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(H2O/LiCl, H2O/CaCl2 ,H2O/LiBr). The experimental data re-
ported are useful for the design of the liquid desiccant systems.
2 Experimental Apparatus and Procedures
The experimental rig, shown in Figs. 1~a! and 1~b!, consists of
an air loop and a desiccant loop. In the first loop ambient air is
heated and humidified to achieve the set conditions at the inlet of
the packed column. The power of the heating element can be
varied from 0 to 2000 W by a PID controller, while the steam
humidifier provides a vapor flow rate from 0 to 5 kg/h. The air
goes through the packed tower where the heat and mass transfer
with the desiccant takes place and then it is discharged. An air
dehumidification process or a desiccant regeneration process oc-
curs depending on the relative values of the partial vapor pressure
on the air and solution side. The tower shell, made of stainless
steel, 725 mm in height and 400 mm in diameter is filled with
randomly packed 25 mm plastic Pall Rings supported by a stain-
less steel net and sprinkled with a liquid distributor. A large cham-
ber at the bottom of the tower provides a good air distribution
entering the column, whereas a stainless steel wire mesh at the top
removes desiccant droplets carried out by the air at the highest
velocities. The air duct, manufactured from a 160 mm diameter
PVC tube, contains two measurement sections located at the inlet
and at the outlet of the tower to measure temperature and humid-
ity ratio.
Each measuring station consists of two temperature taps, instru-
mented with T-type thermocouples, and two humidity taps, con-nected to dew point temperature probes, placed at different posi-
tions in the gas flow. The pressure variation of the air flow across
the tower is measured by a U-tube manometer and by a strain-
gage pressure transducer, while the air flow rate is measured by a
diaphragm inserted in the air duct at the outlet of the tower after
3000 mm of straight tube. The desiccant is maintained at a con-
stant temperature and at a uniform concentration in a stainless
steel tank by a PID controller. From there it is pumped into the
tower and sprinkled onto the packed matrix. The solution, after
the heat and mass transfer with air, flows due to gravity into a
storage tank. The flow rate of the desiccant, varied by the by-pass
valve of the solution tank, is measured by a Coriolis effect mass
flow meter and also by evaluating the variation of the liquid level
in the tank at any fixed time. The temperature of the solution is
measured at the inlet and outlet of the tower by T-type thermo-
couples, whereas the concentration at the inlet and outlet is de-
rived from density measurements on samples. The readings of the
thermocouples and of hygrometers are scanned and recorded by a
data logger, whereas the measurements of the air and desiccant
flow rates and the solution concentration are taken manually and
then implemented into the computer. Table 1 gives the main fea-
tures of the different measuring devices in the experimental rig.
In the present work both air dehumidification and solution re-
generation tests were carried out. Before starting each test the
solution in the tank was recirculated through the by-pass circuit to
ensure uniform conditions. The air and desiccant flow rates were
then established at set values, while temperature and humidity
readings were recorded. Once temperature and humidity steady
state conditions were achieved, readings were collected. Flow and
pressure drop measurements were repeated three times, samples
of the solution were taken at the inlet and outlet of the tower to
measure its concentration. From the measurements collected, a
computer code calculated the heat and mass balances over the