Magnetic control of irreversibility production due to nanofluid free convection in a 3D open trapezoidal cavity

الملخص EN

This study analyzes how entropy production can be controlled via a magnetic field in a 3D open trapezoidal enclosure filled with nanofluid.

The inclined left side is heated and the right one is fully opened to allow the entrance of cold nanofluid while the other sides are assumed to be perfectly insulated.

Based on the finite element method, the investigation was carried out according to the following variables: Rayleigh number (103 ≤ Ra ≤ 105 ), magnetic field inclination angle in the range (0° ≤ α ≤ 90°), nanofluid concentration (0 ≤ φ ≤ 0.05) and Hartmann number (0 ≤ Ha ≤ 100).

The results indicated that the increase in the nanoparticles-concentration increases the total produced entropy with and without the application of the magnetic field.

It was also found that for all inclination angles at all Ha values, the increase in Ra values resulted in an increase in total produced entropy, which is mainly predominated and controlled by heat transfer irreversibility while viscous dissipation had negligible effects.

Furthermore, the application of the external magnetic field resulted in convective heat transfer suppression and diminished the total entropy production rate.

Moreover, the minimum of irreversibility production occurred for α=90° while its maximum occurred with a magnetic field inclination α=60°.

The results of the present study can be used to minimize entropy production in thermal energy systems.

Indeed, in the current case study, an inclination angle α=60° must be avoided whereas the optimum inclination for the magnetic field is α=90°.