Active Thermal Cooling Technologies - Low Energy Cooling for Sustainable Buildings - page 179

Figure 5.67 Liquid desiccant drying unit integrated in a water-cooled heat exchanger for return air
drying

flow rate of 300m 3 h − 1 . Four thermocouples were used to monitor the inlet and outlet
temperatures of the return air and the salt solution. Additionally, two capacity-based
humidity sensors were used to measure the relative humidity of the return air at the
inlet and outlet of the contact matrix absorber unit.

Heat Exchanger Absorber Unit (HEAU) A cross-flow plate heat exchanger
(300

250mm) with 54 channels in each flow direction and a heat transfer
efficiency of 70% was used to build the heat exchanger absorber unit for the most
integrated unit of system 4. The spacing between each plate (0.2mm thickness) of the
heat exchanger is 2mm. The heat exchanger is designed for a maximum air flow rate of
300m 3 h − 1 . As shown in Figure 5.67, the liquid desiccant or water is sprayed onto the
heat exchanger channels by spray nozzles. After passing through the heat exchanger,
the liquids are collected in separate basins at the bottomof the absorber unit case. Eight
spray nozzles on the return air side and on the ambient air side allow a solution/water
flow rate of 100 l h − 1 . The first prototype was made of aluminium, which will not be
a long-term solution due to corrosion problems. Eight thermocouples were used to
monitor the inlet and outlet temperatures of the air on the return and ambient side 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.

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Cooling System Analysis and Supply Air Temperatures

The different dehumidification processes were compared for a constant return air
condition of 26 ◦ C and 55% relative humidity and ambient inlet air conditions of