7 ms·

The Einstein-Szilard Refrigerator (2020)

92 points by Dracophoenix 3y ago

biorach 3y ago
The patents having long expired, presumably there are practical reasons that this design is not competitive with modern compressor designs.. Would have been good if the article had said what these are
- kragen 3y ago
  moving-parts-free ammonia-absorption refrigerators of the einstein-szilard type are in fact in wide use today, especially in camping trailers where the ability to run off propane without electricity is a big plus. i encountered one in a hotel room earlier this year. https://en.wikipedia.org/wiki/Absorption_refrigerator https://en.wikipedia.org/wiki/Absorption_refrigerator vapor-compression types with midgley's cfcs, and derivatives like hcfcs and hfcs, are less likely to kill you if they leak, and i think they also have a higher coefficient of performance ('efficiency'); consequently they are in even wider use einstein and szilard's no-moving-parts design does reduce the risk of leaks, but not to zero, as is obvious if you visit a junkyard to find spare parts for one of these
  - biorach 3y ago
    ...and bingo! Thank you.
  - londons_explore 3y ago
    Leaks in modern fridges are mostly caused by humans using a knife to try to defrost them and puncturing the pipes... And then 2nd most common cause is water leaks or dampness causing the pipes to corrode through. If you run a fridge till it dies like most people, you will probably see a leak on about 15% of cases (other causes of failure are motor capacitor failure, thermostat failure). With an ammonia based refrigerant, every single leak indoors would likely kill a few people, so such a fridge design still wouldn't be considered acceptable for use in the home today.
    - kragen 3y ago
      that depends on the speed of the leak and the amount of ammonia involved; as i said, ammonia-absorption refrigerators are in common use today, including in homes, and they do not have a high death toll (though large industrial ammonia-absorption systems do regularly kill people, about 20 people a year in all of prc, for example: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC9318737/ https://www.ncbi.nlm.nih.gov/pmc/articles/PMC9318737/) osha's idlh level is 300 ppm; in a typical small house of 200m³ that's 60 liters of gas, 2.5 moles at stp, about 40 grams of ammonia; this is a small enough amount of ammonia that you could definitely get it from a home refrigerator (https://www.dometic.com/assets/18/22/operating%20manual_51822.pdf https://www.dometic.com/assets/18/22/operating%20manual_5182... says it contains 226g of ammonia, which would be 1600 ppm in that houseful of air) but only if it's released quickly. lc50 for a one-hour exposure is in the 4000 to 11000 range https://www.cdc.gov/niosh/idlh/7664417.html https://www.cdc.gov/niosh/idlh/7664417.html which is several times more than the entire refrigerator's worth if diluted in a houseful of air the odor threshold is about 5 ppm https://en.wikipedia.org/wiki/Ammonia#Safety https://en.wikipedia.org/wiki/Ammonia#Safety so it's unlikely to go unnoticed
anadem 3y ago
There are refrigerators without any moving parts .. my VW camper has one which runs on either propane or 12V or utility power, and as a child we had one which ran on kerosene.
- deleted 3y ago
  [deleted]
tambourine_man 3y ago
Of course, the big question is efficiency, which is not addressed. Nice article otherwise.
somat 3y ago
Did the article even read the patent? The article goes on about an electromagnetic pump. A device never mentioned in the patent. The patent describes(as best I can tell) an ordinary gas fired absorption refrigerator. of the type found in many RV's. A genius design to be sure. But not one that was suppressed or lost. https://www.dometic.com/en-us/outdoor/rv-and-van/refrigerators/rv-refrigerators/dometic-americana-ii-dm2672-refrigerator-183082 https://www.dometic.com/en-us/outdoor/rv-and-van/refrigerato... My father, who worked for a gas company, used to tell me that Einstein invented the gas fired refrigerator. I always thought he was pulling my leg.
- atombender 3y ago
  They probably got it from Wikipedia [1], which the article appears to have been based on: > One variant, the Einstein–Szilard electromagnetic refrigerator used a Einstein–Szilard electromagnetic pump to compress a working gas, pentane. [1] https://en.wikipedia.org/wiki/Einstein_refrigerator https://en.wikipedia.org/wiki/Einstein_refrigerator
- angiosperm 3y ago
  The absorption refrigerator already existed, but had room for refinement as seen in the patent cited. Einstein's and Szilard's real innovation, maybe not seen there, was for a different, electric design with a moving part, sealed inside, that was moved back and forth by a varying magnetic field applied from outside. It is often described incorrectly as having no moving parts. (I used to think ammonia was itself diamagnetic or ferromagnetic, which would have been very cool, until I got a look at their design.) What was innovative was that it had no need for sealed bearings that might leak. Nowadays just the wires for the motor pierce the fluid chamber, less elegantly than a strictly magnetic coupling. Absorption refrigerators are strictly better than the compressor designs used everywhere today, running continuously, silently, and efficiently. The main driver of the latter was that General Electric wanted people to use electric refrigerators, not gas-fired, and wanted them to buy electric motors. Mass production soon gave GE an insuperable economic advantage except in niche applications. Modern institutional refrigeration systems often use ammonia as their working fluid, but nobody likes putting ammonia systems in houses or cars. The modern alternative to freon/"cfc" and "hfc" is liquid CO2 at very high pressure. Hfc that leaks traps heat more than 2000x as well as CO2, so there is a push on to replace it.
stevefolta 3y ago
Szilard and Einstein would later collaborate on a letter that had a far greater effect on the world than their refrigerator did...
la64710 3y ago
The article has a haunting picture. The caption reads: Nazi storm troopers enforce a boycott of a Jewish-owned department store, Berlin, 1933. The sign reads, "Germans! Defend yourselves! Don’t buy from Jews!" Courtesy of the Bundesarchiv via Wikimedia Advocates of hateful free speech should take note about the dangers of something taken too far.
- zmgsabst 3y ago
  Was the source of that sign in 1933 free speech? — or the effect of a central authority who controlled the media? https://en.wikipedia.org/wiki/Censorship_in_Nazi_Germany https://en.wikipedia.org/wiki/Censorship_in_Nazi_Germany When you say “taken too far”, the outcome certainly was a fascist state with totalitarian control of media; how would staunchly defending freedom and decentralized control lead to that?
  - sidlls 3y ago
    How do you suppose the central authority gained that control in the first place? They fomented this exact sort of "hate of the Other" to whip a certain kind of person into a fearful frenzy. Trump's doing the same thing today with MAGA. Trump-era USA is Germany during the late 20s and 30s.
    - Daz1 3y ago
      Meds
    - hattmall 3y ago
      Jfc, Trump is literally the one being prosecuted by a regime that took control through fear, force, and deceit. Yet somehow even though he is very visibly being subjected to a barrage of transparently meaningless political prosecutions you somehow still fear him as a fascist. So who exactly has been "whipped into a frenzy here?" Who are Trump supporters fearful of, other than the government that is actively attacking them?
      - 3y ago
credit_guy 3y ago
I have a question for the HN community. What exactly was Szilard's contribution to the Manhattan project, aside from the initial letter that started it all? I know that Szilard was the first to envision the idea of chain reaction, and got a (secret) patent for that, but at the time it was more or less idle speculation. When the project actually got going, I know he collaborated with Fermi on the Chicago pile reactor, but 99% of the accomplishment was due to Fermi, not to Szilard. After that, Szilard remain a towering figure inside the project, but did he actually contribute anything?
matthewmcg 3y ago
Here’s a much better article on the collaboration from 1990s Scientific American: https://www.physics.smu.edu/scalise/P3374fa17/EinsteinSzilardRefrigerators.pdf https://www.physics.smu.edu/scalise/P3374fa17/EinsteinSzilar...
MilStdJunkie 3y ago
Anyone ever rig one of these things with a solar concentrator as the heat source? I feel like a fridge that runs colder as the sun gets hotter would be one of the more elegant systems.
- c_o_n_v_e_x 3y ago
  Check out solar absorption chillers
MichaelRo 3y ago
>> unlikely to do anybody any harm Unlikely doesn't mean impossible.
macrolime 3y ago
My parents had an electric absorption refrigerator when I grew up. It was completely silent and lasted for more than 30 years. These days it seems they're only available in small gas fired models for RVs, not sure why.
- cybrox 3y ago
  Aside from other potential factors, who in their right mind would want [to sell] something that lasts 30 years these days /s
rob74 3y ago
> Szilard and his team refined the prototype in their workshop at Germany’s General Electric Corporation in Berlin Better known as Allgemeine Elektricitäts-Gesellschaft (AEG - https://en.wikipedia.org/wiki/AEG https://en.wikipedia.org/wiki/AEG). Some names are better left untranslated. That's the same as writing "Allgemeine Motoren" instead of General Motors in a German article - nobody would know what you're talking about...
- sonicanatidae 3y ago
  He says better known as and throws out this, "Allgemeine Elektricitäts-Gesellschaft". lol
  - rob74 3y ago
    Ok, the brand is (or was) known more under the acronym AEG (at least in Germany/Europe, probably not in the US), not sure if everyone was aware of what the acronym stood for however. I just mentioned the full name first because it explains how the author of the article arrived at the translation "General Electric Corporation"...
    - sonicanatidae 3y ago
      One of my parents were German. Such tortured pronunciation with German.
rjmunro 3y ago
The phrase "Freon is a greenhouse gas that has depleted the earth’s ozone layer" annoys me. A lot of people don't get that the Ozone layer and climate change (the greenhouse effect) are different things. Freon is both a very powerful greenhouse gas, and it destroys the ozone layer. Since Freon and other CFCs were banned, the Ozone layer has been mostly coming back, but climate change is still happening because of the other greenhouse gases.

92 points by Dracophoenix 3y ago

The patents having long expired, presumably there are practical reasons that this design is not competitive with modern compressor designs.. Would have been good if the article had said what these are

kragen 3y ago
moving-parts-free ammonia-absorption refrigerators of the einstein-szilard type are in fact in wide use today, especially in camping trailers where the ability to run off propane without electricity is a big plus. i encountered one in a hotel room earlier this year. https://en.wikipedia.org/wiki/Absorption_refrigerator https://en.wikipedia.org/wiki/Absorption_refrigerator vapor-compression types with midgley's cfcs, and derivatives like hcfcs and hfcs, are less likely to kill you if they leak, and i think they also have a higher coefficient of performance ('efficiency'); consequently they are in even wider use einstein and szilard's no-moving-parts design does reduce the risk of leaks, but not to zero, as is obvious if you visit a junkyard to find spare parts for one of these
- biorach 3y ago
  ...and bingo! Thank you.
- londons_explore 3y ago
  Leaks in modern fridges are mostly caused by humans using a knife to try to defrost them and puncturing the pipes... And then 2nd most common cause is water leaks or dampness causing the pipes to corrode through. If you run a fridge till it dies like most people, you will probably see a leak on about 15% of cases (other causes of failure are motor capacitor failure, thermostat failure). With an ammonia based refrigerant, every single leak indoors would likely kill a few people, so such a fridge design still wouldn't be considered acceptable for use in the home today.
  - kragen 3y ago
    that depends on the speed of the leak and the amount of ammonia involved; as i said, ammonia-absorption refrigerators are in common use today, including in homes, and they do not have a high death toll (though large industrial ammonia-absorption systems do regularly kill people, about 20 people a year in all of prc, for example: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC9318737/ https://www.ncbi.nlm.nih.gov/pmc/articles/PMC9318737/) osha's idlh level is 300 ppm; in a typical small house of 200m³ that's 60 liters of gas, 2.5 moles at stp, about 40 grams of ammonia; this is a small enough amount of ammonia that you could definitely get it from a home refrigerator (https://www.dometic.com/assets/18/22/operating%20manual_51822.pdf https://www.dometic.com/assets/18/22/operating%20manual_5182... says it contains 226g of ammonia, which would be 1600 ppm in that houseful of air) but only if it's released quickly. lc50 for a one-hour exposure is in the 4000 to 11000 range https://www.cdc.gov/niosh/idlh/7664417.html https://www.cdc.gov/niosh/idlh/7664417.html which is several times more than the entire refrigerator's worth if diluted in a houseful of air the odor threshold is about 5 ppm https://en.wikipedia.org/wiki/Ammonia#Safety https://en.wikipedia.org/wiki/Ammonia#Safety so it's unlikely to go unnoticed

anadem 3y ago

There are refrigerators without any moving parts .. my VW camper has one which runs on either propane or 12V or utility power, and as a child we had one which ran on kerosene.

deleted 3y ago
[deleted]

tambourine_man 3y ago

Of course, the big question is efficiency, which is not addressed. Nice article otherwise.

somat 3y ago

Did the article even read the patent? The article goes on about an electromagnetic pump. A device never mentioned in the patent. The patent describes(as best I can tell) an ordinary gas fired absorption refrigerator. of the type found in many RV's. A genius design to be sure. But not one that was suppressed or lost. https://www.dometic.com/en-us/outdoor/rv-and-van/refrigerators/rv-refrigerators/dometic-americana-ii-dm2672-refrigerator-183082 https://www.dometic.com/en-us/outdoor/rv-and-van/refrigerato... My father, who worked for a gas company, used to tell me that Einstein invented the gas fired refrigerator. I always thought he was pulling my leg.

atombender 3y ago
They probably got it from Wikipedia [1], which the article appears to have been based on: > One variant, the Einstein–Szilard electromagnetic refrigerator used a Einstein–Szilard electromagnetic pump to compress a working gas, pentane. [1] https://en.wikipedia.org/wiki/Einstein_refrigerator https://en.wikipedia.org/wiki/Einstein_refrigerator
angiosperm 3y ago
The absorption refrigerator already existed, but had room for refinement as seen in the patent cited. Einstein's and Szilard's real innovation, maybe not seen there, was for a different, electric design with a moving part, sealed inside, that was moved back and forth by a varying magnetic field applied from outside. It is often described incorrectly as having no moving parts. (I used to think ammonia was itself diamagnetic or ferromagnetic, which would have been very cool, until I got a look at their design.) What was innovative was that it had no need for sealed bearings that might leak. Nowadays just the wires for the motor pierce the fluid chamber, less elegantly than a strictly magnetic coupling. Absorption refrigerators are strictly better than the compressor designs used everywhere today, running continuously, silently, and efficiently. The main driver of the latter was that General Electric wanted people to use electric refrigerators, not gas-fired, and wanted them to buy electric motors. Mass production soon gave GE an insuperable economic advantage except in niche applications. Modern institutional refrigeration systems often use ammonia as their working fluid, but nobody likes putting ammonia systems in houses or cars. The modern alternative to freon/"cfc" and "hfc" is liquid CO2 at very high pressure. Hfc that leaks traps heat more than 2000x as well as CO2, so there is a push on to replace it.

stevefolta 3y ago

Szilard and Einstein would later collaborate on a letter that had a far greater effect on the world than their refrigerator did...

la64710 3y ago

The article has a haunting picture. The caption reads: Nazi storm troopers enforce a boycott of a Jewish-owned department store, Berlin, 1933. The sign reads, "Germans! Defend yourselves! Don’t buy from Jews!" Courtesy of the Bundesarchiv via Wikimedia Advocates of hateful free speech should take note about the dangers of something taken too far.

zmgsabst 3y ago
Was the source of that sign in 1933 free speech? — or the effect of a central authority who controlled the media? https://en.wikipedia.org/wiki/Censorship_in_Nazi_Germany https://en.wikipedia.org/wiki/Censorship_in_Nazi_Germany When you say “taken too far”, the outcome certainly was a fascist state with totalitarian control of media; how would staunchly defending freedom and decentralized control lead to that?
- sidlls 3y ago
  How do you suppose the central authority gained that control in the first place? They fomented this exact sort of "hate of the Other" to whip a certain kind of person into a fearful frenzy. Trump's doing the same thing today with MAGA. Trump-era USA is Germany during the late 20s and 30s.
  - Daz1 3y ago
    Meds
  - hattmall 3y ago
    Jfc, Trump is literally the one being prosecuted by a regime that took control through fear, force, and deceit. Yet somehow even though he is very visibly being subjected to a barrage of transparently meaningless political prosecutions you somehow still fear him as a fascist. So who exactly has been "whipped into a frenzy here?" Who are Trump supporters fearful of, other than the government that is actively attacking them?
    - 3y ago

credit_guy 3y ago

I have a question for the HN community. What exactly was Szilard's contribution to the Manhattan project, aside from the initial letter that started it all? I know that Szilard was the first to envision the idea of chain reaction, and got a (secret) patent for that, but at the time it was more or less idle speculation. When the project actually got going, I know he collaborated with Fermi on the Chicago pile reactor, but 99% of the accomplishment was due to Fermi, not to Szilard. After that, Szilard remain a towering figure inside the project, but did he actually contribute anything?

matthewmcg 3y ago

Here’s a much better article on the collaboration from 1990s Scientific American: https://www.physics.smu.edu/scalise/P3374fa17/EinsteinSzilardRefrigerators.pdf https://www.physics.smu.edu/scalise/P3374fa17/EinsteinSzilar...

MilStdJunkie 3y ago

Anyone ever rig one of these things with a solar concentrator as the heat source? I feel like a fridge that runs colder as the sun gets hotter would be one of the more elegant systems.

c_o_n_v_e_x 3y ago
Check out solar absorption chillers

MichaelRo 3y ago

>> unlikely to do anybody any harm Unlikely doesn't mean impossible.

macrolime 3y ago

My parents had an electric absorption refrigerator when I grew up. It was completely silent and lasted for more than 30 years. These days it seems they're only available in small gas fired models for RVs, not sure why.

cybrox 3y ago
Aside from other potential factors, who in their right mind would want [to sell] something that lasts 30 years these days /s

rob74 3y ago

> Szilard and his team refined the prototype in their workshop at Germany’s General Electric Corporation in Berlin Better known as Allgemeine Elektricitäts-Gesellschaft (AEG - https://en.wikipedia.org/wiki/AEG https://en.wikipedia.org/wiki/AEG). Some names are better left untranslated. That's the same as writing "Allgemeine Motoren" instead of General Motors in a German article - nobody would know what you're talking about...

sonicanatidae 3y ago
He says better known as and throws out this, "Allgemeine Elektricitäts-Gesellschaft". lol
- rob74 3y ago
  Ok, the brand is (or was) known more under the acronym AEG (at least in Germany/Europe, probably not in the US), not sure if everyone was aware of what the acronym stood for however. I just mentioned the full name first because it explains how the author of the article arrived at the translation "General Electric Corporation"...
  - sonicanatidae 3y ago
    One of my parents were German. Such tortured pronunciation with German.

rjmunro 3y ago

The phrase "Freon is a greenhouse gas that has depleted the earth’s ozone layer" annoys me. A lot of people don't get that the Ozone layer and climate change (the greenhouse effect) are different things. Freon is both a very powerful greenhouse gas, and it destroys the ozone layer. Since Freon and other CFCs were banned, the Ozone layer has been mostly coming back, but climate change is still happening because of the other greenhouse gases.