Effects of pin-fins geometry and nanofluid on the performance of a pin-fin miniature heat sink (PFMHS)

Experimental and numerical trials are conducted on the pin-fin miniature heat sink (PFMHS) having different shapes of pin-fins, including square, rectangular, rhombic, triangular, hexagonal, trapezoidal, circular, and half circular. Thermo-fluidic characteristics of the studied cases are presented and discussed for water as working fluid. Then, Al2O3/water nanofluid is tested in all cases and the obtained outcomes are compared with water. The experimental data disclose that the shape of pin-fins considerably affects both the thermal and the hydrodynamic characteristics of PFMHS. At the studied range of Reynolds number (i.e. 100-900), the highest values of overall heat transfer coefficient and pressure drop are recorded for the half-circular PFMHS. Based on the considered performance indexes, the circular and hexagonal PFMHSs have the best overall hydrothermal performance. The numerical results are used to explain the velocity and temperature fields in different PFMHSs. It is detected that each shape of pin-fins leads to individual forms of velocity vectors and temperature contours. Furthermore, adding low weight fractions of Al2O3 nanoparticles (i.e. 0.3% and 0.6%) to water leads to considerable enhancements in the overall heat transfer coefficient of all PFMHSs with certain penalties in the pressure drop. However, the experimental data show that the overall efficiency of PFMHSs improves in the range from 5% to 15%.