Environmental Engineering Reference
In-Depth Information
1,0
0,8
0,6
0,4
0,2
0,0
0
20
40
60
80
100
120
Temperature difference θ abs - θ e in K
Fig. 4.7 Characteristic curves of various non-concentrating liquid-type collectors at a
global radiation of 800 W/m 2 (e.g. /4-1/, /4-2/, /4-3/)
Table 4.3 Parameters of various non-concentrating liquid-type collector designs (accord-
ing to /4-1/, /4-2/, /4-3/ and various other sources)
Optical
Efficiency
Thermal loss
factor
Typ. tempe-
rature range a
Required
effort g
Typical
application
in W/(m 2 K)
in °C
Single absorber b
Flat-plate collector 1 c
Flat-plate collector 2 d
Flat-plate collector 3 e
Vacuum flat-plate collector
Vacuum-pipe collector
Accumulation collector f
OASW
DHW
DHW
DHW, SH
DHW, SH, PH
DHW, SH, PH
DHW
OASW Open-air swimming pool; DHW Domestic hot water; SH Space heating; PH Process heat; Typ
typical; a medium working temperatures; b black, non-selective, not covered; c non-selective absorber,
single cover; d non-selective absorber, double glass and supporting foil; e selective absorber, single cover; f
Prototype ISE; g necessary effort for the production of the absorber.
0.92
0.80 - 0.85
0.65 - 0.70
0.75 - 0.81
0.72 - 0.80
0.64 - 0.80
ca. 0.55
12 - 17
5 - 7
4 - 6
3.0 - 4.0
2.4 - 2.8
1.5 - 2.0
0.55
0 - 30
20 - 80
20 - 80
20 - 80
50 - 120
50 - 120
20 - 70
small
medium
medium
medium
large
very large
very large
Collector circuit. In most cases several single collectors are linked together.
These collectors can be either connected in series or in parallel; mainly combina-
tions of the two forms of connection are used. By connecting in series, the achiev-
able temperature rise in the collector is basically increased and the total mass flow
is reduced (Low-Flow). The advantage of being able to supply hot water quickly
is opposed by the disadvantage of a higher thermal loss of the absorber to the
environment, which is due to the larger temperature difference. The higher pres-
sure loss of collectors connected in series can be overcome by the lower pressure
losses in the pipes due to a lower level of total mass flow. The pump output de-
creases due to the lower level of total mass flow. When connecting in series, there
is a more regular flow through the collector areas. The hydraulic layout has to be
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