Thermal chamber for -40 deg. Celsius

[eslavko]

Hello...

I wish to make thermal chamber for -40 degree Celsius. The usable size around 30x20x15cm. I intend to build it from extruded polystirene 10cm thick and calculated loses are around 6W (10-15W should be best). Now I just wonder what to use to chill that chamber. I have some ideas but don't know what is best.

1. Peltier elements. Need to be stacked to get so low temperature so efficiency would be way under 1%.

2. Rankine cycle with compressor. Can't find available unit to suit usage.

3. Wortex hilsch tube running by compressor. Can't find real data if it's possible to reach 60 degree change in single stage.

4. joule thompson throttling. Don't know if I can get anything usable from 8 Bar air pressure. 300 Bar is available but afraid that this pressure is little to much hazard. But I like that as is simple device

5. Dry ice. Must be pre ordered here. And temperature control is hard to do to be steady.

Any idea?

 

[IRstuff]

Thermal chamber to do WHAT and how BIG, exactly? Most thermal chambers are designed to handle upwards of a kilowatt of UUT heat dissipation. We use liquid nitrogen, otherwise, you need extremely dry air, which requires a dryer.

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