Magneto-nanofluid flow in cylinder-embedded discretely heated-cooled annular thermal systems: Conjugate heat transfer and thermodynamic irreversibility

Abstract

The present work investigates magnetohydrodynamics-driven thermal-fluid flow characterization in cylinder-embedded annular thermal systems subjected to peripheral differential heating. It explores Al2O3/water nanofluid flow-associated heat transfer and entropy generation in the presence of a magnetic field and a conducting cylindrical obstruction (block). The consequence of various obstruction sizes on thermo-fluid flow behavior is also analyzed. The transport equations are handled by a finite element-based solver. The thermal-flow analysis is carried out for the relevant vital parameters such as Rayleigh number (Ra), Hartmann number (Ha), magnetic field orientation (γ), and obstruction size. Through the investigation, it is found that Nusselt number (Nu) is greatest when the internal conducting block size is the least. It can thus be inferred that flow circulation plays a dominant role in determining the Nu value. Heat flow dynamics described by the heatlines, as well as flow structure examined by the streamlines, are found to vary depending upon the obstruction size, and the field orientation (γ). Furthermore, the total entropy generation figures out that when the buoyant forces within the thermal systems are low, the entropy generation is uniform along the periphery; however, when the buoyant forces take a significantly higher value, the contours of entropy generation are seen to be more concentrated near the discretely heated and cooled walls. It is seen that if the inner conducting body size increases, the overall entropy production significantly increases. Finally, a generalized single mathematical correlation is developed for both heat transfer and entropy generation. This thermal system configuration has practical relevance and the present findings could enrich the understanding of pre-existing concepts in the area of thermal systems pertaining to effective heat-exchanging devices.