Invention

Part 5 - Refrigeration

Before refrigeration, people cut blocks of ice from rivers in winter and stored it in insulate pits for use in summer. Chinese records from 1000 BCE describe ceremonies for the seasonal filling and emptying of ice cellars and the Greeks and the Romans dug large snow pits insulated with grass, and tree branches as cold storage, to cool beverages in hot weather. 

Early European settlers in Australian soaked wet hessian (burlap) curtains hung from the ceilings of special rooms known as Coolgardie safes. In the hot, dry climate, evaporation cooled the air enough to prevent perishables foods from rapidly spoiling. (When water evaporates, heat is absorbed from the surrounding air). 

In the 1830's Americans began building insulated ice-storerooms and iceboxes and filled them with blocks of ice cut from rivers and lakes in the winter.

Frederic Tudor built icehouses in Charleston, Virginia and Havana, Cuba and shipped ice from New England in specially insulated ships. In the 1830's the price of ice dropped from six cents per pound to a half a cent per pound. In New York City, ice consumption increased from 12,000 tons in 1843 to 100,000 tons in 1856. Scottish professor William Cullen created a small amount of ice when he demonstrated the first refrigeration in 1756. He used a pump to create a partial vacuum over a container of diethyl ether, causing it to boil by absorbing heat from the surrounding air. (Diethyl ether, (or simply ether), has a boiling point of -24 °C at atmospheric pressure which means it is a vapour at room temperature).

In 1758, Benjamin Franklin and John Hadley at Cambridge University, England, investigated the possibility of evaporating volatile liquids, like alcohol and ether, to lower the temperature of an object below the freezing point of water. In 1805, American inventor Oliver Evans described a closed vapour-compression refrigeration cycle for the production of ice using ether under vacuum.

In 1820 England, Michael Faraday used high pressures and low temperatures to liquefy ammonia and other gases and, in 1834, an American, Jacob Perkins, built the first vapour-compression refrigeration system in the world. (At atmospheric pressure, ammonia, NH3, boils at -33.6 °C).In 1850, American engineer Alexander Twining patented a vapour compression system using ether but the first practical ice-making machine was built in Australia by James Harrison in 1851. His 1856 patent described a vapour-compression system using ether, alcohol, or ammonia. By 1861, a dozen of his systems were operating in breweries and meat-packing houses.

In 1859, Ferdinand Carré developed the first gas absorption refrigerator using gaseous ammonia dissolved in water. Southerners used these refrigerators, during the American Civil War, when ice was no longer available from New England.

German engineer, Carl von Linde, patented an improved method of liquefying gases in 1876. His process permitted gases such as ammonia, sulfur dioxide (SO2) and methyl chloride (CH3Cl) to be used as refrigerants and this method remained in use until the late 1920s.

In 1869, Thaddeus Lowe fitted an old steamship with a "Compression Ice Machine" and began shipping fresh fruit from New York to the Gulf Coast area, and fresh meat from Galveston, Texas back to New York.

In 1871, a French immigrant, Andrew Muhl, built an ice-making machine in Waco, Texas and the W.C. Bradley Co. went on to produce the first commercial ice-makers in the USA.

U.S. railroad cars, refrigerated with harvested ice, were introduced in the 1840's. By the 1870's, brewers became aware of sewage contaminated ice taken from rivers and quickly bought the new ice producing machines. Farmers, fishermen and food shippers also rapidly adopted the refrigerators. 

William Soltau Davidson was the first to install a compression refrigeration unit on a ship to transport meat from New Zealand in 1882, and within five years, 172 shipments of frozen meat were sent from New Zealand to the United Kingdom.

By 1900, the meat-packing houses of Chicago had adopted ammonia-cycle commercial refrigeration and by 1914 refrigeration was in use throughout the USA and most of Europe.

By the middle of the 20th century, refrigerated trucks transported perishable goods such as frozen foods, fruit and vegetables and temperature-sensitive chemicals. In 1911 General Electric (GE) designed a household refrigerator powered by gas which eliminated the need for an electric compressor motor and decreased the size of the refrigerator but, by 1927, GE was also selling refrigerators running on electricity.

In 1930, Frigidaire, introduced, DuPont Corporation's synthetic refrigerant, Freon, in smaller, lighter, cheaper refrigerators that were safer than earlier units. (The boiling point of Dichloro-difluoro-methane (aka Freon) is -40.8 °C).Chlorofluorocarbons (CFC's) were thought to be less harmful than the commonly-used refrigerants like methyl formate, ammonia, methyl chloride, and sulfur dioxide but in the 1970s, scientists discovered that CFC's released into the atmosphere destroyed atmospheric ozone (which protects against ultraviolet radiation from the sun) and their use as refrigerants was banned worldwide in 1987.

Refrigeration not only makes ice and keeps foodstuffs fresh for long periods but it is also used to cool (or heat) air condition homes, stores, restaurants, offices and industrial buildings.

In industry, refrigeration liquefies gases like oxygen, carbon-dioxide, nitrogen, propane and natural gas (LNG). In oil refineries and chemical and petrochemical plants, it maintains chemicals at low temperatures.

Most refrigerators use the reverse-Rankine, vapor-compression refrigeration cycle where heat is extracted from the air in one space and delivered to another space. This principle was described mathematically by Sadi Carnot in 1824 as a heat engine or heat pump. 

A refrigerant (such as 1,1,1,2-Tetrafluoroethane , one of the replacements for the now banned chlorofluorocarbons) enters a compressor as a vapour and leaves the compressor at a higher temperature. It then moves through the condenser radiator which cools the vapour until it condenses into a liquid. The now liquid refrigerant goes through an expansion valve where its pressure abruptly decreases, causing flash evaporation and a sharp drop in temperature. The resulting cold liquid/vapour mixture then travels through the evaporator radiator and is completely vaporized again as it absorbs heat from the warmer air in the refrigerated space. The refrigerant vapour then returns to the compressor to complete the cycle.

Ice is still used to cool products to the melting point and, when making ice-cream, salt is added to lower the temperature further.

Dry ice (solid carbon dioxide) is often used as an alternative to refrigeration as it sublimates (vaporizes directly from a solid form) at minus -78.5 °C ( −109.3 °F, 194.65 K).