This flux report computes the heat transfer rate by whichever radiation model you have enabled under the ‘radiation model’ panel. Specifying that a wall has a radiation BC type means that we specify the heat flux at the wall by using the Stefan-Boltzmann law (i.e., such that q = sigma*(T1^4 – T2^4)), but Fluent does not include that flux in the radiation heat transfer rate. If you are not using a radiation model, the radiative flux will always be zero. Saying that a wall has a radiation BC type simply means that we specify the heat flux in the form q = sigma*h*(T1^4 – T2^4). It does not actually enable any of the radiation models. Keywords: flux, radiation, mixed, flux report