In a nutshell, evaporative air coolers and water misters, which are also called as swamp coolers, wet air coolers, and desert coolers, are basically the same. They both use the same principles of water condensation and evaporation to cool the surrounding air. They also can be used indoors and outdoors. However, the mechanics of evaporative air coolers are slightly different from those of water misters.
Instead of depending on water-based mist to cool the air, evaporative air coolers are typically self-enclosed systems containing the following: a water tank that is pumped through water distribution lines, a water pump that does the actual pumping, an evaporating pad that takes the water from the water distribution lines to keep itself wet and then converts hot and dry air from the outside into cool air, and a blower or fan to release the already-cooled air to the outside. Due to the dependence of the cooler on outside air, one does not need to close doors and windows for it to operate smoothly, unlike an air conditioner.
Both water misters and evaporative air coolers are economically and financially feasible due to the following reasons: they both can be easily set up; they both do not use too much electricity due to the absence of complicated concepts such as thermostats and compressors; there are no harmful chemicals that will put the environment at risk; they are both easy to maintain; and they both have the ability to cleanse air of contaminants such as dust. However, due to the greater amount of water that must be required for mist production, water misters usually consume more water than evaporative air coolers.
The principles of water condensation and evaporation involve the change of the water’s phase, from liquid to gas and vice-versa respectively. On a related note, there is a phase change called sublimation, which is the direct change from solid to gas without going through the liquid phase. Sublimation-based cooling can be applied to both the water mister and the evaporative air cooler by applying dry ice. In the case of the water mister, the dry ice can be placed at a considerable distance from the source of the mist and let the mixture of the mist-cooled air mix with the cooled air from the dry ice. In the case of the evaporative air cooler, the dry ice can be placed near the outlet of the already-cooled air without actually blocking it. This way, the cooling effect can be doubled.
As both misting systems and evaporative air coolers use the natural power of water, the source water must be free from all kinds of impurities to ensure their long-term operability. And even though they are both easy to maintain, owners of these units must still be on the lookout for potential mechanical and safety problems such as malfunctioning parts, risk of freezing parts during winter, and improper filtering of both the water and the resultant air. Stagnant or non-flowing water is a breeding ground for mosquitoes. Therefore, the sources and depositories of water must be drained and cleaned regularly.
Care must also be taken when using both misting systems and evaporative air coolers in areas where certain objects can deteriorate due to high humidity. Humidity is beneficial in places such as gardens, patios, greenhouses, farms, food storage facilities, and places where animals are involved such as veterinary clinics and zoos. However, humidity will corrode metals and thus shorten the life of electronics and computers. It will also affect the quality of paper products, books, and wood. Dehumidifiers are recommended to counteract the harmful effects of too much humidity.