Civil Engineering Reference
In-Depth Information
Table 3.9
Comparison of winter models using
e
RMS
S
for sets
S
∈{
TR2, TE2, VA2a, VA2b
}
Model
TR2
TE2
VA2a
VA2b
ANN model with
n
h
=
50
0.0175
0.0172
0.0145
0.0123
Polynomial model order
n
=
7
0.0255
0.0266
0.0296
0.0528
are better, the polynomial model can be derived in an easier way, hence, it can be
linearised around an operation point easily, allowing the implementation of linear
controllers for the HVAC system.
3.3.2 Adaptive Indices
Adaptive indices do not predict the thermal comfort situation, but rather the constant
conditions under which people are in a thermal comfort situation inside buildings.
Generally, people try to adapt themselves and the surroundings to an ideal thermal
condition in order to reduce thermal discomfort. To do that, some conscious actions
such as altering clothing, posture, activity levels, rate of work, diet, ventilation,
air movement and local temperature are performed (ASHRAE
2009
). In addition,
an important factor which influences the adaptive process is the outdoor weather
conditions and people's exposure to them.
In literature there are several adaptive models which allow the reader to estimate a
comfort or neutral temperature as a function of the indoor and outdoor temperatures
(Dear et al.
1997
;Orosa
2009
). Moreover, the international standard ASHRAE 55
has introduced an adaptive model which depends on the mean outdoor temperature,
see Fig.
3.8
. This figure is based on an adaptive model of thermal comfort that is
derived from a global database of 21
000 measurements taken primarily in office
buildings (ASHRAE55
1992
). Therefore, from this figure and according to Eq.
3.14
,
the indoor operative temperature can be inferred for spaces which satisfy that the
metabolic rate associatedwith the physical activitywould be between 1
,
.
.
3met.
However, this model cannot be used when outdoor temperature is outside the range
(
0 and 1
10
◦
C
5
◦
C
,
33
.
)
.
T
a
comf
=
18
.
9
+
0
.
255
T
a
out
(3.14)
where
T
a
comf
is the comfort temperature and
T
a
out
is the outdoor air temperature.
