Removing undesirable heat from one item, substance, or area and transferring it to another is known as refrigeration, sometimes known as chilling. The temperature can be lowered by removing heat, which can be done using ice, snow, cooled water, or mechanical refrigeration.
In order to decrease the temperature of the area or material and then maintain that lower temperature, refrigeration is the act of taking heat from an enclosed space or from a substance and discarding it elsewhere. Any natural or artificial process that dissipates heat is referred to as cooling. Cryogenics is the name given to the branch of science that deals with creating extremely low temperatures artificially. Since cold is the absence of heat, lowering a temperature requires “removing heat” rather than “adding cold.” When heat is removed, work must be done in some way in order to comply with the Second Law of Thermodynamics. Although usually done mechanically, this task can alternatively be accomplished using a laser, magnets, or other technologies.
Ice has been used to chill food from the beginning of time in order to preserve it. Throughout the millennia, the majority of ancient societies, including the Chinese, Hebrews, Greeks, Romans, and Persians, engaged in a seasonal practice of gathering snow and ice. Straw or other insulating materials were used to line caverns or dugouts where ice and snow were kept. Ice was kept in holes known as yakhchals by the Persians. Foods might be kept fresh throughout the warm months by rationing ice. Icehouses were still in use in the twentieth century as a result of this practice’s success over the ages.
One of the early steps towards artificial refrigeration was made in the sixteenth century with the discovery of chemical refrigeration. When added to water, sodium nitrate or potassium nitrate causes the water’s temperature to drop, creating a form of refrigeration bath for chilling items. Such a remedy was applied to cool wine in Italy. American ice harvesting developed into a significant industry in the first part of the nineteenth century. The “Ice King,” a New Englander named Frederic Tudor, worked on creating superior insulating materials for long-distance ice shipping, particularly to tropical regions.
First refrigeration systems
William Cullen presented the first known technique for artificial refrigeration in Scotland’s University of Glasgow in 1756. When Cullen used a pump to partially hoover a container of diethyl ether, the substance boiled and absorbed heat from the atmosphere around it. Even though the experiment produced a little amount of ice, it had no immediate use.
Oliver Evans, a pioneering American inventor, created a vapor-compression refrigeration cycle in 1805 as an alternative to chemical solutions or flammable liquids like ethyl ether. Ammonia and other gases were liquefied in 1820 by British scientist Michael Faraday using high pressures and low temperatures.
In 1834, an American named Jacob Perkins who resided in Great Britain was granted the first patent for a vapor-compression refrigeration device. The prototype system that Perkins created really functioned, despite its commercial failure. John Gorrie, an American physician, created the first method of chilling water to create ice in 1842. He also came up with the concept of air conditioning, which involves employing a refrigeration system to chill the air for comfort in homes and hospitals. His technology compressed air, partially cooled the hot compressed air by adding water, and then allowed it to expand while performing some of the labor necessary to power the air compressor.
According to his invention, which was issued by the U.S. invention Office in 1851, the isentropic expansion lowered the air’s temperature to the point where it could either pass “through a pipe for effecting refrigeration otherwise” or freeze water and make ice. Gorrie created a functional prototype, but his system was not successful in the marketplace.
In 1848, Alexander Twining started experimenting with vapor-compression refrigeration, and in 1850 and 1853, he was granted patents. By 1856, he is credited with starting commercial refrigeration in the US. In the middle of the 1870s, Australian, Argentinean, and American shipping companies experimented with refrigerated shipping. In 1882, William Solti Davidson installed a compression refrigeration unit on the New Zealand ship Dunedin, which resulted in a boom in meat and dairy exports to Australasia and South America. American Civil War balloonist Thaddeus Lowe has conducted several studies on the characteristics of gases. High-volume hydrogen gas manufacturing was one of his key businesses. He also has a number of ice-making machine patents. The “Compression Ice Machine” he created would transform the cold storage sector. He and other partners bought an old steamer in 1869, installed one of Lowe’s refrigeration units onto it, and started transporting fresh produce from Galveston, Texas, back to New York, as well as fresh meat from the Gulf Coast. The venture was an expensive failure due to Lowe’s ignorance of shipping, and it took a while for people to adjust to the concept of being able to eat meat.
Widespread commercial use
Although some still used gathered ice, breweries were by far the biggest consumers of commercial refrigeration systems by the 1870s. Even though the ice harvesting business had expanded significantly by the turn of the 20th century, sewage and pollution had started to contaminate natural ice, which was a concern in the urban areas. Breweries eventually started to complain about contaminated ice. This increased demand for more contemporary refrigeration and ice-making equipment that is suitable for consumers. German inventor Carl von Linde developed a large-scale method for creating liquid oxygen and then liquid air for use in secure home freezers in 1895.
In the 1840s, chilled railway trains were first used in the United States to carry dairy goods over short distances. A refrigerated vehicle with ice tanks at either end and ventilation flaps close to the floor that would provide a gravity draught of cold air through the car was invented in 1867 by J.B. Sutherland of Detroit, Michigan. Chicago’s meat packing facilities had switched to ammonia-cycle commercial refrigeration by 1900. By 1914, artificial refrigeration was employed practically everywhere. The largest meat packers, Armor, Swift, and Wilson, had bought the priciest models and put them on rail carriages, in branch homes, and in storage facilities in the most outlying distribution locations.
Refrigeration units weren’t made to be installed on tractor-trailer rigs (trucks or lorries) until the middle of the 20th century. Perishable products, including frozen meals, fresh produce, and temperature-sensitive chemicals, are transported in refrigerators. The majority of contemporary freezers operate in the -40 to +20 °C range and may hold a maximum payload of around 24 000 kg gross weight (in Europe).
Home and consumer use
Safer refrigerators for residential and consumer use became feasible with the development of synthetic refrigeration systems, which are primarily based on the chemical chlorofluorocarbon (CFC). These CFC refrigerants, as well as subsequent hydrochlorofluorocarbon (HCFC) and hydrofluorocarbon (HFC), are referred to as “Freon,” a trademark of the DuPont Corporation. These refrigerants, which were created in the late 1920s, were thought to be safer than the routinely employed refrigerants of the time, such as methyl formate, ammonia, methyl chloride, and sulphur dioxide. The goal was to supply residential refrigeration equipment while protecting the tenants’ life. These CFC refrigerants provided the solution.
The Montreal Protocol
Because it harms the ozone layer, CFC-based refrigerant has been prohibited since 1989 thanks to the Montreal Protocol. In Montreal, Quebec, Canada, in September 1987, the majority of the CFC-producing and -consuming countries approved the Montreal Protocol. Greenpeace opposed the ratification since the Montreal Protocol authorized the use of HFC refrigeration, which does not deplete the ozone layer but nonetheless contributes significantly to global warming. With help from Greenpeace, duke Shorenstein (Germany) created a propane-based CFC and an HFC-free refrigerator in 1992 while looking for a replacement for home use refrigeration.
In August 1988, the Clean Air Act became law, implementing the Montreal Protocol’s principles in the US. In 1990, the Clean Air Act underwent more changes. This was a direct outcome of a scientific research published in June 1974 by Rowland-Molina, which described how the ozone layer was negatively impacted by chlorine in CFC and HCFC refrigerants. As a result of this analysis, the FDA and EPA decided to outlaw CFCs as a propellant in 1978 (at the time, aerosol can propellant accounted for 50% of CFC consumption).
- Refrigerant recovery from all car air conditioning systems was mandated by the EPA in January 1992 as part of system maintenance.
- The EPA outlawed the venting of CFC and HCFC refrigerants in July 1992.
- The EPA mandated that significant leaks in refrigeration systems be repaired within 30 days in June 1993. A major leak was defined as a leak rate that, if it continued for an entire year, would equal 35% of the system’s total refrigerant charge (for industrial and commercial refrigerant systems) or 15% of the system’s total refrigerant charge (for all other large refrigerant systems).
- The EPA implemented the Safe Disposal Requirements in July 1993, mandating that all refrigerant systems be evacuated before being retired or disposed of.
- The EPA introduced rules for refrigerant reclamation in August 1993. The American Refrigeration Institute (ARI) standard 700-1993 (formerly ARI standard 700-1995) standards for refrigerant purity must be processed and tested before a refrigerant can change ownership.
- The EPA mandated that ARI 740-1993 criteria be met by all refrigerant recovery equipment in November 1993.
- The EPA also put restrictions on releasing HFC refrigerants in November 1995. These have a 0% ODP (ozone depletion potential) since they don’t contain chlorine that might harm the ozone layer, but they nevertheless have a significant potential for global warming.
- The importing and manufacture of CFC refrigerants in the United States were outlawed in December 1995.
HCFC refrigerant import and manufacture are now scheduled to end in 2030, yet this is most likely going to happen sooner.
Current applications of refrigeration
The air conditioning of private residences and public buildings, as well as the refrigeration of goods in homes, restaurants, and big storage warehouses, are perhaps the two most common modern uses of refrigeration. We can now add fresh salads to our meals throughout the year and securely preserve fish and meats for a long time thanks to the refrigerators we use in our homes to store fruits and vegetables.
Refrigeration has a wide range of applications in industry and commerce. Gases like oxygen, nitrogen, propane, and methane, for instance, are liquefied using refrigeration. It is used to condense water vapour from compressed air to lower its moisture content in compressed air purification. Refrigeration is used in chemical, petrochemical, and oil refineries to keep specific processes running at the requisite low temperatures (for instance, the alkylation of butenes and butane to create a high octane petrol component). Steel and cutlery are tempered in refrigerators by metalworkers. Refrigeration is required for carrying items that need to be kept at a specific temperature via trucks, railroads, aircraft, and seagoing vessels.
It was only recently realised that eggs required to be chilled throughout shipment rather than waiting to be chilled after arrival at the grocery store, despite the fact that dairy products require refrigeration continually. Before being marketed, all meats, poultry, and fish must be maintained in climate-controlled conditions. Fruits and vegetables are kept fresher for longer when they are refrigerated. The growth of the sushi and sashimi business in Japan was one of the most significant applications of refrigeration. Before refrigeration was discovered, hepatitis A and other illnesses caused a tremendous deal of morbidity and mortality among sushi lovers. However, due to a lack of research and healthcare access in rural Japan, the hazards of unrefrigerated sashimi were not made public for decades. Midway through the 20th century, the Kyoto-based Zojirushi business developed advancements in refrigerator design that made them more affordable and available to restaurant owners and the general public.