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Gotta give a big ol’ hearty WTF. It completely destroyed my article markup. 
".45 ACP - because shooting twice is just silly" - JSOP, 2010
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You can never have too much ammo - unless you're swimming, or on fire. - JSOP, 2010
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When you pry the gun from my cold dead hands, be careful - the barrel will be very hot. - JSOP, 2013
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Trust my experience: you're quicker the second time 
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Should have used MarkDown instead of MarkUp 
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This is way beyond my professional field. I have no clue at all, that is why I ask:
This corona vaccine must be stored at -70C or lower. The common technology for a fridge, a freezer or a heat pump, is to spray some cooling liquid through a nozzle so that it goes from a liquid to a gas - 'evaporates', if you like. This state transition draw a lot of energy from the environment. But there is a limit to that. If the evaporated gas never goes below, say, -35C, then the environment will not be drawn below that.
So how to you, artificially, create extremely low temperatures? I guess that there exist (most likely extremely expensive) fluids that, by evaporation, can go several degrees below what is used in our deep freezers. But 'several degrees' is not enough when you need forty to fifty of those degrees... The learning I did in my school days simply doesn't cut it!
How to they create super-cold temperatures nowadays? I'd be satisfied with appropriate links to replace explanations. Even suggestions for focused google search terms would be nice!
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Hmmm,
I honestly don't know how the medical profession would do this. But Derek Muller has a video where he uses a helium-based cryocooler to make Liquid Nitrogen in his living room.
https://www.youtube.com/watch?v=dCXkaQa53QQ
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As soon as we can have friends over that's what I'm doing. With beer. Awesome.
cheers
Chris Maunder
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Ultra Low temp freezers like the ones they need for the mRNA vaccines are just like normal freezers, except beefed up a fair bit. Take a peek at How does an Ultrafreezer work?[^] for a super quick overview.
Or they could just move production to Canada and they'd be fine.
(Says the guy who ordered a warm coat a week ago and it's still not here. Sigh)
cheers
Chris Maunder
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30 degrees in Cairns and the wet has just started. Swimming with the dogs at the beach after a morning walk starts the day perfectly. you can call me a bitch, i'm used to it
Never underestimate the power of human stupidity -
RAH
I'm old. I know stuff - JSOP
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Well, the snow and slush today were magnificent. And the coffee, were the cafes open, was probably excellent. I especially enjoyed the wonderful surprise of stepping on what looks like snow to find it's actually a foot of salty water covered in a thin sheen of snow.
cheers
Chris Maunder
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Same principal. But when the temperature difference is large it has to be done in several steps using different gases at different pressures.
Wrong is evil and must be defeated. - Jeff Ello
Never stop dreaming - Freddie Kruger
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Which is called cascade refrigeration. So, it takes different refrigerants with heat exchange between them. The complete arrangement can be called a heat pump, as you might use with a single refrigerant like for your home and your auto.
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trønderen wrote: How to they create super-cold temperatures nowadays?
In my case, it's simple: Tell Herself her butt does look big in that ...
"I have no idea what I did, but I'm taking full credit for it." - ThisOldTony
"Common sense is so rare these days, it should be classified as a super power" - Random T-shirt
AntiTwitter: @DalekDave is now a follower!
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In my house, that would not have a refrigerative effect; quite the opposite, actually.
The wife would turn incendiary, and burn me to ash where I stood.
Software Zen: delete this;
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Remove all the heat!
I'm not sure how many cookies it makes to be happy, but so far it's not 27.
JaxCoder.com
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I ca do it every time I talk to my ex wife.
".45 ACP - because shooting twice is just silly" - JSOP, 2010
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You can never have too much ammo - unless you're swimming, or on fire. - JSOP, 2010
-----
When you pry the gun from my cold dead hands, be careful - the barrel will be very hot. - JSOP, 2013
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Tell her that ‘Yes. Those pants do make your butt look huge’
Temperatures will drop like a stone!
If you can't laugh at yourself - ask me and I will do it for you.
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Liquify gas with pressure, and then release it. This brings the gas to very low temperature due to evaporation.
Cascade this several times, and you get ... liquid nitrogen
Fun fact : Try and spray your favorite deo on a thermometer, you should reach between -30°C and -50°C.
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We used to have cryogenically cooled parametric amplifiers when I worked SATCOM. Temps down to 50K or so, I think, to get "low noise". Cold is pretty easy.
Tanks of helium just sitting there, when we weren't repressurizing the cryo pump.
Tanks just sitting there. Of helium.
So, of course, we used to fill up trash bags with helium, and send them floating over the Wall into East Berlin. Fun times. 
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Even if the vaccine must be stored at very low temperature, it can be stored a regular freeze temperature for while.
Here's one reference (in French) : Pourquoi le vaccin de Pfizer n'aurait finalement pas besoin d'être stocké à -70 °C
"...D'abord, le vaccin de Pfizer supporterait -20 °C pendant quinze jours et même 2 °C à 8 °C pendant cinq jours, d'après nos informations..."
(google translate)
"...First, Pfizer's vaccine would withstand -20 ° C for fifteen days and even 2 ° C to 8 ° C for five days, according to our information."
I'd rather be phishing!
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Heat pumps (normal refrigeration) don't need to have the sink at a lower temperature than the source to keep cooling. Think of air conditioning your house: it's much hotter outside than inside but the pump still can move heat - it just gets less and less efficient (there's an equation for that).
Now, for the COVID vaccine, they temperature is that of Dry Ice (solid CO2 for the newer generations). To make it, they compress the CO2 until it liquifies and let that cool by releasing heat to the surroundings - and then they release the pressure and it gets extremely cold, much of it solidifying and the rest returning to the gas phase (now at ambient pressure). Because of this method, the solid is more like snow and is compressed into blocks (opaque white). You can do this yourself if you've a CO2 fires extinguisher to waste: if turned upside down it will attempt to empty its contents (liquefied gas under pressure) and you'll get some dry-ice snow.
At the extreme end, towards absolute zero (0K = -273C), like liquid helium at 4K, extremely compressed helium is cooled, like the routine for dry ice but cooled to liquid nitrogen temperature, above and when allowed to expand some of it liquefies. It is a particularly energy intensive process as the tiny little helium atoms have virtually no attraction towards one another (compared to any other element). It is a super-fluid and does some creepy stuff like climb out of its container. It's generally difficult to store for any period of time (and dangerous in that it's constantly boiling and creating pressure). I didn't use it but it was used by some of the chemical physicists in my lab. It was ordered so it arrived within a day of when it was needed or it would pretty much be gone. It's stored in specialized dewers (basically thermos bottles).
| Ravings en masse^ |
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| "The difference between genius and stupidity is that genius has its limits." - Albert Einstein | | "If you are searching for perfection in others, then you seek disappointment. If you seek perfection in yourself, then you will find failure." - Balboos HaGadol Mar 2010 |
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Quote: Dry ice is made by liquefying carbon dioxide and injecting it into a holding tank, where it's frozen at a temperature of -109° F and compressed into solid ice.
Hey, maybe the vaccine will help with global warming too!
Oh wait, the dry ice simply evaporates. 
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And if I'd known they would take this long I'd have come home and the gone back to get her!
But ... using the phone as a WiFi hotspot worked well, and the Surface Go 2 survived 5 hours of youtube, surfing, book reading and a short video with about an hour to go in the battery. Not too bad, but I think the older Surface 3 Pro would have done better (until it bricked itself by refusing to talk to it';s charger any more of course). The phone coped brilliantly, using less than 25% on a couple of calls and 5 hours as a WiFi hotspot. Good going!
08:30 the appointment was, 10:30 they actually saw here and started to prep for the procedure. 13:30 they called me to say Herself would be free to go at 14:00. 14:30 we go out of the building ...
The good news was the Welsh Rush Amble: despite peak traffic time we only stopped in traffic once on the way there, and that was at a set of red lights. So much easier than the same distance journey would have been when I worked inside the M25 (LOndon Orbital Motorway). Back then it could take an hour to get through Hindhead Lights ...
"I have no idea what I did, but I'm taking full credit for it." - ThisOldTony
"Common sense is so rare these days, it should be classified as a super power" - Random T-shirt
AntiTwitter: @DalekDave is now a follower!
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OriginalGriff wrote: Hindhead Lights
Yes, I used to commute through there for a number of years. Absolutely deadly on a Friday evening. All replaced now by a nice tunnel under the hogsback.
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Gawd yes. And all it ever took was one idiot to do something really stupid and you could be delayed for ages.
About once a week on average.
"I have no idea what I did, but I'm taking full credit for it." - ThisOldTony
"Common sense is so rare these days, it should be classified as a super power" - Random T-shirt
AntiTwitter: @DalekDave is now a follower!
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