ACCURATE DETERMINATION OF THERMAL CONDUCTIVITY AND LORENZ NUMBER OF METALS

A well-established high temperature technique of determining the Lorenz number and thermal conductivity of metals by taking advantage of the relation between the temperature and electrical potential distributions in a current-carrying specimen has been adapted to enable high accuracy measurements to be made at lower temperatures, particularly in the Curie region of some ferromagnetic metals and alloys. A simple form of apparatus is described which has been used for measurements on nickel and its alloys with copper up to about 450°C. Accuracies of about 1% in the Lorenz number and 2% in the thermal conductivity have been achieved. The performance of the apparatus is discussed in detail and the main sources of error identified.