ANALYSIS OF EMISSIVITY COEFFICIENTS

Abstract

This article presents a comprehensive investigation of the emissivity coefficient of surfaces under various physical and operational conditions. The study emphasizes the fundamental meaning of emissivity, its dependence on radiation angle, surface temperature, material properties, degree of surface treatment, and radiation wavelength. Special attention is devoted to experimental observations of how emissivity evolves during the lifetime of a surface due to oxidation, contamination, or roughness changes, and how these modifications affect the accuracy of non-contact temperature measurements. A mathematical approach is also applied to examine the influence of wavelength variations on the measured temperature values.

The research demonstrates that emissivity is not a constant property but a parameter strongly determined by physical factors such as the geometry of observation, spectral range of measuring instruments, and thermal state of the material. For example, metallic surfaces typically exhibit low emissivity, which increases when oxide layers form at higher temperatures, whereas ceramics or dielectrics tend to maintain relatively stable but wavelength-dependent emissivity values. Furthermore, experimental results confirm that angular deviation from normal measurement can lead to significant errors exceeding 5 °C, while surface treatment—such as polishing or oxidation—also induces notable variations.

The experimental setup included measurements with pyrometers, contact thermometers, and specially designed calibration surfaces, enabling comparison of contact and non-contact results. The findings indicate that neglecting emissivity variations with wavelength or surface state can result in substantial measurement inaccuracies. In practical terms, this has a direct impact on industrial processes, product quality, and safety standards.

The outcomes highlight the necessity of considering emissivity as a dynamic factor in temperature diagnostics, especially when infrared thermography or pyrometric techniques are applied in engineering, metallurgy, and materials science. The conclusions propose further research into the interaction of emissivity with specific influencing factors, aiming to develop refined correction models and measurement methodologies. Such advancements are expected to enhance the reliability of thermal monitoring systems in diverse technical applications.