Environmental Engineering Reference
In-Depth Information
30
20
Temperature ambient air
25
Temperature supply air
15
20
15
10
Sorption rotor
Exhaust air humidifier
10
Supply air humidifier
5
5
0
0
09:00
12:00
15:00
18:00
Time on 22 July
Figure 5.27
Fluctuations of supply air temperature due to control strategy
This dynamic and partially slow response of the components is not adequately
considered in the control strategy of the plant. For example, the measured supply
air temperature often fluctuates by about 6 K when supply air humidifiers and heat
recovery strategies work against each other. At verymoderate ambient air temperatures
of 22
◦
C the combination of exhaust air humidification and full humidification of the
three-stage supply air humidifier leads to a temperature decrease in the supply air
below the setpoint of 17
◦
C in less than 30 minutes (see Figure 5.27).
The humidifiers are consequently switched off and the rotational speed of the sorp-
tion rotor is increased to raise the temperature level in heat recovery mode. Further-
more, the rotating heat exchanger is switched on early (about 10 minutes before the
exhaust air humidifier), so that supply air temperatures increase well above 20
◦
C and
then drop again below 15
◦
C (see Figure 5.28).
30
20
25
Temperature ambient air
Temperature supply air
15
20
15
10
Rotating heat exchanger
10
Sorption rotor
Supply air humidifier
5
5
Exhaust air humidifier
0
0
16:00
16:30
17:00
17:30
18:00
Time on 22 July
Figure 5.28
Details of switching signals and resulting supply air temperature
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