Two-phase analysis of heat transfer of nanofluid flow in a cavity in the presence of a magnetic field, heating element, and a porous medium: A numerical approach

Abstract

By increasing the efficiency of heating systems, more heat flux can be transferred in a certain dimension, thus lowering the operating temperature, or a specific heat flux can be transferred using a smaller heat exchanger. In this study, the flow of a Newtonian nanofluid in a square cavity containing a heating element filled with a porous medium is simulated under the effect of a uniform magnetic field in different rotation angles. The finite volume method (FVM) and two-phase mixture model were used. Water is used as the base fluid and Al2O3 nanoparticles are used as the solid nanoparticles. The heating element inside the cavity, which is filled with porous medium with porosity percentage ε moves up or down to the width of the element. The fields of velocity, streamlines, and temperature are physically plotted, and Nusselt number and entropy generations diagrams are plotted. The results show that the change in the angle of the cavity and the change in position of the heating element on the hot wall have significant effects on the physical patterns. Other results indicate that with increasing volume fraction of nanoparticles and Rayleigh number (Ra), Nusselt number increases. Also, increasing the volume fraction of nanoparticles and Hartmann number (Ha) decreases the entropy generation due to heat transfer and increases the entropy generation due to friction. Also, it was found that in the cavity without a heating element, with increasing θ, the amount of local velocity increases in more places; so that, in case A and θ=90°, it reaches its maximum value in the cavity without a heating element. As can be seen, by placing the heating element at θ=0°, the maximum local velocity occurs above the heating element. Gradually, this value decreases with increasing the angle of the cavity filled with the porous medium relative to the x-axis to reach its minimum value in the cavity with θ=90°.