Fix the mass flow and fluid topology simplification for multiprocessing

src/tespy/components/heat_exchangers/desuperheater.py

@@ -239,6 +239,6 @@ def saturated_gas_deriv(self, increment_filter, k):
         """
         o = self.outl[0]
         if self.is_variable(o.p):
-            self.jacobian[k, o.p.J_col] = -dh_mix_dpQ(o, 1, o.fluid_data)
+            self.jacobian[k, o.p.J_col] = -dh_mix_dpQ(o.p.val_SI, 1, o.fluid_data)
         if self.is_variable(o.h):
             self.jacobian[k, o.h.J_col] = 1

src/tespy/networks/network.py

@@ -690,8 +690,6 @@ def check_network(self):
         self.check_conns()
         self.init_components()
         self.check_components()
-        self.create_massflow_and_fluid_branches()
-        self.create_fluid_wrapper_branches()
 
         # network checked
         self.checked = True
@@ -847,6 +845,25 @@ def initialise(self):
         self.num_conn_vars = 0
         self.variables_dict = {}
 
+        if hasattr(self, "massflow_branches"):
+            # in multiprocessing copies are made of all connections
+            # the mass flow branches and fluid branches hold references to
+            # connections from the original run (where network.checked is False)
+            # The assignment of variable spaces etc. is however made on the
+            # copies of the connections which do not correspond to the mass flow
+            # branches and fluid branches anymore. So the topology simplification
+            # does not actually apply to the copied network, therefore the
+            # branches have to be recreated for this case. We can detect that by
+            # checking whether a network holds a massflow branch with some
+            # connections and compare that with the connection object actually
+            # present in the network
+            first_conn = self.massflow_branches[0]["connections"][0]
+            if self.conns.loc[first_conn.label, "object"] != first_conn:
+                self.create_massflow_and_fluid_branches()
+                self.create_fluid_wrapper_branches()
+        else:
+            self.create_massflow_and_fluid_branches()
+            self.create_fluid_wrapper_branches()
         self.propagate_fluid_wrappers()
         self.presolve_massflow_topology()
         self.presolve_fluid_topology()

src/tespy/tools/fluid_properties/wrappers.py

@@ -16,6 +16,16 @@
 from tespy.tools.global_vars import ERR
 
 
+class SerializableAbstractState(CP.AbstractState):
+
+    def __init__(self, back_end, fluid_name):
+        self.back_end = back_end
+        self.fluid_name = fluid_name
+
+    def __reduce__(self):
+        return (self.__class__, (self.back_end, self.fluid_name))
+
+
 class FluidPropertyWrapper:
 
     def __init__(self, fluid, back_end=None) -> None:
@@ -112,7 +122,7 @@ def __init__(self, fluid, back_end=None) -> None:
             back_end = "HEOS"
 
         super().__init__(fluid, back_end)
-        self.AS = CP.CoolProp.AbstractState(self.back_end, self.fluid)
+        self.AS = SerializableAbstractState(self.back_end, self.fluid)
         self._set_constants()
 
     def _set_constants(self):

tests/test_components/test_combustion.py

@@ -12,8 +12,6 @@
 
 import shutil
 
-import numpy as np
-
 from tespy.components import CombustionChamber
 from tespy.components import CombustionEngine
 from tespy.components import DiabaticCombustionChamber

tests/test_components/test_merge.py

@@ -119,17 +119,3 @@ def test_two_fluid_setup(self):
         target = c1.m.val_SI
         msg = f"Target value for mass flow at connection 3 is {target}"
         assert c6.m.val_SI == approx(target), msg
-
-
-test = TestMerge()
-test.setup_method()
-test.test_single_fluid_at_outlet()
-test.setup_method()
-test.test_massflows_from_two_fluid_fractions()
-
-
-test2 = TestCyclicMerging()
-test2.setup_method()
-test2.test_single_fluid_setup()
-test2.setup_method()
-test2.test_two_fluid_setup()

tests/test_components/test_reactors.py

@@ -12,8 +12,6 @@
 
 import shutil
 
-import numpy as np
-
 from tespy.components import Sink
 from tespy.components import Source
 from tespy.components import WaterElectrolyzer

tutorial/advanced/optimization_example.py

@@ -10,7 +10,6 @@
 from tespy.components import SimpleHeatExchanger
 from tespy.components import Merge
 from tespy.components import Splitter
-from tespy.components import Valve
 from tespy.components import Pump
 from tespy.components import Turbine
 from tespy.connections import Bus
@@ -82,10 +81,7 @@ def __init__(self):
         c32 = Connection(fwh1, "out1", pu3, "in1", label="32")
         c33 = Connection(pu3, "out1", me, "in2", label="33")
 
-        self.nw.add_conns(
-            c21, c22, c23, c24,
-            c31, c32, c33
-        )
+        self.nw.add_conns(c21, c22, c23, c24, c31, c32, c33)
 
         # cooling water
         c41 = Connection(cwi, "out1", con, "in2", label="41")
@@ -108,34 +104,43 @@ def __init__(self):
 
         self.nw.add_busses(self.power, self.heat)
 
+        self.set_design_values()
         # parametrization
         # components
+        self.nw.solve("design")
+        self.stable = "_stable"
+        self.nw.save(self.stable)
+        self.solved = True
+        self.nw.print_results()
+
+    def set_design_values(self):
+        hpt, mpt, lpt = self.nw.get_comp(["high pressure turbine", "mid pressure turbine", "low pressure turbine"])
         hpt.set_attr(eta_s=0.9)
         mpt.set_attr(eta_s=0.9)
         lpt.set_attr(eta_s=0.9)
 
+        pu1, pu2, pu3 = self.nw.get_comp(["feed water pump", "feed water pump 2", "feed water pump 3"])
         pu1.set_attr(eta_s=0.8)
         pu2.set_attr(eta_s=0.8)
         pu3.set_attr(eta_s=0.8)
 
+        sg = self.nw.get_comp("steam generator")
         sg.set_attr(pr=0.92)
 
+        con, fwh1, fwh2, dsh = self.nw.get_comp(["condenser", "feed water preheater 1", "feed water preheater 2", "desuperheater"])
         con.set_attr(pr1=1, pr2=0.99, ttd_u=5)
         fwh1.set_attr(pr1=1, pr2=0.99, ttd_u=5)
         fwh2.set_attr(pr1=1, pr2=0.99, ttd_u=5)
         dsh.set_attr(pr1=0.99, pr2=0.99)
 
+        c1, c2, c4, c41, c42 = self.nw.get_conn(["1", "2", "4", "41", "42"])
         c1.set_attr(m=200, T=650, p=100, fluid={"water": 1})
         c2.set_attr(p=20)
         c4.set_attr(p=3)
 
-        c41.set_attr(T=20, p=3, fluid={"water": 1})
-        c42.set_attr(T=28)
+        c41.set_attr(T=20, p=3, fluid={"INCOMP::Water": 1})
+        c42.set_attr(T=28, p0=3, h0=100)
 
-        self.nw.solve("design")
-        self.stable = "_stable"
-        self.nw.save(self.stable)
-        self.solved = True
 
     # %%[sec_2]