The Einstein-Szilard Refrigerator (2020)
invention.si.edu
invention.si.edu
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/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.
> One variant, the Einstein–Szilard electromagnetic refrigerator used a Einstein–Szilard electromagnetic pump to compress a working gas, pentane.
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.
That's not true! CoP of ammonia absorption refrigerators struggles to get past 1. You can easily get a CoP of 4-5 with a compression refrigerator.
Ammonia absorption fridges are useful when you have a source of waste heat, then it's basically "free" for you.
However, getting close to that limit requires huge evaporators and condensers, big pipes, large amounts of working fluid, and multi stage pumps. All of that costs money, and historically people didn't care much about efficiency if it means spending more money.
Industrial refrigerators can get to CoP of around 4 for this temperature delta. The overall system performance will typically be much lower, due to the need to run fans and other systems.
A couple of interesting technologies to watch in this area:
1. Acoustic refrigerators that use acoustic waves in helium. They theoretically can approach the Carnot limit.
2. Supercritical CO2 cycles. They can be used for larger deltas without losing efficiency.
Electrochemical, magnetohydrodynamic and various other systems are not properly characterized by the Carnot limit and can approach much higher efficiency limits.
I think the systems being discussed are appropriately characterized by the Carnot limit, but it is frequently mischaracterized as an absolute limit on systems that it is not relevant to and for example here it should probably not be considered the absolute limit of refrigeration efficiency.
That usually is a distinction without difference. Other effects limit the efficiency at far lower levels than pure Carnot.
This can be intuitively understood like this: Carnot limits apply to gases, that are the simplest interacting systems. You can realistically model them as just a collection of individual independent particles interacting only via simple collisions.
Anything more complicated like electrons in semiconductors, and you have way more interactions and way more possibilities for your system to have inefficiencies.
Take, for example, solar panels. Sunlight has the optical temperature of around 6000K, so a Carnot engine that uses 6000K hot part and 300K cold part will theoretically have a 95% efficiency. And an infinite stack of solar panels with each layer tuned for a specific wavelength has the theoretically maximum 87% efficiency.
Carnot characterizes classical heat engines and things that work a lot like them, it's not a universal limit of process efficiency and it's not even a good first approximation for many systems.
Your example of a meaningless distinction is a factor of over two in waste energy, in the favor of Carnot in this case, but distinct none-the-less.
As an example, the Titanic had CO2 refrigeration.
Better known as Allgemeine Elektricitäts-Gesellschaft (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...
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
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.
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_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 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 so it's unlikely to go unnoticed
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.
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.
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?
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?
And if you're having a hard time figuring out who the proto-fascists are, look for the ones who don't respect free and fair election results, and look for the ones who try to make it harder for people to vote.
You need to at least be consistent with your complaints.
People who aren't white, people who aren't straight, people who are transgender, people who aren't Christian extremists, people who don't think the government is a giant ball of evil incarnate, etc.
Trump literally tried to overthrow the government in 2020. This isn't debatable: it's a fact. In any sane, functioning democracy, he'd be jailed already. It's scary that such a large fraction of this country fears and hates everyone else so much, and this country so much, that they'd be willing to use violence to overthrow it and install a dictator.
Not sure what it has to do with 'control of the media'. The person who took the photograph was likely part of the media.
Yeah! I remember when these thugs took mayor chunks of cities and fired some police stations and politicians refused to move a finger.
Actually this historical precedent is the reason for the stricter rules on expression in the Germany of the present.
That said: The question if "calling for the genocide of Jews" violates Harvard's rules on bullying and harassment or is acceptable speech is still ongoing and left to the reader. /s
Enforcing it, by physically preventing people from entering the store, not so much.
Unlikely doesn't mean impossible.