Temperature-Dependent Thermal Conductivity and Absorption Coefficient Identification of Quartz Window up to 1100 K

The temperature-dependent absorption coefficient and thermal conductivity of a quartz window are obtained through experimental tests at a wide range of temperatures. A Fourier transform infrared spectrometer with a heated cavity is used for performing the transmittance measurements. The spectral absorption coefficient of the quartz window is inverted by the transmittance information at different temperatures using a genetic algorithm. Then, a quartz window-graphite plate-quartz window multilayer structure is designed, and the transient response of the structure subjected to high-temperature heating is recorded by a self-designed setup. Cooperating with the above absorption coefficient, a non-gray radiative-conductive heat transfer model is built for the multilayer structure, and the intrinsic thermal conductivity of the quartz window is identified. Finally, the effects of the temperature-dependent absorption coefficient and spectral selective features of the medium on the heat transfer characteristics are discussed. The results show that the absorption coefficient gradually increases with temperature. The intrinsic thermal conductivity of the quartz window varies from 1.35 to 2.52 W/(m·K) as the temperature rises, while the effective thermal conductivity is higher than the intrinsic thermal conductivity due to thermal radiation, specifically 26.4% higher at 1100 K. In addition, it is found that the influence of the temperature-dependent absorption coefficient on temperature of unheated side shows a trend of first increasing and then decreasing. When the absorption coefficient varies greatly with wavelength, a non-gray radiative-conductive heat transfer model should be built for the semitransparent materials.