Environmental Engineering Reference
In-Depth Information
At an angle of 45
◦
to the horizontal, the maximum reachable surface wetting on the
heat exchanger plates is limited to about 60%. For the CMAU, a surface wetting of 80%
(LiCl solution) and 90% (CaCl
2
solution) gave good agreement between calculation
and measurement. These high surface wettings can be attributed to the vertical flow
direction of the liquid desiccants on the contact absorber surface. Furthermore, the
hygroscopic cellulose matrix allows better surface wetting than metal surfaces.
Absorber Tests with Variation of the Return and Ambient Air Flow Rate
In
the second set of experiments the air flow rates were varied for constant temperature
conditions (return air 26
◦
C, 55% RH; ambient air 32
◦
C, 40% RH). As shown in
Figure 5.77, the dehumidification in both absorber units decreases with increasing air
flow rates while the outlet temperature increases slightly. Since laminar flow condi-
tions can be assumed in the absorber units, the increase in temperature can be explained
10
10
HEAU
CMAU
8
8
6
6
4
4
2
2
0
0
0
100
200
300
400
0
100
200
300
400
Return/ambient air flow rate / m
3
h
-1
3
h
-1
Return air flow rate / m
(a)
(c)
40
40
HEAU
CMAU
35
35
30
30
25
25
20
20
0
100
200
300
400
0
100
200
300
400
Return/ambient air flow rate / m
3
h
-1
3
h
-1
Return air flow rate / m
LiCl experiment
LiCl calculation
LiCl experiment
LiCl calculation
(b)
(d)
CaCl
2
experiment
CaCl
2
calculation
CaCl
2
experiment
CaCl
2
calculation
Figure 5.77
Comparison of calculations with experiments for return air dehumidification vs. return
and ambient air volume flow rate: a)
+
b) return air dehumidification and outlet temperature, HEAU;
c)
+
d) return air dehumidification and outlet temperature, CMAU
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