In modern microprocessors, thermal management has become one of the main hurdles in continued performance enhancement. Cooling schemes utilizing single phase microfluidics have been investigated extensively for enhanced heat dissipation from microprocessors. However, two-phase fluidic cooling devices are becoming a promising approach, and are less understood. This study aims to examine two-phase flow and heat transfer within a pin-fin enhanced micro-gap. The pin-fin array covered an area of 1cm × 1cm and had a pin diameter, height and pitch of 150μm, 200μm and 225μm, respectively, (aspect ratio of 1.33). Heating from two upstream heaters was considered. The working fluid used was R245fa. The average heat transfer coefficient was evaluated for a range of heat fluxes and flow rates. Flow regime visualization was performed using high-speed imaging. Results indicate a sharp transition to convective flow boiling mechanism. Unique, conically-shaped two-phase wakes are recorded, demonstrating 2D spreading capability of the device. Surface roughness features are also discussed.

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