Component #2: The Condenser
The high temperature refrigerant passes into a condenser coil. As the vapor refrigerant travels through the coil, air from a fan passes over the coil to cool the vapor refrigerant. As the vapor cools it condenses and becomes a liquid, this is referred to as a “change of state”. This “change of state” from vapor to liquid is essential. You may be somewhat familiar with a typical home system where the condensing unit sits outside. When operating you can place your hand over this unit and feel the warm air being blown out. Inside this condensing unit high temperature vapor refrigerant is entering into it, as the heat energy in the vapor is removed by blowing air across the condenser coil, the vapor changes to a liquid. You will soon see that the heat being blown from the condensing unit is the heat that used to be in your home. In the above diagram the liquid is represented by solid red.
Component #3: The Metering Device
The metering device controls the flow of the liquid refrigerant to the next component which is the evaporator. This is a dividing point between the high pressure and low pressure sides of the system. As this high pressure liquid is passing through the metering device and into the evaporator the pressure drops.
Component #4: The Evaporator
After leaving the metering device the refrigerant immediately enters a coil called the evaporator. This coil or evaporator has a fan blowing across it. As the refrigerant enters the coil at a lower pressure it begins to bubble and boil and “change state” back to a vapor. During this process of changing state, energy in the form of heat is being removed from the air passing over the coil and is being absorbed by the refrigerant. The heat that was in the air is transferred into the refrigerant. Since heat was removed from the air blowing over the evaporator coil, the air leaving the evaporator coil is cold. You see that an air conditioner makes cold air by having the heat that is in the air absorbed into the refrigerant.
Now that heat from your computer room, office area etc. is in the refrigerant what do we do with it? The heated refrigerant vapor is sucked into the compressor and pumped back to the condenser coil. Here, in the condenser, the heat that was earlier absorbed by the refrigerant in the evaporator section from the space we are cooling is released and removed. The process of the refrigerant “changing states” from vapor to liquid ( releasing heat through the condenser) and from liquid to vapor(absorbing heat in the evaporator) is how an air conditioner works.”