7.8 Radiation combined with conduction and convection
In industrial processes, in general, the heat transfer at higher temperature has significant portion of radiation along with conduction and convection. For example, a heated surface is shown in the fig. 7.10 with all the three mechanism of heat transfer.
Fig. 7.11: Radiation combined with conduction and convection
At steady state
Heat flux by conduction = heat flux by convention + heat flux by radiation
where, h is the heat transfer coefficient at the surface in contact (outer surface) with atmosphere due to natural and forced convection combined together, 
is the emissivity of the outer surface, and Tatm is the atmospheric temperature.