Influence of Oxidation on the Emissivity of Copper Conductors

Emissivity is an important parameter to consider when analyzing the heat balance of conductors and thus their temperature. Surface emissivity becomes more important at high temperature operation, as it plays a leading role in the radiation loss, since it depends on the fourth power of temperature. This paper analyzes the effect of surface oxidation on the emissivity of a solid copper rod conductor. It is shown that the emissivity changes. For this purpose, the temperature of the copper bar is varied from $20^{\circ} \mathrm{C}$ to about $240^{\circ} \mathrm{C}$ by applying a current of about 1450 A. A large change in the estimated emissivity value from 0.04 to 0.30 is observed, which is attributed to the oxidation of the surface of the polished copper bar. This significant change in emissivity due to the oxidation process has important consequences for the thermal behavior of copper conductors that cannot be ignored.