Experimental investigations of the thermophysical properties of MWCNT–CeO2–Fe3O4 nanofluids

Abstract

Hybrid and tri-hybrid nanofluids have emerged as promising candidates for advanced thermal management due to their enhanced heat transfer capabilities compared to mono-nanoparticle nanofluids and conventional fluids. However, the combined influence of nanoparticle composition and concentration on thermophysical and electrical properties remains insufficiently understood. In this study, nanofluids composed of multi-walled carbon nanotubes (MWCNT), cerium oxide (CeO 2 ), and magnetite (Fe 3 O 4 ) were synthesized at varying volumetric concentrations and weight ratios, including Fe 3 O 4 (15%)/CeO 2 (80%)/MWCNT (5%), Fe 3 O 4 (5%)/CeO 2 (80%)/MWCNT (15%), CeO 2 (80%)/MWCNT (20%), and Fe 3 O 4 (20%)/CeO 2 (80%). The samples were characterized through morphological analysis, thermal conductivity measurements, electrical conductivity evaluation, and viscosity assessment under controlled temperature conditions. The results reveal that thermal conductivity increases with temperature for all formulations, with the CeO 2 (80%)/MWCNT (20%) nanofluid exhibiting the highest thermal conductivity. Electrical conductivity was maximized in the tri-hybrid nanofluid Fe 3 O 4 (15%)/CeO 2 (80%)/MWCNT (5%), indicating the effectiveness of low MWCNT content, while higher MWCNT concentrations adversely affected electrical performance. Morphological analysis confirmed adequate nanoparticle dispersion, and viscosity increased with nanoparticle concentration, with the 0.1% volume fraction sample showing the highest viscosity. An optimal formulation was identified at low MWCNT concentration (5%) combined with Fe 3 O 4 (15%), achieving a balance between enhanced thermal and electrical performance and manageable viscosity. These findings provide valuable insights for the design and optimization of hybrid nanofluids for energy and heat transfer applications.