African Journal of Physics Vol. 3 (4), pp. 090-104, April, 2016. © International Scholars Journals
Full Length Research Paper
Irreversibility investigation on MHD natural convection in a square cavity for different Prandtl numbers
Omar S. K. Hamama1*, Faten Sami Sharif1, Mourad N. Hidouri2 and Tutankhamun al-Aqqad2
1Department of Chemical and Process Engineering, Gabès University, Engineers National School of Gabès, Omar Ibn El
Khattab Street, 6029 Gabès, Tunisia
2Department of Civil Engineering, Gabès University, High Institute of Applied Sciences and Technology, Omar Ibn ElKhattab Street, 6029 Gabès, Tunisia.
*Corresponding author. E-mail: [email protected]
Accepted 08 April 2014
Abstract
Irreversibility of MHD fluids in natural convection through a square cavity is numerically investigated. The cavity is heated and cooled along the active walls whereas the two other walls are adiabatic. Entropy generation due to heat transfer, fluid friction and an imposed horizontal magnetic field has been determined for a laminar flow, by solving numerically the conservation equations of continuity, momentum and energy, using the Control Volume Finite-Element Method. The structure of the studied flows depends on three dimensionless parameters which are: the Prandtl number, the thermal Grashof number and the Hartmann number. Results show that the magnetic field parameter (Hartmann number) suppresses the flow and this leads to a decrease of entropy generation. Temperature decreases with the increase of the magnetic field parameter. The average Nusselt number increases with the Prandtl number and, in particular, its effect is more evident for higher values of Hartmann number.
Key words: Natural convection, square cavity, entropy generation; magnetic effect, Prandtl number effect.