import warnings
from typing import Union
from scipy import optimize
from pythermalcomfort.utilities import (
units_converter,
)
from pythermalcomfort.models.set_tmp import set_tmp
[docs]def cooling_effect(
tdb: Union[float, int],
tr: Union[float, int],
vr: Union[float, int],
rh: Union[float, int],
met: Union[float, int],
clo: Union[float, int],
wme=0,
units="SI",
):
"""Returns the value of the Cooling Effect (`CE`_) calculated in compliance
with the ASHRAE 55 2020 Standard [1]_. The `CE`_ of the elevated air speed
is the value that, when subtracted equally from both the average air
temperature and the mean radiant temperature, yields the same `SET`_ under
still air as in the first `SET`_ calculation under elevated air speed. The
cooling effect is calculated only for air speed higher than 0.1 m/s.
.. _CE: https://en.wikipedia.org/wiki/Thermal_comfort#Cooling_Effect
Parameters
----------
tdb : float
dry bulb air temperature, default in [°C] in [°F] if `units` = 'IP'
tr : float
mean radiant temperature, default in [°C] in [°F] if `units` = 'IP'
vr : float
relative air speed, default in [m/s] in [fps] if `units` = 'IP'
Note: vr is the relative air speed caused by body movement and not the air
speed measured by the air speed sensor. The relative air speed is the sum of the
average air speed measured by the sensor plus the activity-generated air speed
(Vag). Where Vag is the activity-generated air speed caused by motion of
individual body parts. vr can be calculated using the function
:py:meth:`pythermalcomfort.utilities.v_relative`.
rh : float
relative humidity, [%]
met : float
metabolic rate, [met]
clo : float
clothing insulation, [clo]
Note: The activity as well as the air speed modify the insulation characteristics
of the clothing and the adjacent air layer. Consequently the ISO 7730 states that
the clothing insulation shall be corrected [2]_. The ASHRAE 55 Standard corrects
for the effect of the body movement for met equal or higher than 1.2 met using
the equation clo = Icl × (0.6 + 0.4/met) The dynamic clothing insulation, clo,
can be calculated using the function
:py:meth:`pythermalcomfort.utilities.clo_dynamic`.
wme : float, default 0
external work, [met]
units : {'SI', 'IP'} select the SI (International System of Units) or the IP (Imperial Units) system.
Returns
-------
ce : float
Cooling Effect, default in [°C] in [°F] if `units` = 'IP'
Examples
--------
.. code-block:: python
>>> from pythermalcomfort.models import cooling_effect
>>> CE = cooling_effect(tdb=25, tr=25, vr=0.3, rh=50, met=1.2, clo=0.5)
>>> print(CE)
1.64
>>> # for users who wants to use the IP system
>>> CE = cooling_effect(tdb=77, tr=77, vr=1.64, rh=50, met=1, clo=0.6, units="IP")
>>> print(CE)
3.74
Raises
------
ValueError
If the cooling effect could not be calculated
"""
if units.lower() == "ip":
tdb, tr, vr = units_converter(tdb=tdb, tr=tr, v=vr)
if vr <= 0.1:
return 0
still_air_threshold = 0.1
warnings.simplefilter("ignore")
initial_set_tmp = set_tmp(
tdb=tdb,
tr=tr,
v=vr,
rh=rh,
met=met,
clo=clo,
wme=wme,
round=False,
calculate_ce=True,
limit_inputs=False,
)
def function(x):
return (
set_tmp(
tdb - x,
tr - x,
v=still_air_threshold,
rh=rh,
met=met,
clo=clo,
wme=wme,
round=False,
calculate_ce=True,
limit_inputs=False,
)
- initial_set_tmp
)
try:
ce = optimize.brentq(function, 0.0, 40)
except ValueError:
ce = 0
warnings.simplefilter("always")
if ce == 0:
warnings.warn(
"Assuming cooling effect = 0 since it could not be calculated for this set"
f" of inputs {tdb=}, {tr=}, {rh=}, {vr=}, {clo=}, {met=}",
UserWarning,
)
if units.lower() == "ip":
ce = ce / 1.8 * 3.28
return round(ce, 2)