I added a small bowl of water as a thermal mass to simulate having soybeans in the chamber. It's kind of wild how much of a difference that makes. The temperature in the chamber would climb to 120F in maybe 30-40 seconds when it was empty. With the bowl of water in there, it's barely at 93F after 20 minutes.
Yeah, water has a high specific heat, but I didn't expect it to absorb heat from the air *that* fast