Entropy generation and exergy analysis of Ag–MgO/water hybrid nanofluid within a circular heatsink with different number of outputs

This paper presents a thermodynamic analysis of a mini circular heatsink (HS). The investigated HS features four different types with a varying number of outputs and Ag–MgO/water hybrid nanofluid (NF) as the working fluid. In different types of HSs, the number of doors created between the parts of HSs is different. Computational and experimental analyses of this system are conducted to examine the first and second law efficiencies. A physical model of the HSs is, firstly, fabricated and tested for various flow rates. Numerical simulations are then performed using a finite element method. By changing the Reynolds number (Re) and the volume fraction of nanoparticles (φ) for all types of the HS, entropy generation (EnG) and exergy losses are evaluated. The results show that the copper HS could perform more cooling than the aluminum HS. Further, an increment in the Re substantiates thermal EnG (S˙Th)and reduces the frictional EnG (S˙F), which ultimately reduces the total EnG rate (S˙Tot). Yet, the addition of φ slightly enhances EnG. Among the investigated types of HSs, the 4-door type features the lowest EnG. An enhancement in the Re leads to a reduction in the exergy loss as well as the first and second law efficiencies. It is concluded that the addition of φ does not make any favorable effect on the system thermodynamics, as it amplifies EnG, and boosts the losses. An increase of 2% of nanoparticles reduces the maximum the first and second law efficiencies of system by 5.6% and 2.5%, respectively.