ZnO nanostructures modulate the thermo-physical properties of Therminol 55 favorably for heat transfer applications

• Published in: Journal of nanoparticle research : an interdisciplinary forum for nanoscale science and technology 2024-03, Vol.26 (3), p.42, Article 42
• Main Authors: H, Vikraman, V, Hari Suthan, K. S, Rajan, K. S, Suganthi
• Format: Article
• Language: English
• Subjects: Boundary conditions; Brownian motion; Characterization and Evaluation of Materials; Chemistry and Materials Science; Convection; Convection currents; Free convection; Heat conductivity; Heat transfer; Heat transfer coefficients; High temperature; Inorganic Chemistry; Lasers; Low temperature; Materials Science; Nanofluids; Nanoparticles; Nanotechnology; Optical Devices; Optics; Photonics; Physical Chemistry; Physical properties; Room temperature; Temperature; Thermal conductivity; Thermal properties; Thermal resistance; Thermodynamic properties; Viscosity; Zinc oxide
• ISSN: 1388-0764; 1572-896X
• DOI: 10.1007/s11051-024-05952-1

In this work, ZnO nanoparticles were used to improve the thermal performance of Therminol 55 oil. The addition of ZnO nanoparticles to Therminol 55 increased the thermal conductivity and viscosity by 6% and 43.9% respectively at room temperature (27 °C) at a nanoparticle concentration of 2 vol.%. The thermal conductivity-temperature relation of ZnO-Therminol 55 nanofluids was biphasic. Thermal conductivity enhancement was observed at lower temperatures (10% enhancement at 10 °C; ϕ  = 2 vol. %) as well as at higher temperatures (18.3% enhancement at 100 °C; ϕ  = 2 vol. %), which were attributed to the layering of Therminol 55 molecules over ZnO nanoparticles’ surface (at lower temperatures) and Brownian motion of nanoparticles (at higher temperatures) respectively. The relative viscosity of ZnO-Therminol 55 nanofluids also decreased with increasing temperature ( μ r  = 1.44 @ T  = 27 °C; μ r  ~ 1 @ T  = 140 °C). The heat transfer performance of ZnO-Therminol 55 nanofluids was tested under constant temperature boundary conditions. About 154% and 203% enhancements in overall heat transfer coefficient and test fluid side heat transfer coefficient were observed for 2 vol. % ZnO-Therminol 55 nanofluid compared to pure Therminol 55 due to the improved thermal conductivity, natural convection currents resulting from Brownian motion and particle migration. ZnO-Therminol 55 nanofluids depicting improved thermal properties at higher temperatures can be potentially used as heat transfer fluids above 100 °C, when the thermal resistance in the heat transfer fluid is rate-controlling.