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This study examines the flow and thermal behavior of a power-law ferrofluid in a differentially heated enclosure containing a rectangular permanent magnet. The novelty of the present study lies in its exploration of the combined effects of magnetic and gravitational convection on the flow and thermal behavior of a power-law ferrofluid in the presence of a permanent magnet with varying aspect ratios. Unlike previous studies, this work specifically investigates how the magnet's aspect ratio, location, and the ferrofluid's rheological properties influence heat transfer, particularly in microgravity environments. Moreover, the study assesses the impact of the temperature number and the magnetic and gravitational Rayleigh numbers on the flow, temperature distribution, and Nusselt number variations. Findings indicate that strong gravitational effects can hinder magnetic convection, whereas, in microgravity conditions, heat transfer is maximized with a thin magnet (aspect ratio 1:9) in the cavity, yielding up to a 94 % increase in the average Nusselt number compared to a square magnet of the same volume. The average Nusselt number can increase up to four times by reducing the power-law index from 1.3 to 0.7, and by about 70 % when the magnet is moved towards the left hot wall compared to its central placement.

The present study focuses on numerical simulations of magnetohydrodynamic mixed convection and entropy formation in a lid-driven wavy enclosure filled with non-Newtonian power-law ferrofluid. The physical model is a two-dimensional wavy square chamber with thermally adiabatic horizontal boundaries, while the right and left vertical walls maintain a constant temperature of the T C and T H , respectively. For mapping the wavy domain to a simple square domain the Cartesian curvilinear coordinates are used. The governing equations are solved using the finite volume method to explore the mixed convection characteristics in terms of heat transport, velocity, streamlines, isotherms, and entropy formation. Pertinent non-dimensional parameters, such as the Reynolds number (Re), Hartmann number (Ha), power-law index (n), ferroparticle volume fraction (ϕ ), and a fixed Prandtl number ( Pr = 6.8377 ), are used for the numerical simulation. According to the findings, the mean Nusselt numbers ( Nu ¯ ) grow when Ha is reduced and Re, n and ϕ are augmented, and the highest magnitude of Nu ¯ is found, while 4 % ferroparticles are added to the base fluid. The influence of key variables on total entropy production (E s) t reduced by raising Ha. [ABSTRACT FROM AUTHOR]

Magnetohydrodynamic (MHD) natural convection of non-Newtonian ferrofluid and entropy generation in a square enclosure containing a wavy cylinder was investigated. The inner wavy cylinder was assumed to be heated and the outer square enclosure to be cold. The ferrofluid's rheology was presented by the power-law model, while density fluctuations owing to thermal expansion were described using the Boussinesq approximation. Numerical calculations had been performed using dimensionless parameters such as Hartmann number, power-law index, Rayleigh number, wave number, and volume fraction. Results are discussed in terms of isotherms, velocity field, average Nusselt number, and entropy generation, taking into account the variations in physically significant parameters. Results indicate that thermal convection dominates the isotherms of shear-thinning fluids, while conduction is more prominent in shear-thickening fluids. The power-law index (n) greatly influences the streamlines and isotherms. The non-Newtonian ferrofluid's average Nusselt number ( Nu ¯ ) rises as the Hartmann number is reduced and the Rayleigh number (Ra) is increased. In this simulation, the maximum value of Nu ¯ is found to be 8.38 because of the addition of ferroparticles. Additionally, the irreversibility caused by fluid friction, heat transfer, and magnetic field for the shear-thinning (n < 1), Newtonian (n = 1), and shear-thickening (n > 1) cases can be minimized by using the ideal parametric combination. [ABSTRACT FROM AUTHOR]

The aim of this study is to analyze the thermo-magnetic-gravitational convection of a non-Newtonian power law ferrofluid within a circular cavity. The ferrofluid is exposed to the magnetic field of a permanent magnet. The finite element method is employed to solve the non-dimensional controlling equations. A grid sensitivity analysis and the validation of the used method are conducted. The effect of alterable parameters, including the power law index, 0.7 ≤ n ≤ 1.3, gravitational Rayleigh number, 104 ≤ RaT ≤ 106, magnetic Rayleigh number, 105 ≤ RaM ≤ 108, the location of the hot and cold surfaces, 0 ≤ λ ≤ π/2, and the length of the magnet normalized with respect to the diameter of the cavity, 0.1 ≤ L ≤ 0.65, on the flow and heat transfer characteristics are explored. The results show that the heat transfer rate increases at the end of both arcs compared to the central region because of buoyancy effects, and it is greater close to the hot arc. The location of the arcs does not affect the heat transfer rate considerably. An increase in the magnetic Rayleigh number contributes to stronger circulation of the flow inside and higher heat transfer. When the Kelvin force is the only one imposed on the flow, it enhances the heat transfer for magnets of length 0.2 ≤ L ≤ 0.3. [ABSTRACT FROM AUTHOR]

• Thermal performance analysis for cooling a hot oval object via non-Newtonian ferrofluid free convection under effective strategies. • Improving the thermal performance of the system by changing the position of magnetic field applied and via variation of chamber inclination angle. • The possibility of managing the system thermal performance, controlling the effect of the magnetic field and the strength of buoyancy forces through the application of uniform heat absorption. The subject of equipment cooling has always been one of the most important issues that has imbibed the attention of many researchers. In addition to this matter, the system thermal performance analysis in which the cooling process takes place is very momentous. Cooling of an electronic component in a limited space is one of the cases of investigating these phenomena. Due to the importance of this issue, via LBM, the cooling of a hot body through the process of natural convection has been simulated. The cooling chamber is a tilted trapezoidal and contains a non-Newtonian ferrofluid, while the whole set, is under the effect of the magnetic field in different positions. By calculating the amount of entropy produced and the average Nusselt value under the impact of heat absorption, the best thermal performance was determined in this present work. Magnetic field strength (0 ⩽ Ha ⩽ 90), buoyancy forces strength (10 4 ⩽ Ra ⩽ 10 6), the fluid behavioral index (0.8 ⩽ n ⩽ 1.2), heat absorption coefficient (- 20 ⩽ Δ ⩽ 0), the angle of chamber placement (0 ⩽ ζ ⩽ 270), the position of applying magnetic field (0 ⩽ R ⩽ 2H 3) have been evaluated as the main variables. Based on the outcomes, for applying the magnetic field in the position of the middle third of the enclosure, the greatest effect of increasing the Hartmann value is observed. The highest thermal performance coefficient of the system can be obtained for the highest Rayleigh value, the lowest Hartmann value in the absence of heat absorption for the shear thinning fluid. By changing the angle of chamber placement, the system thermal performance can be effectively affected, so that the worst performance was reported at an angle of 270 degrees. For the highest value of heat absorption coefficient, the change in the values of the Hartmann number, power-law index and the Rayleigh number is not noticeable. [ABSTRACT FROM AUTHOR]