This section will describe the instrumentation used on the SDCS. Reference to the SDCS schematic in Fig. 6.1 is made throughout. All fans on the SDCS are
Fig. 6.3 SDCS photograph with labelled components
equipped with variable fan speed controllers to enable control of the volumetric air flow through the cores. The air outlets of the evaporative, dehumidifier and regenerator cores are fitted with 125 mm galvanised steel spiral tube ducting, 500 mm in length. The inlet and outlet air flows have been instrumented with Vaisalia HMP110 humidity and temperature probes. The probes are mounted within the spiral tube ducting using special flanges. The humidity and temperature probes are factory calibrated. Air velocity through the dehumidifier, regenerator and evaporative cooler cores are measured using an RS AM4204 hot wire anemometer at the air ducting outlets. The hot wire anemometer is factory calibrated. Air velocity measurements are recorded at five points across the air duct, and the average taken. The air velocity measurements are validated against a TSI LCA501 rotating vane anemometer.
All liquid flows between the tank and core inlets have been equipped with ball valves (V1-V3) so that the desiccant or water volumetric flow may be set to a desired value. A valve has also been placed on the hot water circuit (V4). All water and desiccant solution flows have been instrumented with sheathed K-Type thermocouples (Nickel Chromium/Nickel Aluminium). Thermocouples have been placed at the inlet to the evaporative, dehumidifier and regenerator cores (T2, T4 and T6) and at the outlets of the evaporative, dehumidifier and regenerator tanks (T1, T3 and T5). Thermocouples have also been placed at the hot water inlet (T7) and outlet (T8) to PX2. The desiccant solution volumetric flow is measured using a 1.5 to 10L.min-1 Parker Liquid Flow Indicator; these are placed on the pipe connecting the tank to the core (dehumidifier—F2 and regenerator—F3). The water volumetric flow is measured using a 0.2-2 L min-1 Parker Liquid Flow Indicator, and has been placed on the pipe connecting the water tank to the core (F1). The flow meters used are calibrated for water at 20 °C according to density and viscosity. Thus, for the water flows used in the system, no correction is required, however for the desiccant solution flow a correction factor is required to equate the volumetric flow shown on the flow meter, to the actual desiccant flow. This correction correlation is presented in Eq. 5.1. The hot water cylinder is equipped with an RS 1-15 L min-1 piston flow meter (F4), designed for flow temperatures of up to 60 °C. All desiccant solution and water flows on the SDCS are equipped with 20 mm PVC-U plastic pipe, with plastic fittings. The hot water cylinder is piped with 22 mm copper pipe and copper fittings. Flexible PVC hot water hose is used to connect the hot water cylinder to PX2 on the SDCS.
For the accurate evaluation of the desiccant system, the working concentration of the desiccant solution needs to be determined. Using a correlation based on the work of Melinder (2007) presented in Eq. 5.2, the desiccant solution concentration can be determined from the solution density and temperature. In the experimental work the density of the desiccant solution is measured using a differential pressure density meter with temperature compensation. The meter has been designed to work in the density range of the potassium formate solution (1400-1550 kg m-3), and has been calibrated with water. The measurement prongs of the differential pressure density meter are placed in the desiccant solution tank and held until a steady state reading is achieved. The temperature of the solution is measured using the K-Type thermocouple at the tank outlet. The concentration is then calculated.
The electrical consumption of fans and pumps is measured using a Brennenstuhl PM230 electricity monitor. This is essential for the COPei calculations. At full load the desiccant system parasitic electrical load is measured at 110 W. The electrical power requirement is measured and recorded for each test. A DataTaker DT500 datalogger is used to record data from the humidity and temperature probes and thermocouples every ten seconds. Further details of the instrumentation and their associated accuracy can be referred to in Table 5.1.
Section 6.2.1 has described the SDCS instrumentation. Next, Sect. 6.2.2 describes the experimental method.