J. KSIAM Vol.21, No.4, 225–244, 2017 http://dx.doi.org/10.12941/jksiam.2017.21.225 A NUMERICAL STUDY ON MHD NATURAL CONVECTIVEHEAT TRANSFER IN AN AG-WATER NANOFLUID FILLED ENCLOSURE WITH CENTER HEATER N. NITHYADEVI AND T. MAHALAKSHMI † DEPARTMENT OF MATHEMATICS,BHARATHIAR UNIVERSITY,COIMBATORE,TAMIL NADU,I NDIA E-mail address: saimaha13@gmail.com ABSTRACT. The natural convective nanofluid flow and heat transfer inside a square enclo- sure with a center heater in the presence of magnetic field has been studied numerically. The vertical walls of the enclosure are cold and the top wall is adiabatic while the bottom wall is considered with constant heat source. The governing differential equations are solved by using a finite volume method based on SIMPLE algorithm. The parametric study is performed to analyze the effect of different lengths of center heater, Hartmann numbers and Rayleigh num- bers. The heater effectiveness and temperature distribution are examined. The effect of all pertinent parameters on streamlines, isotherms, velocity profiles and average Nusselt numbers are presented. It is found that heat transfer increases with the increase of heater length, whereas it decreases with the increase of magnetic field effect. Furthermore, it is found that the value of Nusselt number depends strongly upon the Hartmann number for the increasing values of Rayleigh number. 1. I NTRODUCTION Natural convective heat transfer occurs in many engineering systems, such as power plant, home ventilation, fire prevention, reactor insulation, solar collectors, etc., [1]. Various aspects of natural convection heat transfer in enclosures have been investigated thoroughly by many researchers [2-6]. Transfer of heat from a localized heater inside an enclosure is considered in designing electronic devices and equipment cooling. An efficient cooling is essential for these electronic equipments. Therefore many researchers have investigated natural convection in enclosures with different types of heaters. Sun and Emery [7] examined conjugate heat transfer when the heater is located near the walls of enclosure with heat source both numerically and experimentally. Their results showed that for an enclosure with conductive heater, heat transfer was a function of heater conduction, fluid convection and strength of internal heating. Oztop et al. [8] investigated the effect of position of a heater in an enclosure with cold vertical walls and adiabatic horizontal walls. They showed that more enhancements in heat transfer are obtained when the heated plate located vertically than horizontally. Ben-Nakhi and Received by the editors August 5 2017; Accepted December 10 2017; Published online December 13 2017. Key words and phrases. finite volume method; heat source; isothermal heater; magnetic field; nanofluid flow; natural convection. † Corresponding author. 225