Room Cooler vs Desert Cooler
When it is hot and dry in summers, coolers are an effective way to get rid of high temperatures. These coolers work on the principle of evaporative cooling to bring the temperatures inside a room down to levels that are manageable. As they do not consume much electricity like air conditioners, they are not an expensive way to lower temperatures. Air coolers are known by many names such as room cooler, desert cooler, and swamp cooler and they all work along same lines that is evaporation of water that helps in cooling the surroundings.
Coolers make use of a water pump that circulates water from a tank to all three sides (4th one has a fan fitted) that have a screen filled with an absorbent (mostly wooden grass or hay). When this grass becomes wet, the fan that draws air from outside loses its moisture and is forced out in the room that helps in lowering the temperature of the room. When the air that is sucked from outside comes in contact with wet pads on the three sides of a cooler, its temperature is lowered and is forced inside the room through the forcing fan.
Evaporation of water from a cooler tank lowers the temperature (absorbing the energy from the surroundings) and one feels cool and dry. But one disadvantage of desert coolers is that they work best when the air outside is hot and dry and not laden with moisture which happens when there is humidity in air. Rate of evaporation of water in the tank of a desert cooler on a humid day is lower than it is when the air is hot and dry.
There is another variety of coolers called room coolers that are kept inside the room instead of desert coolers that are fitted outside a window and suck air from outside. As these are kept inside the room, the fan used is a forcing fan instead of an exhaust fan that is used in window desert cooler. Also, room coolers are made of a plastic body to make them look more attractive and are placed on a trolley that helps to move them around which is not possible with desert coolers.