What's air-conditioning?

2023-08-31 14:14

Air conditioning is the process of removing heat/cold and moisture from the interior of an occupied space and often means equipment used for that process. A common air conditioner uses a mechanical system called a “heat pump” that allows for the transfer of heat between indoor and outdoor units, with the help of a gaseous refrigerant. An air conditioner draws heat from the indoor exchanger and releases it to the outdoor exchanger. When cooling, the compressor inside the outdoor unit liquefies the refrigerant to absorb heat. When heating, conversely, heated pressurized gas generated by the heat exchanger and compressor inside the outdoor unit is condensed to heat air in the room. These two cycles can be switched, allowing the system to provide both cooling and heating.

Since prehistoric times, ice and water were used for cooling. Harvesting ice during winter and storing it for use in summer used to be a popular business across the globe. The capability of cooling things all year round that would not require ice producible only in winter had been what ancient people much long dreamed of.

Evaporative Cooling — The Concept behind Air Conditioning Has Been Around Since Ancient Egypt

The basic concept behind today's air conditioning can date back to ancient Egypt. Frescos painted the 25th century BC show that people back then fanning water seeping from fine pores of unglazed pots, cooling the water inside.

Development of Mechanical Cooling—Modern Air Conditioning Emerged from Advances in Chemistry during the 19th Century

In 1758, Benjamin Franklin, an American politician, diplomat, writer, physicist and meteorologist, and John Hadley, a chemistry professor at Cambridge University, explored the principle of evaporation as a means to rapidly cool an object. Franklin and Hadley confirmed that evaporation of highly volatile liquids (such as alcohol and ether) could be used to drive down the temperature of an object past the freezing point of water.

In 1820, British scientist and inventor Michael Faraday discovered that compressing and liquefying ammonia could chill air.
In 1824, Sadi Carnot, a French military engineer and physicist, gave the first successful theory of the refrigeration cycle.
In 1834, Jacob Perkins, an American residing in England, invented the first mechanical vapor-compression refrigeration freezer. Perkins used ethyl ether, repeatedly compressed and expanded manually to produce a refrigeration state.
In 1842, American physician, scientist, and inventor John Gorrie used compressor technology to create ice, which he used to cool air for his patients in his hospital. Gorrie was granted a patent in 1851 for his ice-making machine.

Development of Mechanical Cooling—Modern Air Conditioning Emerged from Advances in Chemistry during the 19th Century

In 1758, Benjamin Franklin, an American politician, diplomat, writer, physicist and meteorologist, and John Hadley, a chemistry professor at Cambridge University, explored the principle of evaporation as a means to rapidly cool an object. Franklin and Hadley confirmed that evaporation of highly volatile liquids (such as alcohol and ether) could be used to drive down the temperature of an object past the freezing point of water.

In 1820, British scientist and inventor Michael Faraday discovered that compressing and liquefying ammonia could chill air.
In 1824, Sadi Carnot, a French military engineer and physicist, gave the first successful theory of the refrigeration cycle.
In 1834, Jacob Perkins, an American residing in England, invented the first mechanical vapor-compression refrigeration freezer. Perkins used ethyl ether, repeatedly compressed and expanded manually to produce a refrigeration state.
In 1842, American physician, scientist, and inventor John Gorrie used compressor technology to create ice, which he used to cool air for his patients in his hospital. Gorrie was granted a patent in 1851 for his ice-making machine.

The Advent of Electric Air Conditioning—Made Temperatures and Humidity Controllable

In 1902, the first modern electric air conditioning unit was invented by Willis Carrier in Buffalo, New York. It was designed in response to an air quality problem experienced at a publishing company and was capable of controlling temperature and humidity. Carrier later founded Carrier Air Conditioning Company of America.

In 1906, engineer and contractor Stuart W. Cramer of Charlotte, North Carolina, was exploring ways to add moisture to the air in his textile mill. He combined moisture with ventilation to condition and change the air in factories, controlling the humidity to meet the required level in textile plants. Cramer is the one known for coining the term "air conditioning.”

Development of Safe and Environment-Friendly Refrigerants

The refrigerant circulates through the indoor and outdoor units of the air conditioner to carry heat, and cools or warms the indoor air. The first air conditioners and refrigerators in the early 20th century employed toxic or flammable gases, such as ammonia, methyl chloride, or propane, that could result in fatal accidents when they leaked.
Thomas Midgley, Jr created the first chlorofluorocarbon gas (CFC) in 1928.
Being chemically stable, non-flammable, and easily liquefied, fluorocarbons had been in use everywhere, as, e.g., refrigerants for air conditioners and refrigerators, foaming agents for heat-insulating materials, cleaning agents for precision parts, and aerosol propellants.
However, ozone depletion came up to the surface as a global issue in the 1970s. CFCs became the culprits mainly responsible for man-made chemical ozone depletion. The Vienna Convention for the Protection of the Ozone Layer signed in 1985 and the Montreal Protocol agreed in 1987 provided frameworks for international reductions in the production and trade of chlorofluorocarbons. These international frameworks encouraged the use of CFC alternatives, such as hydrochlorofluorocarbons (HCFCs) and hydrofluorocarbons (HFCs).
In the 1990s, HCFCs and HFCs were classified into a subset of a larger group of climate-changing greenhouse gases (GHGs). Then, the Kyoto Protocol agreed in 1997 set the broad outlines of emissions targets of GHGs.