Determination of the emissivity, for total radiation, of small diameter platinum-10% rhodium wires in the temperature range 600-1450°C
D. Bradley, A. G. Entwistle
The method of measurement of the emissivities is described. Two different lengths of wire, of the same diameter, were electrically heated in vacuo. By this procedure the end cooling correction could be eliminated experimentally. From the readings of wire resistance and current the net rate of radiant energy loss from the wire to the surroundings, and hence the wire emissivity, could be found. The values of emissivity are compared with those for platinum wires and also with values calculated from wire resistivity on the basis of electromagnetic theory.
Materials
Curve 1
Temperature Range, K: 873-1723
Geometry θ θ' ω': ±1.5
Composition (weight percent), Specifications and Remarks: Pt-10 Rh wires (0. 00057 in. dia) from Johnson Matthey; measured in vacuum (<10-4 mm Hg).