The problem of entropy generation in magneto-hydrodynamic free convection in a square cavity is investigated in this paper. An external magnetic field is assumed acting in the horizontal direction. Two vertical opposite walls are kept at constant but different temperatures and the two horizontal walls are well insulated. The coupled governing equations are solved by SIMPLE algorithm for three values of Rayleigh number, four irreversibility coefficients and five values of Hartmann number. The results show that: (a) the total entropy generation for the same irreversibility coefficient increases with Rayleigh number; (b) the entropy generation due to heat transfer and viscous effects for a certain value of Rayleigh number and irreversibility coefficient decreases with Hartmann number; (c) the Bejan number increases rapidly as the irreversibility coefficient decreases. The contours of streamlines, isotherm lines and iso-entropy generation lines are also plotted for , and different values of Hartmann number.

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