From OpenFOAMWiki

Valid versions: OF Version 21x.png OF Version 22x.png OF Version 23x.png

Source code repository
wallHeatFluxIncompressible at GitHub
Utility adapted from OpenFOAM's wallHeatFlux for incompressible simulations, such as those performed with buoyantBoussinesqSimpleFoam.
Support pages
For OpenFOAM 1.5
see Contrib/wallHeatFlux.

Other examples
  1. Example on how to use the boundary condition turbulentHeatFluxTemperature this utility in conjunction with this utility: BC for People Heat Flow - post #28