DeltaOHM HD32.1, Operating Manual

Page: 8 / 158

HD32.1
- 8 -
V2.1
2. WORKING PRINCIPLE
2.1 T
HE
O
PERATING
P
ROGRAM
A: MICROCLIMATE ANALYSIS
By microclimate is meant those environmental parameters that influence the heat exchange between
the person and the surrounding spaces, and that determinate the so-called " thermal well-being".
The microenvironment climatic factors, together with the type of work performed, generate a series
of biological responses linked to thermal well-being (Comfort) or uneasiness (Discomfort).
The human organism, indeed, tends to maintain a thermal balance so that the body temperature is
optimum.
The
HD32.1, Thermal Microclimate, through its operating program A: Microclimate Analysis
measures the following quantities:
•
t
nw
: natural ventilation wet bulb temperature
•
t
g
: globe thermometer temperature
•
t
a
: environment temperature
•
p
r
: atmospheric pressure
•
RH : relative humidity
•
v
a
: wind speed
In addition to the direct measurements performed with the probes connected, the instrument can
directly calculate and display the following well-being data:
•
WBGT index
•
Tu index
•
WCI index
•
Average radiation temperature t
r
2.1.1 WBGT Index
WBGT (Wet Bulb Globe Temperature) is one of the indexes used to determine the thermal stress of
a person in a hot environment. It represents the value, related to the metabolic output linked to a
specific work activity, that causes a thermal stress when exceeded. The WBGT index combines the
measurements of the natural ventilation wet bulb temperature
t
nw
with the globe thermometer
temperature t
g
and, in some situations, with the air temperature t
a
. The calculation formula is the
following:
•
Inside and outside buildings without solar radiation:
WBG
enclosed spaces
= 0.7 t
nw
+ 0.3 t
g
•
Outside buildings with solar radiation:
WBGT
outdoor spaces
= 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 measured data should be confronted with the limit values prescribed by regulations; when
exceeded you have to: