feat(local): Add a module for computing local thermal discomfort

ladybug_comfort/local.py

@@ -0,0 +1,61 @@
+# coding=utf-8
+"""Utility functions for computing local thermal discomfort according to ASHRAE-55."""
+from __future__ import division
+
+import math
+
+
+def radiant_asymmetry_ppd(radiant_temperature_difference, asymmetry_type):
+    """Calculate the percentage of people dissatisfied from radiant asymmetry.
+
+    The comfort functions used here come from Figure 5.2.4.1 of ASHRAE 55 2010.
+    Note that, if the resulting input results in a PPD beyond what is included
+    in this Figure, the maximum PPD will simply be returned.
+
+    Note:
+        [1] ASHRAE Standard 55 (2010). "Thermal Environmental Conditions
+        for Human Occupancy." American Society of Heating,
+        Refrigerating and Air Conditioning Engineers.
+
+    Args:
+        radiant_temperature_difference: The radiant temperature difference between
+            two sides of the same plane where an occupant is located [C].
+        asymmetry_type: An integer that representing the type of radiant
+            asymmetry being evaluated. Occupants are more sensitive to warm
+            ceilings and cool walls than cool ceilings and warm walls.
+            Choose from the following options.
+
+            * 0 = WarmCeiling
+            * 1 = CoolWall
+            * 2 = CoolCeiling
+            * 3 = WarmWall
+
+    Returns:
+        ppd -- The percentage of people dissatisfied (PPD) for the input
+        radiant asymmetry.
+    """
+    td = radiant_temperature_difference
+    if asymmetry_type == 0:
+        if td > 23:
+            ppd = 100 / (1 + math.exp(2.84 - 0.174 * 23)) - 5.5
+        else:
+            ppd = 100 / (1 + math.exp(2.84 - 0.174 * td)) - 5.5
+    elif asymmetry_type == 1:
+        if td > 15:
+            ppd = 100 / (1 + math.exp(6.61 - 0.345 * 15))
+        else:
+            ppd = 100 / (1 + math.exp(6.61 - 0.345 * td))
+    elif asymmetry_type == 2:
+        if td > 15:
+            ppd = 100 / (1 + math.exp(9.93 - 0.50 * 15))
+        else:
+            ppd = 100 / (1 + math.exp(9.93 - 0.50 * td))
+    elif asymmetry_type == 3:
+        if td > 35:
+            ppd = 100 / (1 + math.exp(3.72 - 0.052 * 35)) - 3.5
+        else:
+            ppd = 100 / (1 + math.exp(3.72 - 0.052 * td)) - 3.5
+    else:
+        raise ValueError(
+            'Radiant asymmetry_type "{}" was not recognized.'.format(asymmetry_type))
+    return ppd