Thermal and flow performance in microchannel heat sink with open-ring fins

A unique type of microchannel heat sinks with inline and staggered open-ring pin fins was developed for thermal management of high heat flux devices. The open-ring pin fin was composed of an internal cavity and two inner small and outside large rings with four openings along and perpendicular to the flow direction. Two types of flow channels, i.e., internal separated and merged passages (ISMP) and external convergent-divergent passages (ECDP), were formed. Both experimental and numerical studies were conducted to explore the flow and heat transfer characteristics of both inline and staggered open-ring pin fin microchannels (ORPFM), and their cooling effectiveness was compared with conventional rectangular microchannels. Single-phase convection tests were conducted at Reynolds number of 160-694 using deionized water. The results indicated the inline and staggered ORPFM presented a 56-220% and 77-260% enhancement in Nusselt number compared to conventional rectangular microchannels, respectively. The ORPFM induced periodic flow separations and convergences, successive flow mixing, and periodic interruptions and redevelopment of boundary layers, which contributed to the above heat transfer enhancement. The staggered ORPFM presented a 6-35% larger heat transfer performance, whereas it induced a 9-27% larger pressure drop than the inline one. The staggered ORPFM showed favorable overall thermal-hydraulic performance, and is more favorable for heat dissipation in high heat flux devices. A unique type of microchannel heat sinks with inline and staggered open-ring pin fins was developed for thermal management of high heat flux devices. The open-ring pin fin was composed of an internal cavity and two inner small and outside large rings with four openings along and perpendicular to the flow direction. Two types of flow channels, i.e., internal separated and merged passages (ISMP) and external convergent-divergent passages (ECDP), were formed. Both experimental and numerical studies were conducted to explore the flow and heat transfer characteristics of both inline and staggered open-ring pin fin microchannels (ORPFM), and their cooling effectiveness was compared with conventional rectangular microchannels. Single-phase convection tests were conducted at Reynolds number of 160-694 using deionized water. The results indicated the inline and staggered ORPFM presented a 56-220% and 77-260% enhancement in Nusselt number compared to conventional rectangular microchannels, respectively. The ORPFM induced periodic flow separations and convergences, successive flow mixing, and periodic interruptions and redevelopment of boundary layers, which contributed to the above heat transfer enhancement. The staggered ORPFM presented a 6-35% larger heat transfer performance, whereas it induced a 9-27% larger pressure drop than the inline one. The staggered ORPFM showed favorable overall thermal-hydraulic performance, and is more favorable for heat dissipation in high heat flux devices.