An overview of direct active and passive evaporative cooling systems

Evaporative cooling systems have long been considered because of their significant advantages such as low installation and operation costs, ease of maintenance and reduction of age of air in buildings. Evaporative coolers require large amount frequent supply water. These systems also are not applicable in humid climates. The aims of this paper are familiarity with the principals of evaporative cooling and introducing the different direct active and passive evaporative cooling systems. An active (mechanical) direct evaporative cooler unit uses a fan to draw air through a pad or wetted membrane. At the following, application and the performance of some traditional active direct evaporative cooling systems such as swamp cooler, slinger cooler, air-washer and so on have been compared. After that, passive direct evaporative coolers have been considered. Passive direct evaporative cooling can occur anywhere that the evaporative cooled water can cool a space without the assist of a fan. This can be achieved through use of natural air flow or by combining the cooler with some other systems such as solar chimney, wind catcher, ventilated walls and the others. In these systems usually the significant portion of the needed energy funded through renewable resources.