Fix tests, compute Reynolds number as in Cigre207 report

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?

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
 #############################
 

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

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,
+        )