source: branches/gui/eml/pressure_changers/valve.mso @ 597

Last change on this file since 597 was 587, checked in by gerson bicca, 14 years ago

updated valve model

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File size: 7.2 KB
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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: Estefane Horn, Núbia do Carmo Ferreira
17*$Id: valve.mso 587 2008-08-04 22:45:14Z bicca $                                                                       
18*-------------------------------------------------------------------*#
19
20using "streams";
21       
22#*-------------------------------------------------------------------
23* Model of a valve (simplified)
24*--------------------------------------------------------------------
25*
26* Author: Paula B. Staudt
27*--------------------------------------------------------------------*#
28Model valve_simplified
29        ATTRIBUTES
30        Pallete         = true;
31        Icon            = "icon/Valve";
32        Brief           = "Model of a very simple valve - used in distillation column models.";
33        Info            =
34"== Assumptions ==
35* no flashing liquid in the valve;
36* the flow in the valve is adiabatic;
37* dynamics in the valve are neglected;
38* linear flow type.
39       
40== Specify ==
41* the inlet stream
42* the plug position (x) OR outlet temperature (Outlet.T) OR outlet pressure (Outlet.P)
43       
44        OR             
45       
46* the inlet stream excluding its flow (Inlet.F)
47* the outlet pressure (Outlet.P) OR outlet flow (Outlet.F)
48* the plug position (x)
49";
50
51        PARAMETERS
52outer PP as Plugin(Type="PP");
53outer NComp as Integer;
54       
55        VARIABLES
56in      Inlet   as stream       (Brief = "Inlet stream", PosX=0, PosY=0.7365, Symbol="_{in}");
57out     Outlet  as streamPH     (Brief = "Outlet stream", PosX=1, PosY=0.7365, Symbol="_{out}");
58        x as fraction (Brief="Plug Position");
59        rho as dens_mass (Brief="Fluid Density", Default=1e3);
60        v as vol_mol (Brief="Specific volume", Default=1e3);
61        Pdrop     as press_delta (Brief = "Pressure Drop", DisplayUnit = 'kPa', Symbol ="\Delta P");
62        Pratio  as positive     (Brief = "Pressure Ratio", Symbol ="P_{ratio}");       
63
64        PARAMETERS
65        rho_ref as dens_mass (Brief="Reference Density", Default=1e4);
66        k as Real (Brief="Valve Constant", Unit='gal/min/psi^0.5');
67
68        EQUATIONS
69        "Overall Molar Balance"
70        Inlet.F = Outlet.F;
71       
72        "Componente Molar Balance"
73        Inlet.z = Outlet.z;
74       
75        "Energy Balance"
76        Inlet.h = Outlet.h;
77
78        "Pressure Drop"
79        Outlet.P  = Inlet.P - Pdrop;
80
81        "Pressure Ratio"
82        Outlet.P = Inlet.P * Pratio;
83
84        "Density"
85        rho = Inlet.v*PP.VapourDensity((Inlet.T+Outlet.T)/2, (Inlet.P+Outlet.P)/2, Outlet.z) +
86                (1-Inlet.v)*PP.LiquidDensity((Inlet.T+Outlet.T)/2, (Inlet.P+Outlet.P)/2, Outlet.z);
87
88        "Volume"
89        v = Inlet.v*PP.VapourVolume((Inlet.T+Outlet.T)/2, (Inlet.P+Outlet.P)/2, Outlet.z) +
90                (1-Inlet.v)*PP.LiquidVolume((Inlet.T+Outlet.T)/2, (Inlet.P+Outlet.P)/2, Outlet.z);
91
92        if Pdrop > 0 then
93                "Flow"
94                Outlet.F * v = k*x*sqrt(Pdrop * rho_ref / rho ) ;
95        else
96                "Closed"
97                Outlet.F = 0 * 'kmol/h';
98        end
99end
100
101Model valve_flow
102        ATTRIBUTES
103        Pallete         = true;
104        Icon            = "icon/Valve";
105        Brief           = "Model of a very simple valve for setting the flow with a controller.";
106        Info            =
107"== Assumptions ==
108* nothing happens in this valve
109       
110== Specify ==
111* the inlet stream
112* the flow fraction
113";
114
115        PARAMETERS
116outer PP as Plugin(Type="PP");
117outer NComp as Integer;
118
119        MinFlow as flow_mol(Default=0);
120        MaxFlow as flow_mol(Default=1000);
121       
122        VARIABLES
123in      Inlet   as stream       (Brief = "Inlet stream", PosX=0, PosY=0.7365, Symbol="_{in}");
124out     Outlet  as stream       (Brief = "Outlet stream", PosX=1, PosY=0.7365, Symbol="_{out}");
125in      FlowFraction as fraction (Brief="Flow Signal", PosX=0.5, PosY=0);
126       
127        EQUATIONS
128        "Overall Molar Balance"
129        Outlet.F = Inlet.F;
130        "Temperature"
131        Outlet.T = Inlet.T;
132        "Pressure"
133        Outlet.P = Inlet.P;
134        "Energy Balance"
135        Outlet.h = Inlet.h;
136        "Vapour fraction"
137        Outlet.v = Inlet.v;
138
139        "Componente Molar Balance"
140        Outlet.z = Inlet.z;
141
142        "Flow computation"
143        Outlet.F = MinFlow + FlowFraction*(MaxFlow-MinFlow);
144end
145
146Model valve
147
148        ATTRIBUTES
149        Pallete         = true;
150        Icon            = "icon/Valve";
151        Brief   = "Model of a valve.";
152        Info            =
153"== Model of valves ==
154* Linear;
155* Parabolic;
156* Equal;
157* Quick;
158* Hyperbolic.
159       
160== Assumptions ==
161* First Order Dynamic;
162* Only Liquid or Only Vapour;
163* Isentalpic.
164       
165== Specify ==
166* the valve type;
167* the Valve Coefficient (Cv);
168* the valve time constant (Tau).
169";
170
171PARAMETERS
172
173outer PP                        as Plugin       (Brief = "External Physical Properties", Type = "PP");
174outer NComp     as Integer      (Brief = "Number of chemical components", Lower = 1);
175
176        ValveType       as Switcher             (Valid = ["linear", "parabolic", "equal", "quick", "hyperbolic"], Default = "linear");
177        ValidPhases     as Switcher             (Brief = "Valid Phases for Flash Calculation", Valid = ["Vapour-Only", "Liquid-Only"], Default="Liquid-Only");
178        Tau                     as time_sec             (Brief="valve time constant");
179        rho60F                  as dens_mass            (Brief = "Water Mass Density at 60 F",Hidden=true);     
180
181VARIABLES
182
183        Pdrop                   as press_delta          (Brief = "Pressure Drop", DisplayUnit = 'kPa', Symbol ="\Delta P");
184        Fvol                            as flow_vol                     (Brief = "Volumetric Flow");
185        fc                              as positive                     (Brief = "Opening Function",Hidden=true);
186        Cv                              as Real                                 (Brief="Valve Flow Coefficient", Unit='gal/min/psi^0.5');
187        StemPosition    as fraction                     (Brief = "Actual valve stem position");
188       
189
190        vm                              as vol_mol                      (Brief = "Mixture Molar Volume");
191        rho                             as dens_mass            (Brief = "Mixture Mass Density");       
192        vsp                             as fraction                     (Brief = "Valve stem position",Hidden=true);
193       
194in              Inlet   as stream                       (Brief = "Inlet stream", PosX=0, PosY=0.7365, Symbol="_{in}");
195out     Outlet  as streamPH             (Brief = "Outlet stream", PosX=1, PosY=0.7365, Symbol="_{out}");
196in              vsignal as fraction             (Brief = "Flow Signal", PosX=0.5, PosY=0);
197
198SET
199
200        rho60F = 984.252        * 'kg/m^3';
201       
202EQUATIONS
203
204"First order valve dynamics"
205        Tau*diff(StemPosition) = vsp-StemPosition;
206
207"Flow Signal"
208        vsp = vsignal;
209
210"Pressure Drop"
211        Outlet.P  = Inlet.P - Pdrop;
212
213"Enthalpy Balance"
214        Outlet.h = Inlet.h;
215       
216"Molar Balance"
217        Outlet.F = Inlet.F;
218       
219"Outlet Composition"
220        Outlet.z = Inlet.z;
221
222switch ValidPhases     
223       
224        case "Liquid-Only":
225       
226if Pdrop > 0 then
227
228"Valve Equation - Liquid Flow"
229        Fvol = fc*(Cv/sqrt(1/rho60F))*sqrt(Pdrop/rho);
230       
231else
232
233"Valve Equation - Liquid Flow"
234        Fvol = fc*(Cv/sqrt(1/rho60F))*sqrt(Pdrop/rho);
235
236end
237       
238"Liquid Mass Density"
239        rho = PP.LiquidDensity(Inlet.T,Inlet.P,Inlet.z);
240
241"Liquid Molar Volume"
242        vm = PP.LiquidVolume(Inlet.T,Inlet.P,Inlet.z);
243
244        case "Vapour-Only":
245       
246if Pdrop > 0 then #Update for gas flow !!!!
247
248"Valve Equation - Vapour Flow"
249        Fvol = fc*(Cv/sqrt(1/rho60F))*sqrt(Pdrop/rho);
250       
251else
252
253"Valve Equation - Vapour Flow"
254        Fvol = fc*(Cv/sqrt(1/rho60F))*sqrt(Pdrop/rho);
255
256end
257       
258"Vapour Mass Density"
259        rho = PP.VapourDensity(Inlet.T,Inlet.P,Inlet.z);
260
261"Vapour Molar Volume"
262        vm = PP.VapourVolume(Inlet.T,Inlet.P,Inlet.z);
263       
264end
265
266"Calculate Mass Flow"
267        Fvol = Inlet.F*vm;     
268       
269switch ValveType #Update the valve Type
270       
271        case "linear":
272
273                "Opening Equation"
274                fc = StemPosition;
275
276        case "parabolic":
277
278                "Opening Equation"
279                fc = StemPosition^2;
280
281        case "equal":
282
283                "Opening Equation"
284                fc = StemPosition^2/(2-StemPosition^4)^(1/2);
285
286        case "quick":
287       
288                "Opening Equation"
289                fc = 10*StemPosition/sqrt(1+99*StemPosition^2);
290
291        case "hyperbolic":
292
293                "Opening Equation"
294                fc = 0.1*StemPosition/sqrt(1-0.99*StemPosition^2);
295
296        end
297
298end
299
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