Effect of twisted rib on the hydrothermal performance and entropy generation behavior in minichannel heat sinks cooled by biologically synthesized Ag/water nanofluid

This numerical research study focuses on impacts of using twisted rib geometry on the hydrothermal performance and entropy generation characteristics of biologically synthesized Ag/water nanofluid flowing in heat sink ‌minichannels. To this end, twelve different twisted rib geometries (Case 1 to 12) were designed where the double-row ribs were twisted at the bottom and top portions with twist angles between − 45° and + 45°. To elucidate the cooling performance comprehensively, four different Reynolds numbers (Re = 500, 1000, 1500, and 2000) and four different nanoparticle concentrations ( \( \varphi \hspace{0.17em}\) $\phi$ = 0%, 0.1%, 0.5%, and 1%) were included in the numerical computations. Results revealed that using twisted ribs significantly smoothen the fluid flow and reduces pressure drop remarkably depending on twist angles, nevertheless, it deteriorates the cooling performance. In Case 12, the convective heat transfer coefficient reduces by up to 15.8% at Re = 2000 and \( \varphi\) $\phi$ =1%, compared to the base case. However, pumping power requirement is decreased by 43.9% in this case. Nanoparticle incorporation contributes to enhancement of convective heat transfer coefficient by up to 13.5% at the lowest Re. Frictional entropy generation considerably decreases (up to 31%) when twisted ribs are utilized. However, thermal entropy generation can increase up to 36%, due to ineffective cooling with twisted ribs. This work can be regarded as a first study in the field concerning the effects of top and bottom twist angles on hydrothermal performance and entropy generation in nanofluid-cooled mini-channel heat sinks.