HD32.3TC
- 7 -
V1.1
3
THERMAL
MICROCLIMATE
Thermal Microclimate
refers to the environmental parameters that influence the thermal ex-
changes between an individual and the environment in confined places, and that determine the
so-called “thermal well-being”.
The micro-environmental climatic factors, together with the type of work done, condition the
worker in a series of biologic responses linked to well-being situations (Comfort) or thermal un-
easiness (Discomfort). In fact, the human body tries to keep the thermal balance in equilibrium
conditions in order to keep the body temperature on optimal values.
The instrument
detects the following quantities:
In
WBGT index
visualization:
•
T
nw
: natural ventilation wet bulb temperature probe
•
T
g
: globe thermometer temperature
•
T
a
: ambient temperature
In
PMV - PPD index
visualization:
•
V
a
: air speed
•
T
g
: globe thermometer temperature
•
T
a
: ambient temperature
•
RH
: relative humidity
In
Turbolence
visualization:
•
V
a
: air speed
•
T
a
: ambient temperature
In addition to the direct measurements made with the probes connected, the instrument calcu-
lates and displays:
•
In
WBGT index
visualization: the
WBGT index
in presence or absence of solar radiation.
•
In
PMV index
visualization: the medium radiant temperature
T
r
, the Predicted Mean Vote
PMV and Predicted Percentage of Dissatisfied
PPD
.
•
In
Turbolence
visualization: the local Turbulence intensity
TU
and the Draft Rate
DR
.
3.1
WBGT
INDEX
WBGT
(Wet Bulb Globe Temperature) is one of the indices used for determining the thermal
stress to which is submitted an individual in a warm environment. It represents the value, with
reference to the metabolic waste associated with a particular activity, beyond which the individ-
ual is in a thermal stress condition. WBGT index combines the natural ventilation wet bulb tem-
perature measurement
T
nw
with the Globe thermometer temperature
T
g
and, in some situations,
with the air temperature
T
a
.
The formula for the calculation is the following, and refers to an
individual with reference cotton work clothing ( I
cl
= 0.6 and i
m
= 0.38):
•
inside and outside the buildings in
absence of solar irradiation
:
WBGT
close environments
= 0.7 T
nw
+ 0.3 T
g
•
outside the building in
presence of solar irradiation
:
WBGT
external environments
= 0.7 T
nw
+ 0.2 T
g
+ 0.1 T
a
where:
T
nw
=
natural ventilation wet bulb temperature
T
g
=
globe thermometer temperature
T
a
=
air temperature
The detected data must be compared with the limit values established by the standard; if they
are exceeded, it is necessary to:
Summary of Contents for Delta OHM HD32.3TCA
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