ValueError in check_enthalpy_bounds when solving network with own component

[HaSchneider]

I wrote my own Pipe Component, which works fine in a smaller example but when I solve this network:

needed_pressure= 10
needed_temperature=150
max_pressure=100
main_pressure=16
h_superheating_max_pressure=3617.9
heat=1000000
Tamb=20

# Setup Network
cond_inj = True
trap=False
nw = Network()
nw.set_attr(iterinfo=False)
nw.set_attr(T_unit='C', p_unit='bar', h_unit='kJ / kg', m_unit = 'kg / s')
#setup components:
boiler = SimpleHeatExchanger('steam boiler' )
bpt = Turbine('back pressure turbine')
pipe_warm =  PipeNet('steam pipe')
valve = Valve('controlvalve')
heat_sink = SimpleHeatExchanger('heat sink', dissipative=False)
pipe_cold= PipeNet('condensate pipe')
feed_pump= Pump('feedpump')
cycl=CycleCloser('CycleCloser')

# setup connection:
c05 = Connection(cycl, 'out1', boiler, 'in1')
c04 = Connection(boiler, 'out1', bpt, 'in1')
c03 = Connection(bpt, 'out1', pipe_warm, 'in1')
c022= Connection(pipe_warm, 'out1', valve, 'in1')

c01= Connection(valve, 'out1', heat_sink, 'in1')
c1 = Connection(heat_sink, 'out1', pipe_cold, 'in1')
c2 = Connection(pipe_cold, 'out1', feed_pump, 'in1')
c5 = Connection(feed_pump, 'out1', cycl, 'in1')

nw.add_conns(c05, c04, c03, c022, c01, 
             c1, c2, c5, 
             )
# busses:
fuel_bus = Bus('boiler bus')
fuel_bus.add_comps({'comp':boiler, 'base':'bus'})

turbine_bus = Bus('turbines')
turbine_bus.add_comps({'comp': bpt, 'char': 0.95})

product_bus =Bus('heat bus')
product_bus.add_comps({'comp':heat_sink, 'base':'component','char': 1},)

pump_bus = Bus('feedpump bus')
pump_bus.add_comps({'comp':feed_pump})

nw.add_busses(turbine_bus, 
                fuel_bus, 
                product_bus, 
                pump_bus)
# configuration:
boiler.set_attr(pr = 1)
c04.set_attr(h= h_superheating_max_pressure)
c05.set_attr(fluid={'water':1}, p=max_pressure)
bpt.set_attr(eta_s = 0.85, )
c03.set_attr(p=main_pressure)
pipe_warm.set_attr(pr=0.91, Tamb = Tamb, #kA= 300,
                    insulation_m=0.1 ,insulation_k= 0.035, pipe_thickness=0.004, material='Steel', wind_speed=10, environment = 'air',
                    L=1000, D='var', ks=4.57e-5, 
        ) 
c01.set_attr(p = needed_pressure)#

heat_sink.set_attr(pr=1,Q=-heat)
c1.set_attr(x=0)
pipe_cold.set_attr(pr=0.95, Tamb = Tamb, kA= 300,
                    #L=1000, D='var',  ks=4.57e-5,
                    # insulation_m=0.1 ,insulation_k= 0.035, pipe_thickness=0.004,material='Steel', wind_speed=10, environment = 'air'
        )
feed_pump.set_attr(eta_s =0.9)

I get this error:

{
	"name": "ValueError",
	"message": "The pressure [nan Pa] cannot be used in p_phase_determination",
	"stack": "---------------------------------------------------------------------------
ValueError                                Traceback (most recent call last)
File c:\\Apps\\anaconda3\\envs\\utility_lca\\Lib\\site-packages\\tespy\\connections\\connection.py:974, in Connection.check_enthalpy_bounds(self, fluid)
    973 try:
--> 974     hmin = self.fluid.wrapper[fluid].h_pT(
    975         self.p.val_SI, self.fluid.wrapper[fluid]._T_min + 1e-1
    976     )
    977 except ValueError:

File c:\\Apps\\anaconda3\\envs\\utility_lca\\Lib\\site-packages\\tespy\\tools\\fluid_properties\\wrappers.py:204, in CoolPropWrapper.h_pT(self, p, T)
    203 def h_pT(self, p, T):
--> 204     self.AS.update(CP.PT_INPUTS, p, T)
    205     return self.AS.hmass()

File CoolProp\\\\AbstractState.pyx:102, in CoolProp.CoolProp.AbstractState.update()

File CoolProp\\\\AbstractState.pyx:104, in CoolProp.CoolProp.AbstractState.update()

ValueError: The pressure [nan Pa] cannot be used in p_phase_determination

During handling of the above exception, another exception occurred:

ValueError                                Traceback (most recent call last)
Cell In[4], line 1
----> 1 nw.solve('design')

File c:\\Apps\\anaconda3\\envs\\utility_lca\\Lib\\site-packages\\tespy\
etworks\
etwork.py:1974, in Network.solve(self, mode, init_path, design_path, max_iter, min_iter, init_only, init_previous, use_cuda, print_results, prepare_fast_lane)
   1970 logger.info(msg)
   1972 self.solve_determination()
-> 1974 self.solve_loop(print_results=print_results)
   1976 if not prepare_fast_lane:
   1977     self._reset_topology_reduction_specifications()

File c:\\Apps\\anaconda3\\envs\\utility_lca\\Lib\\site-packages\\tespy\
etworks\
etwork.py:2028, in Network.solve_loop(self, print_results)
   2026 for self.iter in range(self.max_iter):
   2027     self.increment_filter = np.absolute(self.increment) < ERR ** 2
-> 2028     self.solve_control()
   2029     self.residual_history = np.append(
   2030         self.residual_history, norm(self.residual)
   2031     )
   2033     if self.iterinfo:

File c:\\Apps\\anaconda3\\envs\\utility_lca\\Lib\\site-packages\\tespy\
etworks\
etwork.py:2324, in Network.solve_control(self)
   2321     return
   2323 self.update_variables()
-> 2324 self.check_variable_bounds()

File c:\\Apps\\anaconda3\\envs\\utility_lca\\Lib\\site-packages\\tespy\
etworks\
etwork.py:2293, in Network.check_variable_bounds(self)
   2290             c.fluid.val[fluid] /= total_mass_fractions
   2292     c.build_fluid_data()
-> 2293     self.check_connection_properties(c)
   2295 # second property check for first three iterations without an init_file
   2296 if self.iter < 3:

File c:\\Apps\\anaconda3\\envs\\utility_lca\\Lib\\site-packages\\tespy\
etworks\
etwork.py:2346, in Network.check_connection_properties(self, c)
   2344 if c.h.is_var:
   2345     print(c.label, c.p.val, fl)
-> 2346     c.check_enthalpy_bounds(fl)
   2348     # two-phase related
   2349     if (c.Td_bp.is_set or c.state.is_set) and self.iter < 3:

File c:\\Apps\\anaconda3\\envs\\utility_lca\\Lib\\site-packages\\tespy\\connections\\connection.py:979, in Connection.check_enthalpy_bounds(self, fluid)
    977 except ValueError:
    978     f = 1.05
--> 979     hmin = self.fluid.wrapper[fluid].h_pT(
    980         self.p.val_SI, self.fluid.wrapper[fluid]._T_min * f
    981     )
    982 if self.h.val_SI < hmin:
    983     if hmin < 0:

File c:\\Apps\\anaconda3\\envs\\utility_lca\\Lib\\site-packages\\tespy\\tools\\fluid_properties\\wrappers.py:204, in CoolPropWrapper.h_pT(self, p, T)
    203 def h_pT(self, p, T):
--> 204     self.AS.update(CP.PT_INPUTS, p, T)
    205     return self.AS.hmass()

File CoolProp\\\\AbstractState.pyx:102, in CoolProp.CoolProp.AbstractState.update()

File CoolProp\\\\AbstractState.pyx:104, in CoolProp.CoolProp.AbstractState.update()

ValueError: The pressure [nan Pa] cannot be used in p_phase_determination"
} 

Swithching the pipe_warm parameter to a fixed kA (uncomment kA=300 and comment the line under) works as well.
It seems to be a problem in the check_enthalpy_bounds function due to a not defined pressure, but this is weird as the pressure seems not to be defined in the working networks as well.

[fwitte]

Hi and thank you for reaching out!

Can you provide the source code of your class? Otherwise it is difficult to help. Apparently, there are some nan values in the increment vector (after every iteration the variables are incremented with some value, if there are nan values, the simulation crashes). Usually, I would think this should already be prevented by the linear dependency check on the Jacobian, which should raise an error, in case any equation or any value in the Jacobian holds nan as value, there might be some other issue.

Thank you!

[HaSchneider]

I changed a few things and now the error no longer occurs. I dont know why, but I wont complain..