Merge branch 'fix/drum-equations' into dev

src/tespy/components/nodes/drum.py

@@ -170,6 +170,7 @@ def outlets():
         return ['out1', 'out2']
 
     def get_mandatory_constraints(self):
+        num_mass_eq = 1
         if self.inl[1].m == self.outl[0].m:
             num_mass_eq = 0
         return {
@@ -217,6 +218,7 @@ def mass_flow_func(self):
         if self.inl[1].m == self.outl[0].m:
             return self.inl[0].m.val_SI - self.outl[1].m.val_SI
         else:
+            res = 0
             for i in self.inl:
                 res += i.m.val_SI
             for o in self.outl:

tests/test_components/test_drum.py

@@ -0,0 +1,52 @@
+# -*- coding: utf-8
+
+"""Module for testing components of type merge.
+This file is part of project TESPy (github.com/oemof/tespy). It's copyrighted
+by the contributors recorded in the version control history of the file,
+available from its original location
+tests/test_components/test_merge.py
+SPDX-License-Identifier: MIT
+"""
+from pytest import approx
+from pytest import fixture
+
+from tespy.components import Drum
+from tespy.components import SimpleHeatExchanger
+from tespy.components import Sink
+from tespy.components import Source
+from tespy.components import Splitter
+from tespy.connections import Connection
+from tespy.networks import Network
+
+
+@fixture()
+def drum_network_setup():
+    nw = Network(T_unit="C", p_unit="bar")
+    dr = Drum("drum")
+    so = Source("liquid")
+    si = Sink("vapor")
+    c1 = Connection(so, "out1", dr, "in1", label="1")
+    c2 = Connection(dr, "out2", si, "in1", label="2")
+    nw.add_conns(c1, c2)
+    c1.set_attr(fluid={"R290": 1}, m=10, Td_bp=-10, T=50)
+    yield nw
+
+
+def test_drum_with_blowdown(drum_network_setup):
+    nw = drum_network_setup
+    sp = Splitter("blowdown splitter")
+    si = Sink("blowdown sink")
+    eva = SimpleHeatExchanger("evaporator")
+    dr = nw.get_comp("drum")
+    c3 = Connection(dr, "out1", sp, "in1", label="3")
+    c4 = Connection(sp, "out1", si, "in1", label="4")
+    c5 = Connection(sp, "out2", eva, "in1", label="5")
+    c6 = Connection(eva, "out1", dr, "in2", label="6")
+
+    c6.set_attr(x=0.7, m=15)
+
+    nw.add_conns(c3, c4, c5, c6)
+
+    nw.solve("design")
+
+    assert 0.72728 == approx(c4.m.val_SI)