This bug comes from the following discussion page in the forums, and was found by @kbn.
When a liquid partially evaporates, using a hot donor from above, and the liquid is trapped on both sides and from below, the temperature of the liquid is reset to reflect the hot donor's temp (along with a little heat loss from conduction and I'm guessing some flaking). This was noticed on both the development build, and live build.
Basically, with this bug we can generate insane amounts of heat. I'm not sure if the bug is a temp swap on liquid, or some part of the "splattering" mechanic that accompanies the partial evaporation code. I do like the effect as it mimics the violent effects of steam creation when water and hot oil collide. But something in the code is resetting the water's temp.
Follow the steps above. We'll probably have fun over the next few days making more monstrosities to make it easy to replicate (as always, in hopes to help you identify exactly what causes it, as well as to have a good laugh).