All experimental parameters, such as temperature, air flow, water flow, solar isolations and relative humidity, were measured and recorded using a data logger (DT500). Temperatures were recorded using K-type thermocouples with an accuracy of 0.1 °C. To ensure that all the sensors provided approximately the same reading, they were exposed to the ambient temperature and compared to a mercury- in-glass thermometer with ± 1 division accuracy. They were also immersed in a hot water bath and the same readings were obtained. The accuracy of the thermometer was checked with a handheld digital thermometer which has 0.1 °C accuracy.
Prior to the experiments, the solar desalination system was assembled so that all its sections were horizontal and covered by thermo-insulation materials of thickness 100 mm, as shown in Fig. 27.3. The heat conduction coefficient for the insulation material is 0.023 W/mK. The synthetic brackish water with a high level of total dissolved solids (TDS) and electrical conductivity was prepared and used to fill the storage tank.
The system was tested in conditions simulating a typical spring semester in the Middle East region. For this, information on the variation of the solar radiation during Spring 2004 was used, as shown in Fig. 27.5. The voltage level of electrical power supplied to floodlights was changed every 20 min using the floodlight irradiation measurement results presented in Fig. 27.6.
The fluid mass flow rate through the collector was kept at 180 kg/h, as recommended by the manufacturer. The tests were repeated several times and the water that condensed during the experiments were collected into a metering cylinder and measured after a 24 h period (daylight and unheated periods). An analysis of the water quality was also performed at the end of the experiments.