Study of cobalt ferrite/engine oil nanofluid flow in a closed porous triangular cavity

Purpose Engine oil-based nanofluid is primarily used as a nanolubricant in many industrial and engineering processes. Due to various applications of engine oil-based nanofluid in the auto industry, this study explores the use of engine oil as a base fluid with cobalt ferrite nanostructures dispersed in a closed triangular enclosure. Design/methodology/approach The nanofluid is in a closed triangular porous conduit. The horizontal boundary is heated uniformly and sinusoidally, while the congruent walls are kept isothermally cooled. The walls are stationary, and the Boussinesq approximation models the free convection within the conduit. Scaling analysis converts the transport PDEs into non-dimensional forms, which are then solved numerically using a penalty-based finite element method. Findings The effects of Darcy number (Da: 10−5 ≤ Da ≤ 10−3), Rayleigh number (Ra: 103 ≤ Ra ≤ 106) and cobalt ferrite concentration (ϕns: 0.01% ≤ ϕns ≤ 0.05%) on average Nusselt number, streamlines, local Nusselt number and temperature are explained graphically. A comparison with existing literature for a specific case is also provided. The dispersion of nanostructured particles into the engine oil significantly enhances the overall rate of heat transfer within the enclosure up-to 15%. Research limitations/implications The study focuses on cobalt ferrite nanoparticles and engine oil, limiting the generalization of the results to other types of nanoparticles or base fluids with different thermal properties. Practical implications The findings of this study have several practical implications for enhancing heat transfer in engineering applications. The observation that the average Nusselt number increases with higher percentages of nano-solids and Rayleigh number suggests that the use of cobalt ferrite/engine oil nanofluid can significantly improve thermal performance in systems requiring efficient heat dissipation. The higher heat transfer rate for uniformly heated conditions (UHC) compared to sinusoidally heated conditions (SHC) implies that maintaining a uniform heating profile can optimize thermal efficiency. The higher local Nusselt number on the inclined wall compared to the bottom wall highlights the importance of wall orientation in designing heat exchangers and cooling systems to maximize heat transfer. Additionally, the increased circulation pattern with a higher Darcy number indicates that permeability in porous media can enhance convective flow, thereby improving overall thermal management. The symmetric pattern of streamlines and isotherms along the line X = 1 provides insights into achieving uniform temperature distribution, which is crucial for applications like electronic cooling, where consistent thermal conditions are necessary to prevent hotspots and ensure reliability. Social implications Overall, these findings can guide the design and optimization of various thermal systems, the economic and environmental impact of nano technology leading to more efficient and effective cooling solutions. Originality/value To the best of the authors’ knowledge, no investigation has been investigated yet that explores the free convective flow of a nano-lubricant inside a porous triangular closed cavity with a differentially heated horizontal wall.