Gas Thermal-Conductivity Studies at High Temperature. Line-Source Technique and Results in N2, CO2, and N2-CO2 Mixtures

Abstract

A new technique for measuring the thermal conductivity of gases over a fairly wide temperature range is described. The method makes use of precise measurements of the thermal‐wake widths downstream of a steady line source of heat in a uniform laminar flow of the test gas. The theory and practice of the method are discussed, and it is shown to have advantages over conventional methods in that it is an absolute technique requiring measurement only of distance, gas velocity, and relative temperature differences. The technique has been tested on N₂ and CO₂ over the range 300–1100°K with results that agree well with previously reported work done by conventional means. Measurements on N₂‐CO₂ mixtures covering the entire composition range and in the same temperature interval are also presented. These are compared with kinetic‐theory calculations using the best available input data. The results are then used to predict the thermal conductivity of N₂, CO₂, and N₂‐CO₂ mixtures up to 2000°K with what is believed to be the most reliability which is presently possible.