From fe42a313e7646cf72ac239f76ea11a1f22cb9581 Mon Sep 17 00:00:00 2001
From: Halvor Lund <halvor.lund@statnett.no>
Date: Wed, 29 May 2024 14:20:09 +0200
Subject: [PATCH] Fix tests, compute Reynolds number as in Cigre207 report

---
 linerate/equations/cigre207/ac_resistance.py  |  34 +--
 .../equations/cigre207/convective_cooling.py  |  38 ++-
 linerate/models/Cigre207.md                   |   2 +-
 linerate/models/cigre207.py                   |  49 +++-
 .../cigre601/test_convective_cooling.py       | 241 +-----------------
 ...ing.py => test_ieee_convective_cooling.py} |  36 ---
 tests/equations/test_convective_cooling.py    |  97 +++++++
 tests/equations/test_dimensionless.py         | 157 ++++++++++++
 8 files changed, 346 insertions(+), 308 deletions(-)
 rename tests/equations/ieee738/{test_convective_cooling.py => test_ieee_convective_cooling.py} (89%)
 create mode 100644 tests/equations/test_convective_cooling.py
 create mode 100644 tests/equations/test_dimensionless.py

diff --git a/linerate/equations/cigre207/ac_resistance.py b/linerate/equations/cigre207/ac_resistance.py
index 86fa2ff..748baef 100644
--- a/linerate/equations/cigre207/ac_resistance.py
+++ b/linerate/equations/cigre207/ac_resistance.py
@@ -1,45 +1,27 @@
 from typing import Union
 
-from linerate.units import OhmPerMeter, Ampere, SquareMeter, Unitless, SquareMeterPerAmpere
+from linerate.units import OhmPerMeter
 
 
-def correct_resistance_acsr_magnetic_core_loss_simple(
-    ac_resistance: OhmPerMeter,
-    current: Ampere,
-    aluminium_cross_section_area: SquareMeter,
-    constant_magnetic_effect: Union[Unitless, None],
-    current_density_proportional_magnetic_effect: Union[SquareMeterPerAmpere, None],
-    max_relative_increase: Unitless,
+def correct_resistance_for_skin_effect(
+    dc_resistance: OhmPerMeter,
 ) -> OhmPerMeter:
     r"""
-    Return resistance with constant correction for magnetic effects, using simple method from
+    Return resistance with constant correction for skin effect, using simple method from
     Cigre 207, see section 2.1.1.
 
     Parameters
     ----------
-    ac_resistance:
-        :math:`R~\left[\Omega\right]`. The AC resistance of the conductor.
-    current:
-        :math:`I~\left[\text{A}\right]`. The current going through the conductor.
-    aluminium_cross_section_area:
-        :math:`A_{\text{Al}}~\left[\text{m}^2\right]`. The cross sectional area of the aluminium
-        strands in the conductor.
-    constant_magnetic_effect:
-        :math:`b`. The constant magnetic effect, most likely equal to 1. If ``None``, then no
-        correction is used (useful for non-ACSR cables).
-    current_density_proportional_magnetic_effect:
-        :math:`m`. The current density proportional magnetic effect. If ``None``, then it is
-        assumed equal to 0.
-    max_relative_increase:
-        :math:`c_\text{max}`. Saturation point of the relative increase in conductor resistance.
+    dc_resistance:
+        :math:`R~\left[\Omega\right]`. The DC resistance of the conductor.
 
     Returns
     -------
     Union[float, float64, ndarray[Any, dtype[float64]]]
         :math:`R_\text{corrected}~\left[\Omega\right]`. The resistance of the conductor after
-        taking steel core magnetization effects into account.
+        taking skin effect into account.
     """
-    return 1.0123 * ac_resistance
+    return 1.0123 * dc_resistance
 
 
 # TODO: Implement section 2.1.2?
\ No newline at end of file
diff --git a/linerate/equations/cigre207/convective_cooling.py b/linerate/equations/cigre207/convective_cooling.py
index e3b12f7..78e7215 100644
--- a/linerate/equations/cigre207/convective_cooling.py
+++ b/linerate/equations/cigre207/convective_cooling.py
@@ -10,7 +10,7 @@
     MeterPerSecond,
     Radian,
     Unitless,
-    WattPerMeterPerKelvin,
+    WattPerMeterPerKelvin, SquareMeterPerSecond,
 )
 
 
@@ -107,6 +107,42 @@ def compute_prandtl_number(
     return 0.715 - 2.5e-4*film_temperature
 
 
+def compute_reynolds_number(
+    wind_speed: MeterPerSecond,
+    conductor_diameter: Meter,
+    kinematic_viscosity_of_air: SquareMeterPerSecond,
+    relative_air_density: Unitless
+) -> Unitless:
+    r"""Compute the Reynolds number using the conductor diameter as characteristic length scale.
+
+    Defined on page 5 of :cite:p:`cigre207`.
+    This is a non-standard definition which seems to indicate that the kinematic viscosity has to
+    be corrected for the density.
+
+    Parameters
+    ----------
+    wind_speed:
+        :math:`v~\left[\text{m}~\text{s}^{-1}\right]`. The wind speed.
+    conductor_diameter:
+        :math:`D~\left[\text{m}\right]`. Outer diameter of the conductor.
+    kinematic_viscosity_of_air:
+        :math:`\nu_f~\left[\text{m}^2~\text{s}^{-1}\right]`. The kinematic viscosity of air.
+    relative_air_density:
+        :math:`\rho_r~1`. The air density relative to density at sea level.
+
+    Returns
+    -------
+    Union[float, float64, ndarray[Any, dtype[float64]]]
+        :math:`\text{Re}`. The Reynolds number.
+    """
+    v = wind_speed
+    D = conductor_diameter
+    nu_f = kinematic_viscosity_of_air
+    rho_r = relative_air_density
+    return rho_r * v * D / nu_f
+
+
+
 ## Nusselt number calculation
 #############################
 
diff --git a/linerate/models/Cigre207.md b/linerate/models/Cigre207.md
index b3702ed..3912193 100644
--- a/linerate/models/Cigre207.md
+++ b/linerate/models/Cigre207.md
@@ -3,7 +3,7 @@
 ## Cigre 207 vs 601
 
 The Cigre 601 report states that 601 takes into account improvements in the calculation of AC resistance of stranded
-conductors, includes a more realistic estimation of the axial and radial temeprature distributions, more coherent
+conductors, includes a more realistic estimation of the axial and radial temperature distributions, more coherent
 convection model for low wind speeds, and has a more flexible solar radiation model.
 
 ## Skin effect
diff --git a/linerate/models/cigre207.py b/linerate/models/cigre207.py
index c15c0e3..9f2ae92 100644
--- a/linerate/models/cigre207.py
+++ b/linerate/models/cigre207.py
@@ -1,8 +1,10 @@
+from abc import abstractmethod
+
 from linerate import ThermalModel, Span, Weather
-from linerate.equations import solar_angles, cigre601, math, cigre207, dimensionless, convective_cooling
+from linerate.equations import solar_angles, cigre601, math, cigre207, dimensionless, convective_cooling, joule_heating
 from linerate.equations.math import switch_cos_sin
 from linerate.model import _copy_method_docstring
-from linerate.units import Date, Celsius, Ampere, WattPerMeter
+from linerate.units import Date, Celsius, Ampere, WattPerMeter, OhmPerMeter
 
 
 class Cigre207(ThermalModel):
@@ -63,8 +65,8 @@ def compute_convective_cooling(
     ) -> WattPerMeter:
         D = self.span.conductor.conductor_diameter
         d = self.span.conductor.outer_layer_strand_diameter
-        y = self.span.conductor_altitude
         V = self.weather.wind_speed
+        y = self.span.conductor_altitude
         T_a = self.weather.air_temperature
         T_c = conductor_temperature
         T_f = 0.5 * (T_c + T_a)
@@ -80,7 +82,8 @@ def compute_convective_cooling(
         # Reynolds number is defined in the text on page 5 of :cite:p:`cigre207`.
         # The definition includes a relative air density, which does not make sense, so we omit it here and use the
         # standard definition of Reynolds number instead.
-        Re = dimensionless.compute_reynolds_number(V, D, nu_f)
+        rho_r = cigre207.convective_cooling.compute_relative_air_density(y)
+        Re = cigre207.convective_cooling.compute_reynolds_number(V, D, nu_f, rho_r)
         Gr = dimensionless.compute_grashof_number(D, T_c, T_a, nu_f)
         Pr = cigre207.convective_cooling.compute_prandtl_number(T_f)
         Rs = dimensionless.compute_conductor_roughness(D, d)
@@ -115,3 +118,41 @@ def compute_radiative_cooling(
         return super().compute_radiative_cooling(
             conductor_temperature=conductor_temperature, current=current
         )
+
+    @abstractmethod
+    def compute_resistance(self, conductor_temperature: Celsius, current: Ampere) -> OhmPerMeter:
+        r"""Compute the conductor resistance, :math:`R~\left[\Omega~\text{m}^{-1}\right]`.
+
+        Parameters
+        ----------
+        conductor_temperature:
+            :math:`T_\text{av}~\left[^\circ\text{C}\right]`. The average conductor temperature.
+        current:
+            :math:`I~\left[\text{A}\right]`. The current.
+
+        Returns
+        -------
+        Union[float, float64, ndarray[Any, dtype[float64]]]
+            :math:`R~\left[\Omega\right]`. The resistance at the given temperature and current.
+        """
+        resistance = joule_heating.compute_resistance(
+            conductor_temperature,
+            temperature1=self.span.conductor.temperature1,
+            temperature2=self.span.conductor.temperature2,
+            resistance_at_temperature1=self.span.conductor.resistance_at_temperature1,
+            resistance_at_temperature2=self.span.conductor.resistance_at_temperature2,
+        )
+
+        A = self.span.conductor.aluminium_cross_section_area
+        b = self.span.conductor.constant_magnetic_effect
+        m = self.span.conductor.current_density_proportional_magnetic_effect
+        max_increase = self.span.conductor.max_magnetic_core_relative_resistance_increase
+
+        return joule_heating.correct_resistance_acsr_magnetic_core_loss(
+            ac_resistance=resistance,
+            current=current,
+            aluminium_cross_section_area=A,
+            constant_magnetic_effect=b,
+            current_density_proportional_magnetic_effect=m,
+            max_relative_increase=max_increase,
+        )
diff --git a/tests/equations/cigre601/test_convective_cooling.py b/tests/equations/cigre601/test_convective_cooling.py
index 13a74c4..6e690c4 100644
--- a/tests/equations/cigre601/test_convective_cooling.py
+++ b/tests/equations/cigre601/test_convective_cooling.py
@@ -7,6 +7,7 @@
 
 import linerate.equations.cigre601.convective_cooling as convective_cooling
 
+
 # Tests for physical quantities
 ###############################
 
@@ -259,155 +260,6 @@ def test_kinematic_viscosity_of_air_with_example():
     assert convective_cooling.compute_kinematic_viscosity_of_air(mu_f, gamma) == approx(1)
 
 
-# Tests for unitless quantities
-###############################
-
-
-@hypothesis.given(wind_speed=st.floats(min_value=0, max_value=1000, allow_nan=False))
-def test_reynolds_number_scales_linearly_with_wind_speed(wind_speed):
-    V = wind_speed
-    D = 1
-    Nu_f = 1
-
-    assert convective_cooling.compute_reynolds_number(V, D, Nu_f) == pytest.approx(V)
-
-
-@hypothesis.given(conductor_diameter=st.floats(min_value=0, max_value=1000, allow_nan=False))
-def test_reynolds_number_scales_linearly_with_diameter(conductor_diameter):
-    V = 1
-    D = conductor_diameter
-    Nu_f = 1
-
-    assert convective_cooling.compute_reynolds_number(V, D, Nu_f) == pytest.approx(D)
-
-
-@hypothesis.given(kinematic_viscosity=st.floats(min_value=1e-10, allow_nan=False))
-def test_reynolds_number_scales_inversly_with_kinematic_viscosity(kinematic_viscosity):
-    V = 1
-    D = 1
-    Nu_f = kinematic_viscosity
-
-    assert convective_cooling.compute_reynolds_number(V, D, Nu_f) == approx(1 / Nu_f)
-
-
-def test_reynolds_number_with_example():
-    V = 0.1
-    D = 1.2
-    Nu_f = 10
-
-    assert convective_cooling.compute_reynolds_number(V, D, Nu_f) == approx(0.012)
-
-
-@hypothesis.given(conductor_diameter=st.floats(min_value=1e-5, max_value=1e5, allow_nan=False))
-def test_grashof_number_scales_cubic_with_conductor_diameter(conductor_diameter):
-    D = conductor_diameter
-    T_s = 1
-    T_a = 0
-    Nu_f = 1
-    g = 273.65  # 0.5*T_s in Kelvin
-
-    Gr = convective_cooling.compute_grashof_number(D, T_s, T_a, Nu_f, g)
-    assert Gr == approx(D**3)
-
-
-@hypothesis.given(surface_temperature=st.floats(min_value=273, max_value=1000, allow_nan=False))
-def test_grashof_number_scales_correctly_with_surface_temperature(surface_temperature):
-    D = 1
-    T_s = surface_temperature
-    T_a = 0
-    Nu_f = 1
-    g = 0.5 * T_s + 273.15
-
-    Gr = convective_cooling.compute_grashof_number(D, T_s, T_a, Nu_f, g)
-    assert Gr == approx(abs(T_s))
-
-
-@hypothesis.given(air_temperature=st.floats(min_value=273, max_value=1000, allow_nan=False))
-def test_grashof_number_scales_correctly_with_air_temperature(air_temperature):
-    D = 1
-    T_s = 0
-    T_a = air_temperature
-    Nu_f = 1
-    g = 0.5 * T_a + 273.15
-
-    Gr = convective_cooling.compute_grashof_number(D, T_s, T_a, Nu_f, g)
-    assert Gr == approx(abs(T_a))
-
-
-@hypothesis.given(
-    kinematic_viscosity_of_air=st.floats(min_value=1e-5, max_value=1e10, allow_nan=False)
-)
-def test_grashof_number_scales_inversely_squared_with_kinematic_viscosity(
-    kinematic_viscosity_of_air,
-):
-    D = 1
-    T_s = 1
-    T_a = 0
-    Nu_f = kinematic_viscosity_of_air
-    g = 273.65  # 0.5*T_s in Kelvin
-
-    Gr = convective_cooling.compute_grashof_number(D, T_s, T_a, Nu_f, g)
-    assert Gr == approx(1 / (Nu_f**2))
-
-
-@hypothesis.given(coefficient_of_gravity=st.floats(min_value=1e-3, max_value=1e3, allow_nan=False))
-def test_grashof_number_scales_linearly_with_gravity(coefficient_of_gravity):
-    D = 1
-    T_s = 1
-    T_a = 0
-    Nu_f = np.sqrt(1 / 273.65)
-    g = coefficient_of_gravity
-
-    Gr = convective_cooling.compute_grashof_number(D, T_s, T_a, Nu_f, g)
-    assert Gr == approx(g)
-
-
-def test_grashof_number_with_example():
-    D = 4
-    T_s = 4
-    T_a = 2
-    Nu_f = 2
-    g = 276.15
-
-    Gr = convective_cooling.compute_grashof_number(D, T_s, T_a, Nu_f, g)
-    assert Gr == approx(32)
-
-
-@hypothesis.given(thermal_conductivity=st.floats(min_value=1e-10, max_value=1e10, allow_nan=False))
-def test_prandtl_number_scales_inversely_with_thermal_conductivity(thermal_conductivity):
-    c_f = 1
-    mu_f = 1
-    lambda_f = thermal_conductivity
-
-    assert convective_cooling.compute_prandtl_number(lambda_f, mu_f, c_f) == approx(1 / lambda_f)
-
-
-@hypothesis.given(dynamic_viscosity=st.floats(min_value=1e-10, max_value=1e10, allow_nan=False))
-def test_prandtl_number_scales_linearly_with_dynamic_viscosity(dynamic_viscosity):
-    c_f = 1
-    mu_f = dynamic_viscosity
-    lambda_f = 1
-
-    assert convective_cooling.compute_prandtl_number(lambda_f, mu_f, c_f) == approx(mu_f)
-
-
-@hypothesis.given(
-    specific_heat_capacity=st.floats(min_value=1e-10, max_value=1e10, allow_nan=False)
-)
-def test_prandtl_number_scales_linearly_with_specific_heat_capacity(specific_heat_capacity):
-    c_f = specific_heat_capacity
-    mu_f = 1
-    lambda_f = 1
-
-    assert convective_cooling.compute_prandtl_number(lambda_f, mu_f, c_f) == approx(c_f)
-
-
-def test_compute_prandtl_number_with_example():
-    c_f = 0.5
-    mu_f = 3
-    lambda_f = 0.5
-
-    assert convective_cooling.compute_prandtl_number(lambda_f, mu_f, c_f) == approx(3)
 
 
 ## Nusselt number calculation
@@ -646,94 +498,3 @@ def test_compute_nusselt_number(forced_convection_nusselt_number, natural_nussel
     Nu_est = convective_cooling.compute_nusselt_number(Nu_delta, Nu_beta)
 
     assert Nu == Nu_est
-
-
-@hypothesis.given(
-    nusselt_number=st.floats(
-        min_value=0,
-        max_value=1e10,
-        allow_nan=False,
-    )
-)
-def test_convective_cooling_scales_linearly_with_nusselt_number(nusselt_number):
-    Nu = nusselt_number
-    T_s = 1
-    T_a = 0
-    lambda_f = 1 / np.pi
-
-    assert convective_cooling.compute_convective_cooling(T_s, T_a, Nu, lambda_f) == approx(Nu)
-
-
-@hypothesis.given(
-    thermal_conductivity_of_air=st.floats(
-        min_value=0,
-        max_value=1e10,
-        allow_nan=False,
-    )
-)
-def test_convective_cooling_scales_linearly_with_thermal_conductivity_of_air(
-    thermal_conductivity_of_air,
-):
-    Nu = 1 / np.pi
-    T_s = 1
-    T_a = 0
-    lambda_f = thermal_conductivity_of_air
-
-    assert convective_cooling.compute_convective_cooling(T_s, T_a, Nu, lambda_f) == approx(lambda_f)
-
-
-@hypothesis.given(
-    surface_temperature=st.floats(
-        min_value=-1e10,
-        max_value=1e10,
-        allow_nan=False,
-    ),
-    air_temperature=st.floats(
-        min_value=-1e10,
-        max_value=1e10,
-        allow_nan=False,
-    ),
-)
-def test_convective_cooling_scales_linearly_with_temperature_difference(
-    surface_temperature, air_temperature
-):
-    Nu = 1
-    T_s = surface_temperature
-    T_a = air_temperature
-    lambda_f = 1 / np.pi
-
-    assert convective_cooling.compute_convective_cooling(T_s, T_a, Nu, lambda_f) == approx(
-        T_s - T_a
-    )
-
-
-@hypothesis.given(
-    air_temperature=st.floats(
-        min_value=-1e10,
-        max_value=1e10,
-        allow_nan=False,
-    )
-)
-def test_convective_cooling_scales_affinely_with_air_temperature(air_temperature):
-    Nu = 1
-    T_s = 1
-    T_a = air_temperature
-    lambda_f = 1 / np.pi
-
-    assert 1 - convective_cooling.compute_convective_cooling(T_s, T_a, Nu, lambda_f) == approx(T_a)
-
-
-@hypothesis.given(
-    surface_temperature=st.floats(
-        min_value=-1e10,
-        max_value=1e10,
-        allow_nan=False,
-    ),
-)
-def test_convective_cooling_scales_affinely_with_surface_temperature(surface_temperature):
-    Nu = 1
-    T_s = surface_temperature
-    T_a = 1
-    lambda_f = 1 / np.pi
-
-    assert convective_cooling.compute_convective_cooling(T_s, T_a, Nu, lambda_f) + 1 == approx(T_s)
diff --git a/tests/equations/ieee738/test_convective_cooling.py b/tests/equations/ieee738/test_ieee_convective_cooling.py
similarity index 89%
rename from tests/equations/ieee738/test_convective_cooling.py
rename to tests/equations/ieee738/test_ieee_convective_cooling.py
index 2d9a887..2d7c97e 100644
--- a/tests/equations/ieee738/test_convective_cooling.py
+++ b/tests/equations/ieee738/test_ieee_convective_cooling.py
@@ -1,7 +1,6 @@
 import hypothesis
 import hypothesis.strategies as st
 import numpy as np
-import pytest
 from pytest import approx
 from scipy.interpolate import lagrange
 
@@ -102,41 +101,6 @@ def test_kinematic_viscosity_of_air_with_example():
     assert convective_cooling.compute_kinematic_viscosity_of_air(mu_f, rho_f) == approx(1)
 
 
-@hypothesis.given(wind_speed=st.floats(min_value=0, max_value=1000, allow_nan=False))
-def test_reynolds_number_scales_linearly_with_wind_speed(wind_speed):
-    v = wind_speed
-    D = 1
-    nu_f = 1
-
-    assert convective_cooling.compute_reynolds_number(v, D, nu_f) == pytest.approx(v)
-
-
-@hypothesis.given(conductor_diameter=st.floats(min_value=0, max_value=1000, allow_nan=False))
-def test_reynolds_number_scales_linearly_with_diameter(conductor_diameter):
-    v = 1
-    D = conductor_diameter
-    nu_f = 1
-
-    assert convective_cooling.compute_reynolds_number(v, D, nu_f) == pytest.approx(D)
-
-
-@hypothesis.given(kinematic_viscosity=st.floats(min_value=1e-10, allow_nan=False))
-def test_reynolds_number_scales_inversly_with_kinematic_viscosity(kinematic_viscosity):
-    v = 1
-    D = 1
-    nu_f = kinematic_viscosity
-
-    assert convective_cooling.compute_reynolds_number(v, D, nu_f) == approx(1 / nu_f)
-
-
-def test_reynolds_number_with_example():
-    v = 0.1
-    D = 1.2
-    nu_f = 10
-
-    assert convective_cooling.compute_reynolds_number(v, D, nu_f) == approx(0.012)
-
-
 def test_wind_direction_factor_with_example():
     Phi = 0
     assert convective_cooling.compute_wind_direction_factor(Phi) == approx(0.388)
diff --git a/tests/equations/test_convective_cooling.py b/tests/equations/test_convective_cooling.py
new file mode 100644
index 0000000..876f749
--- /dev/null
+++ b/tests/equations/test_convective_cooling.py
@@ -0,0 +1,97 @@
+import hypothesis
+import hypothesis.strategies as st
+import numpy as np
+
+from pytest import approx
+from linerate.equations import convective_cooling
+
+
+@hypothesis.given(
+    nusselt_number=st.floats(
+        min_value=0,
+        max_value=1e10,
+        allow_nan=False,
+    )
+)
+def test_convective_cooling_scales_linearly_with_nusselt_number(nusselt_number):
+    Nu = nusselt_number
+    T_s = 1
+    T_a = 0
+    lambda_f = 1 / np.pi
+
+    assert convective_cooling.compute_convective_cooling(T_s, T_a, Nu, lambda_f) == approx(Nu)
+
+
+@hypothesis.given(
+    thermal_conductivity_of_air=st.floats(
+        min_value=0,
+        max_value=1e10,
+        allow_nan=False,
+    )
+)
+def test_convective_cooling_scales_linearly_with_thermal_conductivity_of_air(
+    thermal_conductivity_of_air,
+):
+    Nu = 1 / np.pi
+    T_s = 1
+    T_a = 0
+    lambda_f = thermal_conductivity_of_air
+
+    assert convective_cooling.compute_convective_cooling(T_s, T_a, Nu, lambda_f) == approx(lambda_f)
+
+
+@hypothesis.given(
+    surface_temperature=st.floats(
+        min_value=-1e10,
+        max_value=1e10,
+        allow_nan=False,
+    ),
+    air_temperature=st.floats(
+        min_value=-1e10,
+        max_value=1e10,
+        allow_nan=False,
+    ),
+)
+def test_convective_cooling_scales_linearly_with_temperature_difference(
+    surface_temperature, air_temperature
+):
+    Nu = 1
+    T_s = surface_temperature
+    T_a = air_temperature
+    lambda_f = 1 / np.pi
+
+    assert convective_cooling.compute_convective_cooling(T_s, T_a, Nu, lambda_f) == approx(
+        T_s - T_a
+    )
+
+
+@hypothesis.given(
+    air_temperature=st.floats(
+        min_value=-1e10,
+        max_value=1e10,
+        allow_nan=False,
+    )
+)
+def test_convective_cooling_scales_affinely_with_air_temperature(air_temperature):
+    Nu = 1
+    T_s = 1
+    T_a = air_temperature
+    lambda_f = 1 / np.pi
+
+    assert 1 - convective_cooling.compute_convective_cooling(T_s, T_a, Nu, lambda_f) == approx(T_a)
+
+
+@hypothesis.given(
+    surface_temperature=st.floats(
+        min_value=-1e10,
+        max_value=1e10,
+        allow_nan=False,
+    ),
+)
+def test_convective_cooling_scales_affinely_with_surface_temperature(surface_temperature):
+    Nu = 1
+    T_s = surface_temperature
+    T_a = 1
+    lambda_f = 1 / np.pi
+
+    assert convective_cooling.compute_convective_cooling(T_s, T_a, Nu, lambda_f) + 1 == approx(T_s)
diff --git a/tests/equations/test_dimensionless.py b/tests/equations/test_dimensionless.py
new file mode 100644
index 0000000..efbf4ba
--- /dev/null
+++ b/tests/equations/test_dimensionless.py
@@ -0,0 +1,157 @@
+# Tests for unitless quantities
+###############################
+
+import hypothesis
+import hypothesis.strategies as st
+import numpy as np
+import pytest
+from pytest import approx
+
+from linerate.equations import dimensionless
+
+
+@hypothesis.given(wind_speed=st.floats(min_value=0, max_value=1000, allow_nan=False))
+def test_reynolds_number_scales_linearly_with_wind_speed(wind_speed):
+    V = wind_speed
+    D = 1
+    Nu_f = 1
+
+    assert dimensionless.compute_reynolds_number(V, D, Nu_f) == pytest.approx(V)
+
+
+@hypothesis.given(conductor_diameter=st.floats(min_value=0, max_value=1000, allow_nan=False))
+def test_reynolds_number_scales_linearly_with_diameter(conductor_diameter):
+    V = 1
+    D = conductor_diameter
+    Nu_f = 1
+
+    assert dimensionless.compute_reynolds_number(V, D, Nu_f) == pytest.approx(D)
+
+
+@hypothesis.given(kinematic_viscosity=st.floats(min_value=1e-10, allow_nan=False))
+def test_reynolds_number_scales_inversly_with_kinematic_viscosity(kinematic_viscosity):
+    V = 1
+    D = 1
+    Nu_f = kinematic_viscosity
+
+    assert dimensionless.compute_reynolds_number(V, D, Nu_f) == approx(1 / Nu_f)
+
+
+def test_reynolds_number_with_example():
+    V = 0.1
+    D = 1.2
+    Nu_f = 10
+
+    assert dimensionless.compute_reynolds_number(V, D, Nu_f) == approx(0.012)
+
+
+@hypothesis.given(conductor_diameter=st.floats(min_value=1e-5, max_value=1e5, allow_nan=False))
+def test_grashof_number_scales_cubic_with_conductor_diameter(conductor_diameter):
+    D = conductor_diameter
+    T_s = 1
+    T_a = 0
+    Nu_f = 1
+    g = 273.65  # 0.5*T_s in Kelvin
+
+    Gr = dimensionless.compute_grashof_number(D, T_s, T_a, Nu_f, g)
+    assert Gr == approx(D**3)
+
+
+@hypothesis.given(surface_temperature=st.floats(min_value=273, max_value=1000, allow_nan=False))
+def test_grashof_number_scales_correctly_with_surface_temperature(surface_temperature):
+    D = 1
+    T_s = surface_temperature
+    T_a = 0
+    Nu_f = 1
+    g = 0.5 * T_s + 273.15
+
+    Gr = dimensionless.compute_grashof_number(D, T_s, T_a, Nu_f, g)
+    assert Gr == approx(abs(T_s))
+
+
+@hypothesis.given(air_temperature=st.floats(min_value=273, max_value=1000, allow_nan=False))
+def test_grashof_number_scales_correctly_with_air_temperature(air_temperature):
+    D = 1
+    T_s = 0
+    T_a = air_temperature
+    Nu_f = 1
+    g = 0.5 * T_a + 273.15
+
+    Gr = dimensionless.compute_grashof_number(D, T_s, T_a, Nu_f, g)
+    assert Gr == approx(abs(T_a))
+
+
+@hypothesis.given(
+    kinematic_viscosity_of_air=st.floats(min_value=1e-5, max_value=1e10, allow_nan=False)
+)
+def test_grashof_number_scales_inversely_squared_with_kinematic_viscosity(
+    kinematic_viscosity_of_air,
+):
+    D = 1
+    T_s = 1
+    T_a = 0
+    Nu_f = kinematic_viscosity_of_air
+    g = 273.65  # 0.5*T_s in Kelvin
+
+    Gr = dimensionless.compute_grashof_number(D, T_s, T_a, Nu_f, g)
+    assert Gr == approx(1 / (Nu_f**2))
+
+
+@hypothesis.given(coefficient_of_gravity=st.floats(min_value=1e-3, max_value=1e3, allow_nan=False))
+def test_grashof_number_scales_linearly_with_gravity(coefficient_of_gravity):
+    D = 1
+    T_s = 1
+    T_a = 0
+    Nu_f = np.sqrt(1 / 273.65)
+    g = coefficient_of_gravity
+
+    Gr = dimensionless.compute_grashof_number(D, T_s, T_a, Nu_f, g)
+    assert Gr == approx(g)
+
+
+def test_grashof_number_with_example():
+    D = 4
+    T_s = 4
+    T_a = 2
+    Nu_f = 2
+    g = 276.15
+
+    Gr = dimensionless.compute_grashof_number(D, T_s, T_a, Nu_f, g)
+    assert Gr == approx(32)
+
+
+@hypothesis.given(thermal_conductivity=st.floats(min_value=1e-10, max_value=1e10, allow_nan=False))
+def test_prandtl_number_scales_inversely_with_thermal_conductivity(thermal_conductivity):
+    c_f = 1
+    mu_f = 1
+    lambda_f = thermal_conductivity
+
+    assert dimensionless.compute_prandtl_number(lambda_f, mu_f, c_f) == approx(1 / lambda_f)
+
+
+@hypothesis.given(dynamic_viscosity=st.floats(min_value=1e-10, max_value=1e10, allow_nan=False))
+def test_prandtl_number_scales_linearly_with_dynamic_viscosity(dynamic_viscosity):
+    c_f = 1
+    mu_f = dynamic_viscosity
+    lambda_f = 1
+
+    assert dimensionless.compute_prandtl_number(lambda_f, mu_f, c_f) == approx(mu_f)
+
+
+@hypothesis.given(
+    specific_heat_capacity=st.floats(min_value=1e-10, max_value=1e10, allow_nan=False)
+)
+def test_prandtl_number_scales_linearly_with_specific_heat_capacity(specific_heat_capacity):
+    c_f = specific_heat_capacity
+    mu_f = 1
+    lambda_f = 1
+
+    assert dimensionless.compute_prandtl_number(lambda_f, mu_f, c_f) == approx(c_f)
+
+
+def test_compute_prandtl_number_with_example():
+    c_f = 0.5
+    mu_f = 3
+    lambda_f = 0.5
+
+    assert dimensionless.compute_prandtl_number(lambda_f, mu_f, c_f) == approx(3)