Akademik Veri Yönetim Sistemi
ENGINEERING SCIENCE AND TECHNOLOGY-AN INTERNATIONAL JOURNAL-JESTECH, cilt.25, ss.1-10, 2021 (SCI-Expanded)
Heavy machinery operating in outdoor environments is exposed to both solar radiation and intensive load-bearing during operation. The long operating life of these machines and their components is enabled by the greases used in their bearings. The thermal properties of these greases play a crucial role in dissipating both the heat generated by friction in the bearings and the heat absorbed via solar radiation. In this study, we focus on maintaining successful heat transfer management in these machines. We select two types of grease, thickened with lithium and caoutchouc, containing CuO, TiO2 and graphite microparticles at 0.02, 3.33 and 10 wt%., respectively, which are used as additives to improve the heat transfer effects. A test rig is prepared to investigate the changes in temperature and torque under real operation conditions. The radiative properties of the non-additive greases are examined in the ultraviolet-visible range, and the greases with additives are examined over a wavelength range of 2.5–20 μm. The absorption properties of the greases are numerically determined based on the discrete dipole approximation for two different values of the imaginary part (k) of the complex refractive indices (m = n + ki) of the additive materials. Uncertainty analyses of the experimental results were performed using SPSS software. The temperature and torque distributions varied according to the weight fraction of the metallic microparticles and the type of grease, with the caoutchouc-thickened grease reaching higher temperatures and torques than the lithium-thickened grease. The temperature distributions of the lithium-thickened grease with additives were lower than for the same grease with no additives, while the temperature distributions of the caoutchouc-thickened grease with additives were higher than those for the same grease with no additives. The absorption values of the greases containing additives were lower than for samples with no additives in the infrared wavelength spectrum, except for a mixture of graphite and TiO2 at 10 wt%. The added microparticles positively influenced the heat transfer management of the greases.