Electronics > Metrology

Low temperature chamber (-60C and below)

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Leo Bodnar:
Do we have any successful projects to build thermal chamber that goes down  to -60C and below?

I don't want to deal with dry ice or liquid Nitrogen.

At the moment I am using a chest freezer that reaches -42C inside within an hour of turning on empty at room temperature.
I put a small 12V car coolbox with its "electronics" removed and Peltier/fan connected to external PSU and this setup goes to -50C..-55C inside the coolbox.

Maybe someone knows efficient and inexpensive car freezer that I can use instead.

Cheers
Leo

Labrat101:
Hi Leo ,
Did you try butting a 3rd box inside the -55 cooler box just a thought .
even though in theory its possible to cascade Peltier cooling and each level
will decrease in efficiency but adding a 3 level will give you hopefully  another
minus 8 to 12 degrees maybe more 15. would be about max.
..
I did build a minus 80 cooler when I was working in Kinston for a company.
for testing equipment before sending to the Antarctica . . That was a very long time ago early 80's .  It was done by converting an R12 freezer and changing the gas to 13B1 which was very expense and I believe it is now been band from use in the UK . >:D 
The freezer you are using is probably one of the new Green Gases . maybe
R161 which is basically  butane or R404 or similar .
What I think you need is to get hold of a second hand lab freezers which
I believe use R508B and can go down to close to minus 80 .
I am retired now so I have lost track on the new refrigerants .

I would Try Cascading Peltier plates with an external power supply is certainly the cheapest way . You can sandwich Peltier plates but you need
a very good thermal grease between each and a thin copper sheet .
to help with thermal movement as they expand and contract the copper  sheet will reduce the ceramic from cracking .with luck . and lots of Power amps.
Note ( Make sure the Peltier plates are orientated  hot,cold,hot,cold )
placing 1 plate wrong it won't work . also the power has to be monitored
the first sage will use more than the second .
The first sage is the one within the -42 side  (Edited due to Typo )
second as final or if 3 stages and so on .
I have only ever used 2 stages . as they become hard to mount .
A tension plate with springs should be used to hold them together

Leo Bodnar:
Thanks, Labrat101.

I have not had much success stacking Peltiers in the past.  They quickly reach a point where they just pump the energy they generate themselves.
The chest freezer is only a few years old so I assume it will be a modern green variety (and thus incapable of reaching high temperature differentials.)

I will try to find a larger and smaller cool boxes but it is not dissimilar to stacking Peltiers.  Outside freezer should be capable of removing heat at the rate that internal boxes generate.

Leo

Labrat101:

--- Quote from: Leo Bodnar on July 18, 2021, 09:38:54 pm ---Thanks, Labrat101.

I have not had much success stacking Peltiers in the past.  They quickly reach a point where they just pump the energy they generate themselves.
The chest freezer is only a few years old so I assume it will be a modern green variety (and thus incapable of reaching high temperature differentials.)

I will try to find a larger and smaller cool boxes but it is not dissimilar to stacking Peltiers.  Outside freezer should be capable of removing heat at the rate that internal boxes generate.

Leo

--- End quote ---

That should also work .  ;D .
Using the Russian doll effect . I guess your freezer will take the extra loading it may just
take a little long to cool . Turn the fast freeze switch ON . or if it doest have and has a mechanical thermostat just short it out so it runs continuously . The fast freeze switch
just shorts the thermostat out any way .  this is ok for about 2 to 4 hours . or better still
replace the thermostat with a programmable one

PS put a bottle of vodka in the freeze as well . That for the end to Drink

Anders Petersson:

--- Quote from: Leo Bodnar on July 18, 2021, 08:01:26 pm ---At the moment I am using a chest freezer that reaches -42C inside within an hour of turning on empty at room temperature.
I put a small 12V car coolbox with its "electronics" removed and Peltier/fan connected to external PSU and this setup goes to -50C..-55C inside the coolbox.

--- End quote ---

Hi Leo. I'm also interested in reaching -60 C or thereabout. My research so far has only yielded expensive environmental chambers; The Chinese and therefore hopefully relatively inexpensive www.lib-industry.com quoted their smallest chamber T-50 last year at USD 7300 for -70 C and USD 13800 for -86 C. And shipping weight is 180 kg so that incurs a real cost too. And then the hassle of moving and housing the 1 m3 unit (inner space is 320*350*450 mm). Interestingly, humidity control only added a marginal cost.

Without being an expert, I doubt -60 C is possible with peltiers regardless how small the temperature delta is. In fact I'd be thankful if you want to share details/pictures of your current setup for -50 - -55 C? It's a good result as is.

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