Heat Transfer Augmentation of Microencapsulated Phase Change Material Slurry in Herringbone microchannel heat sink

Abstract

The advancement of technologies such as artificial intelligence (AI), the Internet of Things(IoT), and cloud computing has driven the miniaturization of electronic devices while significantly increasing their power densities and compactness. This evolution has led to higher heat fluxes that must be effectively managed to ensure device reliability and optimal performance. Effective thermal management is crucial, as inadequate cooling can result in thermal stresses, reduced efficiency, and potential component failure. While air-cooled systems were traditionally sufficient, the growing power demands of modern electronics have necessitated the adoption of more advanced cooling strategies. Microchannel heat sinks(MCHS), introduced in 1981, have been extensively studied for their ability to reduce junction temperatures. These heat sinks are part of various thermal management solutions, including single-phase liquid cooling, two-phase flow boiling, and jet impingement cooling in microchannels. Studies have shown that single-phase liquid cooling can effectively dissipate high heat fluxes of up to 1000 W/cm2. However, despite their effectiveness in heat dissipation, single-phase liquid cooling systems in microchannel heat sinks experience diminishing returns in efficiency due to high-pressure drops at higher volumetric flow rates. Two-phase or multiphase cooling strategies have also been studied to overcome these limitations. These approaches rely on the phase change of the coolant and leverage the high heat capacity to improve heat transfer efficiency while maintaining a high thermal-hydraulic performance. However, they face challenges related to the flow instabilities during boiling and diminished heat removal rate at critical heat fluxes, which can undermine reliability. A promising alternative involves suspending microencapsulated phase change material (MEPCM) particles in a thermal fluid to create a slurry. MEPCM slurries typically consist of a base fluid, like water, mixed with MEPCM particles that enhance effective heat capacity through their high specific and latent heat. These particles absorb and release heat during phase transitions, significantly improving heat dissipation and storage in thermal-fluid systems. However, despite their high thermal capacity, the relatively low thermal conductivity of MEPCM particles can hinder their ability to melt uniformly and transfer heat effectively. To address these challenges, this study investigates a novel heat transfer enhancement approach by incorporating herringbone microstructures within microchannels to induce helical mixing. The herringbone design facilitates out-of-plane mixing, which promotes the effective utilization of MEPCM particles and enhances heat transfer without the instabilities associated with traditional two-phase boiling. This creates a pseudo ’two-phase’ flow within the microchannel heat sink, allowing MEPCM slurries to achieve high thermal performance, balancing effective heat transfer with reduced flow instabilities and manageable pressure drops.