Numerical analysis of the effects of fins with orifices on hydrothermal and entropy generation characteristics in a cylindrical helical minichannel heat sink

To dissipate high heat flux in the cylindrical electronic devices/components (such as batteries, LED, electromotor), a cylindrical helical minichannel heat sink with circular orifices in the fin between two adjacent minichannel is designed, and the width and height of the minichannel are 1 mm and 3 mm, respectively. The hydrothermal performance and entropy generation in this new heat sink are investigated numerically. The effects of orifice sizes (theta = 0.4, 0.6 and 0.8 mm) and positions (phi = 20, 21, 22, 23 and 24 mm) on performances are examined using the full factor method to obtain the best orifice parameters. Results show that the orifices have a significant effect on the flow field and heat transfer performance with the Nusselt number increasing up to 19.7% compared to the smooth helical minichannel (SHMC), because the orifices cause the hydraulic boundary layer to reinitialize and thinner. The perforated helical minichannel (PHMC) with a larger orifice size yields a higher heat transfer efficiency. In contrast, the increase in the orifice position of PHMC shows different heat transfer trends in the studied range of Reynolds numbers (Re = 188-698). Specifically, the orifice position at phi = 22 mm is better suited for heat transfer at lower Re, while the orifice position at phi = 21 mm is optimal at higher Re. In addition, the entropy generation analysis reveals that compared with SHMC, the PHMCs produce lower thermal entropy generation. The most notable reduction in the entropy generation is observed in PL-22 (theta = 0.8 mm and phi = 22 mm), with an average decrease of 25.7%. The values of performance evaluation criteria (PEC) based on the helical channel are greater than unity, with the best PEC obtained by PL-22 under lower Re values (Re < 443) (PEC = 1.28) and PL-21 (theta = 0.8 mm and phi =21 mm) at higher Re (Re = 698) (PEC = 1.13). Moreover, a correlation for predicting Nusselt number in PHMCs is proposed, which shows good agreement with numerical data, evidenced by an average relative error of 2.5%. Overall, the results suggest that drilling orifices in the fin effectively improves heat transfer and comprehensive performances in cylindrical helical minichannel heat sinks.