Getting stuff *really* cold is difficult, dangerous, and lots of fun. Our group is preparing to send an autonomous glider up to about 100,000 feet, so we needed a way to chill our electronics to -70c to test their use before these edge-of-space flights.
Just using dry ice in a cooler will result in about 0c air. In order to chill air much colder, a fan is used to circulate the air to reach -42c. In order to hit -70c or colder, liquid nitrogen and a heat exchange (coil) is used.
This test chamber uses dry ice and liquid nitrogen to cool the air.
This instructable is part of our edge-of-space project. Watch for updates over on Hackerbot Labs
Step 1: Acquire parts for building
- 25' of 3/8" copper pipe (hardware store)
- Fittings to adapt up to 1/2" ID pipe (hardware store)
- 2' of 1/2" pipe to use as a reservoir
- Fiberglass wrap insulation for reservoir
- Teflon tape for the threads (hardware store)
- 4" diameter PVC pipe (just for forming the coil, about 2' will do)
- A large ice cooler which you can remove the lid from.
- 2" thick pink insulation foam. a full sheet is handy, but it needs to be the size of your cooler
- A powerful fan which can fit in the ice cooler for air circulation
- One or more thermal probes for monitoring the temp (K type thermocouples work best here)
- A large cooler/ice chest with a lid which can be completely removed.
- "ice" packs. The sealed kind you reuse. A bunch of them
- A funnel
- Some stiff plastic tubing
WARNING: This stuff is cold - so cold that it will burn you. Seriously. It can blind you. It can freeze off a finger or a limb, and I'm not even going to get into what would happen to your insides if you drink it. Use proper care while handling. Eye protection is very important while interacting with liquid nitrogen. Ventilation is extremely important as well. USE AT YOUR OWN RISK.
- Several blocks of dry ice. 10 lbs will do, 20 is better. This can be sourced at most grocery stores. Some states require you to be 18 or older to purchase and consume Dry Ice.
- a large dewar of liquid nitrogen. This can be sourced at most welding supply shops. Dewars can be rented or borrowed.