It is called "heat of reaction" in "file - export - solution data". You can also find it by plotting a contour of "reaction - heat of reaction", where the dimension is shown to be W.

It seems to be the heat release/absorption of all the reactions at the node, but that does not make sense with W instead of W/m^3 or W/m^2.

So you are probably right that it might be something else, and I am curious about what it is, and how I can get the heat of reactions at each node.