Three-dimensional flue gas flow fields and temperature profiles are calculated in a 4/2/1 split coil naphtha-cracking furnace with long flame burners and an asymmetric flue gas outlet. The heat streams in the furnace connected to the asymmetric flue gas flow fields are found to be compensated for by a net radiative heat transfer in the opposite direction. As a result, the temperature distribution in the furnace remains nearly symmetrical. A furnace simulation under conditions of nonuniform heating confirms the compensating nature of radiative heat streams in the furnace. Furthermore, nonuniform heating was found to improve the thermal efficiency of the furnace and the cracking results. Optimization of heating conditions remains a point of interest.