Civil Engineering Reference
In-Depth Information
Table 3.4
Thermal sensation scale
PMV
Sensation
+
3
Hot
+
2
Warm
+
1
Slightly warm
±
0
Neutral
−
1
Slightly cool
−
2
Cool
−
3
Cold
Table 3.5
Variables which define comfort (IDAE
2007
)
Parameter
Symbol
Range
Unit
met (W/m
2
)
Metabolic rate
M
0.8-4
clo (m
2
◦
C/W)
Clothing insulation
Is
cl
0-2
◦
C
Indoor air temperature
T
a
in
10-30
◦
C
Mean radiant temperature
T
mr
10-40
Indoor air velocity
v
a
in
0-1
m/s
Air relative humidity
Rh
30-70
%
except in controlled experiments. The main reason is that they depend on the current
situation of the users at every instant. The values of both variables can be found in
manuals and standards such as ISO7730 (
1994
) and Fanger (
1972
). For example,
clothing insulation values for a typical office are 1
5clo
1
for winter and
summer, respectively, whereas a typical value used for human activity in an office is
1
.
0 clo and 0
.
0met.
2
Finally, mean radiant temperature (
T
mr
in (
◦
C)), that can be defined as the
uniform temperature of an imaginary enclosure in which radiant heat transfer from
the human body equals the radiant heat transfer in the actual non-uniform enclosure
(ASHRAE
2009
), can be estimated using different methods:
•
.
From the plane radiant temperature,
T
pr
in (
◦
C), in six opposite directions, weighted
according to the projected area factors for a person, as Eq.
3.1
. Using this method-
ology a set of six sensors used exclusively to estimate mean radiant temperature
is necessary (ASHRAE55
1992
).
T
mr
=
(
0
.
18
[
T
pr
(
up
)
+
T
pr
(
down
)
]+
0
.
22
[
T
pr
(
right
)
+
T
pr
(
left
)
]
+
0
.
30
[
T
pr
(
front
)
+
T
pr
(
back
)
]
)/(
2
[
0
.
18
+
0
.
22
+
0
.
30
]
)
(3.1)
•
From a black globe thermometer, which consists of a hollow sphere usually of
150mm in diameter, coated with flat black paint with a thermocouple built at its
centre (ASHRAE
2009
). Thus, the mean radiant temperature can be calculated as a
1
1clo
0.155 m
2
◦
C/W.
=
2
1met
58.15 W/m
2
.
=
