What they are
First of all, a portable air cooler is not an air conditioner. Though air coolers work on the same scientific principal as air conditioners, their actual operation is quite different.
Air coolers are often called evaporative cooler or swamp coolers and there are three main types- the smaller personal-sized air cooler, the larger home or room sized models, and the even larger industrial sized models. The industrial sized models are often used in warehouses and you may have seen them on the sidelines at professional football games. The larger home or room sized models are common in the hot, dry climate of the American Southwest, and they often require that windows be left open to expel hot, dry air as the units operate. The personal models are usually designed for indoor use, to boost the cooling in areas that are not cooled well. This article focuses mainly on personal air coolers, although the larger versions work on the same principles.
Air coolers have a few main parts:
- The water tank holds water to be used in the cooling process
- The wick absorbs water from the water tank and allows it to evaporate when air is blown over it
- The fan blows air over the wick and the water held in the wick
To operate an air cooler, you must first fill the water tank with water. The bottom of the wick is immersed in the water and it "sucks" water from the tank and pulls up into itself. A fan is located behind the wick. It blows air over the wick and out of the machine into your room. As the air is blown over the wick, the water in the wick evaporates. Evaporation is an endothermic reaction- it absorbs heat- so the air that is blown over the wick and out into your room has had some of the heat absorbed out of it. Of course, the water that evaporated and absorbed heat from the air is carried out into your room as water vapor.
Air coolers work best in dry climates, and they are not very effective in climates with a high humidity, since they relay on water evaporating to produce cooling. Also, you should note that they do humidify the air, and as such are never a good option for cooling servers or electrical equipment.
Air coolers are often confused with air conditioners, but they have no compressor, refrigerant, or sealed system. A better way to envision them is as souped-up fans- they will cool the air they (by up to 12°F), but they will not cool a room.
More information on Air Coolers
jbmailroom.com: The Care and Feeding of a Swamp Cooler