Air conditioners are almost a basic necessity of life and there are only a few people left that do not have these revolutionary machines. Most people have air conditioning units in their homes to keep their selves comfortable and away from the heat and humidity. Almost all offices, factories and plants have air conditioning units as well.
There are several air conditioning units for different kinds of interiors. There are small units used mostly for houses or apartments and there are large units used for shopping malls or offices.
There are different kinds of air conditioning units and among the most common units are the window and through-wall types. These types of air conditioners can be categorized as unitary or packaged terminal units. The unitary systems are designed to be used in small rooms and they are fitted in a wall or window with an exhaust sticking outside the wall. This machine works by sending air from the room over an evaporator thus cooling it. At the same time this machine takes the heat from the room and brings it out to the environment.
The packaged terminal units or PTAC systems are more commonly used in large rooms such as hotel lobbies and ballrooms. The PTAC systems are designed with two units called terminal packages. The first unit which is the evaporative unit can be found in the interior of a large building or room, while the condensing unit can be found in the exterior. Both units are connected to each other by a tube wherein the air outside passes through it to be cooled and sent to the interior while hot air from the room is sent out to the environment.
Another unit is the evaporative cooler. This machine is commonly used in the Middle East and it is so common in Iran that some people refer to it as "Persian coolers". These air conditioners work by taking in air from outside and sending through a wet sponge which decreases the sensible heat (energy exchange during a change in temperature).
Portable air conditioners are air conditioning units that can be carried around to different locations in a building or room to cool a specific location. Most of these air conditioners are designed to be refrigeration-based machines and not evaporative. Refrigeration-type air conditioners cool air by continually sending air through the machine and out until the temperature of the room adjusts to the desired setting.