Magnetohydrodynamics natural convection and entropy generation in a hybrid nanofluid complex enclosure considering finned-heater

The current study investigates the influence of MHD on the natural heat transfer considering the irreversibility in a complex-shaped cavity with the existence of inner roundish heater with four attached fins utilizing finite element formulation. Three different cases are considered to figure out the major characteristics of temperature, stream function and total generated entropy, Nusselt number in addition to Bejan number. Concentrated attention is directed to the enclosure geometry modifications and the varied length of attached fins and their impacts. The parameters of study are ranged as follows; Rayleigh number 10(3) <= Ra <= 10(6), Hartmann number 0 <= Ha <= 60, fins' length 0.1 <= H <= 0.3. The novelty of the present work is on studying all of these parameters in the complex enclosure considering three different cases of the shape of the outer walls so that the star-shaped enclosure is classified as case 1. With increasing the length that separated between the outer arc of the star enclosure, the octagonal-shaped enclosure will appear as denoted in case 2 and 3. It had been seen that at low Rayleigh number (Ra = 10(4)), case one is the best choice in heat transfer bettering while it is the lowest case at high Rayleigh number (Ra = 10(6)). Additionally, the influence of Hartmann number on the total entropy generation reduction percentage for case three is 63.57% while it is 51.11% for case two while Hartmann number had negligible impact of entropy generation reduction for case one. Lastly, the highest Bejan number is at fin length (H = 0.3) is recorded for case one.