Active Thermal Cooling Technologies - Low Energy Cooling for Sustainable Buildings - page 190

h S,in , m

ξ S,in ,

in S,

z

h R,in ,x R,in

y

h Abs.

1

m W

2

Q

C, R

h R,out ,x R,out

h S,out , m

ξ S,out ,

out S,

Figure 5.75 Nodes for energy and mass balances in the CMAU

Model Validation and Performance Analysis

Absorber Tests with Variation of the Return Air Relative Humidity The
dehumidification performance of the two developed absorber units has been tested
by varying the relative humidity of the return air (26 ◦ C) from 50% to 70%. Vol-
ume flows were 200m 3 h − 1 and the ambient air conditions for the spray humidifier
side in the HEAU were 32 ◦ C and 40% relative humidity. The results depicted in
Figure 5.76 show the obtained return air dehumidification and return air outlet tem-
perature of both the examined absorber units versus the inlet relative humidity of the
return air. The HEAU reaches a considerable higher dehumidification, combined with
lower outlet temperatures of the return air. This positive effect can be explained by
the very effective indirect evaporative cooling function of the HEAU.
With increasing inlet relative humidity of the return air from 50 to 70%, the
dehumidification increases from about 5 to 7 g water kg − 1

air if LiCl solution is used as
the liquid desiccant. The simple CMAU reaches about 1.5 g water kg − 1

air lower dehu-
midification rates. In both absorber units CaCl 2 solution offers a significantly lower
dehumidification potential.
A comparison of the return air outlet temperatures in Figure 5.76 illustrates the good
performance of the integrated evaporative cooling function of the HEAU. Whereas
the return air outlet temperature of the HEAU is lower than the inlet temperature,