I'm not sure what's happening under the hood, but the Heat Exchanger, Component Heat Exchanger, and Advanced Heat Exchanger seem to dupe heat when dealing with minuscule amounts of heat.

Using a 60k Coolant Cell that is at 59997 durability across all demonstrations, as well as an LZH-Condensator, there ends up being more than 3 heat total in the system afterward, indicating that heat is being duplicated in some way.

Mod list/versions are shown at the start of the video.
https://youtu.be/AYiv__zbMa4