IEA Solar Heating and Cooling Programm - NachhaltigWirtschaften.at

IEA SHC Task 38 Solar Air Conditioning and Refrigeration
Subtask A Report, Date:…
Often it can be observed that the chillers run continuously for several hours thereby taking
advantage of the big range in the driving temperature. Figure 7 shows an exemplary day with
cooling operation of absorption chiller 1. In contrast to the relatively steady temperature in
the upper part of the storage the driving temperature to the chiller oscillates periodically in a
stronger manner. This oscillations correlate exactly with the collector outlet temperature and
the periodical pump operation in the collector circuit (“bucket principle”). It is still not clear
why the driving temperature is evened by the storage just on a small scale. The measuring
point of the upper storage temperature shows clearly a temperature course which is more
straightened.
In contrast to the pump in the collector circuit the pump in the driving circuit of the chiller runs
continuously from 9:00 until 17:00 with a short interruption before 12:00. Altogether with the
low driving temperature chilling capacities between 6 and 8 kW are achieved. According to
the temperature and capacity oscillations in the hot water circuit of the chiller the thermal
COP varies strongly as well.
5.3 Detailed Analysis
Figure 8 shows the frequency distribution of driving, cooling water and chilled water
temperatures of both chillers in serial connection in 2010. The frequency maximum for the
driving temperature of chiller 1 lies between 65°C and 70°C. Temperatures greater than
83°C appear rarely. Chiller 1 produces most frequen tly chilled water temperatures in the
range of 13°C to 15°C. The chilled water range of c hiller 2 is widely distributed and on a
higher temperature level as well. The driving temperature level of chiller 2 is shifted about
10 K downwards. The maxima of the cooling water temperatures are relatively clear.
However, the values differ with 4 K from each other.
The frequency distributions show just values when the pumps in the three circuits are in
operation. Though, the first operation minutes after the chiller starts can for example show
higher chilled water temperatures until a steady operation is reached. However, these values
are not filtered out from the shown graphics.
1200
1000
Frequency
800
600
400
Intput Driving
Heat AbCH1
Intput Driving
Heat AbCH2
200
0
50 52 54 56 58 60 62 64 66 68 70 72 74 76 78 80 82 84 86 88 90
Temperature [°C]