HVAC - History and Importance

Air Conditioning

Almost everyone living in the United States can afford the luxury of air conditioning. Many apartments and houses come with an air conditioning unit already installed. Even if the apartment or house does not come with one, a unit can be bought for an average of $500. However, some can be found as low as $300 or as high as $700. It depends on the individual's preference and budget.

In Northern Virginia, it tends to get very humid and hot during the Summer. Therefore, to people living in Northern Virginia, an air conditioner is essential, not optional.

History of Air Conditioning

The Ancient Romans implemented a similar idea of air conditioning by circulating aqueduct water through the walls of the house. In Medieval Persia, they would use wind towers and cisterns to cool off buildings. A cistern is a tank that stores water.

During the 2nd century in China, Ding Huane invented a form of air conditioning that used a rotary fan with seven wheels 9.8 feet in diameter. This invention was manually operated, however. In 747, water was used to power the rotary fan.

Reaching 1758, John Hadley and Benjamin Franklin regulated an experiment that utilized the principle of evaporation for cooling. It was found that evaporation of high volatile liquids could be used to reduce the temperature of an object below the freezing point.

Later on in 1820, a well-known British inventor and scientist, Michael Faraday, learned that compressing and liquefying ammonia cooled off the air.

Finally in 1902, the first modern air conditioner was invented by Willis Haviland Carrier in New York. This device was designated to improve manufacturing process control in a printing plant. Unlike the models before this electrical air conditioner, this one controlled both temperature and humidity.

The only problem with the first air conditioners was that they used flammable and/or toxic gases, such as methyl chloride, ammonia, and propane. If the unit were to have a leak, accidents could occur.

Thomas Midgley, Jr. found the solution to this problem in 1928 with his invention of Freon. Freon was the first chlorofluorocarbon gas that is now commonly known simply as a refrigerant.

Currently, research on air conditioning continues in order to improve energy efficiency and indoor air quality.

Air Conditioning Applications

Air conditioning applications are divided into two categories, comfort and process. Comfort applications aim to maintain a comfortable indoor environment for people, regardless of changes in external weather or internal heat loads. Comfort applications can vary depending on the type of building being used, such as low-rise residential (small apartment buildings, single family houses, and duplexes); high-rise residential (apartment blocks and tall dormitories); institutional (government, hospital, academic); sports stadiums; commercial (malls, restaurants, offices, shopping centers); and industrial. Aside from buildings, comfort applications also include uses in transportation, such as in cars, trains, and airplanes.

The goal of process applications is to maintain a proper environment for a certain process to be carried out, despite external weather and internal heat loads. Process applications do not take human comfort into consideration. Some examples of these are hospital operating rooms; facilities for breeding laboratory animals; data centers; physical testing facilities; nuclear power facilities; mining; food cooking and processing areas; cleanrooms; textile manufacturing; plants and farm growing areas; biological and chemical laboratories; and industrial environments.

Health Issues

Air conditioning can cause the growth and spread of numerous microorganisms, such as Legionella pneumophila, when the unit is not kept clean. As long as the device is kept clean, an air conditioner can actually provide cleaner than average air.

Energy Use

Any energy input into a thermodynamically closed system that is being maintained at a certain temperature requires the energy removal rate to increase. Therefore, the air conditioner must increase its consumption by the inverse of its efficiency multiplied by the input of energy.

Overall, the concept of air conditioning has come a long way from the 2nd century. Even now, people are researching new methods in order to improve energy efficiency and indoor air quality. Once upon a time, air conditioning was either circulating aqueduct water through walls or using a rotary fan with wheels. Eventually, in 1758, it was discovered that evaporating high volatile liquids reduces the temperature of an object to below the freezing point. This concept is what is used in modern air conditioning units.