Numerical Analysis of the Thermophysical Properties of Hybrid Nanofluids for Industrial Use
Okello John Achola
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Hybrid nanofluids engineered using two or more different types of nanoparticles suspended in the base fluid have numerous industrial and engineering applications. The applications range from heat transfer (coolant) fluids in industrial thermal processes, automotive industry, electronic devices, to being used in the biomedical field in areas such as nanocryosurgery, nano-drug delivery, magnetic fluid hyperthermia, etc. The current study examines the thermophysical properties of hybrid nanofluids for application as industrial coolants and lubricant additives (nanolubricants). The hybrid nanofluid (hybrid nanocoolant) consists of ethyleneglycol as the base fluid with Copper-Alumina (Cu-Al2O3), Copper-Titania (Cu-TiO2), and Titania-Alumina (TiO2-Al2O3) as the hybrid nanoparticles. The partial differential equations governing the flow of the hybrid nanofluid are formulated and transformed into a system of coupled non-linear ordinary differential equations using suitable similarity transformation variables. The shooting technique together with the fourthorder Runge-Kutta-Fehlberg integration scheme was used to obtain the numerical solutions to the coupled non-linear ordinary differential equations. The numerical analysis and simulation is achieved using MATLAB and the graphical results are depicted for the various pertinent parameters involved in the flow. The presence of nanoparticles makes the fluid susceptible to the effects of magnetic field. Increasing magnetic field intensity (𝐻𝑎) applied to the flow retards the flow of the fluid and enhances the fluid’s thermal boundary layer thickness maximizing the cooling effect of the hybrid nanofluid. The (TiO2-Al2O3/EG) hybrid nanofluid maintains a low temperature profile thus emerging as the optimal industrial coolant. For the nanolubricant study, the fluid’s velocity profiles, temperature profiles, local Nusselt number and skin friction coefficient were investigated for different pertinent parameters namely; Eckert number (𝐸𝑐), suction/injection parameter (𝑓𝑤), magnetic field intensity (𝐻𝑎), slip parameter (𝛽), nanoparticle volume fraction (𝜙), and Grashof number (𝐺𝑟). The study considered MHD incompressible boundary layer flow of engine oil-based ((MWCNTs-Cu), (MWCNTs-Al2O3), and (MWCNTs- TiO2)) conducting hybrid nanofluids past a convectively heated vertical porous plate with Navier slip boundary conditions. The study revealed increment in fluids velocity and a decrease in local skin friction with increasing values of the slip parameter (𝛽). The (MWCNTs-TiO2/engine oil) hybrid nanofluid registered the least coefficient of skin friction thus emerging as the most suitable nanolubricant. The (TiO2-Al2O3/EG) hybrid nanofluid that emerged as the best nanocoolant can be utilized in the cooling of electronic devices, transformers, in the automobile radiators, cooling of drilling equipment and sensors used in the extraction of geothermal energy, cooling of nuclear reactors etc. The best nanolubricant (MWCNTs-TiO2/engine oil) can be used as a lubricant in high temperature applications (lubrication).