| Thermodynamics | ||||||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|
 The classicalCarnot heat engine | ||||||||||||
| ||||||||||||
TheEinstein–Szilard orEinstein refrigerator is anabsorption refrigerator which has nomoving parts, operates at constantpressure, and requires only aheat source to operate. It was jointly invented in 1926 byAlbert Einstein and his former studentLeó Szilárd, whopatented it in the U.S. on November 11, 1930 (U.S. patent 1,781,541). The three working fluids in this design arewater,ammonia, andbutane.[1] The Einstein refrigerator is a development of the original three-fluid patent by the Swedish inventorsBaltzar von Platen andCarl Munters.
From 1926 until 1934 Einstein and Szilárd collaborated on ways to improve homerefrigeration 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 differentrefrigeration cycles. 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.[2]
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,[2] but others assert that Einstein contributed design work to the project.[3]
The refrigerator was less efficient than existing appliances, although having no moving parts made it more reliable; the introduction ofFreon to replace refrigerant gases toxic to humans made it even less attractive commercially.[2] TheGreat Depression of 1929 dried up funding for development, and the widespread political violence inNazi 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.)[4] It was not immediately put into commercial production, although the most promising of the patents were quickly bought up by the Swedish companyElectrolux. Einstein and Szilárd earned $750 (the equivalent of $10,000 in 2017).[3] A few demonstration units were constructed from other patents.
One variant, the Einstein–Szilard electromagnetic refrigerator used a Einstein–Szilardelectromagnetic pump to compress aworking gas, pentane.[2] Although the refrigerator was not a commercial success, the Einstein–Szilard pump was later used for coolingbreeder reactors, where its inherent reliability and safety were important.[2]
In 2008, electrical engineers atOxford University's Energy and Power Group, part of the university'sDepartment of Engineering Science,[5] revived the Einstein refrigerator as an attempt to produce a refrigerator suitable for use in rural areas without electricity.[1] The group, led by Malcolm McCulloch noted that the design was still "nowhere near commercialised",[1] but might allow the efficiency of the original Einstein–Szilárd design to be quadrupled.[6]
