| 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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