Temperature profiles and thermal losses in 150 W high-intensity discharge lamps

Abstract

A series of 150 W quartz metal-halide test lamps containing four different chemistries has been studied with optical emission spectroscopy and x-ray absorption imaging. The four chemistries are pure Hg, Hg–HgI2, Hg–NaI and Hg–NaI–DyI3. Core temperatures and comprehensive distributions of Hg vapour densities were measured and combined to obtain comprehensive gas temperature distributions. The concentrations of additives in these specially designed test lamps were found to be much smaller than is typical for a commercial metal-halide lamp. As a consequence, the core temperatures in all lamps are largely characteristic of a pure Hg discharge. The gas temperature distributions have been used to determine power losses resulting from thermal conduction through the Hg vapour. The fraction of total input power dissipated thermally was found to be 0.49 ± 0.01 in pure Hg, similar to published measurements for such lamps. In the Hg–NaI and Hg–NaI–DyI3 lamps, thermal losses are 0.41 ± 0.01 and 0.42 ± 0.01, respectively. The Hg–HgI2 lamp has thermal losses of 0.29 ± 0.03.