/[ascend]/trunk/models/johnpye/combinedcycle.a4c
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revision 2180 by jpye, Thu Apr 8 08:52:05 2010 UTC revision 2181 by jpye, Mon Apr 12 05:02:15 2010 UTC
# Line 25  Line 25 
25      See also Example 10-9 from the book Çengel & Boles      See also Example 10-9 from the book Çengel & Boles
26      'Thermodynamcs: An Engineering Approach, 6th Ed, McGraw-Hill, 2008.      'Thermodynamcs: An Engineering Approach, 6th Ed, McGraw-Hill, 2008.
27    
28        At the current revision (12 Apr 2010), this model seems to be working OK.
29        The Cengel model needs convopt=RELNOM_SCALE with the QRSlv solver. The
30        Moran example just works.
31    
32      TODO: add exergy accounting to the model.      TODO: add exergy accounting to the model.
33    
34      Author: John Pye      Author: John Pye
# Line 42  MODEL air_steam_heat_exchanger REFINES a Line 46  MODEL air_steam_heat_exchanger REFINES a
46      inlet_cold.mdot, outlet_cold.mdot ARE_THE_SAME;      inlet_cold.mdot, outlet_cold.mdot ARE_THE_SAME;
47      mdot_cold ALIASES inlet_cold.mdot;      mdot_cold ALIASES inlet_cold.mdot;
48    
49      (* for perfect eps=1 case: inlet_cold.T, outlet.T ARE_THE_SAME;*)      (* we don't have epsilon worked out or specified here, so the heat exchanged
50        will depend on values specified outside this model. *)
     epsilon IS_A fraction;  
51    
52      Qdot IS_A energy_rate;      Qdot IS_A energy_rate;
     mdot_min IS_A mass_rate;  
     mdot_min = inlet.mdot + 0.5*(inlet.mdot - inlet_cold.mdot + abs(inlet.mdot - inlet_cold.mdot));  
   
     Qdot = epsilon * mdot_min * (inlet_cold.h - inlet.h);  
53      outlet.h = inlet.h + Qdot/inlet.mdot;      outlet.h = inlet.h + Qdot/inlet.mdot;
54      outlet_cold.h = inlet_cold.h - Qdot/inlet_cold.mdot;      outlet_cold.h = inlet_cold.h - Qdot/inlet_cold.mdot;
55  END air_steam_heat_exchanger;  END air_steam_heat_exchanger;
# Line 76  MODEL combinedcycle; Line 75  MODEL combinedcycle;
75      HE.outlet_cold, TU.inlet ARE_THE_SAME;      HE.outlet_cold, TU.inlet ARE_THE_SAME;
76      TU.outlet, CO.inlet ARE_THE_SAME;      TU.outlet, CO.inlet ARE_THE_SAME;
77      CO.outlet, PU.inlet ARE_THE_SAME;      CO.outlet, PU.inlet ARE_THE_SAME;
78      PU.outlet, HE.outlet_cold ARE_THE_SAME;      PU.outlet, HE.inlet_cold ARE_THE_SAME;
79    
80      Wdot, Wdot_gas, Wdot_vap IS_A energy_rate;      Wdot, Wdot_gas, Wdot_vap IS_A energy_rate;
81      Wdot_gas = GC.Wdot + GT.Wdot;      Wdot_gas = GC.Wdot + GT.Wdot;
# Line 130  METHOD moran_ex_9_13; Line 129  METHOD moran_ex_9_13;
129      PU.eta := 0.8;      PU.eta := 0.8;
130    
131      HE.outlet_cold.h := 3000 {kJ/kg};      HE.outlet_cold.h := 3000 {kJ/kg};
     FIX HE.epsilon;  
     HE.epsilon := 1;  
132      FIX BU.eta;      FIX BU.eta;
133      BU.eta := 1;      BU.eta := 1;
134    
135      FIX CO.outlet.x;      FIX CO.outlet.x;
136      CO.outlet.x := 0.001;      CO.outlet.x := 0.001;
137    
138        HE.outlet_cold.h := 3000 {kJ/kg};
139  END moran_ex_9_13;  END moran_ex_9_13;
140    
141  METHOD cengel_ex_10_9;  METHOD cengel_ex_10_9;
# Line 154  METHOD cengel_ex_10_9; Line 153  METHOD cengel_ex_10_9;
153      FIX GC.eta; GC.eta := 0.8;      FIX GC.eta; GC.eta := 0.8;
154      FIX GT.eta; GT.eta := 0.85;      FIX GT.eta; GT.eta := 0.85;
155            
156      FIX TU.inlet.p, TU.outlet.p;      FIX TU.inlet.p, CO.outlet.p;
157      TU.inlet.p := 7 {MPa};      TU.inlet.p := 7 {MPa};
158      TU.outlet.p := 5 {kPa};      CO.outlet.p := 5 {kPa};
159      FIX CO.outlet.x;      FIX CO.outlet.x;
160      CO.outlet.x := 0.001;      CO.outlet.x := 0.001;
161      FIX TU.inlet.T;      FIX TU.inlet.T;
# Line 167  METHOD cengel_ex_10_9; Line 166  METHOD cengel_ex_10_9;
166      FIX BU.eta; BU.eta := 1;      FIX BU.eta; BU.eta := 1;
167      FIX TU.eta; TU.eta := 1;      FIX TU.eta; TU.eta := 1;
168      FIX PU.eta; PU.eta := 1;      FIX PU.eta; PU.eta := 1;
169      FREE PU.eta;  
170        HE.outlet_cold.h := 3000 {kJ/kg};
171    
172        PU.dp.nominal := 50 {bar};
173        TU.dp.nominal := -50 {bar};
174    
175        
176  END cengel_ex_10_9;  END cengel_ex_10_9;
177    
178  END combinedcycle;    END combinedcycle;  

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john.pye@anu.edu.au
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