Hello，I want to konw what else do I need to set to solve the valve's zeta value as a variable.

[WangJ501]

I want to build a pipe network model that includes heat dissipation. Here is a simple model.
Test.py

from tespy.networks import Network
nw = Network(fluids=['IF97::water'])
nw.units.set_defaults(
    temperature="degC", pressure="MPa", enthalpy="kJ / kg", power="MW", heat="MW",mass_flow='kg / h',length='m'
)

from tespy.connections import Connection, Ref
from tespy.components import(Source,Sink,Pipe,Valve,Splitter)
so0=Source('source')
sin1=Sink('sin1')
sin2=Sink('sin2')
sin3=Sink('sin3')
sin4=Sink('sin4')
va1=Valve('va1')
va2=Valve('va2')

p1=Pipe('p1')
c1=Connection(so0,'out1',p1,'in1',label='1')
sp1=Splitter('sp1',num_out=2)
sp2=Splitter('sp2',num_out=2)
sp3=Splitter('sp3',num_out=2)
sp4=Splitter('sp4',num_out=2)
p2=Pipe('p2')
p3=Pipe('p3')
p4=Pipe('p4')
p5=Pipe('p5')
p6=Pipe('p6')
p7=Pipe('p7')
p8=Pipe('p8')
p9=Pipe('p9')
p10=Pipe('p10')
p11=Pipe('p11')
c2=Connection(p1,'out1',sp1,'in1',label='2')
c3=Connection(sp1,'out2',p2,'in1',label='3')
c4=Connection(p2,'out1',va1,'in1',label='4')
c5=Connection(va1,'out1',p3,'in1',label='5')
c6=Connection(p3,'out1',sp2,'in1',label='6')
c7=Connection(sp2,'out1',p4,'in1',label='7')
c8=Connection(p4,'out1',sin1,'in1',label='8')
c9=Connection(sp2,'out2',p5,'in1',label='9')
c10=Connection(p5,'out1',sin2,'in1',label='10')
c11=Connection(sp1,'out1',p6,'in1',label='11')
c12=Connection(p6,'out1',va2,'in1',label='12')
c15=Connection(va2,'out1',p8,'in1',label='15')
c16=Connection(p8,'out1',sp4,'in1',label='16')
c17=Connection(sp4,'out1',p9,'in1',label='17')
c18=Connection(sp4,'out2',p10,'in1',label='18')
c19=Connection(p9,'out1',sin3,'in1',label='19')
c20=Connection(p10,'out1',sin4,'in1',label='20')

nw.add_conns(c1, c2, c3, c4, c5, c6, c7, c8, c9, c10, c11, c12,
c15, c16, c17, c18, c19, c20)

# va1.set_attr(zeta=120)
# va2.set_attr(zeta=120)
va1.set_attr(zeta='var')
va2.set_attr(zeta='var')
# c3.set_attr(m=4.806e+02)
# c11.set_attr(m=4.806e+02)

p1.set_attr(L=16, D=0.05, ks=1e-3,Tamb=25,environment_media='air',insulation_thickness=0.1, insulation_tc=0.035,pipe_thickness=0.003, material='Steel', wind_velocity=1.0)
p2.set_attr(L=16, D=0.05, ks=1e-3,Tamb=25,environment_media='air',insulation_thickness=0.1, insulation_tc=0.035,pipe_thickness=0.003, material='Steel', wind_velocity=1.0)
p3.set_attr(L=16, D=0.05, ks=1e-3,Tamb=25,environment_media='air',insulation_thickness=0.1, insulation_tc=0.035,pipe_thickness=0.003, material='Steel', wind_velocity=1.0)
p4.set_attr(L=16, D=0.05, ks=1e-3,Tamb=25,environment_media='air',insulation_thickness=0.1, insulation_tc=0.035,pipe_thickness=0.003, material='Steel', wind_velocity=1.0)
p5.set_attr(L=16, D=0.05, ks=1e-3,Tamb=25,environment_media='air',insulation_thickness=0.1, insulation_tc=0.035,pipe_thickness=0.003, material='Steel', wind_velocity=1.0)
p6.set_attr(L=16, D=0.05, ks=1e-3,Tamb=25,environment_media='air',insulation_thickness=0.1, insulation_tc=0.035,pipe_thickness=0.003, material='Steel', wind_velocity=1.0)
p8.set_attr(L=16, D=0.05, ks=1e-3,Tamb=25,environment_media='air',insulation_thickness=0.1, insulation_tc=0.035,pipe_thickness=0.003, material='Steel', wind_velocity=1.0)
p9.set_attr(L=16, D=0.05, ks=1e-3,Tamb=25,environment_media='air',insulation_thickness=0.1, insulation_tc=0.035,pipe_thickness=0.003, material='Steel', wind_velocity=1.0)
p10.set_attr(L=16, D=0.05, ks=1e-3,Tamb=25,environment_media='air',insulation_thickness=0.1, insulation_tc=0.035,pipe_thickness=0.003, material='Steel', wind_velocity=1.0)


c1.set_attr(fluid={'water':1},T=300,p=0.4)
c8.set_attr(p=0.2)
c10.set_attr(p=0.2)
c19.set_attr(p=0.2)
c20.set_attr(p=0.2)

nw.solve('design',max_iter=50)
nw.print_results()

Thanks for helping.

[fwitte]

Hi @WangJ501,

I do not think it is currently possible to integrate zeta as a variable in the problem. But since it is a single parameter equation, you can just simply run the model without setting zeta="var" and get zeta from the results. Setting a component parameter a variable really only makes sense in multi-parameter equations. For all other equations the parameter will always be a result of the component postcalculation if not specified.

Best

[WangJ501]

Thanks. I also want to know how does the ks value function in the pipe component? Can you provide me with some formulas related to ks values?

[fwitte]

That is the surface roughness https://en.wikipedia.org/wiki/Surface_roughness in context of https://en.wikipedia.org/wiki/Darcy_friction_factor_formulae, this page (German) might help you with some typical values: https://www.schweizer-fn.de/stroemung/rauhigkeit/rauhigkeit.php

[WangJ501]

I'm sorry to disturb you. I may have a lot of questions lately.
I have recently encountered a similar problem as this.https://github.com/CoolProp/CoolProp/issues/1526
Could you please explain this solution？

[fwitte]

P and T min and max values are available in CoolProp, e.g. https://coolprop.org/fluid_properties/fluids/Water.html, from those you can evaluate H... I use that in tespy, e.g. I evaluate h(T_max, p_actual) in each Newton iteration and modify h to be lower than that one (or higher than h(T_min, p_actual) in the next iteration.