This article describes the determination of the radiation heat transfer coefficient in radiant platen superheaters and on convective heating surfaces. A new simple formula for determination of the heat transfer coefficient is derived on the basis of a diffusivity model of radiation heat exchange. The radiation heat transfer coefficients are determined on the tube surface in a convective evaporator, in a second stage convective heat superheater, and in a platen superheater of a pulverized coal-fired boiler. The calculations were carried out applying the method presented in this article, the Central Institute for Boilers and Turbines method, and formulas resulting from the analysis of heat exchange in an enclosure containing a gas of a constant temperature. In order to assess the accuracy of the achieved results, the flow of flue gas and the heat exchange were modeled using a commercial computational fluid dynamics program.