Transient Method for Measuring Total Hemispherical Emissivities of Thin Wires

Abstract

An improved transient calorimetric method for measuring total hemispherical emissivities ε_h of thin metal wires is reported. In order to reduce heat losses through a pair of thermocouple leads suspending a specimen, guard wires are carefully designed and used. Copper and iron wires of about 0.5 mm diameter are used as samples. Measurements of ε_h have been made in the temperature range 300∼800 K. The lead-wire heat losses and the temperature distributions of the specimens are exactly analyzed. It is confirmed that the heat losses have been kept considerably small by using the guard wires. The ε_h values are determined by taking account of the heat losses. Comparisons of the results are made with the data of previous investigators and those carried out for disk- and wire-type specimens. The examination of the experimental results reveals that the present technique is suitable even for thin metal wires.