Radial Outflow High Temperature Thermal Conductivity Measurements: Some Experimental Developments

Abstract

We have been conducting radial outflow (ROF) high temperature thermal conductivity measurements in GE/RESD’s Valley Forge Space Center Laboratories since 1967, when we obtained a commercially available instrument, described in Ref. 1. At the time of acquisition, our primary need was for high temperature (1000–3000 K) measurements on low conductivity materials such as the chars of carbon- and silica-phenolic composites. Because of the small samples available, a small specimen size was necessary, and our original specifications called for a 2“ O.D. maximum cylindrical specimen. The instrument has worked very well for low to intermediate conductivity materials at temperatures up to approximately 2000 K; however, our high temperature work has been concentrated on high conductivity materials such as the ATJ graphite series. Although the small sample size causes a loss in sensitivity at low temperatures, causing the lower temperature limit of the measurements to rise to the range 1100–1400 K, the more serious experimental difficulty with this class of measurements has been the electrical power measurement at high temperature, in particular the gage section voltage.