Environmental Engineering Reference
In-Depth Information
For the validation of the developed theoretical models additional operating con-
ditions were investigated for the contact matrix and heat exchanger absorber unit.
During the first set of experiments the air flow and liquid flow rates were kept constant
(200m
3
h
−
1
return and ambient air, 100 l h
−
1
liquid desiccant and water), while the
relative humidity of the return air was varied from 50 to 70%. During the second
set, the air flow rates of the return and ambient air were varied from 100 to 300m
3
h
−
1
, while all other parameters were kept constant. To examine the performance of
two different liquid desiccants, all experiments were carried out using both lithium
chloride and calcium chloride solutions, each at a concentration of 43%mass fraction.
Before starting the experiments the solutions and water were heated to a temperature
level of about 27
2
◦
C to demonstrate the most realistic summer conditions.
±
Desiccant Rotor (AWheel)
A silica gel desiccant rotor with a diameter of 350mm
was used as a reference desiccant system (system 2), which is already commercially
available. The rotation velocity used for the experimental analysis was 20 rotations per
hour, with a volume flow rate of 200m
3
h
−
1
on the return air side and 185m
3
h
−
1
on the
regeneration air sides. For regeneration, ambient air was heated to 70
◦
C, resulting in a
relative humidity of 6%. Four thermocouples (
0.1 K accuracy) were used to monitor
the inlet and outlet temperatures of the air on the return air and regeneration air sides as
well as the inlet and outlet temperatures of the water and the solution. Additionally, on
each air side the relative humidity was measured using four capacity-based humidity
sensors (
±
±
1% accuracy).
Contact Matrix Absorber Unit (CMAU)
A cellulose matrix (300
×
150mm) offering a specific contact area of 600m
2
m
−
3
was used for the direct contact
matrix absorber unit (system 3). For dehumidification, the return air is brought into
contact with the liquid desiccant running down the cellulose matrix of the absorber
unit in cross-flow to the air stream as shown in Figure 5.66. Eight water spray nozzles
with a spray angle of 60
◦
are placed above the cellulose matrix at a distance of 6 cm, to
distribute the liquid desiccant uniformly over the matrix, allowing a minimum solution
flow rate of 100 l h
−
1
. The contact matrix absorber unit is designed for a maximum air
×
200
Figure 5.66
Contact matrix absorber unit for drying the room exhaust air
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