Abstract
Entropy generation for a paramagnetic fluid in a square enclosure with thermomagnetic convection is numerically investigated under the influence of a magnetic quadrupole field. The magnetic field is calculated using the scalar magnetic potential approach. The finite-volume method is applied to solve the coupled equation for flow, energy, and entropy generation. Simulations are conducted to obtain streamlines, isotherms, Nusselt numbers, entropy generation, and the Bejan number for various magnetic forces (1 ≤ γ ≤ 100) and Rayleigh numbers (104 ≤ Ra ≤ 106). In the absence of gravity, the total entropy generation increases with the increasing magnetic field number, but the average Bejan number decreases. In the gravitational field, the total entropy generation respects the insensitive trend to the change of the magnetic force for low Rayleigh numbers, while it changes significantly for high Rayleigh numbers. When the magnetic field enhances, the share of viscous dissipation in energy losses keeps growing.
Highlights
With the development of superconducting magnets providing strong magnetic induction, the study of thermomagnetic convection is becoming attractive
The results showed that the magnetic field and the presence of nanoparticle had a substantial influence on flow pattern, heat transfer, and entropy generation
It is assumed that the irreversibility due to the magnetic field is ignored because the electrical conductivity of the paramagnetic fluid is infinitely small
Summary
With the development of superconducting magnets providing strong magnetic induction, the study of thermomagnetic convection is becoming attractive. Kenjeres et al [22,23], numerically and experimentally, studied the flow and heat transfer of a paramagnetic fluid under various strong non-uniform magnetic field gradients. Jery et al [31] numerically investigated the influence of an inclination angle of the magnetic field on entropy generation in natural convection for air and liquid gallium. Mahmud and Fraser [33] studied entropy generation in a porous cavity for laminar natural convection in the presence of the magnetic field acted towards the direction of gravity. The effects of Rayleigh number and magnetic force number on the total entropy generation (Stotal ), average Bejan number (Beav ), and average Nusselt number (Num ) are studied to analyze the relative importance of heat transfer and fluid friction irreversibilities
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