Entropy generation characteristics of different nanoparticle shapes are explored considering a nanofluid-cooled helical heat sink system for both laminar and turbulent flow regimes. For each flow regime, four different Reynolds numbers are considered, ranging from Re=500 to 20,000. Five different particle shapes (spherical, bricks, blades, cylindrical and platelets) are included for this comparative study, and their thermal, frictional, and total entropy generation characteristics are evaluated for four different nanoparticle volume concentrations (ϕ=0.5, 1.0, 1.5, and 2.0%), and the outcomes are compared to the base fluid case (ϕ=0%) as well as a comparison is considered among the investigated nanoparticles. Obtained results revealed that in the turbulent flow regime, the thermal entropy generation tends to decrease with increasing particle volume fraction, and the highest decrements are obtained for platelet shape (43%). The frictional entropy generation shows an opposite trend, and the platelet nanoparticles yield the highest increment, around 6.32 folds in both laminar and turbulent flow. In both flow regimes, the spherical particles have the smallest impact on the entropy generation among the examined ones. In addition to that, increment in Re results in a decrement in the thermal entropy generation, while it causes a remarkable increase in the frictional entropy generation.
