Reply To: Heat transfer flux vs volume-integral UDF energy source

[Rob]

That command works on the surface interiors, don't use it on the "volume" interiors. The distinction is important as the former typically have cells on both sides too. In your case as it's a volume you should use volume reports. 

For various reasons Fluent must store the volume-interior facets in a surface label; it's generally a very bad idea to interact with that label.