Environmental Engineering Reference
In-Depth Information
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dehumidification potential (HfT)
dehumidification potential (Sauter)
Figure 5.24
Measured dehumidification from the building management system (Sauter) and averaged
individual sensors (HfT)
If the difference between the exterior air absolute humidity and the supply humid-
ity after the sorption wheel is now calculated, it can be seen that the values taken
from the building management system are not usable (see Figure 5.24). As simi-
lar experiences were found in the commercial desiccant cooling unit in Germany,
more measurements were done on the laboratory test side in Stuttgart in order to
establish the enthalpy changes during dehumidification. If the enthalpy change is
known, the dehumidification can then be calculated from the temperature change
alone.
5.2.4 Monitoring Results in Althengstett
Component and Control Strategy Analysis
Monitoring results are available for the whole summer period fromMarch to Septem-
ber 2002. First of all, efficiencies were determined for all components from the
desiccant cooling plant. The heat recovery efficiency of the rotating heat exchanger
was only 62% at rotation rates of 600 turns per hour. At a measured mass flow ratio
of supply to exhaust air of 1.16 the manufacturer's given value was 73%. The contact
evaporators reached 85% humidification efficiency, compared with the 92.4% given
by the manufacturer. Using this constant humidification efficiency, the humidification
rates can be simulated based on the room exhaust air temperature and relative humid-
ity and correspond well with the measured data (see Figure 5.25). The steady-state
model, however, does not consider the dynamics of the humidification process, so the
calculated absolute humidity after the humidifier immediately takes on the exhaust
air humidity, whereas the measured humidity stays high (see Figure 5.25 with the
switching signal set to 1 for humidifier operation).
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