kelvin radius and term (#315)

particula/util/kelvin_correction.py

@@ -0,0 +1,37 @@
+""" calculate kelvin correction """
+
+import numpy as np
+
+from particula import u
+from particula.util.input_handling import in_temperature, in_density, in_radius
+from particula.util.input_handling import in_handling, in_molecular_weight
+from particula.constants import GAS_CONSTANT
+
+
+def kelvin_radius(surface_tension, molecular_weight, density, temperature):
+    """ Kelvin radius (Neil's definition)
+        https://en.wikipedia.org/wiki/Kelvin_equation
+    """
+
+    temperature = in_temperature(temperature).to_base_units()
+    molecular_weight = in_molecular_weight(molecular_weight).to_base_units()
+    density = in_density(density).to_base_units()
+    surface_tension = in_handling(surface_tension, u.N/u.m)  # type: ignore
+
+    return 2 * surface_tension * molecular_weight / (
+        GAS_CONSTANT * temperature * density
+    )
+
+
+def kelvin_term(surface_tension, molecular_weight, density, temperature, radius):
+    """ Kelvin term (Neil's definition)
+        https://en.wikipedia.org/wiki/Kelvin_equation
+    """
+
+    rad = in_radius(radius)
+
+    kelvin_rad = kelvin_radius(
+        surface_tension, molecular_weight, density, temperature
+    )
+
+    return np.exp(kelvin_rad / rad)

particula/util/tests/kelvin_correction_test.py

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+""" test kelvin correct """
+
+from particula import u
+
+from particula.util.kelvin_correction import kelvin_radius, kelvin_term
+
+
+def test_kelvin_radius():
+    """ test: parcelona.kelvin_radius """
+    assert kelvin_radius(
+        surface_tension=0.072 * u.N/u.m,
+        molecular_weight=0.01815 * u.kg/u.mol,
+        density=1000 * u.kg/u.m**3,
+        temperature=300
+    ).u == u.m
+
+
+def test_kelvin_term():
+    """ test: parcelona.kelvin_term """
+    assert kelvin_term(
+        surface_tension=0.072 * u.N/u.m,
+        molecular_weight=0.01815 * u.kg/u.mol,
+        density=1000 * u.kg/u.m**3,
+        temperature=300,
+        radius=1 * u.m
+    ).u == u.dimensionless