Facts of the Matter
Facts of the Matter
Air conditioning spurred
growth of Sun Belt citiesThat cool air blowing out of the air conditioner on these warm summer days is more than merely a convenience.
It is responsible for the growth of cities in the Sun Belt, fresh fruit in supermarkets, department stores, and movies with sound.
A hundred years ago this month, Willis Carrier, a young engineer just out of college, installed the first air conditioner in a printing plant in Brooklyn where expansion of paper ruined the registration of color prints.
It wasn't the first air conditioner. One of the earliest uses of air conditioning was in the Middle East where wind towers were designed to assure a continuous flow of air to lower indoor temperatures. Roman emperors had snow brought down from the mountains.
Air conditioning technology has come a long ways since Carrier installed his invention, a centrifugal cooler, in the Hudson department store in Detroit in 1924. Hudson's bargain basement was so hot in the summer that customers had fainted because of the intense heat that built up in the summer months.
The birth of the summer blockbuster movie began in 1925 when the Rivoli theater in New York's Times Square was air-conditioned. By 1930, patrons in 300 theaters nationwide were enjoying "comfort cool" seating for movies. For decades thereafter people went to the movies to escape the summer heat.
Not only that, but for the first time Hollywood studios could keep their doors closed to eliminate outside noise, allowing for the production of "talkies," as movies with sound were called then.
In the 1940s home refrigerators using variations of Carrier's chillers replaced the icebox and made the iceman's home delivery obsolete.
It wasn't until the 1950s that home air conditioners became available. By 1965, 10 percent of American homes were air-conditioned. By 1995 more than 75 percent of American homes were air-conditioned, and today in some portions areas of the country, 90 percent of homes have comfort cooling.
In Carrier's invention, as in today's chilling systems, evaporation and condensation occur in a controlled, closed cycle.
Everyone has experienced the chill of water evaporating from the skin. The mechanical chiller operates on the same principle. In a continuous cycle, a working fluid is allowed to evaporate indoors, drawing heat from the surroundings. The fluid is then pumped outdoors where it gives up its heat as it is condensed by a compressor. The fluid is pumped under pressure to the evaporator where the cycle repeats.
In the natural environment, water is the working fluid in heat transfer. Evaporation cools Earth's surface and adds water vapor to the air. When the moist air rises it cools, and the vapor condenses to form clouds as it releases heat into the atmosphere. It is this process that provides the tremendous energy that drives weather systems such as hurricanes.
In chilling systems energy must be continuously added to the compressor to work against the natural flow of heat from hot to cold. Insulation restricts the flow of heat back into the cooled area and increases cooling efficiency.
In order to function, the chilling system must have an indoor and an outdoor part. If a mechanical chiller were to be used indoors, it would produce more heat than it removed, since some of the energy used to power the motor and compressor is converted to heat.
Air conditioners exhaust the heat that is removed from the room into the outside air so that in window units the box containing the mechanism sits half inside and half outside the window.
The refrigerator dumps the heat that it removes from inside into the room and actually heats up the room. It would heat the room slightly even if the door was left open since the amount of heat produced by the motor and compressor is added to the heat transferred from inside the fridge.
The working fluid of chilling systems must have certain properties to make the cooling process both efficient and safe. It must be able to condense under pressure at high temperature. It must be nontoxic and noncorrosive, readily available, inexpensive, and it must be environmentally friendly.
At one time ammonia was used, but it proved to be toxic when the system sprung a leak. Most modern chillers use chlorinated fluorocarbons, or CFCs, as a working fluid, but these chemicals have been implicated as a major factor in damaging stratospheric ozone and are being replaced with more benign substances.
Those northeast trades provide a natural air conditioning for us here in the islands, but there are those days when running the AC at home, shopping at the mall or attending a movie is the best way to beat the summer heat.
We could all be a little smarter, no? Richard Brill picks up
where your high school science teacher left off. He is a professor of science
at Honolulu Community College, where he teaches earth and physical
science and investigates life and the universe.
He can be contacted by e-mail at rickb@hcc.hawaii.edu