source: branches/gui/eml/stage_separators/flash.mso @ 825

Last change on this file since 825 was 825, checked in by mamuller, 13 years ago

fixed unit symbol and display unit for the new pressure variables.

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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* Author: Paula B. Staudt
16* $Id: flash.mso 825 2009-08-12 13:43:17Z mamuller $
17*--------------------------------------------------------------------*#
18
19using "streams";
20
21Model flash
22
23ATTRIBUTES
24        Pallete         = true;
25        Icon            = "icon/Flash";
26        Brief           = "Model of a Dynamic Flash Vessel.";
27        Info            =
28"== ASSUMPTIONS ==
29* perfect mixing of both phases;
30* thermodynamics equilibrium.
31
32== SET ==
33*Orientation: vessel position - vertical or horizontal;
34*Heads (bottom and top heads are identical)
35**elliptical: 2:1 elliptical heads (25% of vessel diameter);
36**hemispherical: hemispherical heads (50% of vessel diameter);
37**flat: flat heads (0% of vessel diameter);
38*Diameter: Vessel diameter;
39*Lenght: Side length of the cylinder shell;
40       
41== SPECIFY ==
42* the Inlet stream;
43* the outlet flows: OutletVapour.F and OutletLiquid.F;
44* the InletQ (the model requires an energy stream, also you can use a controller for setting the heat duty using the heat_flow model).
45
46== OPTIONAL ==
47* the Flash model has three control ports
48** TI OutletLiquid Temperature Indicator;
49** PI OutletLiquid Pressure Indicator;
50** LI Level Indicator;
51
52== INITIAL CONDITIONS ==
53* Initial_Temperature :  the Flash temperature (OutletLiquid.T);
54* Initial_Level : the Flash liquid level (Level);
55* Initial_Composition : (NoComps) OutletLiquid compositions.
56";
57       
58PARAMETERS
59outer PP                as Plugin       (Brief = "External Physical Properties", Type="PP");
60outer NComp     as Integer      (Brief = "Number of components", Lower = 1);
61
62        Mw(NComp)               as molweight    (Brief="Mol Weight", Hidden=true);
63        pi                      as positive             (Brief="Pi value", Default=3.141593,Hidden=true, Symbol="\pi");
64        g                               as acceleration         (Brief="Gravity Acceleration",Default=9.81,Hidden=true);
65       
66        Orientation     as Switcher     (Valid=["vertical","horizontal"],Default="vertical");
67        Heads                   as Switcher     (Valid=["elliptical","hemispherical","flat"],Default="flat");
68        Diameter                as length               (Brief="Vessel diameter", Symbol="D_{i}");
69        Lenght                  as length               (Brief="Side length of the cylinder shell", Symbol="L_{vessel}");
70       
71        Vhead_elliptical                as volume               (Brief="Elliptical Head Total Volume",Hidden=true, Symbol="V_{head}^{elliptical}");
72        Vhead_hemispherical     as volume               (Brief="Hemispherical Head Total Volume",Hidden=true, Symbol="V_{head}^{hemispherical}");
73        Vcylinder                               as volume               (Brief="Cylinder Total Volume",Hidden=true, Symbol="V_{cylinder}");
74        radius                                  as length               (Brief="Vessel radius",Hidden=true, Symbol="R_{cylinder}");
75       
76        Levelpercent_Initial                    as positive     (Brief="Initial liquid height in Percent", Default = 0.70);
77        Temperature_Initial                             as temperature  (Brief="Initial Liquid Temperature", Default = 330);
78        Composition_Initial(NComp)              as fraction             (Brief="Initial Composition", Default = 0.10);
79
80SET
81
82        Mw=PP.MolecularWeight();
83
84        Vhead_elliptical        = (pi*Diameter^3)/12;
85        Vhead_hemispherical = (pi*Diameter^3)/6;
86        Vcylinder = 0.25*(pi*Diameter^2)*Lenght;
87        radius = 0.5*Diameter;
88        g = 9.81 * 'm/(s^2)';
89
90VARIABLES
91
92in      Inlet                   as stream                       (Brief="Feed Stream", PosX=0, PosY=0.48, Symbol="_{in}");
93out     OutletLiquid    as liquid_stream        (Brief="Liquid outlet stream", PosX=0.43, PosY=1, Symbol="_{out}^{Liquid}");
94out     OutletVapour    as vapour_stream        (Brief="Vapour outlet stream", PosX=0.43, PosY=0, Symbol="_{out}^{Vapour}");
95in      InletQ                  as power                        (Brief="Heat Duty", PosX=1, PosY=0.81, Protected =true,Symbol="Q_{in}");
96
97        Vtotal                  as volume                       (Brief="Vessel total volume",Protected=true, Symbol="V_{total}");
98        Vfilled                 as volume                       (Brief="Vessel volume content",Protected=true, Symbol="V_{filled}");
99
100        TotalHoldup(NComp)              as mol  (Brief="Molar Holdup in the Vessel", Protected=true);
101        LiquidHoldup                    as mol  (Brief="Molar liquid holdup", Protected=true);
102        VapourHoldup                    as mol  (Brief="Molar vapour holdup", Protected=true);
103       
104        E                       as energy               (Brief="Total Energy Holdup in the Vessel", Protected=true);
105        vL                      as volume_mol   (Brief="Liquid Molar Volume", Protected=true);
106        vV                      as volume_mol   (Brief="Vapour Molar volume", Protected=true);
107        Level           as length               (Brief="liquid height", Protected=true);
108        Across          as area                 (Brief="Vessel cylinder shell Cross section area", Hidden=true, Symbol="A_{cross}");
109        vfrac           as positive     (Brief="Vapourization fraction", Symbol="\phi", Protected=true);
110        Pratio          as positive             (Brief = "Pressure Ratio", Symbol ="P_{ratio}", Protected=true);       
111        Pdrop           as press_delta  (Brief = "Pressure Drop", DisplayUnit = 'kPa', Symbol ="\Delta P", Protected=true);
112
113        Peq             as pressure             (Brief="Equilibrium pressure on the liquid surface", Protected=true, Symbol="\Delta P_{eq}");
114        Pstatic         as pressure             (Brief="Static head at the bottom of the tank", Protected = true, Symbol="P_{static}^{Liquid}");
115
116out     TI as control_signal    (Brief="Temperature Indicator", PosX=1, PosY=0.39, Protected=true);
117out     PI as control_signal    (Brief="Pressure Indicator", PosX=1, PosY=0.21, Protected=true);
118out     LI as control_signal    (Brief="Level Indicator", PosX=1, PosY=0.59, Protected=true);
119
120INITIAL
121
122"Initial level Percent"
123        LI = Levelpercent_Initial;
124       
125"Initial Outlet Liquid Temperature"
126        OutletLiquid.T = Temperature_Initial;
127       
128"Initial Outlet Liquid Composition Normalized"
129        OutletLiquid.z(1:NComp - 1) = Composition_Initial(1:NComp - 1)/sum(Composition_Initial);
130
131EQUATIONS
132
133switch Orientation
134
135case "vertical":
136
137"Vessel Cross Section Area"
138        Across = 0.25*(pi*Diameter^2);
139
140switch Heads
141
142case "elliptical":
143
144"Vessel Total Volume"
145        Vtotal = Vhead_elliptical +     Vcylinder;
146
147if Level < 0.25*Diameter then
148
149"Vessel Filled Volume"
150        Vfilled = 0.25*pi*(((Diameter*Level)/(0.25*Diameter))^2)*(0.25*Diameter-Level/3);
151
152else
153
154"Vessel Filled Volume"
155        Vfilled = 0.25*pi*(Diameter^2)*(Level - 0.25*Diameter/3);
156
157end
158
159case "hemispherical":
160
161"Vessel Total Volume"
162        Vtotal = Vhead_hemispherical + Vcylinder;
163
164if Level < 0.5*Diameter then
165
166"Vessel Filled Volume"
167        Vfilled = 0.25*pi*(Level^2)*(2*Diameter-4*Level/3);
168
169else
170
171"Vessel Filled Volume"
172        Vfilled = 0.25*pi*((2/3)*((0.5*Diameter)^3) - (0.25*(Diameter)^3) + Level*Diameter^2);
173
174end
175
176case "flat":
177
178"Vessel Total Volume"
179        Vtotal = Vcylinder;
180
181"Vessel Filled Volume"
182        Vfilled = Across*Level;
183
184end
185
186case "horizontal":
187
188"Vessel Cross Section Area"
189        Across = (radius^2)*acos((radius-Level)/radius)-(radius-Level)*sqrt((2*radius*Level-Level^2));
190
191switch Heads
192
193case "elliptical":
194
195"Vessel Total Volume"
196        Vtotal = Vhead_elliptical +     Vcylinder;
197
198"Vessel Filled Volume"
199        Vfilled = 0.5236*Level^2*(1.5*Diameter-Level) + Across*Lenght;
200
201case "hemispherical":
202
203"Vessel Total Volume"
204        Vtotal = Vhead_hemispherical + Vcylinder;
205
206"Vessel Filled Volume"
207        Vfilled = 1.0472*Level^2*(1.5*Diameter-Level) + Across*Lenght;
208
209case "flat":
210
211"Vessel Total Volume"
212        Vtotal = Vcylinder;
213
214"Vessel Filled Volume"
215        Vfilled = Across*Lenght;
216
217end
218
219end
220
221"Component Molar Balance"
222        diff(TotalHoldup)=Inlet.F*Inlet.z - OutletLiquid.F*OutletLiquid.z - OutletVapour.F*OutletVapour.z;
223       
224"Energy Balance"
225        diff(E) = Inlet.F*Inlet.h - OutletLiquid.F*OutletLiquid.h - OutletVapour.F*OutletVapour.h + InletQ;
226       
227"Molar Holdup"
228        TotalHoldup = LiquidHoldup*OutletLiquid.z + VapourHoldup*OutletVapour.z;
229       
230"Energy Holdup"
231        E = LiquidHoldup*OutletLiquid.h + VapourHoldup*OutletVapour.h - OutletLiquid.P*Vtotal;
232       
233"Mol fraction normalisation"
234        sum(OutletLiquid.z)=1.0;
235
236"Mol fraction normalisation"
237        sum(OutletLiquid.z)=sum(OutletVapour.z);
238
239"Vaporization Fraction"
240        OutletVapour.F = Inlet.F * vfrac;
241
242"Liquid Volume"
243        vL = PP.LiquidVolume(OutletLiquid.T, Peq, OutletLiquid.z);
244
245"Vapour Volume"
246        vV = PP.VapourVolume(OutletVapour.T, Peq, OutletVapour.z);
247       
248"Chemical Equilibrium"
249        PP.LiquidFugacityCoefficient(OutletLiquid.T, Peq, OutletLiquid.z)*OutletLiquid.z =
250                PP.VapourFugacityCoefficient(OutletVapour.T, Peq, OutletVapour.z)*OutletVapour.z;
251       
252"Thermal Equilibrium"
253        OutletVapour.T = OutletLiquid.T;
254
255"Mechanical Equilibrium for the Vapour Phase"
256        OutletVapour.P = Peq;
257       
258"Static Head"   
259        Pstatic = PP.LiquidDensity(OutletLiquid.T, Peq, OutletLiquid.z) * g * Level;
260
261"Mechanical Equilibrium for the Liquid Phase"
262        OutletLiquid.P = Peq + Pstatic;
263
264"Pressure Drop"
265        OutletLiquid.P  = Inlet.P - Pdrop;
266
267"Pressure Ratio"
268        OutletLiquid.P = Inlet.P * Pratio;
269
270"Geometry Constraint"
271        Vtotal = LiquidHoldup * vL + VapourHoldup * vV;
272
273"Temperature indicator"
274        TI * 'K' = OutletLiquid.T;
275
276"Pressure indicator"
277        PI * 'atm' = OutletLiquid.P;
278
279"Level indicator"
280        LI*Vtotal= Vfilled;
281
282"Liquid Level"
283        LiquidHoldup * vL = Vfilled;
284
285end
286
287Model flash_steady
288
289ATTRIBUTES
290        Pallete         = true;
291        Icon            = "icon/Flash";
292        Brief           = "Model of a static PH flash.";
293        Info            =
294"This model is for using the flashPH routine available on VRTherm.
295
296== ASSUMPTIONS ==
297* perfect mixing of both phases;
298* thermodynamics equilibrium.
299* static model.
300
301== SPECIFY ==
302* The Inlet stream;
303* The heat duty;
304* The outlet pressure.
305";     
306
307PARAMETERS
308
309outer PP                as Plugin(Brief = "External Physical Properties", Type="PP");
310outer NComp     as Integer;
311
312VARIABLES
313
314in      Inlet                   as stream                       (Brief="Feed Stream", PosX=0, PosY=0.48, Symbol="_{in}");
315out     OutletLiquid    as liquid_stream        (Brief="Liquid outlet stream", PosX=0.43, PosY=1, Symbol="_{out}^{Liquid}");
316out     OutletVapour    as vapour_stream        (Brief="Vapour outlet stream", PosX=0.43, PosY=0, Symbol="_{out}^{Vapour}");
317in      InletQ                  as power                        (Brief="Heat Duty", PosX=1, PosY=0.81, Protected =true,Symbol="Q_{in}");
318
319        vfrac           as fraction             (Brief="Vaporization fraction", Symbol="\phi", Protected =true);
320        h                       as enth_mol             (Brief="Mixture enthalpy", Hidden =true);
321        Pratio          as positive     (Brief = "Pressure Ratio", Symbol ="P_{ratio}", Protected =true);       
322        Pdrop           as press_delta  (Brief = "Pressure Drop", DisplayUnit = 'kPa', Symbol ="\Delta P", Protected =true);
323
324EQUATIONS
325
326if vfrac > 0 and vfrac <1
327
328then
329"The flash calculation"
330        [vfrac, OutletLiquid.z, OutletVapour.z] = PP.Flash(OutletVapour.T, OutletVapour.P, Inlet.z);
331
332else
333"Chemical equilibrium"
334        [vfrac,OutletLiquid.z,OutletVapour.z]=PP.FlashPH(OutletLiquid.P,h,Inlet.z);
335
336end
337
338"Global Molar Balance"
339        Inlet.F = OutletVapour.F + OutletLiquid.F;
340
341"Vapour Fraction"
342        OutletVapour.F = Inlet.F * vfrac;
343
344"Energy Balance"
345        Inlet.F*(h - Inlet.h) = InletQ;
346        Inlet.F*h = Inlet.F*(1-vfrac)*OutletLiquid.h + Inlet.F*vfrac*OutletVapour.h;
347
348"Thermal Equilibrium"
349        OutletVapour.T = OutletLiquid.T;
350       
351"Mechanical Equilibrium"
352        OutletVapour.P = OutletLiquid.P;
353
354"Pressure Drop"
355        OutletLiquid.P  = Inlet.P - Pdrop;
356
357"Pressure Ratio"
358        OutletLiquid.P = Inlet.P * Pratio;
359
360end
361
362Model FlashPHSteady
363        ATTRIBUTES
364        Pallete         = false;
365        Icon            = "icon/Flash";
366        Brief           = "Another model of a static PH flash.";
367        Info            =
368"This model shows how to model a pressure enthalpy flash
369directly with the EMSO modeling language.
370
371This model is for demonstration purposes only, the flashPH
372routine available on VRTherm is much more robust.
373
374== Assumptions ==
375* perfect mixing of both phases;
376
377== Specify ==
378* the feed stream;
379* the heat duty;
380* the outlet pressure.
381";     
382       
383        PARAMETERS
384outer PP as Plugin(Brief = "External Physical Properties", Type="PP");
385outer NComp as Integer;
386        B as Real(Default=1000, Brief="Regularization Factor");
387
388        VARIABLES
389in      Inlet as stream(Brief="Feed Stream", PosX=0, PosY=0.5421, Symbol="_{in}");
390out     OutletL as liquid_stream(Brief="Liquid outlet stream", PosX=0.4790, PosY=1, Symbol="_{outL}");
391out     OutletV as vapour_stream(Brief="Vapour outlet stream", PosX=0.4877, PosY=0, Symbol="_{outV}");
392in      InletQ as power (Brief="Rate of heat supply", PosX=1, PosY=0.7559, Symbol="_{in}");
393        vfrac as fraction(Brief="Vaporization fraction", Symbol="\phi");
394        vsat as Real(Lower=-0.1, Upper=1.1, Brief="Vaporization fraction if saturated", Symbol="\phi_{sat}");
395        Tsat as temperature(Lower=173, Upper=1473, Brief="Temperature if saturated");
396        xsat(NComp) as Real(Lower=0, Upper=1, Brief="Liquid composition if saturated");
397        ysat(NComp) as Real(Lower=0, Upper=1, Brief="Vapour composition if saturated");
398        Pratio as positive (Brief = "Pressure Ratio", Symbol ="P_{ratio}");     
399        Pdrop as press_delta (Brief = "Pressure Drop", DisplayUnit = 'kPa', Symbol ="\Delta P");
400       
401        zero_one as fraction(Brief="Regularization Variable");
402        one_zero as fraction(Brief="Regularization Variable");
403
404        EQUATIONS
405        "Chemical equilibrium"
406        PP.LiquidFugacityCoefficient(Tsat, OutletL.P, xsat)*xsat =
407                PP.VapourFugacityCoefficient(Tsat, OutletV.P, ysat)*ysat;
408
409        "Global Molar Balance"
410        Inlet.F = OutletV.F + OutletL.F;
411        OutletV.F = Inlet.F * vfrac;
412
413        "Component Molar Balance"
414        Inlet.F*Inlet.z = OutletL.F*xsat + OutletV.F*ysat;
415        sum(xsat) = sum(ysat);
416
417        "Energy Balance if saturated"
418        Inlet.F*Inlet.h  + InletQ =
419                Inlet.F*(1-vsat)*PP.LiquidEnthalpy(Tsat, OutletL.P, xsat) +
420                Inlet.F*vsat*PP.VapourEnthalpy(Tsat, OutletV.P, ysat);
421
422        "Real Energy Balance"
423        Inlet.F*Inlet.h  + InletQ =
424                Inlet.F*(1-vfrac)*OutletL.h + Inlet.F*vfrac*OutletV.h;
425
426        "Thermal Equilibrium"
427        OutletV.T = OutletL.T;
428       
429        "Mechanical Equilibrium"
430        OutletV.P = OutletL.P;
431
432        "Pressure Drop"
433        OutletL.P  = Inlet.P - Pdrop;
434
435        "Pressure Ratio"
436        OutletL.P = Inlet.P * Pratio;
437
438        # regularization functions
439        zero_one = (1 + tanh(B * vsat))/2;
440        one_zero = (1 - tanh(B * (vsat - 1)))/2;
441       
442        vfrac = zero_one * one_zero * vsat + 1 - one_zero;
443        OutletL.z = zero_one*one_zero*xsat + (1-zero_one*one_zero)*Inlet.z;
444        OutletV.z = zero_one*one_zero*ysat + (1-zero_one*one_zero)*Inlet.z;
445end
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