climate in the central part of Saudi Arabia is extremely hot and dry. Passive evaporative cooling systems are highly suitable and effective. evaporative cooling towers were introduced in Saudi Arabia in the nineties of last century. This research paper aimed to investigate the performance and efficiency of evaporative cooling tower within hot and dry climate context. A full-scale evaporative cooling tower and rooms were built for this purpose. evaporation within the tower was accomplished by

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... aying water over water bags made of special fabric 'heavy canvas'. The tower cools the room through the tower's lower opening. To compare the performance of the tower, another uncooled room was prepared as a control room. Weather station, calibrated thermocouples and automated data gathering system were provided to gather and record various types of measurements. Three modes of operation during summer were adopted: first, continuous operation of the water pump; second, continuous operation of the water pump together with the air-pushing fans; and third, operation of the water pump for 30 min every 5.5 h. Analysis of the collected measurements has shown that the third operation mode was the best. It showed reasonable reduction in room temperature, less water and electric consumption, and suitable humidity level within the room space.