Add Mixer block for 2-stream algebraic mixing

Author: milanofthe

src/pathsim_chem/process/mixer.py

@@ -0,0 +1,55 @@
+#########################################################################################
+##
+##                              2-Stream Mixer Block
+##
+#########################################################################################
+
+# IMPORTS ===============================================================================
+
+from pathsim.blocks.function import Function
+
+# BLOCKS ================================================================================
+
+class Mixer(Function):
+    """Algebraic 2-stream mixer with mass and energy balance.
+
+    Mixes two streams by mass balance (additive flows) and energy balance
+    (flow-weighted temperature mixing). No phase change or reaction.
+
+    Mathematical Formulation
+    -------------------------
+    .. math::
+
+        F_{out} = F_1 + F_2
+
+    .. math::
+
+        T_{out} = \\frac{F_1 \\, T_1 + F_2 \\, T_2}{F_{out}}
+
+    Parameters
+    ----------
+    None — this is a purely algebraic block.
+    """
+
+    input_port_labels = {
+        "F_1": 0,
+        "T_1": 1,
+        "F_2": 2,
+        "T_2": 3,
+    }
+
+    output_port_labels = {
+        "F_out": 0,
+        "T_out": 1,
+    }
+
+    def __init__(self):
+        super().__init__(func=self._eval)
+
+    def _eval(self, F_1, T_1, F_2, T_2):
+        F_out = F_1 + F_2
+        if F_out > 0:
+            T_out = (F_1 * T_1 + F_2 * T_2) / F_out
+        else:
+            T_out = 0.5 * (T_1 + T_2)
+        return (F_out, T_out)

tests/process/test_mixer.py

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+########################################################################################
+##
+##                                  TESTS FOR
+##                             'process.mixer.py'
+##
+########################################################################################
+
+# IMPORTS ==============================================================================
+
+import unittest
+
+from pathsim_chem.process import Mixer
+
+
+# TESTS ================================================================================
+
+class TestMixer(unittest.TestCase):
+    """Test the 2-stream mixer block."""
+
+    def test_port_labels(self):
+        """Test port label definitions."""
+        self.assertEqual(Mixer.input_port_labels["F_1"], 0)
+        self.assertEqual(Mixer.input_port_labels["T_1"], 1)
+        self.assertEqual(Mixer.input_port_labels["F_2"], 2)
+        self.assertEqual(Mixer.input_port_labels["T_2"], 3)
+        self.assertEqual(Mixer.output_port_labels["F_out"], 0)
+        self.assertEqual(Mixer.output_port_labels["T_out"], 1)
+
+    def test_mass_balance(self):
+        """F_out should equal F_1 + F_2."""
+        M = Mixer()
+        M.inputs[0] = 5.0    # F_1
+        M.inputs[1] = 350.0  # T_1
+        M.inputs[2] = 3.0    # F_2
+        M.inputs[3] = 300.0  # T_2
+
+        M.update(None)
+
+        self.assertAlmostEqual(M.outputs[0], 8.0)  # F_out
+
+    def test_energy_balance(self):
+        """F_1*T_1 + F_2*T_2 should equal F_out*T_out."""
+        M = Mixer()
+        F_1, T_1 = 5.0, 350.0
+        F_2, T_2 = 3.0, 300.0
+
+        M.inputs[0] = F_1
+        M.inputs[1] = T_1
+        M.inputs[2] = F_2
+        M.inputs[3] = T_2
+
+        M.update(None)
+
+        F_out = M.outputs[0]
+        T_out = M.outputs[1]
+        self.assertAlmostEqual(F_1 * T_1 + F_2 * T_2, F_out * T_out, places=8)
+
+    def test_equal_temperatures(self):
+        """When both streams at same T, output T should match."""
+        M = Mixer()
+        M.inputs[0] = 5.0
+        M.inputs[1] = 350.0
+        M.inputs[2] = 3.0
+        M.inputs[3] = 350.0
+
+        M.update(None)
+
+        self.assertAlmostEqual(M.outputs[1], 350.0)
+
+    def test_zero_flow_one_stream(self):
+        """With one stream at zero flow, output should match the other."""
+        M = Mixer()
+        M.inputs[0] = 0.0
+        M.inputs[1] = 300.0
+        M.inputs[2] = 5.0
+        M.inputs[3] = 400.0
+
+        M.update(None)
+
+        self.assertAlmostEqual(M.outputs[0], 5.0)
+        self.assertAlmostEqual(M.outputs[1], 400.0)
+
+    def test_zero_total_flow(self):
+        """With zero total flow, should not crash."""
+        M = Mixer()
+        M.inputs[0] = 0.0
+        M.inputs[1] = 300.0
+        M.inputs[2] = 0.0
+        M.inputs[3] = 400.0
+
+        M.update(None)
+
+        self.assertAlmostEqual(M.outputs[0], 0.0)
+
+
+# RUN TESTS LOCALLY ====================================================================
+
+if __name__ == '__main__':
+    unittest.main(verbosity=2)