
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275 | == References == |
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276 | [1] E.A.D. Saunders, Heat Exchangers: Selection, Design and |
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277 | Construction, Longman, Harlow, 1988. |
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278 | |
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279 | "; |
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280 | |
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281 | PARAMETERS |
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282 | |
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283 | ExchangerType as Switcher (Brief="Type of Heat Exchanger",Valid=["Counter Flow","Cocurrent Flow", "Shell and Tube"],Default="Cocurrent Flow"); |
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284 | |
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285 | VARIABLES |
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286 | |
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287 | Method as NTU_Basic (Brief="NTU Method of Calculation", Symbol =" "); |
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288 | |
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289 | xh(NComp) as fraction (Brief = "Liquid Molar Fraction in Hot Side",Hidden=true); |
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290 | yh(NComp) as fraction (Brief = "Vapour Molar Fraction in Hot Side",Hidden=true); |
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291 | vh as fraction (Brief = "Vapour Fraction in Hot Side",Hidden=true); |
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292 | |
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293 | xc(NComp) as fraction (Brief = "Liquid Molar Fraction in Cold Side",Hidden=true); |
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294 | yc(NComp) as fraction (Brief = "Vapour Molar Fraction in Cold Side",Hidden=true); |
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295 | vc as fraction (Brief = "Vapour Fraction in Cold Side",Hidden=true); |
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296 | |
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297 | EQUATIONS |
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298 | |
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299 | "Flash Calculation in Hot Side" |
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300 | [vh, xh, yh] = PP.Flash(InletHot.T, InletHot.P, InletHot.z); |
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301 | |
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302 | "Flash Calculation in Cold Side" |
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303 | [vc, xc, yc] = PP.Flash(InletCold.T, InletCold.P, InletCold.z); |
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304 | |
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305 | "Number of Units Transference" |
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306 | Method.NTU*Method.Cmin = U*A; |
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307 | |
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308 | "Minimum Heat Capacity" |
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309 | Method.Cmin = min([Method.Ch,Method.Cc]); |
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310 | |
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311 | "Maximum Heat Capacity" |
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312 | Method.Cmax = max([Method.Ch,Method.Cc]); |
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313 | |
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314 | "Thermal Capacity Ratio" |
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315 | Method.Cr = Method.Cmin/Method.Cmax; |
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316 | |
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317 | "Duty" |
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318 | Q = Method.Eft*Method.Cmin*(InletHot.T-InletCold.T); |
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319 | |
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320 | "Hot Stream Average Heat Capacity" |
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321 | Method.Ch = InletHot.F*((1-InletHot.v)*PP.LiquidCp(0.5*InletHot.T+0.5*OutletHot.T,0.5*InletHot.P+0.5*OutletHot.P,xh)+ |
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322 | InletHot.v*PP.VapourCp(0.5*InletHot.T+0.5*OutletHot.T,0.5*InletHot.P+0.5*OutletHot.P,yh)); |
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323 | |
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324 | "Cold Stream Average Heat Capacity" |
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325 | Method.Cc = InletCold.F*((1-InletCold.v)*PP.LiquidCp(0.5*InletCold.T+0.5*OutletCold.T,0.5*InletCold.P+0.5*OutletCold.P,xc)+ |
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326 | InletCold.v*PP.VapourCp(0.5*InletCold.T+0.5*OutletCold.T,0.5*InletCold.P+0.5*OutletCold.P,yc)); |
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327 | |
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328 | "Effectiveness Correction" |
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329 | Method.Eft1 = 1; |
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330 | |
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331 | if Method.Cr equal 0 |
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332 | |
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333 | then |
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334 | |
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335 | "Effectiveness" |
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336 | Method.Eft = 1-exp(-Method.NTU); |
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337 | |
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338 | else |
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339 | |
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340 | switch ExchangerType |
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341 | |
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342 | case "Cocurrent Flow": |
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343 | |
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344 | "Effectiveness in Cocurrent Flow" |
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345 | Method.Eft = (1-exp(-Method.NTU*(1+Method.Cr)))/(1+Method.Cr); |
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346 | |
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347 | case "Counter Flow": |
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348 | |
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349 | if Method.Cr equal 1 |
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350 | |
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351 | then |
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352 | "Effectiveness in Counter Flow" |
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353 | Method.Eft = Method.NTU/(1+Method.NTU); |
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354 | |
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355 | else |
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356 | "Effectiveness in Counter Flow" |
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357 | Method.Eft = (1-exp(-Method.NTU*(1-Method.Cr)))/(1-Method.Cr*exp(-Method.NTU*(1-Method.Cr))); |
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358 | |
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359 | end |
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360 | |
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361 | case "Shell and Tube": |
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362 | |
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363 | "TEMA E Shell Effectiveness" |
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364 | Method.Eft = 2*(1+Method.Cr+sqrt(1+Method.Cr^2)*((1+exp(-Method.NTU*sqrt(1+Method.Cr^2)))/(1-exp(-Method.NTU*sqrt(1+Method.Cr^2)))) )^(-1); |
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365 | |
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366 | end |
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367 | |
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368 | |
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369 | end |
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370 | |
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371 | end |
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