For same initial conditions different behavious of solver

[sitanshup31]

Forcode with exactly same initial conditions sometimes code converes and sometimes generates error.
Is this expected or due to complexity or inappropriate conditions.

[sitanshup31]

anyone else encoutered such issue?

[fwitte]

Hi and thank you for reporting. That is not expected/intended, can you post a reproducible example?

[sitanshup31]

Please see the code below
This code runs sometimes and generates error sometimes

from tespy.networks import Network
from tespy.components import Sink, Source, SteamTurbine,Merge,Pump,CycleCloser,PowerBus, HeatExchanger,Splitter,PowerSink,PowerBus,Condenser,SimpleHeatExchanger
from tespy.components.power.generator import Generator
from tespy.connections import Connection,PowerConnection,Ref

# 1. Initialize Network
nw = Network()
nw.units.set_defaults(
    temperature="degC", pressure="bar", enthalpy="kJ/kg", mass_flow='t/h', power="MW", heat="MW")
# 2. Define Components
steam_source = Source('Steam Source')
cc = CycleCloser('cycle closer')
cw_source=Source('Cw_in')
da=Merge('da',num_in=3)
hph1_merge=Merge('hph1_merge',num_in=2)
cond_mix=Merge('cond_mix',num_in=3)
cep=Pump('cep')
bfp=Pump('bfp')
gen=Generator('generator')
grid=PowerSink("grid")
cep.set_attr(eta_s=0.9)
bfp.set_attr(eta_s=0.9)
gen.set_attr(eta=0.987)
hpt1_0 = SteamTurbine('High Pressure Turbine1')
hpt1_1 = SteamTurbine('High Pressure Turbine2')
ipt1_0 = SteamTurbine('IP Turbine1')
ipt1_1 = SteamTurbine('IP Turbine2')
lpt1_0 = SteamTurbine('LP Turbine1')
lpt1_1 = SteamTurbine('LP Turbine2')
bfpt=SteamTurbine('bfpt')
cond1= Condenser("cond1")
cw_sink = Sink('cw_sink')
da_sink = Sink('da_sink')
ext_sink = Sink('ext_sink')
cond_sink = Sink('cond_sink')
s1=Splitter('s1',num_out=3) #HPT Outlet
shaft1=PowerBus("shaft1", num_in=6, num_out=1)
shaft2=PowerBus("shaft2", num_in=1, num_out=1)
#for HP Heater
s2=Splitter('s2',num_out=2)
# for LP Trubine Extraction/LPH
s3=Splitter('s3',num_out=2)
s4=Splitter('s4',num_out=2)
#Boilers
sg1 = SimpleHeatExchanger('steam generator1')
sg2 = SimpleHeatExchanger('steam generator2')

#introducing HP Heater from CRH
hph1= Condenser("hph1")
hph2= Condenser("hph2")

hph6a= HeatExchanger("hph6a")
#introducing LPH
lph1= Condenser("lph1")
#generator = Generator("generator")
#generator.set_attr(eta=0.98)
#grid=PowerSink("grid")
# 3. Create Connections

c1_1 = Connection(cc, 'out1', hpt1_0, 'in1', label='c1')
#c1_1=Connection(sg1,'out1',cc,'in1',label='c1_1')
c1_2 = Connection(sg1, 'out1', cc, 'in1')
#c2 = Connection(hpt1, 'out1', ipt1_0, 'in1')
# HPT Connections

c2_1_1=Connection(hpt1_0,'out1',s4,'in1')
c2_1_2=Connection(s4,'out1',hpt1_1,'in1')
c2_1_3=Connection(s4,'out2',hph2,'in1')
c2_1=Connection(hpt1_1,'out1',s2,'in1')
#Rheater Introduced
c2_2 = Connection(s2, 'out1', sg2, 'in1')
c2_1_4=Connection(hph2,'out1',hph1_merge,'in1')
#CRH to HPH
c2_1_5=Connection(s2,'out2',hph1_merge,'in2')
c2_3=Connection(hph1_merge,'out1',hph1,'in1')

#HPH Drip to D/A

c2_4=Connection(hph1,'out1',da,'in3')

#Reheater outlet to IPT

c3=Connection(sg2, 'out1', ipt1_0, 'in1')
#IPT Extraction @12  kg

c4_1=Connection(ipt1_0,'out1',s1,'in1')

c4_2 = Connection(s1, 'out1', ipt1_1, 'in1') 
#Extraction to D/A
#Commenting D/A Direct Connection
#c4_3 = Connection(s1, 'out2', da, 'in2') 
#Extraction to BFPT

c4_4 = Connection(s1, 'out3', bfpt, 'in1')
#introduce Simple Heater
c4_3 = Connection(s1, 'out2', hph6a, 'in1')
c4_5=Connection(hph6a,'out1',da,'in2')
#cooling water connections
c5 = Connection(cw_source, 'out1', cond1, 'in2') 

c6 = Connection(cond1, 'out2', cw_sink, 'in1') 

#Condenser o/l to CEP
c7_1=Connection(cond1, 'out1', cep, 'in1') 


c7_2=Connection(cep, 'out1', lph1, 'in2')
c7_3=Connection(lph1,'out2',da, 'in1')

 
#D/A o/l to BFP
c8_1=Connection(da,'out1',bfp,'in1')
#introducing hph6a
c8_5=Connection(bfp,'out1',hph6a,'in2')
c8_2=Connection(hph6a,'out2',hph1,'in2')
c8_3=Connection(hph1,'out2',hph2,'in2')
c8_4=Connection(hph2,'out2',sg1,'in1')
#Introducing LPT
c9=Connection(ipt1_1,'out1',lpt1_0,'in1')
#LPT Connections
c10_1=Connection(lpt1_0,'out1',s3,'in1')
c10_2=Connection(s3,'out1',lpt1_1,'in1')
c10_3=Connection(s3,'out2',lph1,'in1')
#Condenser Connections


c11_1=Connection(lpt1_1,'out1',cond_mix,'in1')
c11_2=Connection(bfpt,'out1',cond_mix,'in2')

c11_3=Connection(lph1,'out1',cond_mix,'in3')
c11_4=Connection(cond_mix,'out1',cond1,'in1')

e1=PowerConnection(bfpt,'power',shaft2,"power_in1",label="e1")
e2=PowerConnection(shaft2,'power_out1',bfp,"power",label="e2")
e3=PowerConnection(hpt1_0,'power',shaft1,"power_in1", label='e3')
e3_1=PowerConnection(hpt1_1,'power',shaft1,"power_in6", label='e3_1')
e4=PowerConnection(ipt1_0,'power',shaft1,"power_in2", label='e4')
e5=PowerConnection(ipt1_1,'power',shaft1,"power_in3", label='e5')
e6=PowerConnection(lpt1_0,'power',shaft1,"power_in4", label='e6')
e7=PowerConnection(lpt1_1,'power',shaft1,"power_in5", label='e7')
e8=PowerConnection(shaft1,'power_out1',gen,"power_in",label="e8")
e9=PowerConnection(gen,"power_out",grid,"power", label="e9")
nw.add_conns(c1_1,c1_2,c2_1,c2_1_1,c2_1_2,c2_1_3, c2_1_4,c2_1_5,c2_2,c2_3,c2_4,c3,c4_1,c4_2,c4_3,c4_4,c4_5,c5,c6,c7_1,c7_2,c7_3,c8_1,c8_2,c8_3,c8_4,c8_5,c9,c10_1,c10_2,c10_3,c11_1,c11_2,c11_3,c11_4,e1,e2,e3,e3_1,e4,e5,e6,e7,e8,e9)


# 4. Set Parameters
c1_1.set_attr(p=256, T=600,m=1827, fluid={'Water': 1})
c2_1_1.set_attr(p=80)
#HPT EXhaust/CRH
c2_1.set_attr(p=62)
#IP EXtraction
c4_1.set_attr(p=12)
#HRH Temp
c3.set_attr(T=610)
# CW in and out
c5.set_attr(p=2, T=33, fluid={'Water': 1}) 
c6.set_attr( p=1.5,T=42)
#Steam Generators
sg1.set_attr(pr=0.9)
sg2.set_attr(pr=0.9)
#Main Condenser
cond1.set_attr(pr1=1)
#either set this or set Condensate Temperature tofollow two step appraoch
#cond1.set_attr(ttd_u=2.5)
c7_1.set_attr(T=42)
#D/A outlet saturated water
c8_1.set_attr(x=0)

#set parameter for hph6a
t_ref_hph6a_ol=Ref(c4_3, 1.0, -110)

c4_5.set_attr(T=t_ref_hph6a_ol)
#Turbine Efficiencies
hpt1_0.set_attr(eta_s=0.9)
hpt1_1.set_attr(eta_s=0.9)
ipt1_0.set_attr(eta_s=0.9)
ipt1_1.set_attr(eta_s=0.9)
lpt1_0.set_attr(eta_s=0.9)
lpt1_1.set_attr(eta_s=0.9)
bfpt.set_attr(eta_s=0.9)

#IPT Exhaust
c9.set_attr(p=5.5)

#LP Extraction Pressure
c10_1.set_attr(p=2)


#HPH Parameters
hph1.set_attr(pr2=.95)
hph2.set_attr(pr2=.95)
hph6a.set_attr(pr2=.95)
#either set o/l temp or ttd
#hph1.set_attr(ttd_u=10)
#hph1.set_attr(ttd_u=10)
c8_2.set_attr(T=113)
c8_3.set_attr(T=140)
c8_4.set_attr(T=160)
#LPH Parameters
lph1.set_attr(pr2=.95)
#either set o/l temp or ttd
#lph1.set_attr(ttd_u=5)
c7_3.set_attr(T=115)

#hph1.set_attr(ttd_u=5)

nw.solve(mode='design')
nw.print_results()
cond1.set_attr(ttd_u=2.5)
hph1.set_attr(ttd_u=-2)
hph2.set_attr(ttd_u=-2)
lph1.set_attr(ttd_u=5)
c7_1.set_attr(T=None)
c7_3.set_attr(T=None)
#c10_3.set_attr(T=None)
c8_3.set_attr(T=None)
c8_4.set_attr(T=None)
#c8_2.set_attr(T=None)
nw.solve(mode='design')
#eq=nw.get_linear_dependent_variables()
#print(nw.get_presolved_variables())
#print(eq)
nw.print_results()

[fwitte]

What version are you using? I cannot get the first simulation to work at all.

[sitanshup31]

Version is 0.9.13 - Kelvin's Kingdom

Reproduced below is solution from one of the successful runs

| | m | p | h | T | x | phase |
|----------------------------------------+------------+-----------+-----------+-----------+-------------+----------------------|
| Cw_in:out1_cond1:in2 | 6.447e+04 | 2.000e+00 | 1.385e+02 | 3.300e+01 | 0.000e+00 | l |
| High Pressure Turbine1:out1_s4:in1 | 1.827e+03 | 8.000e+01 | 3.163e+03 | 4.086e+02 | -1.000e+00 | g |
| High Pressure Turbine2:out1_s2:in1 | 1.746e+03 | 6.200e+01 | 3.101e+03 | 3.722e+02 | 1.000e+00 | g |
| IP Turbine1:out1_s1:in1 | 1.258e+03 | 1.200e+01 | 3.218e+03 | 3.796e+02 | -1.000e+00 | g |
| IP Turbine2:out1_LP Turbine1:in1 | 1.394e+03 | 5.500e+00 | 3.027e+03 | 2.826e+02 | 1.000e+00 | g |
| LP Turbine1:out1_s3:in1 | 1.394e+03 | 2.000e+00 | 2.822e+03 | 1.761e+02 | 1.000e+00 | g |
| LP Turbine2:out1_cond_mix:in1 | 1.015e+03 | 9.351e-02 | 2.386e+03 | 4.450e+01 | 9.183e-01 | tp |
| bfp:out1_hph6a:in2 | 1.827e+03 | 3.318e+02 | 5.219e+02 | 1.187e+02 | nan | phase not recognized |
| bfpt:out1_cond_mix:in2 | 8.587e+01 | 9.351e-02 | 2.400e+03 | 4.450e+01 | 9.240e-01 | tp |
| c1 | 1.827e+03 | 2.560e+02 | 3.488e+03 | 6.000e+02 | nan | phase not recognized |
| cep:out1_lph1:in2 | 1.480e+03 | 1.793e+00 | 1.865e+02 | 4.451e+01 | 0.000e+00 | l |
| cond1:out1_cep:in1 | 1.480e+03 | 9.351e-02 | 1.863e+02 | 4.450e+01 | 1.739e-15 | tp |
| cond1:out2_cw_sink:in1 | 6.447e+04 | 1.500e+00 | 1.760e+02 | 4.200e+01 | 0.000e+00 | l |
| cond_mix:out1_cond1:in1 | 1.480e+03 | 9.351e-02 | 1.823e+03 | 4.450e+01 | 6.832e-01 | tp |
| da:out1_bfp:in1 | 1.827e+03 | 1.703e+00 | 4.835e+02 | 1.152e+02 | 0.000e+00 | tp |
| hph1:out1_da:in3 | 5.687e+02 | 1.703e+00 | 4.835e+02 | 1.152e+02 | 0.000e+00 | tp |
| hph1:out2_hph2:in2 | 1.827e+03 | 2.994e+02 | 1.228e+03 | 2.797e+02 | nan | phase not recognized |
| hph1_merge:out1_hph1:in1 | 5.687e+02 | 6.200e+01 | 2.834e+03 | 2.891e+02 | 1.000e+00 | g |
| hph2:out1_hph1_merge:in1 | 8.092e+01 | 6.200e+01 | 1.225e+03 | 2.777e+02 | -1.297e-16 | tp |
| hph2:out2_steam generator1:in1 | 1.827e+03 | 2.844e+02 | 1.314e+03 | 2.970e+02 | nan | phase not recognized |
| hph6a:out1_da:in2 | -2.218e+02 | 1.703e+00 | 3.012e+03 | 2.696e+02 | 1.000e+00 | g |
| hph6a:out2_hph1:in2 | 1.827e+03 | 3.152e+02 | 4.969e+02 | 1.130e+02 | nan | phase not recognized |
| lph1:out1_cond_mix:in3 | 3.794e+02 | 9.351e-02 | 1.863e+02 | 4.450e+01 | 1.739e-15 | tp |
| lph1:out2_da:in1 | 1.480e+03 | 1.703e+00 | 8.623e+02 | 1.152e+02 | 1.710e-01 | tp |
| s1:out1_IP Turbine2:in1 | 1.394e+03 | 1.200e+01 | 3.218e+03 | 3.796e+02 | -1.000e+00 | g |
| s1:out2_hph6a:in1 | -2.218e+02 | 1.200e+01 | 3.218e+03 | 3.796e+02 | -1.000e+00 | g |
| s1:out3_bfpt:in1 | 8.587e+01 | 1.200e+01 | 3.218e+03 | 3.796e+02 | -1.000e+00 | g |
| s2:out1_steam generator2:in1 | 1.258e+03 | 6.200e+01 | 3.101e+03 | 3.722e+02 | 1.000e+00 | g |
| s2:out2_hph1_merge:in2 | 4.877e+02 | 6.200e+01 | 3.101e+03 | 3.722e+02 | 1.000e+00 | g |
| s3:out1_LP Turbine2:in1 | 1.015e+03 | 2.000e+00 | 2.822e+03 | 1.761e+02 | 1.000e+00 | g |
| s3:out2_lph1:in1 | 3.794e+02 | 2.000e+00 | 2.822e+03 | 1.761e+02 | 1.000e+00 | g |
| s4:out1_High Pressure Turbine2:in1 | 1.746e+03 | 8.000e+01 | 3.163e+03 | 4.086e+02 | -1.000e+00 | g |
| s4:out2_hph2:in1 | 8.092e+01 | 8.000e+01 | 3.163e+03 | 4.086e+02 | -1.000e+00 | g |
| steam generator1:out1_cycle closer:in1 | 1.827e+03 | 2.560e+02 | 3.488e+03 | 6.000e+02 | nan | phase not recognized |
| steam generator2:out1_IP Turbine1:in1 | 1.258e+03 | 5.580e+01 | 3.686e+03 | 6.100e+02 | -1.000e+00 | g |
+----------------------------------------+------------+-----------+-----------+-----------+-------------+----------------------+

[sitanshup31]

usually runs once in 6/7 attempts

[fwitte]

It never does for me... In any case: The isentropic efficiency equations can be troublesome as well sometimes. I usually set an enthalpy difference for some of the turbines in the first simulation, then switch to the efficiency:

in initial simulation:

# hpt1_0.set_attr(eta_s=0.9)
c2_1_1.set_attr(h=Ref(c1_1, 1, -300))

and then in the second simulation:

hpt1_0.set_attr(eta_s=0.9)
c2_1_1.set_attr(h=None)

already reliably makes the model work for me. In fact, you could do that for all the turbines... With so many components it is sometimes quite difficult to have a good initial guess without any context. I plan to put some work into improving this in the future, I'd invite you to help :). In case you are based in Europe, there is going to be a user meeting in April in Brunswick, which could be relevant to you: https://github.com/oemof/oemof/wiki/Meeting-2026.04:-tespy-user-meeting.

[sitanshup31]

Thank You for help and quick response. Will do it for all theturbines. The model is stable till DESH is introduced in HP heater circuit. once DESH is introduced it generates problem.
I am based out of India. Certainly will like to help. I am working on a jscript based front end to model the objects/cycle through a web based front end and solve it on server side using tespy. In preliminary stage as of now.

[fwitte]

Are you planning to do that open source? If yes, we could work together on it. I starting some ideas in that direction as well... ;)

[sitanshup31]

Yes, if successful I have no issues with sharing it/open source

[sitanshup31]

Certainly we can work on it will appreciate any help/support from your side