Impacts of conductive inner L-shaped obstacle and elastic bottom wall on MHD forced convection of a nanofluid in vented cavity

Abstract

Forced convection of nanofluid in a vented cavity with elastic bottom wall is studied by using an inner conductive L-shaped object and magnetic field. Simulations are performed using the finite element method when the impacts of various pertinent parameters, such as Reynolds number (between 100 and 500), Hartmann number (between 0 and 40), elastic modulus of the flexible wall (between10and109 solid nanoparticle volume fraction (between 0 and 0.04), size (between 0.1 and 0.4H), inclination (between - 90 and 90) and location (xc between 0.25 and 0.75Handycbetween 0.15 and 0.65H) of the L-shaped object on the fluid flow and heat transfer features, are investigated. It was observed that wall flexibility effects are influential for the configuration with strong convection and maximum of11%enhancement in the average heat transfer rate for the bottom wall is achieved. Suppression of the recirculations in the vented cavity and around the L-shaped object is observed with magnetic field. It is observed that impact of magnetic field on heat transfer enhancement is different for different segments of hot wall. When the cases with the highest magnetic field and in the absence of magnetic field are compared, the average heat transfer enhancement of5.5%is achieved for bottom elastic wall while24.5% of reduction in the average heat transfer is seen for upper hot wall. The overall Nusselt number reduces slightly when the magnetic field strength is increased. Significant impacts of the size, inclination and location of the of the L-shaped conductive object on the fluid flow such as branching of the main flow stream, size of the vortex below the inlet port and heat transfer are observed.31.6%rise of the average heat transfer for left vertical wall and34.6% reduction of average heat transfer for bottom wall are achieved when the minimum and maximum of the orientation angles are compared. The location of the L-shaped object has a significant impact on the flow and thermal pattern variations. The highest variation in the contribution to the overall heat transfer is seen for right vertical hot wall segment when the Nusselt numbers at the lowest and highest values of the horizontal and vertical locations of the object are compared. L-shaped object was found to be an efficient tool to control the heat transfer features of the vented cavity. Nanofluid inclusion resulted in heat transfer enhancement in the range of 8.5-16.5% while amount of enhancement is different for different hot wall segments either in the absence or in the presence of magnetic field effects. Finally, a polynomial-type correlation for the average Nusselt number of each hot wall segments of the vented cavity is proposed for water and for nanofluid at phi=0.04.