Thermal Radiation Properties of Molten Salts (3rd Report, Properties of Alkali Metal Carbonates)

Thermal radiation properties are investigated by a spectral experiment on three molten alkali metal carbonates: lithium carbonate, sodium carbonate and potassium carbonate. Reflectance spectra of the salt layers are measured at wavelengths from 0.5 to 13.0 µm. The results are analyzed to obtain the spectra of the refractive index n and absorption coefficient K. Since the semi-transparent wavelength region of the salts ranges in the main part of the Planckian distribution, the values of K are obtained most carefully. The spectra of n and K are described by continuous functions of wavelength of radiation for the heat transfer engineering application. The fundamental features of the radiation properties are summarized on the molten nitrides, chlorides and carbonates of the three alkali metals, lithium, sodium and potassium.