The efficiency of the application of high-emissivity coatings on reactor tubes and furnace walls in steam-cracking technology can be evaluated only on the basis of a description of radiative heat transfer infrequency bands. For the flue gases in the furnace, a radiation model is introduced in which the gas emits and absorbs radiation in discrete bands only; for the surfaces a nongray surface approach is applied. First, the influence of the model changes on the calculated radiative energy exchange is evaluated theoretically. Next, different furnace simulations are performed to do a numerical evaluation of the introduction of banded radiation models. The changes in the furnace thermal efficiency, attributed to the application of high-emissivity coatings on furnace walls and tube skins in steam-cracking furnaces, are calculated. (c) 2005 American Institute of Chemical Engineers.