Heat transfer and two-phase flow of deionized water in heat sink with micro-pin fins

• Micro-pin fins enhance HTC by ∼47 % over plain surface. • In-line micropillar arrays achieve ∼60 % higher HTC at 1200 kg/m²s versus plain surface. • Staggered arrays yield 20 % and 35 % HTC gains at inlet subcooling of 10°C and 20°C, respectively. • Increasing mass flux intensifies convective boiling, consistently boosting HTC. • Higher inlet subcooling delays the Onset Nucleate Boiling but enhances single-phase convective heat transfer. Numerous studies have focused on maximizing heat dissipation from compact surfaces due to advancements in microfabrication technology. Progress in the field requires efficient methods for thermal management, encompassing both single-phase and two-phase heat transfer in flow and pool boiling. Surface modifications, such as extended structures, are promising ways to enhance heat transfer efficiency. Among these modifications, pin fin heat sinks have been extensively researched, offering improved heat transfer through surface area augmentation and enhancement of fluid-solid interactions. In this context, the current study analyzes how the geometry and arrangement of micro-pin fins influence the thermal and fluid dynamic behavior during the two-phase flow of deionized water. The square micro-pin fins have a width of 300 μm, a height of 350 μm, and an inter-fin spacing of 250 μm and were manufactured on a copper substrate. For comparison purposes, a single-channel heat sink was also experimentally analyzed. Two-phase flow tests were conducted over a wide range of input heat power, with different mass velocities (1000 and 1200 kg/m²s) and at different inlet subcooling (10 and 20°C). The results showed that, independently of the geometry and arrangement, the micro-pin fins affect the fluid flow behavior and, consequently, heat transfer performance. Regarding the heat transfer coefficient, an average augmentation of 47 % is observed for the micro-pin fins heat sinks compared to the single-channel one.