The Influence of Slots in Heat Sink Fins within a Cavity, with/without Internal Bodies, Filled with a Hybrid Nanofluid

Natural heat transfer is studied in a square enclosure containing a heat sink in the presence of a hybrid nanofluid (MWCNT and Fe3O4). The right wall is kept cool (Tc), while the left wall is hot (Th), and the upper wall and lower wall are thermally insulated. The study is carried out by making slots with different thicknesses (st = 0.01 and 0.02) and lengths (sh = 0.1 to 0.4) for each fin of the heat sink to increase heat transfer in the heat sink by using a Rayleigh number of 103 to 106 and a solid volume fraction (ϕ = 0.02). Also, internal circular cold bodies are added in the tip and between the fins with a diameter of 0.05 and different numbers (No = 2, 4, 6, 8, and 12). According to numerical results, the average Nusselt number increases with the Rayleigh number, slot thickness, and length. The optimal condition was slot thickness (st = 0.02) and length (sh = 0.4), which increased the average Nusselt number by 37.7% over solid fins. When cold circular internal bodies are present, an increase in the stream function and a better distribution of isotherm lines are generally observed. Nu increases by 62% when there are internal bodies at the tip of the fins (No = 6), 71.5% when there are internal bodies between the fins (No = 6), and 78% when there are internal bodies at the tip and between the fins (No = 12).