Einstein's Forgotten Invention: A Fridge That Could Have Saved Lives
The Einstein-Szilard Refrigerator
In the 1920s, toxic gas leaks from refrigerator compressors killed families in their sleep. Albert Einstein and physicist Leo Szilard invented a safer pump with no moving parts, using electromagnetism instead. They patented it in 1930, but the Great Depression, Nazi violence, and the rise of Freon doomed their invention. Decades later, a working model proved its viability—and its potential to have prevented countless tragedies.
It isn’t possible to know what Einstein and Szilard might have accomplished, had their professional and personal lives not been interrupted.
- HPsquared
It's a very clever trick: a refrigerator without a compressor which uses heat as the energy source. It could run on either a gas flame or an electric heating element.
There are three working fluids (butane, water and ammonia) and it works by exploiting differences in partial pressure (that is, the pressure contributed by each component of a gas mixture). Instead of using a compressor to change the overall pressure, it changes the composition of the mixture.
The cycle basically works by adding and removing ammonia at different points to make the butane refrigerant evaporate and condense in the appropriate places.
On the "condenser" side of things, water is used to remove the ammonia from the gas mixture by absorption. Because the total pressure is approximately the same throughout the system, removing ammonia increases the butane mole fraction and therefore its partial pressure, causing the butane to condense. This is the heat rejection side.
On the evaporator side, ammonia is added again. This lowers the butane partial pressure, shifting the equilibrium and causing the liquid butane to evaporate. That's where the cooling effect occurs.
The other part of the cycle is regenerating the ammonia by separating it from the water again. That's where heat is added, and that heat input is what ultimately drives the process.
- robotixonic
This post reminded me of the movie “The Mosquito Coast” from 1986 starring Harrison Ford, who set out to build a refrigerator in the jungle to produce ice from heat. He used the Platen-Munters principle, which is similar to the Einstein -Szilard principle.
Both machines use heat instead of a mechanical compressor, both can operate with essentially no moving mechanical parts, and both exploit partial pressure so a refrigerant can evaporate at a low temperature. The crucial difference is which fluid does which job.
The conventional diffusion-absorption refrigerator, developed by Platen and Munters in the 1920s, uses ammonia as the refrigerant. Hydrogen occupies the evaporator and lowers ammonia’s partial pressure, allowing liquid ammonia to evaporate at a low temperature. The ammonia vapor is subsequently absorbed into water. This is the basic technology that became familiar in gas-powered and RV refrigerators.
From the specific standpoint of a field-built jungle refrigerator, the Einstein–Szilard working-fluid combination arguably makes the better plot device. The Platen–Munters choice has the advantage of commercial precedent, but the hydrogen charge is decidedly the awkward ingredient. Even though once the system is charged the constituent chemicals stay put, I would rather schlep through the jungle with butane in a canister than the requisite amount of hydrogen.
“The Mosquito Coast” is an interesting movie.
- macrolime
My parents had a completely noiseless refrigerator similar to this. It did not have a compressor and had an electric heating element instead. It was very durable and worked for many decades until the plastic and door hinges etc was too damaged for it to be used any more.
I actually found a picture of the exact model from a museum
https://digitaltmuseum.no/011014769284/evalet-kjoleskap/
I looked at bit more and it seems the original article is quite misleading. It seems the Einstein-Szilard refrigerator is a type of absorption fridge and a major reason they did not come to market was a related absorption fridge, the Platen-Munters absorption refrigerator made by Electrolux and Evalet. The Einstein-Szilard refrigerator was not completely unique, but an attempt at improving this design with other gases.
- slfnflctd
Since I haven't seen anyone bring up the viability of this method yet, here are a few additional bits of info I dug up:
> the total mass of the completed apparatus is around 400 kg with 20 kg of alcohol in the refrigeration cycle
> The group, led by Malcolm McCulloch noted that the design was still "nowhere near commercialised", but might allow the efficiency of the original Einstein–Szilárd design to be quadrupled.
It would be great if someone could improve this tech to where there's a breakeven point of ownership (preferably less than 20 years) when it becomes a better deal than other modern refrigerators.
- Qem
Szilard is an underrated genius. Also was an early formulator of the nuclear chain reaction concept, to tap into nuclear energy, but did not zero in uranium right at the outset as the element to make it feasible.