**ABSTRACT**

This paper concerns with the effect of a magnetic field on the entropy generation due to natural convection of Al2O3-water nanofluid flow between coaxial cylinders of aspect ratio H/D = 2. The inner and outer cylinders are maintained at hot and cold temperatures, respectively. The top and bottom walls are thermally insulated. The finite volume method was used to discretize the mathematical equations. The present results are compared with those found in the literature, which reveal a very good agreement. The influence of dimensionless parameters such as Hartmann number, Rayleigh number, solid volume fraction of nanoparticules, ϕ, and inclination angle of magnetic field on streamlines, isotherms contours, local entropy generation, mean Nusselt number, total entropy generation, St, and Bejan number is discussed. The results show that the local entropy generation are strongly influenced by the application of magnetic field. The increase in heat transfer and entropy generation by adding the nanoparticles to the base fluid depends on the magnetic field strength and direction.

**KEYWORDS**

PAPER SUBMITTED: 2017-12-23

PAPER REVISED: 2018-02-20

PAPER ACCEPTED: 2018-03-01

PUBLISHED ONLINE: 2018-04-28

**THERMAL SCIENCE** YEAR

**2019**, VOLUME

**23**, ISSUE

**6**, PAGES [3467 - 3479]

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