Measurement of Total Hemispherical Emissivities of Metal Wires by Using Transient Calorimetric Technique

Abstract

An application of the transient calorimetric technique was studied for measuring total hemispherical emissivities of metal wires. A unique idea of using guard wires, which have a function similar to usual guard heaters, was incorporated into the emissivity apparatus to reduce conduction heat losses through thermocouple leads suspending a specimen. Emissivity measurements were performed by using a copper wire as a specimen. The heat losses through the leads were analyzed in considering radiation heat transfer from the leads, and the effect of the guard wires on the heat losses was clarified. Temperature distributions in the specimen were also obtained analytically. From these results, it was found that an improved transient calorimetric technique in this work is applicable to the emissivity measurement on metal wires, and that the accuracy in the measurements is adequate.