During 1900 there was hardly anything people could do during a hot spell apart from grumbling about the weather. Those who could afford it went to the seashore or the mountains. All of this has been changed with the advent of air conditioning. Thanks to air conditioning, you can remain comfortable anywhere indoors, even on the stickiest and hottest day of the year. You are sure to find air conditioning in the restaurants where you eat, in the majority of the stores where your family goes shopping, and in the movie theaters you attend. You can enjoy the cool air even in your home.
What is air conditioning?
You are well aware that air conditioning makes you feel cool. But this gadget is more than just cooling. It implies keeping the humidity (moisture content) and temperature of the air in a confined space at just the right temperature for the comfort of the people within it, be it an entire building or a single room. It means circulating the air and adding humidity if necessary as well. During the summer, it implies removing heat by passing the air over chilled tubes that collect water from the air, just as water droplets condense on a glass of cold water on a hot and humid day. As a matter of fact, we might nearly say that air conditioning implies creating an artificial and comfortable climate. We shall discuss only cooling in this article.
Air can be cooled easily in dry climates. The cooler is simply a large fan that sucks hot and dry air through a fiber mat soaked with water. The evaporation of the water cools the air. To begin with, the air is so dry that there will be no discomfort due to the added moisture. (It is not the same in humid climates).
Apart from keeping us cool, air conditioning has many uses. Many industries rely on it to keep the air within their plants cool, clean, and at the right humidity level. For instance, textile fiber such as cotton and wool will shrink or stretch due to the fluctuations in the moisture content of the air. As a result, it leads to variations in the quality of the cloth. Excessive humidity on a worker’s fingertips, or even in the air, will corrode delicate metal parts such as precision instruments or rocket components. Wrong temperatures can even damage a batch of antibiotic culture. One can prevent such mishaps through proper air conditioning.
The deep gold and diamond mines of South Africa employ air conditioning to allow miners, working thousands of feet below the ground, to comfortably work in what would otherwise be stifling heat. From making missiles to keeping track of them tracking them in the atmosphere, air conditioning plays a huge role in each part of the United States space program.
For years, scientists have toyed with different methods of air conditioning. Ancient Romans and Egyptians used to get relief from the heat by dangling woven mats soaked with water across the entrance of their houses. This chilled the air entering inside through evaporation. The famous inventor and artist built a water-powered fan in 15th century A.D.
As the number of scientists increased, so did the number of methods of getting cool. Although there was no dearth of ideas, none of them actually worked. In reality, quite a number of the ideas made individuals feel uncomfortable because they increased the humidity amount of the air. Air is akin to a sponge. It soaks up water and makes people feel uncomfortable and sticky, particularly in hot weather. When the air is laden with moisture, we say the humidity level is high. On the contrary, the humidity level decreases when the air is dry, and we feel comfortable.
In 1902, Willis H. Carrier, known as “the father of air conditioning,” built the first gadget that cooled the air and kept the humidity low simultaneously. Carrier built this gadget for a Brooklyn, New York-based printing plant that faced problems printing in color. Paper shrinks when the air is dry and stretches when the air is humid. Since it was necessary to print each color separately, the printing of different colors on the same paper sheet did not align accurately, as the size of the paper changed between printings. The machine by Carrier ensured that the humidity level of the air in the press was constant by sucking the air over a coil of chilled pipes that condensed excessive humidity. It made the people in the plant feel cool and ensured that the size of the paper did not fluctuate. This invention of Carrier marked the beginning of scientific air conditioning.
It was not long before many factories started using air conditioning, such as ammo plants that made ammunition during World War I. But people had no idea about this invention until the 1920s when hundreds of restaurants, departmental stores, and movie theaters installed air conditioners. Often, people came into these places to seek relief from the humid, hot air outside.
Central air conditioning systems were developed as air conditioning gained in popularity during the 1930s. They could cool the entire apartment building or office from a single centrally located unit, just as one big furnace in the basement heated entire buildings instead of using little stoves in each room. The same period saw the development of small units, which could cool the air of a single room. Private homes started using large numbers of small units after World War II. In a later development, they were used increasingly in private homes and public buildings, integrated cooling, and heating units in one system.
How does the gadget work?
Contrary to popular belief, the air conditioning unit functions by removing heat from the air rather than add coolness to it. The air conditioner works on the same principle as a fridge, though its design does not allow it to generate such low temperatures. The rapid expansion of a refrigerant (cooling substances) takes heat from the air as it turns from a liquid to a gas at high pressure. The included illustration displays the operation cycle of a small home air conditioner. Here the machine directly cools the air. For simplicity’s sake, motors and filters filter are not displayed in this diagram. In large, central installations, like those in schools and office buildings, a machine cools water that is circulated through a series of coils. The building’s air is drawn over the coils and dispersed through the building blowers.
To work efficiently, an air conditioner should maintain a steady temperature. Else, users would have to turn their units on and off continually as the temperature becomes too hot or too cold. A temperature-regulating device called the thermostat achieves this effect automatically. One needs to set the thermostat at the desired temperature. The thermostat then switches the air conditioner on and off as needed.
The futuristic air conditioning systems may work on the principle of thermoelectric. Such a unit is very quiet and very small. It consists of tiny “couples,” each couple comprising of a pair of semiconductors, connected in parallel. These couples produce heating at one end and cooling at the other when direct flow through them. It is known as the Peatier effect. The heating and cooling reverse when the current is reversed. When a method is discovered to mass-produce this tiny thermoelectric unit cheaply, it may heat and cool your entire house.