The effect of arrangement type and pitch ratio on the performance of micro-pin-fin heat sinks

This study focuses on comparison of in-line and staggered arrangements of circular micro-pin fins (MPF) in a rectangular micro-channel with the dimensions (l′ × w′ × h′) of 0.5 × 1.5 × 0.1 mm3. The height (H) and diameter (D) of the MPFs are both 0.1 mm. Two horizontal (SL) and vertical (ST) distances of 0.15 and 0.3 mm are considered with each type of arrangement, which results in four in-line and four staggered configurations. The simulations are run at five Reynolds numbers (Re) between 20 and 150, and a constant heat flux (HF) of 30 W cm−2 was applied through the bottom surface of the MHS as well as the liquid interacting surfaces of MPFs. The results are analyzed using four evaluative parameters, namely pressure drop, friction factor (FF), Nusselt number (Nu) and thermal–hydraulic performance index (TPI). These parameters were significantly affected by the wake length behind MPFs. In cases with a large horizontal pitch ratio (SL/D = 3), the wake length behind all columns (except the last one) could extend more (up to 2D) which in cases with the in-line arrangement typically resulted in higher pressure drop and FF (up to 10%) compared to similar cases with SL/D = 1.5. In cases with ST/D = 3, the larger available cross section among MPFs typically resulted in lower pressure drop (up to 36%) and Nu (up to 8%) compared to similar cases with ST/D = 1.5. With the same SL/D and ST/D, staggered arrangements generally had higher pressure drop, FF and Nu (up to 56, 39 and 9%, respectively) compared to similar in-line arrangements. Finally, the best TPI was attained with staggered arrangements with ST/D = 1.5 with 10% higher TPI compared to the reference case.