Active Thermal Cooling Technologies - Low Energy Cooling for Sustainable Buildings - page 191

10 10

CMAU

HEAU

8 8

6 6

4 4

2 2

0 0

45 50 55 60 65 70 75 45 50 55 60 65 70 75

Relative humidity return air / %

Relative humidity return air / %

(a) (c)

40

40

CMAU

HEAU

35

35

30 30

25

25

20 20

45 50 55 60 65 70 75 45 50 55 60 65 70 75

Relative humidity return air / % Relative humidity return air / %

LiCl experiment LiCl calculation

LiCl experiment LiCl calculation

(b) (d) CaCl 2 experiment CaCl 2 calculation

CaCl 2 experiment CaCl 2 calculation

Figure 5.76 Comparison of calculations with experiments for return air dehumidification vs. return air
inlet relative humidity; a) + b) return air dehumidification and outlet temperature, HEAU; c) + d) return
air dehumidification and outlet temperature, CMAU

the return air temperature increases considerably during the absorption process in the
CMAU. The small fluctuations within the experimental results are due to imprecise
control of the two humidifiers used for the conditioning of return and ambient air,
combined with measurement inaccuracies (thermocouples, humidity sensors, air flow
measuring device, etc.).
The experimental resultswere then comparedwith the developed theoreticalmodels.
The calculated return air dehumidification (dashed lines) corresponds very well to the
results of the experiments (solid lines) for both the HEAU and CMAU. The calculated
outlet temperatures are slightly higher than the experimental results. This can be
attributed to the neglect of heat losses in themodel. Since the prototypes of the absorber
units are not insulated, this simplification is visible in the obtained results.
The surface wetting of the HEAU and CMAU was calculated iteratively. For the
HEAU, good agreement between calculated andmeasured dehumidification is reached
for surface wettings of 35% in the case of the LiCl solution and 45% in the case of
the CaCl 2 solution. The worse surface wetting of the LiCl solution can be explained
as a result of the higher surface tension of concentrated LiCl solution.