Environmental Engineering Reference
In-Depth Information
of high room temperatures, heat is slowly absorbed by thermal mass which is
gradually heated up by the space. If, by contrast, the room temperature falls below
the thermal mass surface temperature, the stored heat is released back into the
space.
The established heat flow q . depends on the temperature (θ) difference between
the warm and the cold accumulator, the specific thermal capacity c p , the density
ρ SM and the thermal conductivity λ of the storage medium, as well as on the heat-
ing and heat dissipation time t . Within a very short period of time, for instance,
the accumulator will only heat up at the surface, and the absorbed energy quantity
is thus only little.
The heat flow q . is calculated by Fourier's (one-dimensional) law on heat con-
duction according to Equation (3.6) and by the heat flow into and from the storage
element (storage equation, Equation (3.7)).
θ
&
q
=
λ
(3.6)
x
&
2
q
θ
θ
=
λ
=
ρ
c
(3.7)
SM
p
2
x
x
t
24
17 h
23
22
19 h
21 h
23 h
1 h
21
15 h
13 h
11 h
9 h
7 h
5 h
20
19
3 h
18
-0.1
0
0.1
0.2
0.3
0.4
Wall thickness in m
Fig. 3.6 Temperature flow within an internal wall exposed to radiation and varying tem-
peratures on one side (left) /see 3-9/
As an example, Fig. 3.6 illustrates the room and wall temperatures of an inter-
nal concrete wall (storage wall) within the course of 24 hours. Within this period
the temperature varies by 6 °C on one room side, whereas the stored and released
 
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