Notes

Refrigeration

Refrigeration.

People have used the cooling effects of snow and ice to delay the spoilage of food for centuries, but the term refrigerator was coined by Thomas Moore in 1800. He built what today would be called an icebox: A cedar tub, lined with rabbit fur, filled with ice and used to transport butter from his farm in rural Maryland to Washington D.C.

The process of refrigeration is the removal of heat from a space, resulting in a reduced temperature within the space. When a liquid is vaporized, the quickly expanding vapour draws kinetic energy from its surroundings, reducing its energy level, thus lowering its temperature. William Cullen demonstrated the first refrigerant at the University of Glasgow in 1748. In 1805, Oliver Evans, an American, designed the first refrigeration machine using this principle, but the first practical machine honours go to Jacob Perkins, an American who moved to England in 1818. In 1834 he used ether in a vacuum compressor to demonstrate a machine that could keep its content cold, indefinitely. From the mid 1800s people used toxic gases such as ammonia and methyl chloride but after several fatal accidents in 1929, when the gases leaked, three American companies joined forces to develop Freon.

In the 1970s scientists discovered that Freon and other CFCs were breaking down the ozone layer at high altitudes. 86 nations agreed in 1992, to end the production of CFCs in the industrialized world by the end of 1995, and in the developing world by 2005.

The story of refrigeration offers a glimpse into the GLG saga.  Early machines had the motor, compressor and radiator mounted on the top of the machine, allowing the heat extracted from the cold space to rise into the air without affecting the cold space. Manufacturers discovered that by mounting the motor and parts below the cold space they could use a thinner case, increasing the cold space volume. They could sell a bigger machine for the same price and the customer ended up paying for it forever more, in higher energy costs. And they kept doing this. There were models in the 1970s which used such thin skins for the metal case, that the outside would be cold to the touch, causing moisture to condense on it. Instead of using thicker insulation or stronger cases, the manufacturers opted to put heaters in the case! A typical refrigerator in 1976 used an average of 1800 kilowatt-hours of electricity per year – versus a machine from the 1950s which used 500 kilowatt-hours a year. The earlier models had their motors on top. According to David Goldstein (Natural Resources Defence Council scientist), by 1981, US models consumed twice the energy of Japanese refrigerators. The price of electricity is obviously much higher in Japan, than in the USA.

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