The thermal conductivity of refractories

The usefulness of correct data in regard to the thermal conductivity of refractories and other materials used in the construction of metallurgical and industrial furnaces is quite generally recognized. Numerous investigations of this property of refractories have been conducted, and in many cases the published data of different investigators are somewhat conflicting. This is particularly true of figures pertaining to materials intended for use at high temperatures, and it is with such materials that the metallurgist is mot interested. The difficulties in the way of precise determinations of thermal conductivities at elevated temperatures are numerous, and it is not particularly surprising that there exists a set of data for each method of determination, the figures of which fail to agree closely with those obtained by other methods. However, it should be remembered that the variations in the figures of different observers are doubtless due to variations in the materials tested as well as to differences between, or inaccuracies of, the methods employed. The present paper deals with the methods and results of an investigation designed to develop a practical and reasonably accurate means of determining the thermal conductivity of regular kinds of brick, under conditions approaching those of practice, and without the necessity of preparing special shapes or samples of the materials being tested. In reviewing the methods that have been used and proposed for determining the conductivity of refractory materials, they fall naturally into three general classes, calorimeter methods, measured heat-input methods, and comparison methods --Page 285