Like a number of other ‘staples’ of modern life, from plastic to Teflon, air conditioning was an unexpected benefit from another process. Early in the 20th century a printing company in Brooklyn, NY, needed something to help prevent their paper from becoming too moist for printing during the hot humid summer months. In 1902, Willis Haviland Carrier solved their problem by creating a machine to pull the moisture from the air. Coincidentally, the process also lowered the air temperature in the plant. Carrier realized the future potential of this side benefit, and air conditioning was born. Although only used in large public buildings for a long time, the 1950’s saw A/C enter American homes in a big way. Air conditioning enabled the industrial development of the South and the unprecedented growth in the Sunbelt during the second half of the 20th century. Most of us live with it for months at a time, but few of us understand how it works.
Air conditioning is actually a relatively simple process, very similar to the way that your refrigerator works. It involves only four major parts, and it’s based on the simple fact that when a liquid is converted to a gas, it absorbs heat. In an air conditioner, a liquid that will change its state at a low temperature (called a refrigerant) is forced to convert back and forth repeatedly. Each time through the process it absorbs heat from the air. The cooled air is blown into the house by a fan, and the absorbed heat is vented outdoors by another fan. Although the chemical compounds used as refrigerants have changed over the years, the process has remained pretty much the same.
The liquid refrigerant is expanded and converted to a gaseous state by the evaporator and then sent through the cooling coils. A fan blows air across these coils, cooling the air and sending it into the house. Then the refrigerant is changed back to its liquid state by being pressurized in the compressor and cooled in the condenser coils. A second fan blows across those coils to disperse the heat outside the unit. An expansion valve controls the flow of the refrigerant back to the evaporator, and the sequence begins again.
In a window unit, this all happens inside the unit’s housing. The ‘cool’ side faces into the room and the ‘hot’ side remains outside the window frame. Because reducing the temperature of air causes it to release moisture, drains and drip pans are used to dispose of the excess water. Ironically, this dehumidifying effect was the primary function of Carrier’s original installation in 1902, but it’s now become the side benefit.
Central air conditioning functions in exactly the same way except the ‘hot’ and ‘cool’ sides of the process are split apart. The cooling apparatus is installed indoors inside a furnace or other air handling mechanism to spread the cooled air throughout the house. The heat dispersal part of the process is located outdoors along with the water drainage system.
Apart from the move to safer, more environmentally friendly refrigerants, the newest change in air conditioning is currently only in use in about 3,000 large buildings worldwide. Known as ‘ice cooling’, it involves freezing large vats of water overnight. Air is then sent blowing over the ice, rather than across cooling coils, and the cooled air goes on out through the ductwork into the building. The melted ice is then simply frozen again the next night. Although still very expensive to install and requiring a lot of space, ‘ice cooled’ air conditioning is becoming more popular, particularly with large corporations, because it’s kinder to the environment, the power grid, and the monthly electric bill. The bulk of the power that’s used is to freeze the water, which is done overnight when the temperatures are lower, the energy demand is much less, and the rates are much cheaper. For now, the rest of us will need to continue to use basic air conditioning.
Air conditioning is actually a relatively simple process, very similar to the way that your refrigerator works. It involves only four major parts, and it’s based on the simple fact that when a liquid is converted to a gas, it absorbs heat. In an air conditioner, a liquid that will change its state at a low temperature (called a refrigerant) is forced to convert back and forth repeatedly. Each time through the process it absorbs heat from the air. The cooled air is blown into the house by a fan, and the absorbed heat is vented outdoors by another fan. Although the chemical compounds used as refrigerants have changed over the years, the process has remained pretty much the same.
The liquid refrigerant is expanded and converted to a gaseous state by the evaporator and then sent through the cooling coils. A fan blows air across these coils, cooling the air and sending it into the house. Then the refrigerant is changed back to its liquid state by being pressurized in the compressor and cooled in the condenser coils. A second fan blows across those coils to disperse the heat outside the unit. An expansion valve controls the flow of the refrigerant back to the evaporator, and the sequence begins again.
In a window unit, this all happens inside the unit’s housing. The ‘cool’ side faces into the room and the ‘hot’ side remains outside the window frame. Because reducing the temperature of air causes it to release moisture, drains and drip pans are used to dispose of the excess water. Ironically, this dehumidifying effect was the primary function of Carrier’s original installation in 1902, but it’s now become the side benefit.
Central air conditioning functions in exactly the same way except the ‘hot’ and ‘cool’ sides of the process are split apart. The cooling apparatus is installed indoors inside a furnace or other air handling mechanism to spread the cooled air throughout the house. The heat dispersal part of the process is located outdoors along with the water drainage system.
Apart from the move to safer, more environmentally friendly refrigerants, the newest change in air conditioning is currently only in use in about 3,000 large buildings worldwide. Known as ‘ice cooling’, it involves freezing large vats of water overnight. Air is then sent blowing over the ice, rather than across cooling coils, and the cooled air goes on out through the ductwork into the building. The melted ice is then simply frozen again the next night. Although still very expensive to install and requiring a lot of space, ‘ice cooled’ air conditioning is becoming more popular, particularly with large corporations, because it’s kinder to the environment, the power grid, and the monthly electric bill. The bulk of the power that’s used is to freeze the water, which is done overnight when the temperatures are lower, the energy demand is much less, and the rates are much cheaper. For now, the rest of us will need to continue to use basic air conditioning.