Need help on my district heating code

[Delilay]

Hello everyone,
I need help with my code, please! I used TESPy to model a district heating system with a single consumer in order to find the optimal supply temperature, and it works very well. However, once I add more consumers, I have an issue with the initial values, and it doesn't work. I tried using the documentation for the initial value errors, but I can't solve it! I need your advice and help, please! Thank you.

[fwitte]

Hi @Delilay,

can you share a code example, that is failing and is as small as possible?

Thank you very much!

Best

[Delilay]

I did it for multiple customers but her it is one small code just for 2 customers.

from tespy.components.basics.cycle_closer import CycleCloser
from tespy.networks import Network
from tespy.components import (
   Pipe, Pump, Valve, SimpleHeatExchanger, Merge, Splitter
)
from tespy.connections import Connection

nw = Network()
nw.set_attr(T_unit='C', p_unit='bar', m_unit='kg / s', h_unit='kJ / kg')

# central heating plant
hs = SimpleHeatExchanger('chaufferie')
cc = CycleCloser('cycle closer1')
cc2 = CycleCloser('cycle closer2')

pu = Pump('feed pump')

# consumer
cons1 = SimpleHeatExchanger('stade')
cons2 = SimpleHeatExchanger('ancienne école')
val1 = Valve('control valve1')
val2 = Valve('control valve2')

# pipes for the stadium
pipe_feed1 = Pipe('feed pipe1')
pipe_feed2 = Pipe('feed pipe2')

pipe_return1 = Pipe('return pipe1')
pipe_return2 = Pipe('return pipe2')

# pipes pour l'école
fp2 = Pipe('feed pipe ecole')
rp2 = Pipe('return pipe ecole')

me1 = Merge('merge1', num_in=2)
sp1 = Splitter('splitter1', num_out=2)

# connections stade
c0 = Connection(cc, "out1", hs, "in1", label="0")
c1 = Connection(hs, "out1", pu, "in1", label="1")
c2 = Connection(pu, "out1", pipe_feed1, "in1", label="2")
c3 = Connection(pipe_feed1, "out1", sp1, "in1", label="3")
c4 = Connection(sp1, "out1", pipe_feed2, "in1", label="4")
c5 = Connection(pipe_feed2, "out1", val1, "in1", label="5")
c8 = Connection(val1, "out1", cons1, "in1", label="8")
c9 = Connection(cons1, "out1", pipe_return2, "in1", label="9")
c12 = Connection(pipe_return2, "out1", me1, "in1", label="12")
c13 = Connection(me1, "out1", pipe_return1, "in1", label="13")
c14 = Connection(pipe_return1, "out1", cc, "in1", label="14")

#connections ancienne école
c00 = Connection(sp1, "out2", fp2, "in1", label="00")
c01 = Connection(fp2, "out1", val2, "in1", label="01")
c02 = Connection(val2, "out1", cons2, "in1", label="02")
c03 = Connection(cons2, "out1", rp2, "in1", label="03")
c04 = Connection(rp2, "out1", me1, "in2", label="04")



nw.add_conns(c0, c1, c2, c3, c4, c5, c8, c9, c12, c13, c14)
nw.add_conns(c00, c01, c02, c03, c04)

hs.set_attr(pr=1)
pu.set_attr(eta_s=0.75)

# Consumer 1 (stade)
cons1.set_attr(Q=-17e4, pr=1)
pipe_return1.set_attr(Q=-182, pr=0.98)
pipe_feed2.set_attr(Q=-250, pr=0.98)
c1.set_attr(T=82, p=10, fluid={'INCOMP::Water': 1})
c2.set_attr(p=15)
#c8.set_attr(p=15)
c5.set_attr(T=62)

# Consumer 2 (ancienne école)
cons2.set_attr(Q=-14e4, pr=1)
fp2.set_attr(Q=-50, pr=0.98)
rp2.set_attr(Q=-150, pr=0.98)
c01.set_attr(T=82, p=14.47)
c00.set_attr(p=15)
c04.set_attr(p=10)
c0.set_attr(T=62)

# Résolution du réseau
nw.solve(mode="design")
nw.print_results()

[fwitte]

Hi, I am out of office currently, so thank you for your patience. There are a couple of issues, I marked them

from tespy.components.basics.cycle_closer import CycleCloser
from tespy.networks import Network
from tespy.components import (
   Pipe, Pump, Valve, SimpleHeatExchanger, Merge, Splitter
)
from tespy.connections import Connection

nw = Network()
nw.set_attr(T_unit='C', p_unit='bar', m_unit='kg / s', h_unit='kJ / kg')

# central heating plant
hs = SimpleHeatExchanger('chaufferie')
cc = CycleCloser('cycle closer1')
cc2 = CycleCloser('cycle closer2')

pu = Pump('feed pump')

# consumer
cons1 = SimpleHeatExchanger('stade')
cons2 = SimpleHeatExchanger('ancienne école')
val1 = Valve('control valve1')
val2 = Valve('control valve2')

# pipes for the stadium
pipe_feed1 = Pipe('feed pipe1')
pipe_feed2 = Pipe('feed pipe2')

pipe_return1 = Pipe('return pipe1')
pipe_return2 = Pipe('return pipe2')

# pipes pour l'école
fp2 = Pipe('feed pipe ecole')
rp2 = Pipe('return pipe ecole')

me1 = Merge('merge1', num_in=2)
sp1 = Splitter('splitter1', num_out=2)

# connections stade
c0 = Connection(cc, "out1", hs, "in1", label="0")
c1 = Connection(hs, "out1", pu, "in1", label="1")
c2 = Connection(pu, "out1", pipe_feed1, "in1", label="2")
c3 = Connection(pipe_feed1, "out1", sp1, "in1", label="3")
c4 = Connection(sp1, "out1", pipe_feed2, "in1", label="4")
c5 = Connection(pipe_feed2, "out1", val1, "in1", label="5")
c8 = Connection(val1, "out1", cons1, "in1", label="8")
c9 = Connection(cons1, "out1", pipe_return2, "in1", label="9")
c12 = Connection(pipe_return2, "out1", me1, "in1", label="12")
c13 = Connection(me1, "out1", pipe_return1, "in1", label="13")
c14 = Connection(pipe_return1, "out1", cc, "in1", label="14")

#connections ancienne école
c00 = Connection(sp1, "out2", fp2, "in1", label="00")
c01 = Connection(fp2, "out1", val2, "in1", label="01")
c02 = Connection(val2, "out1", cons2, "in1", label="02")
c03 = Connection(cons2, "out1", rp2, "in1", label="03")
c04 = Connection(rp2, "out1", me1, "in2", label="04")



nw.add_conns(c0, c1, c2, c3, c4, c5, c8, c9, c12, c13, c14)
nw.add_conns(c00, c01, c02, c03, c04)

hs.set_attr(pr=1)
pu.set_attr(eta_s=0.75)

# Consumer 1 (stade)
cons1.set_attr(Q=-17e4, pr=1)
# there is no heat loss information on the return pipe 1 yet
pipe_return1.set_attr(Q=-182)
pipe_return2.set_attr(Q=-182, pr=0.98)
pipe_feed2.set_attr(Q=-250, pr=0.98)
c1.set_attr(T=82, p=10, fluid={'INCOMP::Water': 1})
c2.set_attr(p=15)
#c8.set_attr(p=15)
c9.set_attr(T=62)  # this specification would be placed behind the consumer?

# Consumer 2 (ancienne école)
cons2.set_attr(Q=-14e4, pr=1)
fp2.set_attr(Q=-50, pr=0.98)
rp2.set_attr(Q=-150, pr=0.98)
c00.set_attr(p=14.9, T=80)  # a temperature is missing after the pipe
c01.set_attr()  # pressure is already know here due to the pressure at the previous connection + pressure loss
c04.set_attr(p=10)
c0.set_attr(T=62)

# manually setting starting enthalpy values helps sometimes when working with incompressibles,
# does not seem to be required in this case
# [c.set_attr(h0=100) for c in nw.conns["object"]]

# Résolution du réseau
nw.solve(mode="design")
nw.print_results()

Generally, you need to look at the system carefully and try to understand, where a pressure/enthalpy value is known through what specification. In your code some of the values where overdetermined (consequently some others underdetermined).

Have a nice day

Francesco

[Delilay]

Hello Francesco,
Can you please explain to me how to do it for multiple customers ( more then 6 ). On what exactly should i focus ? Because i did it for 4 customers but i cannot do better
Thank you

[fwitte]

Hi, this is a little bit difficult to guess without seeing the actual problem. You need to understand, what are all the variables that have to be determined in your model, what variables are determined by the implicit constraints of your components (e.g. mass flow equality for 1to1 components like pipes or pressure equality for all connections of splitters and mergers) and what variables are determined by component settings and what variables are determined by connections specifications.

My workflow suggestion for you is:

• Have a running model
• Add a single component to that model and make the specifications you want
• Run the model and see if it works as intended
• If you succeeded repeat until you completed the whole model and if not, try to understand what the issue is

Best