Banded gas and nongray surface radiation models for high‐emissivity coatings

Abstract

Abstract 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 in frequency 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. © 2005 American Institute of Chemical Engineers AIChE J, 2005