Editing Einstein refrigerator

{{Short description|Absorption refrigerator invented in 1930}}
{{Thermodynamics sidebar|cTopic=Processes and Cycles}}
[[File:Einstein Refrigerator.png|thumb|200px|Einstein's and Szilárd's patent application]]
[[File:Einstein Refrigerator pat1781541 clarified.jpg|thumb|200px|Annotated patent drawing]]

The '''Einstein–Szilard''' or '''Einstein refrigerator''' is an [[absorption refrigerator]] which has no [[moving parts]], operates at constant [[pressure]], and requires only a [[heat|heat source]] to operate. It was jointly invented in 1926 by [[Albert Einstein]] and his former student [[Leó Szilárd]], who [[patent]]ed it in the U.S. on November 11, 1930 ({{US patent|1,781,541}}). The three working fluids in this design are [[water]], [[ammonia]], and [[butane]].<ref name=go>{{cite news |title=Einstein's Refrigerator Using No Electricity/No Freon Revived at Oxford |url=https://www.greenoptimistic.com/einstein-refrigerator/ |date=6 February 2015 |publisher=The Green Optimistic}}</ref> The Einstein refrigerator is a development of the original three-fluid patent by the Swedish inventors [[Baltzar von Platen (inventor)|Baltzar von Platen]] and [[Carl Munters]].

==History==
From 1926 until 1934 Einstein and Szilárd collaborated on ways to improve home [[refrigeration]] technology. The two were motivated by contemporary newspaper reports of a Berlin family who had been killed when a seal in their refrigerator failed and leaked toxic fumes into their home. Einstein and Szilárd proposed that a device without moving parts would eliminate the potential for seal failure, and explored practical applications for different [[refrigeration cycle]]s. Einstein had worked in the Swiss Patent Office, and used his experience to apply for valid patents for their inventions in several countries. The two were eventually granted 45 patents in six countries for three different models.<ref name=dannen/>

It has been suggested that most of the actual inventing was done by Szilárd, with Einstein merely acting as a consultant and helping with the patent-related paperwork,<ref name=dannen>{{cite journal
|last=Dannen
|first=Gene
|title=The Einstein–Szilard Refrigerators
|journal=[[Scientific American]]
|volume=276
|issue=1
|pages=90–95
|date=January 1997
|bibcode=1997SciAm.276a..90D
|doi=10.1038/scientificamerican0197-90
|url=http://www.sciamdigital.com/gsp_qpdf.cfm?ISSUEID_CHAR=6E731865-2EE0-4A4F-9DE4-6702DA7E2AE&ARTICLEID_CHAR=2E0F4600-5E37-4953-A4D4-24BBC99F092
|access-date=2020-01-12
|archive-date=2013-02-01
|archive-url=https://archive.today/20130201193859/http://www.sciamdigital.com/gsp_qpdf.cfm?ISSUEID_CHAR=6E731865-2EE0-4A4F-9DE4-6702DA7E2AE&ARTICLEID_CHAR=2E0F4600-5E37-4953-A4D4-24BBC99F092
|url-status=unfit
|url-access=subscription
}}</ref> but others assert that Einstein contributed design work to the project.<ref name=SamKean>{{cite book |last1=Kean |first1=Sam |title=Caesar's Last Breath |date=2017 |publisher=Hachette |location=New York |isbn=9780316381635 |url=https://www.wired.com/story/einsteins-little-known-passion-project-a-refrigerator/ |access-date=24 July 2017}}</ref>

The refrigerator was less efficient than existing appliances, although having no moving parts made it more reliable; the introduction of [[Freon]] to replace refrigerant gases toxic to humans made it even less attractive commercially.<ref name=dannen/> The [[Great Depression]] of 1929 dried up funding for development, and the widespread political violence in [[Nazi Germany]], where the inventors lived, particularly towards Jews such as Einstein and Szilard, contributed to the device's lack of commercial success. (The inventors fled Germany in the early 1930s.)<ref name=bisno>{{cite web |title=The Einstein–Szilard Refrigerator |last=Bisno |first=Adam |work=Lemelson Center for the Study of Invention and Innovation, Smithsonian Museum |date=8 December 2020 |url=https://invention.si.edu/einstein-szilard-refrigerator}}</ref> It was not immediately put into commercial production, although the most promising of the patents were quickly bought up by the Swedish company [[Electrolux]]. Einstein and Szilárd earned $750 (the equivalent of $10,000 in 2017).<ref name=SamKean/> A few demonstration units were constructed from other patents.

One variant, the Einstein–Szilard electromagnetic refrigerator used a Einstein–Szilard [[electromagnetic pump]] to compress a [[working gas]], pentane.<ref name=dannen/> Although the refrigerator was not a commercial success, the Einstein–Szilard pump was later used for cooling [[breeder reactor]]s, where its inherent reliability and safety were important.<ref name=dannen/>

In 2008, electrical engineers at [[Oxford University|Oxford University's]] Energy and Power Group, part of the university's [[Department of Engineering Science, University of Oxford|Department of Engineering Science]],<ref>{{cite web |title=Malcolm McCulloch - Profile |url=https://ae4h.org/.profile/mmcculloch3 |website=Affordable Energy for Humanity (AE4H) |publisher=University of Waterloo |access-date=12 November 2019 |archive-date=12 November 2019 |archive-url=https://web.archive.org/web/20191112210254/https://ae4h.org/.profile/mmcculloch3 |url-status=dead }}</ref> revived the Einstein refrigerator as an attempt to produce a refrigerator suitable for use in rural areas without electricity.<ref name=go/> The group, led by Malcolm McCulloch noted that the design was still "nowhere near commercialised",<ref name=go/> but might allow the efficiency of the original Einstein–Szilárd design to be quadrupled.<ref>{{cite news |last=Alok |first=Jha |title=Einstein fridge design can help global cooling |newspaper=[[The Guardian]] |date=21 September 2008 |url=https://www.theguardian.com/science/2008/sep/21/scienceofclimatechange.climatechange |access-date=12 November 2019}}</ref>

==See also==
* [[Rudolf Goldschmidt]] (for the Einstein–Goldschmidt hearing aid)
* [[Icyball]]
* [[Timeline of low-temperature technology]]

==Notes==
{{Reflist}}

==References==
* Einstein, A., L. Szilárd, "Refrigeration" (Appl: 16 December 1927; Priority: Germany, 16 December 1926) {{US patent|1781541}}, 11 November 1930.
* Einstein, A., L. Szilárd, "Accompanying notes and remarks for Pat. No. 1,781,541". Mandeville Special Collections Library USC. Box 35, Folder 3, 1927; 52 pages.
* Einstein, A., L. Szilárd, "Improvements Relating to Refrigerating Apparatus." (Appl: 16 December. 1927; Priority: Germany, 16 December 1926). Patent Number 282,428 (United Kingdom). Complete accept.: 5 November 1928.

==External links==
* Flanigan, Allen, "[http://www.presse.uni-oldenburg.de/f-aktuell/05-363.html ''Einsteins "Automatischer Beton-Volks-Kühlschrank"''] (German site) Wolfgang Engels from the [[University of Oldenburg]] rebuilt the original concept—the housing is manufactured out of [[concrete]], i.e. the total mass of the completed apparatus is around 400&nbsp;kg with 20&nbsp;kg of [[alcohol (chemistry)|alcohol]] in the refrigeration cycle. The project was completed in 2005.
* [https://worldwide.espacenet.com/publicationDetails/originalDocument?CC=US&NR=1781541 US patent 1781541] (European Patent Office)
* [https://worldwide.espacenet.com/publicationDetails/originalDocument?CC=GB&NR=282428 GB patent 282428] (European Patent Office)
* [https://web.archive.org/web/20061206174734/http://www.cam.net.uk/home/StKilda/electrolux.html How kerosene refrigerators work]. (archived)

{{Albert Einstein}}
{{Thermodynamic cycles}}
{{HVAC}}

[[Category:Albert Einstein|Refrigerator]]
[[Category:Cooling technology]]
[[Category:Gas technologies]]
[[Category:Heating, ventilation, and air conditioning]]
[[Category:Thermodynamic cycles]]
[[Category:1926 in science]]
[[Category:1930 in science]]
[[Category:Refrigerators]]