2 ENGINEERING ACHIEVEMENTS
Refrigeration and air conditioning
Before engineers learnt how to cool air, life was very different. Food had to be bought the same day it was used. Most foodstuffs could not be transported long distances, so people had to live close to the source of food. Most foodstuffs could not be stored, so surplus food could not be kept. A lot of food went bad and had to be thrown away, or gave people food poisoning. In addition, in many countries, it was impossible to work during the heat of the day and many areas were uninhabitable during the summer months. Some ancient peoples designed cooling methods for food and spaces. Some people kept fresh food under running water. The Indians had wet mats hanging at windows. The Arabs had cooling towers which sucked hot air out of the rooms at their base. However, these early cooling systems were limited in their extent and efficiency.
The inventor of refrigeration was Jacob Perkins. He was an American, but he lived most of his life in Britain. Perkins was a true mechanical engineer. He invented a machine for cutting and heading nails and he was the first person to use steel to make plates for engraving bank notes. He invented machines for measuring the depth of water and the speed of a ship. He improved gun manufacture. In 1830, he invented a radiator which attached to a steam engine, an early form of central heating. But perhaps his greatest invention was the first refrigerator.
In 1834, Perkins obtained a patent for a vapour compression system of cooling. In his patent application, he described how the device worked by ‘constantly condensing volatile fluids and bringing them again and again into operation without waste.’ The recycling of fluids was an important feature of the process as, later, it enabled refrigeration engineers to use hazardous fluids and gases, such as CFCs.
Perkins often does not get the credit for his important invention, because he did not develop it. This was done by a Scottish printer, James Harrison. He showed his design at the International Exhibition of 1862 in London. Like all good engineers, Harrison was responding to a problem. He realized that there was a surplus of meat in Australia, a British colony at the time, while at the same time there was starvation in Britain. In 1873, he made his first attempt to bring frozen meat from Australia to Britain, but it was a disaster. However, his idea sparked the development of the worldwide ‘cold chain’ which we have today.
The work of Perkins and Harrison did not directly lead to the cooling of rooms. That honour belongs to an American called Willis Carrier. However, Carrier did not start with space cooling. He worked, instead, on devices for cooling machines. When machines work, surfaces rub against each other and this contact causes friction, which in turn produces heat. Hot machines are dangerous and inefficient. If a machine overheats, it can break down or even explode.
After cooling machines, Carrier moved on to rooms. In 1907, he founded the Carrier Air Conditioning Company, using a term that was only two years old. He designed an apparatus to cool air using water sprays. He controlled the dew point of the air, which is the point at which water vapour condenses out of the gas. This way he conditioned the air, making it cooler and less humid.
In 1922, Carrier built his first true air-conditioning machine. The new invention spread quickly through the United States and then the world. Carrier is often called ‘the father of air conditioning’, not just for his inventions, but also for his ‘psychrometric chart’ which is still in use today. This chart defines the relationship between air, water and energy.
Mechanisms for cooling air have had a profound effect on human life all over the world. With cooled air, we can chill or freeze food to store it or to transport it long distances. We can keep medical supplies in good condition. We can cool machines to keep them running efficiently. Finally, we can cool factories, offices, homes and cars to make them habitable even in the highest ambient temperatures.
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