source: mso/eml/heat_exchangers/DoublePipe.mso @ 110

Last change on this file since 110 was 110, checked in by gerson bicca, 15 years ago

modified some equations

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1#*-------------------------------------------------------------------
2* EMSO Model Library (EML) Copyright (C) 2004 - 2007 ALSOC.
3*
4* This LIBRARY is free software; you can distribute it and/or modify
5* it under the therms of the ALSOC FREE LICENSE as available at
6* http://www.enq.ufrgs.br/alsoc.
7*
8* EMSO Copyright (C) 2004 - 2007 ALSOC, original code
9* from http://www.rps.eng.br Copyright (C) 2002-2004.
10* All rights reserved.
11*
12* EMSO is distributed under the therms of the ALSOC LICENSE as
13* available at http://www.enq.ufrgs.br/alsoc.
14*
15*--------------------------------------------------------------------
16* Author: Gerson Balbueno Bicca
17* $Id: DoublePipe.mso 110 2007-01-12 18:44:02Z bicca $
18*------------------------------------------------------------------*#
19
20using "HEX_Engine";
21#+++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++#
22#       Basic Models for Double Pipe Heat Exchangers
23#+++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++#
24
25Model DoublePipe_Basic
26       
27PARAMETERS
28ext PP          as CalcObject   (Brief="External Physical Properties");
29ext NComp       as Integer      (Brief="Number of Components");
30        M(NComp)        as molweight    (Brief="Component Mol Weight");
31       
32VARIABLES
33
34in  Inlet               as Inlet_Main_Stream;   # Hot and Cold Inlets
35out Outlet              as Outlet_Main_Stream;  # Hot and Cold Outlets
36        Properties      as Main_Properties;             # Hot and Cold Properties
37        Details         as Details_Main;
38        Inner                   as Main_DoublePipe;
39        Outer                   as Main_DoublePipe;
40        Resistances     as Main_Resistances;
41
42SET
43
44        M  = PP.MolecularWeight();
45
46EQUATIONS
47
48"Hot Stream Average Temperature"
49        Properties.Hot.Average.T = 0.5*Inlet.Hot.T + 0.5*Outlet.Hot.T;
50       
51"Cold Stream Average Temperature"
52        Properties.Cold.Average.T = 0.5*Inlet.Cold.T + 0.5*Outlet.Cold.T;
53       
54"Hot Stream Average Pressure"
55        Properties.Hot.Average.P = 0.5*Inlet.Hot.P+0.5*Outlet.Hot.P;
56       
57"Cold Stream Average Pressure"
58        Properties.Cold.Average.P = 0.5*Inlet.Cold.P+0.5*Outlet.Cold.P;
59
60"Cold Stream Wall Temperature"
61        Properties.Cold.Wall.Twall =   0.5*Properties.Hot.Average.T + 0.5*Properties.Cold.Average.T;
62
63"Hot Stream Wall Temperature"
64        Properties.Hot.Wall.Twall =   0.5*Properties.Hot.Average.T + 0.5*Properties.Cold.Average.T;
65
66"Hot Stream Average Molecular Weight"
67        Properties.Hot.Average.Mw = sum(M*Inlet.Hot.z);
68
69"Cold Stream Average Molecular Weight"
70        Properties.Cold.Average.Mw = sum(M*Inlet.Cold.z);
71
72if Inlet.Cold.v equal 0
73        then   
74"Heat Capacity Cold Stream"
75        Properties.Cold.Average.Cp              =       PP.LiquidCp(Properties.Cold.Average.T,Properties.Cold.Average.P,Inlet.Cold.z);
76        Properties.Cold.Inlet.Cp                =       PP.LiquidCp(Inlet.Cold.T,Inlet.Cold.P,Inlet.Cold.z);
77        Properties.Cold.Outlet.Cp               =       PP.LiquidCp(Outlet.Cold.T,Outlet.Cold.P,Outlet.Cold.z);
78
79"Mass Density Cold Stream"
80        Properties.Cold.Average.rho     =       PP.LiquidDensity(Properties.Cold.Average.T,Properties.Cold.Average.P,Inlet.Cold.z);
81        Properties.Cold.Inlet.rho               =       PP.LiquidDensity(Inlet.Cold.T,Inlet.Cold.P,Inlet.Cold.z);
82        Properties.Cold.Outlet.rho              =       PP.LiquidDensity(Outlet.Cold.T,Outlet.Cold.P,Outlet.Cold.z);
83
84"Viscosity Cold Stream"
85        Properties.Cold.Average.Mu              =       PP.LiquidViscosity(Properties.Cold.Average.T,Properties.Cold.Average.P,Inlet.Cold.z);
86        Properties.Cold.Inlet.Mu                =       PP.LiquidViscosity(Inlet.Cold.T,Inlet.Cold.P,Inlet.Cold.z);
87        Properties.Cold.Outlet.Mu               =       PP.LiquidViscosity(Outlet.Cold.T,Outlet.Cold.P,Outlet.Cold.z);
88
89"Conductivity Cold Stream"
90        Properties.Cold.Average.K               =       PP.LiquidThermalConductivity(Properties.Cold.Average.T,Properties.Cold.Average.P,Inlet.Cold.z);
91        Properties.Cold.Inlet.K                 =       PP.LiquidThermalConductivity(Inlet.Cold.T,Inlet.Cold.P,Inlet.Cold.z);
92        Properties.Cold.Outlet.K                =       PP.LiquidThermalConductivity(Outlet.Cold.T,Outlet.Cold.P,Outlet.Cold.z);
93
94"Heat Capacity Cold Stream"
95        Properties.Cold.Wall.Cp                 =       PP.LiquidCp(Properties.Cold.Wall.Twall,Properties.Cold.Average.P,Inlet.Cold.z);
96       
97"Viscosity Cold Stream"
98        Properties.Cold.Wall.Mu                 =       PP.LiquidViscosity(Properties.Cold.Wall.Twall,Properties.Cold.Average.P,Inlet.Cold.z);
99
100"Conductivity Cold Stream"
101        Properties.Cold.Wall.K                  =       PP.LiquidThermalConductivity(Properties.Cold.Wall.Twall,Properties.Cold.Average.P,Inlet.Cold.z);
102
103
104        else
105
106"Heat Capacity Cold Stream"
107        Properties.Cold.Average.Cp      =       PP.VapourCp(Properties.Cold.Average.T,Properties.Cold.Average.P,Inlet.Cold.z);
108        Properties.Cold.Inlet.Cp        =       PP.VapourCp(Inlet.Cold.T,Inlet.Cold.P,Inlet.Cold.z);
109        Properties.Cold.Outlet.Cp       =       PP.VapourCp(Outlet.Cold.T,Outlet.Cold.P,Outlet.Cold.z);
110
111"Mass Density Cold Stream"
112        Properties.Cold.Average.rho     =       PP.VapourDensity(Properties.Cold.Average.T,Properties.Cold.Average.P,Inlet.Cold.z);
113        Properties.Cold.Inlet.rho               =       PP.VapourDensity(Inlet.Cold.T,Inlet.Cold.P,Inlet.Cold.z);
114        Properties.Cold.Outlet.rho              =       PP.VapourDensity(Outlet.Cold.T,Outlet.Cold.P,Outlet.Cold.z);
115
116"Viscosity Cold Stream"
117        Properties.Cold.Average.Mu              =       PP.VapourViscosity(Properties.Cold.Average.T,Properties.Cold.Average.P,Inlet.Cold.z);
118        Properties.Cold.Inlet.Mu                =       PP.VapourViscosity(Inlet.Cold.T,Inlet.Cold.P,Inlet.Cold.z);
119        Properties.Cold.Outlet.Mu               =       PP.VapourViscosity(Outlet.Cold.T,Outlet.Cold.P,Outlet.Cold.z);
120
121"Conductivity Cold Stream"
122        Properties.Cold.Average.K               =       PP.VapourThermalConductivity(Properties.Cold.Average.T,Properties.Cold.Average.P,Inlet.Cold.z);
123        Properties.Cold.Inlet.K                 =       PP.VapourThermalConductivity(Inlet.Cold.T,Inlet.Cold.P,Inlet.Cold.z);
124        Properties.Cold.Outlet.K                =       PP.VapourThermalConductivity(Outlet.Cold.T,Outlet.Cold.P,Outlet.Cold.z);
125       
126"Heat Capacity Cold Stream"
127        Properties.Cold.Wall.Cp                 =       PP.VapourCp(Properties.Cold.Wall.Twall,Properties.Cold.Average.P,Inlet.Cold.z);
128
129
130"Viscosity Cold Stream"
131        Properties.Cold.Wall.Mu                 =       PP.VapourViscosity(Properties.Cold.Wall.Twall,Properties.Cold.Average.P,Inlet.Cold.z);
132
133"Conductivity Cold Stream"
134        Properties.Cold.Wall.K                  =       PP.VapourThermalConductivity(Properties.Cold.Wall.Twall,Properties.Cold.Average.P,Inlet.Cold.z);
135       
136       
137       
138end
139
140if Inlet.Hot.v equal 0
141
142        then
143
144"Heat Capacity Hot Stream"
145        Properties.Hot.Average.Cp       =               PP.LiquidCp(Properties.Hot.Average.T,Properties.Hot.Average.P,Inlet.Hot.z);
146        Properties.Hot.Inlet.Cp         =               PP.LiquidCp(Inlet.Hot.T,Inlet.Hot.P,Inlet.Hot.z);
147        Properties.Hot.Outlet.Cp        =               PP.LiquidCp(Outlet.Hot.T,Outlet.Hot.P,Outlet.Hot.z);
148
149"Mass Density Hot Stream"
150        Properties.Hot.Average.rho      =               PP.LiquidDensity(Properties.Hot.Average.T,Properties.Hot.Average.P,Inlet.Hot.z);
151        Properties.Hot.Inlet.rho        =               PP.LiquidDensity(Inlet.Hot.T,Inlet.Hot.P,Inlet.Hot.z);
152        Properties.Hot.Outlet.rho       =               PP.LiquidDensity(Outlet.Hot.T,Outlet.Hot.P,Outlet.Hot.z);
153
154"Viscosity Hot Stream"
155        Properties.Hot.Average.Mu       =               PP.LiquidViscosity(Properties.Hot.Average.T,Properties.Hot.Average.P,Inlet.Hot.z);     
156        Properties.Hot.Inlet.Mu         =               PP.LiquidViscosity(Inlet.Hot.T,Inlet.Hot.P,Inlet.Hot.z);       
157        Properties.Hot.Outlet.Mu        =               PP.LiquidViscosity(Outlet.Hot.T,Outlet.Hot.P,Outlet.Hot.z);     
158
159"Conductivity Hot Stream"
160        Properties.Hot.Average.K        =               PP.LiquidThermalConductivity(Properties.Hot.Average.T,Properties.Hot.Average.P,Inlet.Hot.z);   
161        Properties.Hot.Inlet.K          =               PP.LiquidThermalConductivity(Inlet.Hot.T,Inlet.Hot.P,Inlet.Hot.z);     
162        Properties.Hot.Outlet.K         =               PP.LiquidThermalConductivity(Outlet.Hot.T,Outlet.Hot.P,Outlet.Hot.z);   
163
164"Heat Capacity Hot Stream"
165        Properties.Hot.Wall.Cp          =               PP.LiquidCp(Properties.Hot.Wall.Twall,Properties.Hot.Average.P,Inlet.Hot.z);
166
167"Viscosity Hot Stream"
168        Properties.Hot.Wall.Mu          =               PP.LiquidViscosity(Properties.Hot.Wall.Twall,Properties.Hot.Average.P,Inlet.Hot.z);     
169
170"Conductivity Hot Stream"
171        Properties.Hot.Wall.K           =               PP.LiquidThermalConductivity(Properties.Hot.Wall.Twall,Properties.Hot.Average.P,Inlet.Hot.z);   
172       
173
174        else
175
176"Heat Capacity Hot Stream"
177        Properties.Hot.Average.Cp       =               PP.VapourCp(Properties.Hot.Average.T,Properties.Hot.Average.P,Inlet.Hot.z);
178        Properties.Hot.Inlet.Cp         =               PP.VapourCp(Inlet.Hot.T,Inlet.Hot.P,Inlet.Hot.z);
179        Properties.Hot.Outlet.Cp        =               PP.VapourCp(Outlet.Hot.T,Outlet.Hot.P,Outlet.Hot.z);
180
181"Mass Density Hot Stream"
182        Properties.Hot.Average.rho      =               PP.VapourDensity(Properties.Hot.Average.T,Properties.Hot.Average.P,Inlet.Hot.z);
183        Properties.Hot.Inlet.rho        =               PP.VapourDensity(Inlet.Hot.T,Inlet.Hot.P,Inlet.Hot.z);
184        Properties.Hot.Outlet.rho       =               PP.VapourDensity(Outlet.Hot.T,Outlet.Hot.P,Outlet.Hot.z);
185
186"Viscosity Hot Stream"
187        Properties.Hot.Average.Mu       =               PP.VapourViscosity(Properties.Hot.Average.T,Properties.Hot.Average.P,Inlet.Hot.z);
188        Properties.Hot.Inlet.Mu         =               PP.VapourViscosity(Inlet.Hot.T,Inlet.Hot.P,Inlet.Hot.z);
189        Properties.Hot.Outlet.Mu        =               PP.VapourViscosity(Outlet.Hot.T,Outlet.Hot.P,Outlet.Hot.z);
190
191"Conductivity Hot Stream"
192        Properties.Hot.Average.K        =               PP.VapourThermalConductivity(Properties.Hot.Average.T,Properties.Hot.Average.P,Inlet.Hot.z);   
193        Properties.Hot.Inlet.K          =               PP.VapourThermalConductivity(Inlet.Hot.T,Inlet.Hot.P,Inlet.Hot.z);     
194        Properties.Hot.Outlet.K         =               PP.VapourThermalConductivity(Outlet.Hot.T,Outlet.Hot.P,Outlet.Hot.z);   
195
196"Heat Capacity Hot Stream"
197        Properties.Hot.Wall.Cp          =               PP.VapourCp(Properties.Hot.Wall.Twall,Properties.Hot.Average.P,Inlet.Hot.z);
198
199"Viscosity Hot Stream"
200        Properties.Hot.Wall.Mu          =               PP.VapourViscosity(Properties.Hot.Wall.Twall,Properties.Hot.Average.P,Inlet.Hot.z);
201
202"Conductivity Hot Stream"
203        Properties.Hot.Wall.K           =               PP.VapourThermalConductivity(Properties.Hot.Wall.Twall,Properties.Hot.Average.P,Inlet.Hot.z);   
204
205
206end
207
208#+++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++#
209#       Thermal Details
210#+++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++#
211"Hot Stream Heat Capacity"
212        Details.Ch =Inlet.Hot.F*Properties.Hot.Average.Cp;
213       
214"Cold Stream Heat Capacity"
215        Details.Cc =Inlet.Cold.F*Properties.Cold.Average.Cp;
216
217"Minimum Heat Capacity"
218        Details.Cmin  = min([Details.Ch,Details.Cc]);
219
220"Maximum Heat Capacity"
221        Details.Cmax  = max([Details.Ch,Details.Cc]);
222
223"Heat Capacity Ratio"   
224        Details.Cr*Details.Cmax   = Details.Cmin;
225       
226#--------------------------------------------------------------------
227#       Energy Balance
228#--------------------------------------------------------------------
229
230"Energy Balance Hot Stream"
231        Details.Q = Inlet.Hot.F*(Inlet.Hot.h-Outlet.Hot.h);
232
233"Energy Balance Cold Stream"
234        Details.Q = Inlet.Cold.F*(Outlet.Cold.h - Inlet.Cold.h);
235
236#--------------------------------------------------------------------
237#       Material Balance
238#--------------------------------------------------------------------
239
240"Flow Mass Inlet Cold Stream"
241        Properties.Cold.Inlet.Fw        =  sum(M*Inlet.Cold.z)*Inlet.Cold.F;
242
243"Flow Mass Outlet Cold Stream"
244        Properties.Cold.Outlet.Fw       =  sum(M*Outlet.Cold.z)*Outlet.Cold.F;
245
246"Flow Mass Inlet Hot Stream"
247        Properties.Hot.Inlet.Fw         =  sum(M*Inlet.Hot.z)*Inlet.Hot.F;
248
249"Flow Mass Outlet Hot Stream"   
250        Properties.Hot.Outlet.Fw        =  sum(M*Outlet.Hot.z)*Outlet.Hot.F;
251
252"Molar Balance Hot Stream"
253        Inlet.Hot.F  = Outlet.Hot.F;
254       
255"Molar Balance Cold Stream"
256        Inlet.Cold.F = Outlet.Cold.F;
257
258#+++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++#
259#       Constraints
260#+++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++#
261"Hot Stream Molar Fraction Constraint"
262        Outlet.Hot.z=Inlet.Hot.z;
263       
264"Cold Stream Molar Fraction Constraint"
265        Outlet.Cold.z=Inlet.Cold.z;
266       
267"No Phase Change In Cold Stream"
268        Inlet.Cold.v=Outlet.Cold.v;
269
270"No Phase Change In Hot Stream"
271        Inlet.Hot.v=Outlet.Hot.v;
272       
273if Inner.PressureDrop.Re < 2300
274
275        then
276"Inner Side Friction Factor - laminar Flow"
277        Inner.PressureDrop.fi*Inner.PressureDrop.Re = 16;
278
279        else
280"Inner Side Friction Factor - Turbulent Flow"
281        (Inner.PressureDrop.fi-0.0035)*(Inner.PressureDrop.Re^0.42) = 0.264;
282
283end     
284
285
286if Outer.PressureDrop.Re < 2300
287
288        then
289"Inner Side Friction Factor - laminar Flow"
290        Outer.PressureDrop.fi*Outer.PressureDrop.Re = 16;
291
292        else
293"Inner Side Friction Factor - Turbulent Flow"
294        (Outer.PressureDrop.fi - 0.0035)*(Outer.PressureDrop.Re^0.42) = 0.264;
295
296end
297
298end
299
300Model DoublePipe                                        as DoublePipe_Basic
301       
302PARAMETERS
303
304        HE              as CalcObject   (Brief="STHE Calculations",File="heatex");
305        Pi                      as constant     (Brief="Pi Number",Default=3.14159265);
306        Hside       as Integer          (Brief="Fluid Alocation Flag-Default:Outer",Lower=0,Upper=1);
307        Side            as Integer              (Brief="Flow Direction",Lower=0,Upper=1);
308        DoInner         as length               (Brief="Outside Diameter of Inner Pipe",Lower=1e-6);
309        DiInner         as length               (Brief="Inside Diameter of Inner Pipe",Lower=1e-10);
310        DiOuter         as length               (Brief="Inside Diameter of Outer pipe",Lower=1e-10);
311        Lpipe           as length               (Brief="Effective Tube Length",Lower=0.1);
312        Kwall           as conductivity (Brief="Tube Wall Material Thermal Conductivity",Default=1.0);
313       
314SET
315        Pi      = 3.14159265;
316        Hside   = HE.FluidAlocation();
317        Side    = HE.FlowDir();
318
319#"Inner Pipe Cross Sectional Area for Flow"
320        Inner.HeatTransfer.As=Pi*DiInner*DiInner/4;
321       
322#"Outer Pipe Cross Sectional Area for Flow"
323        Outer.HeatTransfer.As=Pi*(DiOuter*DiOuter-DoInner*DoInner)/4;
324       
325#"Inner Pipe Hydraulic Diameter for Heat Transfer"
326        Inner.HeatTransfer.Dh=DiInner;
327       
328#"Outer Pipe Hydraulic Diameter for Heat Transfer"
329        Outer.HeatTransfer.Dh=(DiOuter*DiOuter-DoInner*DoInner)/DoInner;
330
331#"Inner Pipe Hydraulic Diameter for Pressure Drop"
332        Inner.PressureDrop.Dh=DiInner;
333       
334#"Outer Pipe Hydraulic Diameter for Pressure Drop"
335        Outer.PressureDrop.Dh=DiOuter-DoInner;
336
337EQUATIONS
338
339"Exchange Surface Area"
340        Details.A=Pi*DoInner*Lpipe;
341
342if Hside equal 1
343       
344        then
345       
346"Pressure Drop Hot Stream"
347        Outlet.Hot.P  = Inlet.Hot.P - Outer.PressureDrop.Pdrop;
348
349"Pressure Drop Cold Stream"
350        Outlet.Cold.P  = Inlet.Cold.P - Inner.PressureDrop.Pdrop;
351       
352"Outer Pipe Film Coefficient"
353        Outer.HeatTransfer.hcoeff= HE.PipeFilmCoeff(Outer.HeatTransfer.Re,Outer.HeatTransfer.PR,Properties.Hot.Average.K,Outer.HeatTransfer.Dh,Lpipe)*Outer.HeatTransfer.Phi;
354
355"Inner Pipe Film Coefficient"
356        Inner.HeatTransfer.hcoeff= HE.PipeFilmCoeff(Inner.HeatTransfer.Re,Inner.HeatTransfer.PR,Properties.Cold.Average.K,DiInner,Lpipe)*Inner.HeatTransfer.Phi;
357
358"Outer Pipe Pressure Drop"
359        Outer.PressureDrop.Pdrop = (2*Outer.PressureDrop.fi*Lpipe*Properties.Hot.Average.rho*Outer.HeatTransfer.Vmean^2)/(Outer.PressureDrop.Dh*Outer.HeatTransfer.Phi);
360       
361"Inner Pipe Pressure Drop"
362        Inner.PressureDrop.Pdrop = (2*Inner.PressureDrop.fi*Lpipe*Properties.Cold.Average.rho*Inner.HeatTransfer.Vmean^2)/(DiInner*Inner.HeatTransfer.Phi);
363
364"Outer Pipe Phi correction"
365        Outer.HeatTransfer.Phi = HE.PhiCorrection(Properties.Hot.Average.Mu,Properties.Hot.Wall.Mu);
366       
367"Inner Pipe Phi correction"
368        Inner.HeatTransfer.Phi  = HE.PhiCorrection(Properties.Cold.Average.Mu,Properties.Cold.Wall.Mu);
369
370"Outer Pipe Prandtl Number"
371        Outer.HeatTransfer.PR = ((Properties.Hot.Average.Cp/Properties.Hot.Average.Mw)*Properties.Hot.Average.Mu)/Properties.Hot.Average.K;
372
373"Inner Pipe Prandtl Number"
374        Inner.HeatTransfer.PR = ((Properties.Cold.Average.Cp/Properties.Cold.Average.Mw)*Properties.Cold.Average.Mu)/Properties.Cold.Average.K;
375
376"Outer Pipe Reynolds Number for Heat Transfer"
377        Outer.HeatTransfer.Re = (Properties.Hot.Average.rho*Outer.HeatTransfer.Vmean*Outer.HeatTransfer.Dh)/Properties.Hot.Average.Mu;
378
379"Outer Pipe Reynolds Number for Pressure Drop"
380        Outer.PressureDrop.Re = (Properties.Hot.Average.rho*Outer.HeatTransfer.Vmean*Outer.PressureDrop.Dh)/Properties.Hot.Average.Mu;
381
382"Inner Pipe Reynolds Number for Heat Transfer"
383        Inner.HeatTransfer.Re = (Properties.Cold.Average.rho*Inner.HeatTransfer.Vmean*Inner.HeatTransfer.Dh)/Properties.Cold.Average.Mu;
384
385"Inner Pipe Reynolds Number for Pressure Drop"
386        Inner.PressureDrop.Re = Inner.HeatTransfer.Re;
387
388"Outer Pipe Velocity"
389        Outer.HeatTransfer.Vmean*(Outer.HeatTransfer.As*Properties.Hot.Average.rho)  = Properties.Hot.Inlet.Fw;
390
391"Inner Pipe Velocity"
392        Inner.HeatTransfer.Vmean*(Inner.HeatTransfer.As*Properties.Cold.Average.rho)  = Properties.Cold.Inlet.Fw;
393
394        else
395       
396"Pressure Drop Hot Stream"
397        Outlet.Hot.P  = Inlet.Hot.P - Inner.PressureDrop.Pdrop;
398
399"Pressure Drop Cold Stream"
400        Outlet.Cold.P  = Inlet.Cold.P - Outer.PressureDrop.Pdrop;
401       
402"Inner Pipe Film Coefficient"
403        Inner.HeatTransfer.hcoeff= HE.PipeFilmCoeff(Inner.HeatTransfer.Re,Inner.HeatTransfer.PR,Properties.Hot.Average.K,DiInner,Lpipe)*Inner.HeatTransfer.Phi;
404
405"Outer Pipe Film Coefficient"
406        Outer.HeatTransfer.hcoeff= HE.PipeFilmCoeff(Outer.HeatTransfer.Re,Outer.HeatTransfer.PR,Properties.Cold.Average.K,Outer.HeatTransfer.Dh,Lpipe)*Outer.HeatTransfer.Phi;
407
408"Outer Pipe Pressure Drop"
409        Outer.PressureDrop.Pdrop = (2*Outer.PressureDrop.fi*Lpipe*Properties.Cold.Average.rho*Outer.HeatTransfer.Vmean^2)/(Outer.PressureDrop.Dh*Outer.HeatTransfer.Phi);
410       
411"Inner Pipe Pressure Drop"
412        Inner.PressureDrop.Pdrop        = (2*Inner.PressureDrop.fi*Lpipe*Properties.Hot.Average.rho*Inner.HeatTransfer.Vmean^2)/(DiInner*Inner.HeatTransfer.Phi);
413
414"Outer Pipe Phi correction"
415        Outer.HeatTransfer.Phi          = HE.PhiCorrection(Properties.Cold.Average.Mu,Properties.Cold.Wall.Mu);
416       
417"Inner Pipe Phi correction"
418        Inner.HeatTransfer.Phi          = HE.PhiCorrection(Properties.Hot.Average.Mu,Properties.Hot.Wall.Mu);
419       
420"Outer Pipe Prandtl Number"
421        Outer.HeatTransfer.PR           = ((Properties.Cold.Average.Cp/Properties.Cold.Average.Mw)*Properties.Cold.Average.Mu)/Properties.Cold.Average.K;
422
423"Inner Pipe Prandtl Number"
424        Inner.HeatTransfer.PR           = ((Properties.Hot.Average.Cp/Properties.Hot.Average.Mw)*Properties.Hot.Average.Mu)/Properties.Hot.Average.K;
425
426"Outer Pipe Reynolds Number for Heat Transfer"
427        Outer.HeatTransfer.Re           = (Properties.Cold.Average.rho*Outer.HeatTransfer.Vmean*Outer.HeatTransfer.Dh)/Properties.Cold.Average.Mu;
428
429"Outer Pipe Reynolds Number for Pressure Drop"
430        Outer.PressureDrop.Re           = (Properties.Cold.Average.rho*Outer.HeatTransfer.Vmean*Outer.PressureDrop.Dh)/Properties.Cold.Average.Mu;
431
432"Inner Pipe Reynolds Number for Pressure Drop"
433        Inner.PressureDrop.Re           = Inner.HeatTransfer.Re;
434
435"Inner Pipe Reynolds Number for Heat Transfer"
436        Inner.HeatTransfer.Re           = (Properties.Hot.Average.rho*Inner.HeatTransfer.Vmean*Inner.HeatTransfer.Dh)/Properties.Hot.Average.Mu;
437
438"Outer Pipe Velocity"
439        Outer.HeatTransfer.Vmean*(Outer.HeatTransfer.As*Properties.Cold.Average.rho)= Properties.Cold.Inlet.Fw;
440       
441"Inner Pipe Velocity"
442        Inner.HeatTransfer.Vmean*(Inner.HeatTransfer.As*Properties.Hot.Average.rho)     = Properties.Hot.Inlet.Fw;
443
444end
445
446"Inner Pipe Resistance"
447        Resistances.Rtube*(Inner.HeatTransfer.hcoeff*DiInner) = DoInner;
448       
449"Wall Resistance"
450        Resistances.Rwall*(2*Kwall) = DoInner*ln(DoInner/DiInner);
451
452"Outer Pipe Resistance"
453        Resistances.Rshell*(Outer.HeatTransfer.hcoeff)=1;
454
455"Overall Heat Transfer Coefficient Clean"
456        Details.Uc*(Resistances.Rtube+Resistances.Rwall+Resistances.Rshell)=1;
457
458"Overall Heat Transfer Coefficient Dirty"
459        Details.Ud*(Resistances.Rfi*(DoInner/DiInner) + Resistances.Rfo + Resistances.Rtube + Resistances.Rwall + Resistances.Rshell)=1;
460       
461end
462
463Model DoublePipe_Basic_NTU                      as DoublePipe
464#+++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++#
465#       Basic Model Double Pipe Heat Exchanger - NTU Method
466#+++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++#
467VARIABLES
468
469Eft       as positive (Brief="Effectiveness",Default=0.5,Lower=1e-12);
470
471EQUATIONS       
472
473"Energy Balance"
474        Details.Q       = Eft*Details.Cmin*(Inlet.Hot.T-Inlet.Cold.T); 
475
476
477end
478
479Model DoublePipe_Basic_LMTD                     as DoublePipe
480#+++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++#
481#       Basic Model for Double Pipe Heat Exchanger- LMTD Method
482#+++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++#
483VARIABLES
484
485DT0     as temp_delta   (Brief="Temperature Difference at Inlet",Lower=1);
486DTL             as temp_delta   (Brief="Temperature Difference at Outlet",Lower=1);
487LMTD    as temp_delta   (Brief="Logarithmic Mean Temperature Difference",Lower=1);
488
489EQUATIONS
490#+++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++#
491#                       Log Mean Temperature Difference
492#+++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++#
493
494if abs(DT0 - DTL) > 0.05*max(abs([DT0,DTL]))
495       
496        then
497"Log Mean Temperature Difference"
498        LMTD*ln(DT0/DTL) = (DT0-DTL);
499
500        else
501       
502if DT0*DTL equal 0
503       
504        then
505"Log Mean Temperature Difference"
506        LMTD = 0.5*(DT0+DTL);
507
508        else
509"Log Mean Temperature Difference"
510        LMTD = 0.5*(DT0+DTL)*(1-(DT0-DTL)^2/(DT0*DTL)*(1+(DT0-DTL)^2/(DT0*DTL)/2)/12);
511       
512end
513       
514end
515
516"Exchange Surface Area"
517        Details.Q = Details.Ud*Pi*DoInner*Lpipe*LMTD;
518
519end
520
521Model DoublePipe_LMTD                           as DoublePipe_Basic_LMTD
522
523EQUATIONS
524
525if Side equal 0
526
527        then
528"Temperature Difference at Inlet - Cocurrent Flow"
529        DT0 = Inlet.Hot.T - Inlet.Cold.T;
530
531"Temperature Difference at Outlet - Cocurrent Flow"
532        DTL = Outlet.Hot.T - Outlet.Cold.T;
533
534        else
535"Temperature Difference at Inlet - Counter Flow"
536        DT0 = Inlet.Hot.T - Outlet.Cold.T;
537
538"Temperature Difference at Outlet - Counter Flow"
539        DTL = Outlet.Hot.T - Inlet.Cold.T;
540end
541       
542end
543
544Model DoublePipe_NTU                            as DoublePipe_Basic_NTU
545
546EQUATIONS
547
548if Details.Cr equal 0
549       
550        then   
551"Effectiveness"
552        Eft = 1-exp(-Details.NTU);
553       
554        else
555
556if Side equal 0
557
558then
559"Effectiveness in Cocurrent Flow"
560        Eft*(1+Details.Cr) = (1-exp(-Details.NTU*(1+Details.Cr)));
561       
562        else
563
564if Details.Cr equal 1
565       
566        then
567"Effectiveness in Counter Flow"
568        Eft*(1+Details.NTU) = Details.NTU;
569       
570        else
571"Effectiveness in Counter Flow"
572        Eft*(1-Details.Cr*exp(-Details.NTU*(1-Details.Cr))) = (1-exp(-Details.NTU*(1-Details.Cr)));
573       
574end
575
576end
577
578
579end
580
581end
582
583Model Multitubular_Basic
584       
585PARAMETERS
586
587        Npipe           as Integer              (Brief="N Pipe in Series",Default=2);
588ext PP                  as CalcObject   (Brief="External Physical Properties");
589        HE              as CalcObject   (Brief="STHE Calculations",File="heatex");
590        Pi                      as constant     (Brief="Pi Number",Default=3.14159265);
591        Hside       as Integer          (Brief="Fluid Alocation Flag-Default:Outer",Lower=0,Upper=1);
592        DoInner         as length               (Brief="Outside Diameter of Inner Pipe",Lower=1e-6);
593        DiInner         as length               (Brief="Inside Diameter of Inner Pipe",Lower=1e-10);
594        DiOuter         as length               (Brief="Inside Diameter of Outer pipe",Lower=1e-10);
595        Lpipe           as length               (Brief="Effective Tube Length",Lower=0.1);
596        Kwall           as conductivity (Brief="Tube Wall Material Thermal Conductivity",Default=1.0);
597
598VARIABLES
599
600Unity(Npipe)  as DoublePipe_Basic;
601
602SET
603        Pi      = 3.14159265;
604        Hside   = HE.FluidAlocation();
605       
606#"Inner Pipe Cross Sectional Area for Flow"
607        Unity.Inner.HeatTransfer.As=Pi*DiInner*DiInner/4;
608       
609#"Outer Pipe Cross Sectional Area for Flow"
610        Unity.Outer.HeatTransfer.As=Pi*(DiOuter*DiOuter-DoInner*DoInner)/4;
611       
612#"Inner Pipe Hydraulic Diameter for Heat Transfer"
613        Unity.Inner.HeatTransfer.Dh=DiInner;
614       
615#"Outer Pipe Hydraulic Diameter for Heat Transfer"
616        Unity.Outer.HeatTransfer.Dh=(DiOuter*DiOuter-DoInner*DoInner)/DoInner;
617
618#"Inner Pipe Hydraulic Diameter for Pressure Drop"
619        Unity.Inner.PressureDrop.Dh=DiInner;
620       
621#"Outer Pipe Hydraulic Diameter for Pressure Drop"
622        Unity.Outer.PressureDrop.Dh=DiOuter-DoInner;
623
624EQUATIONS
625
626for i in [1:Npipe]
627
628"Overall Heat Transfer Coefficient Clean"
629        Unity(i).Details.Uc*(Unity(i).Resistances.Rtube+Unity(i).Resistances.Rwall+Unity(i).Resistances.Rshell)=1;
630
631"Overall Heat Transfer Coefficient Dirty"
632        Unity(i).Details.Ud*(Unity(i).Resistances.Rfi*(DoInner/DiInner) + Unity(i).Resistances.Rfo + Unity(i).Resistances.Rtube + Unity(i).Resistances.Rwall + Unity(i).Resistances.Rshell)=1;
633
634"Exchange Surface Area"
635        Unity(i).Details.A=Pi*DoInner*Lpipe;
636       
637if Hside equal 1
638       
639        then
640       
641"Pressure Drop Hot Stream"
642        Unity(i).Outlet.Hot.P  = Unity(i).Inlet.Hot.P - Unity(i).Outer.PressureDrop.Pdrop;
643
644"Pressure Drop Cold Stream"
645        Unity(i).Outlet.Cold.P  = Unity(i).Inlet.Cold.P - Unity(i).Inner.PressureDrop.Pdrop;
646       
647"Outer Pipe Film Coefficient"
648        Unity(i).Outer.HeatTransfer.hcoeff= HE.PipeFilmCoeff(Unity(i).Outer.HeatTransfer.Re,Unity(i).Outer.HeatTransfer.PR,Unity(i).Properties.Hot.Average.K,Unity(i).Outer.HeatTransfer.Dh,Lpipe)*Unity(i).Outer.HeatTransfer.Phi;
649
650"Inner Pipe Film Coefficient"
651        Unity(i).Inner.HeatTransfer.hcoeff= HE.PipeFilmCoeff(Unity(i).Inner.HeatTransfer.Re,Unity(i).Inner.HeatTransfer.PR,Unity(i).Properties.Cold.Average.K,DiInner,Lpipe)*Unity(i).Inner.HeatTransfer.Phi;
652
653"Outer Pipe Pressure Drop"
654        Unity(i).Outer.PressureDrop.Pdrop = (2*Unity(i).Outer.PressureDrop.fi*Lpipe*Unity(i).Properties.Hot.Average.rho*Unity(i).Outer.HeatTransfer.Vmean^2)/(Unity(i).Outer.PressureDrop.Dh*Unity(i).Outer.HeatTransfer.Phi);
655       
656"Inner Pipe Pressure Drop"
657        Unity(i).Inner.PressureDrop.Pdrop = (2*Unity(i).Inner.PressureDrop.fi*Lpipe*Unity(i).Properties.Cold.Average.rho*Unity(i).Inner.HeatTransfer.Vmean^2)/(DiInner*Unity(i).Inner.HeatTransfer.Phi);
658
659"Outer Pipe Phi correction"
660        Unity(i).Outer.HeatTransfer.Phi = HE.PhiCorrection(Unity(i).Properties.Hot.Average.Mu,Unity(i).Properties.Hot.Wall.Mu);
661       
662"Inner Pipe Phi correction"
663        Unity(i).Inner.HeatTransfer.Phi  = HE.PhiCorrection(Unity(i).Properties.Cold.Average.Mu,Unity(i).Properties.Cold.Wall.Mu);
664
665"Outer Pipe Prandtl Number"
666        Unity(i).Outer.HeatTransfer.PR = ((Unity(i).Properties.Hot.Average.Cp/Unity(i).Properties.Hot.Average.Mw)*Unity(i).Properties.Hot.Average.Mu)/Unity(i).Properties.Hot.Average.K;
667
668"Inner Pipe Prandtl Number"
669        Unity(i).Inner.HeatTransfer.PR = ((Unity(i).Properties.Cold.Average.Cp/Unity(i).Properties.Cold.Average.Mw)*Unity(i).Properties.Cold.Average.Mu)/Unity(i).Properties.Cold.Average.K;
670
671"Outer Pipe Reynolds Number for Heat Transfer"
672        Unity(i).Outer.HeatTransfer.Re =        (Unity(i).Properties.Hot.Average.rho*Unity(i).Outer.HeatTransfer.Vmean*Unity(i).Outer.HeatTransfer.Dh)/Unity(i).Properties.Hot.Average.Mu;
673
674"Outer Pipe Reynolds Number for Pressure Drop"
675        Unity(i).Outer.PressureDrop.Re =        (Unity(i).Properties.Hot.Average.rho*Unity(i).Outer.HeatTransfer.Vmean*Unity(i).Outer.PressureDrop.Dh)/Unity(i).Properties.Hot.Average.Mu;
676
677"Inner Pipe Reynolds Number for Heat Transfer"
678        Unity(i).Inner.HeatTransfer.Re =        (Unity(i).Properties.Cold.Average.rho*Unity(i).Inner.HeatTransfer.Vmean*Unity(i).Inner.HeatTransfer.Dh)/Unity(i).Properties.Cold.Average.Mu;
679
680"Inner Pipe Reynolds Number for Pressure Drop"
681        Unity(i).Inner.PressureDrop.Re =        Unity(i).Inner.HeatTransfer.Re;
682
683"Outer Pipe Velocity"
684        Unity(i).Outer.HeatTransfer.Vmean  = Unity(i).Properties.Hot.Inlet.Fw/(Unity(i).Outer.HeatTransfer.As*Unity(i).Properties.Hot.Average.rho);
685
686"Inner Pipe Velocity"
687        Unity(i).Inner.HeatTransfer.Vmean  = Unity(i).Properties.Cold.Inlet.Fw/(Unity(i).Inner.HeatTransfer.As*Unity(i).Properties.Cold.Average.rho);
688
689        else
690       
691"Pressure Drop Hot Stream"
692        Unity(i).Outlet.Hot.P  = Unity(i).Inlet.Hot.P - Unity(i).Inner.PressureDrop.Pdrop;
693
694"Pressure Drop Cold Stream"
695        Unity(i).Outlet.Cold.P  = Unity(i).Inlet.Cold.P - Unity(i).Outer.PressureDrop.Pdrop;
696       
697"Inner Pipe Film Coefficient"
698        Unity(i).Inner.HeatTransfer.hcoeff= HE.PipeFilmCoeff(Unity(i).Inner.HeatTransfer.Re,Unity(i).Inner.HeatTransfer.PR,Unity(i).Properties.Hot.Average.K,DiInner,Lpipe)*Unity(i).Inner.HeatTransfer.Phi;
699
700"Outer Pipe Film Coefficient"
701        Unity(i).Outer.HeatTransfer.hcoeff= HE.PipeFilmCoeff(Unity(i).Outer.HeatTransfer.Re,Unity(i).Outer.HeatTransfer.PR,Unity(i).Properties.Cold.Average.K,Unity(i).Outer.HeatTransfer.Dh,Lpipe)*Unity(i).Outer.HeatTransfer.Phi;
702       
703"Outer Pipe Pressure Drop"
704        Unity(i).Outer.PressureDrop.Pdrop = (2*Unity(i).Outer.PressureDrop.fi*Lpipe*Unity(i).Properties.Cold.Average.rho*Unity(i).Outer.HeatTransfer.Vmean^2)/(Unity(i).Outer.PressureDrop.Dh*Unity(i).Outer.HeatTransfer.Phi);
705       
706"Inner Pipe Pressure Drop"
707        Unity(i).Inner.PressureDrop.Pdrop       = (2*Unity(i).Inner.PressureDrop.fi*Lpipe*Unity(i).Properties.Hot.Average.rho*Unity(i).Inner.HeatTransfer.Vmean^2)/(DiInner*Unity(i).Inner.HeatTransfer.Phi);
708
709"Outer Pipe Phi correction"
710        Unity(i).Outer.HeatTransfer.Phi         = HE.PhiCorrection(Unity(i).Properties.Cold.Average.Mu,Unity(i).Properties.Cold.Wall.Mu);
711       
712"Inner Pipe Phi correction"
713        Unity(i).Inner.HeatTransfer.Phi         = HE.PhiCorrection(Unity(i).Properties.Hot.Average.Mu,Unity(i).Properties.Hot.Wall.Mu);
714       
715"Outer Pipe Prandtl Number"
716        Unity(i).Outer.HeatTransfer.PR          = ((Unity(i).Properties.Cold.Average.Cp/Unity(i).Properties.Cold.Average.Mw)*Unity(i).Properties.Cold.Average.Mu)/Unity(i).Properties.Cold.Average.K;
717
718"Inner Pipe Prandtl Number"
719        Unity(i).Inner.HeatTransfer.PR          = ((Unity(i).Properties.Hot.Average.Cp/Unity(i).Properties.Hot.Average.Mw)*Unity(i).Properties.Hot.Average.Mu)/Unity(i).Properties.Hot.Average.K;
720
721"Outer Pipe Reynolds Number for Heat Transfer"
722        Unity(i).Outer.HeatTransfer.Re          = (Unity(i).Properties.Cold.Average.rho*Unity(i).Outer.HeatTransfer.Vmean*Unity(i).Outer.HeatTransfer.Dh)/Unity(i).Properties.Cold.Average.Mu;
723
724"Outer Pipe Reynolds Number for Pressure Drop"
725        Unity(i).Outer.PressureDrop.Re          = (Unity(i).Properties.Cold.Average.rho*Unity(i).Outer.HeatTransfer.Vmean*Unity(i).Outer.PressureDrop.Dh)/Unity(i).Properties.Cold.Average.Mu;
726
727"Inner Pipe Reynolds Number for Pressure Drop"
728        Unity(i).Inner.PressureDrop.Re          = Unity(i).Inner.HeatTransfer.Re;
729
730"Inner Pipe Reynolds Number for Heat Transfer"
731        Unity(i).Inner.HeatTransfer.Re          = (Unity(i).Properties.Hot.Average.rho*Unity(i).Inner.HeatTransfer.Vmean*Unity(i).Inner.HeatTransfer.Dh)/Unity(i).Properties.Hot.Average.Mu;
732
733"Outer Pipe Velocity"
734        Unity(i).Outer.HeatTransfer.Vmean       = Unity(i).Properties.Cold.Inlet.Fw/(Unity(i).Outer.HeatTransfer.As*Unity(i).Properties.Cold.Average.rho);
735
736"Inner Pipe Velocity"
737        Unity(i).Inner.HeatTransfer.Vmean       = Unity(i).Properties.Hot.Inlet.Fw/(Unity(i).Inner.HeatTransfer.As*Unity(i).Properties.Hot.Average.rho);
738
739end
740
741"Inner Pipe Resistance"
742        Unity(i).Resistances.Rtube*(Unity(i).Inner.HeatTransfer.hcoeff*DiInner) = DoInner;
743       
744"Wall Resistance"
745        Unity(i).Resistances.Rwall=DoInner*ln(DoInner/DiInner)/(2*Kwall);
746
747"Outer Pipe Resistance"
748        Unity(i).Resistances.Rshell*(Unity(i).Outer.HeatTransfer.hcoeff)=1;
749       
750end
751
752
753end
754
755Model Multitubular_Basic_LMTD           as Multitubular_Basic
756#+++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++#
757#       Basic Model for Double Pipe Heat Exchanger- LMTD Method
758#+++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++#
759VARIABLES
760
761DT0(Npipe)      as temp_delta   (Brief="Temperature Difference at Inlet",Lower=1);
762DTL(Npipe)              as temp_delta   (Brief="Temperature Difference at Outlet",Lower=1);
763LMTD(Npipe)             as temp_delta   (Brief="Logarithmic Mean Temperature Difference",Lower=1);
764
765EQUATIONS
766#+++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++#
767#                       Log Mean Temperature Difference
768#+++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++#
769for i in [1:Npipe]
770       
771if abs(DT0(i) - DTL(i)) > 0.05*max(abs([DT0(i),DTL(i)]))
772       
773        then
774"Log Mean Temperature Difference"
775        LMTD(i)= (DT0(i)-DTL(i))/ln(DT0(i)/DTL(i));
776
777        else
778       
779if DT0(i)*DTL(i) equal 0
780       
781        then
782"Log Mean Temperature Difference"
783        LMTD(i) = 0.5*(DT0(i)+DTL(i));
784       
785        else
786"Log Mean Temperature Difference"
787        LMTD(i) = 0.5*(DT0(i)+DTL(i))*(1-(DT0(i)-DTL(i))^2/(DT0(i)*DTL(i))*(1+(DT0(i)-DTL(i))^2/(DT0(i)*DTL(i))/2)/12);
788       
789end
790       
791end
792
793"Exchange Surface Area"
794        Unity(i).Details.Q = Unity(i).Details.Ud*Unity(i).Details.A*LMTD(i);
795
796end
797
798end
799
800Model Multitubular_Counter_NTU          as Multitubular_Basic
801
802VARIABLES
803
804Eft(Npipe)        as positive (Brief="Effectiveness",Default=0.05,Lower=1e-8);
805
806CONNECTIONS
807
808Unity([1:Npipe-1]).Outlet.Hot   to Unity([2:Npipe]).Inlet.Hot;
809Unity([2:Npipe]).Outlet.Cold    to Unity([1:Npipe-1]).Inlet.Cold;
810
811EQUATIONS
812
813for i in [1:Npipe]
814
815if Unity(i).Details.Cr equal 0
816       
817        then   
818"Effectiveness"
819        Eft(i) = 1-exp(-Unity(i).Details.NTU);
820       
821        else
822
823if Unity(i).Details.Cr equal 1
824       
825        then
826"Effectiveness in Counter Flow"
827        Eft(i) = Unity(i).Details.NTU/(1+Unity(i).Details.NTU);
828       
829        else
830"Effectiveness in Counter Flow"
831        Eft(i)*(1-Unity(i).Details.Cr*exp(-Unity(i).Details.NTU*(1-Unity(i).Details.Cr))) = (1-exp(-Unity(i).Details.NTU*(1-Unity(i).Details.Cr)));
832       
833end
834
835
836end
837
838"Energy Balance"
839        Unity(i).Details.Q      = Eft(i)*Unity(i).Details.Cmin*(Unity(i).Inlet.Hot.T-Unity(i).Inlet.Cold.T);
840       
841end
842
843end
844
845Model Multitubular_Cocurrent_NTU        as Multitubular_Basic
846
847VARIABLES
848
849Eft(Npipe)        as positive (Brief="Effectiveness",Default=0.05,Lower=1e-8);
850
851CONNECTIONS
852
853Unity([1:Npipe-1]).Outlet.Hot   to Unity([2:Npipe]).Inlet.Hot;
854Unity([1:Npipe-1]).Outlet.Cold  to Unity([2:Npipe]).Inlet.Cold;
855
856EQUATIONS
857
858for i in [1:Npipe]
859
860if Unity(i).Details.Cr equal 0
861       
862        then   
863"Effectiveness"
864        Eft(i) = 1-exp(-Unity(i).Details.NTU);
865       
866        else
867"Effectiveness in Cocurrent Flow"
868        Eft(i) = (1-exp(-Unity(i).Details.NTU*(1+Unity(i).Details.Cr)))/(1+Unity(i).Details.Cr);
869
870end
871
872"Energy Balance"
873        Unity(i).Details.Q      = Eft(i)*Unity(i).Details.Cmin*(Unity(i).Inlet.Hot.T-Unity(i).Inlet.Cold.T);
874       
875end
876
877end
878
879Model Multitubular_Counter_LMTD         as Multitubular_Basic_LMTD
880
881CONNECTIONS
882
883Unity([1:Npipe-1]).Outlet.Hot   to Unity([2:Npipe]).Inlet.Hot;
884Unity([2:Npipe]).Outlet.Cold    to Unity([1:Npipe-1]).Inlet.Cold;
885
886EQUATIONS
887for i in [1:Npipe]
888       
889"Temperature Difference at Inlet - Counter Flow"
890        DT0(i) = Unity(i).Inlet.Hot.T - Unity(i).Outlet.Cold.T;
891
892"Temperature Difference at Outlet - Counter Flow"
893        DTL(i) = Unity(i).Outlet.Hot.T - Unity(i).Inlet.Cold.T;
894       
895end
896
897end
898
899Model Multitubular_Cocurrent_LMTD       as Multitubular_Basic_LMTD
900
901CONNECTIONS
902
903Unity([1:Npipe-1]).Outlet.Hot   to Unity([2:Npipe]).Inlet.Hot;
904Unity([1:Npipe-1]).Outlet.Cold  to Unity([2:Npipe]).Inlet.Cold;
905
906EQUATIONS
907
908for i in [1:Npipe]
909       
910"Temperature Difference at Inlet - Cocurrent Flow"
911        DT0(i) = Unity(i).Inlet.Hot.T - Unity(i).Inlet.Cold.T;
912
913"Temperature Difference at Outlet - Cocurrent Flow"
914        DTL(i) = Unity(i).Outlet.Hot.T - Unity(i).Outlet.Cold.T;
915       
916end
917
918end
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