Thermal conductivity enhancement in hybrid Co@MWCNT/SiC nanofluids: An experimental investigation

In this study, we investigated the thermal conductivity characteristics of MWCNT, cobalt-encapsulated MWCNT (Co@MWCNT), and hybrid Co@MWCNT/SiC nanofluids, focusing on their thermal conductivity coefficients and specific heat under varying temperature and volume fraction conditions. The cobalt nanoparticles encapsulated in carbon nanotubes were synthesized using chemical methods and characterized through TEM, XRD, and FTIR techniques. The results indicate that cobalt nanocrystals are successfully encapsulated within carbon nanotubes, and SiC nanoparticles exhibit strong interactions with them. Notably, the hybrid composites can produce stable nanofluids with magnetic properties. The thermal conductivity coefficient is influenced by the pH of the solution, with optimal values typically found between pH 6 and 8 due to enhanced nanoparticle dispersion and reduced agglomeration in this range. As the concentration of cobalt and SiC nanoparticles increases, the thermal conductivity follows the trend of hybrid composites > Co@MWCNT > MWCNT. For instance, a 0.01 % increase in the volume fraction of hybrid nanoparticles can lead to a thermal capacity increase of up to 33 % compared to the base fluid. Moreover, applying a magnetic field of 0.05T can alter the thermal conductivity coefficient by enhancing the magnetic order of the cobalt atoms, often resulting in a 50 % increase in thermal capacity. Overall, the specific heat of these nanofluids varies with temperature and volume fractions, demonstrating a strong dependence on these factors. This study enhances the understanding of hybrid nanofluid properties and lays the groundwork for their practical applications in thermal management and energy systems.