The effects of pin-fin shapes on heat sink effectiveness in the presence of a turbulent nanofluid regime

In this study, the effects of adding pin-fins on heat sink effectiveness were investigated. To boost the pin-fin efficacy on heat rejection capability, four cross-sections were defined. Two arrangements (ES and ET) were defined to examine the effects of velocity patterns on heat transfer and irreversibility. To solve the problem, the transient solution of the momentum, continuity, and energy equations for nanofluid was utilized. Increasing the velocity in the channel increases the amount of velocity gradient especially between the fins. But in different arrangements and different velocities, using different fins may lead to a reduction in entropy generation due to viscous dissipation. Velocity changes between the fins are very important in this regard. The ET arrangement results in higher entropy generation due to viscous dissipation compared to another model, indicating rapid velocity changes in this arrangement. The fin with better heat transfer has lower entropy generation. Better heat transfer reduces heat loss. It also reduces the temperature gradient and sudden temperature changes in this area, resulting in less thermal entropy generation. The use of brick-shaped nanoparticles results in less thermal entropy generation due to the higher thermal conductivity of this type of nanoparticles. It was found that the total entropy generation decreased with fluid velocity, leading to an improvement in heat transfer. Also, the circular fin has minimum thermal entropy generation and maximum heat transfer. Between different arrangements, the TE model has less total entropy generation.