Impact of pin-fin structural parameters on flow and heat transfer in embedded hybrid microchannel heat sinks based on a hotspot-oriented comprehensive evaluation framework

• A novel embedded hybrid microchannel with pin–fin structures is proposed for efficient microscale thermal management under high heat flux conditions. • The effects of pin–fin geometry, height, and porosity on flow and heat transfer are systematically analyzed through CFD simulations. • A comprehensive performance evaluation system (R th , ΔP, Nu, f, PEC) is established to assess thermo-hydraulic characteristics. • Field synergy theory is employed to reveal the intrinsic mechanism of enhanced heat transfer via the temperature–velocity field interaction. • The circular pin–fin demonstrates superior thermal performance with reduced pressure drop and improved field synergy.、 • The optimized pin–fin height (0.12 mm) and porosity (0.18) significantly enhance the performance evaluation coefficient (PEC) and reduce the field synergy angle. Hybrid microchannels with pin–fin structures have demonstrated strong potential for mitigating localized hotspots in high heat flux electronic devices. Embedded microchannels further enhance thermal performance by shortening the heat transfer path within the silicon substrate. In this study, a hotspot-oriented pin–fin embedded microchannel heat sink is proposed, in which pin–fin structures are selectively integrated into the central high heat flux region to achieve efficient localized cooling. A three-dimensional computational fluid dynamics (CFD) model is developed to systematically investigate the effects of pin–fin structural parameters, including geometry shape, height, and porosity. Rather than relying on isolated performance indicators, a comprehensive evaluation framework is developed by integrating multiple thermal–hydraulic metrics, including thermal resistance ( R th ), pressure drop (Δ P ), Nusselt number ( Nu ), friction factor ( f ), and performance evaluation criterion ( PEC ). In addition, field synergy theory was incorporated to elucidate the coupling characteristics between the velocity field and the temperature gradient field. This framework enables a physically consistent assessment of hotspot cooling performance and elucidates the mechanisms governing heat transfer enhancement. The results show that the introduction of pin–fin structures significantly improves hotspot thermal performance. Among the investigated configurations, circular pin-fins exhibit lower pressure losses and more favorable field synergy characteristics, leading to superior overall performance. Moreover, optimal pin–fin height (0.16 mm) and porosity (0.18) are identified through the proposed evaluation framework, yielding a marked enhancement in PEC and a reduced field synergy angle. The proposed comprehensive evaluation framework and associated physical insights offer practical and generalizable guidance for microscale thermal management of high-power density electronic devices.