Thermal performance of a heat sink having open-ring pin fins (ORPF) and cooled by biologically synthesized silver-water nanofluid is explored in terms of first and second laws of thermodynamics within the present work by focusing on the arrangement of ORPFs, namely the in-line and staggered ones. Influences of four different volumetric fractions of nanoparticles (φ=0–1%) and four different Reynolds numbers (Re=500–2000) on the thermal performance and entropy generation behavior of the nanofluid are numerically evaluated. Outcomes revealed that the convective heat transfer coefficient is improved by up to 71% and 19.3% in the in-line, and 65% and 24.7% in the staggered ORPF configurations, respectively, due to the increment in Re and addition of nanoparticles (at Re=500). Moreover, a decline in the pumping power is noticed by adding φ=1% of nanoparticles at Re=1500, compared to base fluid. The pumping power, on the other hand, is increased by 10.5% at Re=2000 and φ=0% when staggered configuration is considered instead of in-line one. Thermal and frictional entropy generation rates are remarkably reduced by incorporation of nanoparticles. In addition, using staggered ORPF arrangement instead of the in-line one can decrease the frictional and thermal entropy generation rates by up to 17% and 4.4%, respectively, at Re=2000.
