Publications
Total Hemispherical Emissivity of Metals Applicable to Radiant Heat Testing
Total hemispherical emissivities are a commonly used property in radiative heat transfer analysis. Measurements made in the course of testing become far more useful to thermal analysts if they are compiled with a sufficient level of detail, and summarized in a manner that allows the most appropriate value or trend to be located quickly. This report collects emissivity measurements from recent years, made in the course of testing metallic surfaces at Sandia's Radiant Heat Test Facility, and compares them to a selection of previous summary documents. These measurements are organized by material type, surface finish, and degree of oxidation. The comparisons also consider the temperature dependence of total hemispherical emissivity. Materials considered include Inconel 600, SS304, 17-4PH SS, silicon carbide, and aluminum alloys. A limited selection of high-temperature paints and other surface coatings are also considered. Recommendations are made for frequency of measurements and level of detail in reporting emissivities in future test series. A more limited scope is recommended for the use of high-temperature paints at Sandia's Radiant Heat Test Facility; pre-oxidation of Inconel and stainless steel surfaces is preferred in many circumstances. ACKNOWLEDGEMENTS Thanks are due to Fredd Rodriguez and Jim Nakos for promoting this work for the benefit of their own programs and many others. The greatest share of the data in this report was provided by Jill Suo-Anttila, Jim Nakos, Walt Gill, and Burl Donaldson. The thoughtful suggestions of Brantley Mills on making the summaries more useful to thermal analysts are greatly appreciated. Thoughtful reviews and assistance with formatting from Ethan Zepper and Monica Bigney were also very valuable.