Solver not converging with feed water tank

[Cody722]

Hey everyone,

This is my first ever content on github so sorry in advance if I did something incorrectly.

I'm currently doing a small task at university where I'm supposed to make a combination of GT + HRSG which supplies steam at 3 different pressure levels (40,14, and 4). The system is relatively simple as the incoming supply of condensate is separated into 3 branches with each branch supplying steam at each pressure level with help of pumps. So far I have successfully solved the system without incorporating a feed water tank (merger) on the low pressure branch, but once I incorporate it, the solver can't seem to converge on a solution (singularity in Jacobian Matrix).

Stream 15 should have a vapour content of 0. I have tried simulating this system in Ebsilon and it works so I don't think the scheme itself is badly designed.

Below is the code I use, any help would be very much welcome.

from tespy.networks import Network
from tespy.components import (Valve, SimpleHeatExchanger, Compressor, CycleCloser, Drum, Splitter, CombustionChamber, Merge, Sink, Source, HeatExchanger, CycleCloser, Turbine, Compressor,Pump, DropletSeparator)
from tespy.connections import Connection, Bus, Ref
from CoolProp.CoolProp import PropsSI
from CoolProp.CoolProp import Props
import numpy as np
import shutil
from tespy.tools import ExergyAnalysis


nw = Network(p_unit='bar', T_unit='C', m_unit= 't / h',h_unit='kJ / kg',iterinfo=False) #Defining Network
sf = Source('fuel') #Defining the fuel source
fg = Sink('flue gas outlet') #Defining the flue gas sink
amb = Source('ambient air') #Defining the ambient air source
sink = Sink('sink 1')
fluid = "H2O"
fuel = "CH4"
aircomp = Compressor('air compressor')
aircomp.set_attr(eta_s=0.8)
comb = CombustionChamber('combustion chamber')
turb = Turbine ('gas turbine')
turb.set_attr(eta_s=0.9)
ec3 = HeatExchanger('Fuel pre-heater')
ec3.set_attr(pr1=1,pr2=1)
ev1 = HeatExchanger('evaporator 40 bar')
ev1.set_attr(pr1=1,pr2=1)
ec1 = HeatExchanger('economiser 40 bar')
ec1.set_attr(pr1=1,pr2=1)
cons_closer1 = Sink("consumer 1")
pump_steam1 = Pump('compressor 40 bar')
fg = Sink('flue gas outlet') #Defining the flue gas sink
condensate = Source("Source of condensate")
pump_condensate = Pump('compressor for condensate')
pump_condensate.set_attr(eta_s=0.8)
split_steam_1 = Splitter('splitter 1', num_out=2)
split_steam_2 = Splitter('splitter 2', num_out=2)
cons_closer2 = Sink("consumer 2")
pump_steam2 = Pump('pump 2')
ev2 = HeatExchanger('evaporator 14 bar')
ev2.set_attr(pr1=1,pr2=1)
ec2 = HeatExchanger('economiser 14 bar')
ec2.set_attr(pr1=1,pr2=1)
cons_closer3 = Sink("consumer 3")
ev3 = HeatExchanger('evaporator 4 bar')
ev3.set_attr(pr1=1,pr2=1)
drum = Merge('water tank',num_in=2)
split_low = Splitter('splitter 3',num_out=2)


######################################################


c1=Connection(amb,'out1',aircomp,'in1', label="1" )
c2 = Connection(aircomp, 'out1', comb, 'in2',label="2")
c3 =Connection(sf,'out1', ec3,'in2',label="3")
c4 = Connection(ec3,'out2',comb,'in1',label="4")
c5 =Connection(comb,'out1',turb,'in1',label="5")
c6 = Connection(turb,'out1',ev1,'in1',label="6")
c7 = Connection(ev1,'out1',ev2,'in1',label="7")
c8 = Connection(ev2,'out1',ev3,'in1',label="8")
c9 = Connection(ev3,'out1',ec1,'in1',label="9")
c10 = Connection(ec1,'out1',ec2,'in1',label="10")
c11 = Connection(ec2,'out1',ec3,'in1',label="11")
c12 = Connection(ec3,'out1',fg,'in1',label="12")
c28 = Connection(ev1,'out2',cons_closer1,'in1',label="28")
c18 = Connection(split_steam_1,'out1',pump_steam1,'in1',label="18")
c21 = Connection(pump_steam1,'out1',ec1,'in2',label="21")
c23 = Connection(ec1,'out2',ev1,'in2',label="23")
c27 = Connection(ev2,'out2',cons_closer2,'in1',label="27")
c17 = Connection(split_steam_1,'out2',pump_steam2,'in1',label="17")
c20 = Connection(pump_steam2,'out1',ec2,'in2',label="20")
c22 = Connection(ec2,'out2',ev2,'in2',label="22")
c24 = Connection(ev3,'out2',split_low,'in1',label="24")
c25 = Connection(split_low,'out1',drum,'in1',label="25")
c26 = Connection(split_low,'out2',cons_closer3,'in1',label="26")
c19 = Connection(split_steam_2,'out1',ev3,'in2',label="19")
c16 = Connection(split_steam_2,'out2',split_steam_1,'in1',label="16")
c13 = Connection(condensate,'out1',pump_condensate,'in1',label="13")
c14 = Connection(pump_condensate,'out1',drum,'in2',label="14")
c15 = Connection(drum,'out1',split_steam_2,'in1',label="15")

nw.add_conns(c1,c2,c3,c4,c5,c6,c7,c8,c9,c10,c11,c12,c13,c14,c15,c16,c17,c18,c19,c20,c21,c22,c23,c24,c25,c26,c27,c28)


##################################################################


pump_steam1.set_attr(eta_s=0.8)
pump_steam2.set_attr(eta_s=0.8)
c1.set_attr(m=6408, p=1, T=15, fluid={ 'N2': 0.79, 'O2': 0.21})
c3.set_attr(p=30, T=15, fluid={ 'CH4': 1})
c4.set_attr(T=230)
c5.set_attr(h=2400)
c6.set_attr(p=1)
c14.set_attr(p=4)
c15.set_attr(x=0)
Tc28_guess = PropsSI("T", "Q", 1, "P", 40*1e5, fluid)+1.6
Hc28_guess= PropsSI("H", "Q",1, "T", Tc28_guess,fluid)/1e3
c28.set_attr(h=Hc28_guess)
c13.set_attr(p=1,T=60,m=1350)
c15.set_attr(fluid={fluid:1})
c18.set_attr(m=90)
c21.set_attr(p=40)
Tc23_guess = PropsSI("T", "Q", 0, "P", 40*1e5, fluid)-3
Hc23_guess= PropsSI("H", "Q",0, "T", Tc23_guess,fluid)/1e3
c23.set_attr(h=Hc23_guess)
Tc27_guess = PropsSI("T", "Q", 1, "P", 14*1e5, fluid)+1
Hc27_guess= PropsSI("H", "Q",1, "T", Tc27_guess,fluid)/1e3
c27.set_attr(h=Hc27_guess)
c20.set_attr(p=14)
c17.set_attr(m=360)
Tc22_guess = PropsSI("T", "Q", 0, "P", 14*1e5, fluid)-3
Hc22_guess= PropsSI("H", "Q",0, "T", Tc22_guess,fluid)/1e3
c22.set_attr(h=Hc22_guess)
Tc24_guess = PropsSI("T", "Q", 1, "P", 4*1e5, fluid)+1.6
Hc24_guess= PropsSI("H", "Q",1, "T", Tc24_guess,fluid)/1e3
c24.set_attr(h=Hc24_guess)

nw.solve('design')
nw.print_results()

[fwitte]

Hi @Cody722 ,

I can give you a response later this week.

Have a nice day!

[fwitte]

Hi @Cody722,

this fell off my table, is help still needed? If yes, could you provide a flow chart to make it more readable? For me it shows one parameter too much specified btw.

best