Experimental Investigation of Direct-to-Chip Evaporative Cooling Using Hollow Micropillar Arrays for High-Power AI Accelerators

International Journal of Heat and Mass Transfer, Volume 272, 2027, 129512, ISSN 0017-9310, DOI: https://doi.org/10.1016/j.ijheatmasstransfer.2026.129512

Experimental Investigation of Direct-to-Chip Evaporative Cooling Using Hollow Micropillar Arrays for High-Power AI Accelerators

Kidus Guye¹, Vivek V. Manepalli¹, Ayşenur Ateş¹, Baris Dogruoz², Samuel Graham¹ and Damena Agonafer¹

¹Mechanical Engineering, University of Maryland, College Park, 20742, MD, USA
² Microsoft, Mountain View, CA, USA

For more information about this article and related research, please contact Prof. Damena Agonafer.

Abstract:

The rapid growth of data center rack power density driven by artificial intelligence (AI) workloads requires cooling solutions beyond conventional air and single-phase liquid cooling. Traditional approaches rely on very low inlet temperatures to maintain acceptable junction temperatures. This places significant strain on cooling infrastructure, leading to higher cooling energy consumption and increased power usage effectiveness. Two-phase direct-to-chip evaporative cooling (DCEC) provides a promising alternative, utilizing phase-change heat transfer to achieve high heat-flux dissipation while reducing dependence on inlet temperature. This study experimentally investigates a two-phase DCEC device and its operating principles. Experiments were conducted in a controlled environmental chamber using water at a saturation temperature of 50 ◦C and inlet pressures ranging from 21 to 61 kPa. At higher inlet pressures, the evaporator initially operates in a flooded regime. As heat flux increases, progressive thinning of the liquid film reduces thermal resistance and enhances heat transfer until critical heat flux (CHF) is reached. At higher heat loads, the top liquid layer completely evaporates and the hollow micropillars serve as vapor-venting pathways. The device achieves a maximum CHF of 220 W/cm2 and a heat transfer coefficient of 1.1 × 105 W/m2 K. An area-normalized thermal resistance below 0.1 cm2 K/W is obtained with 5× lower pumping power than state-of-the-art single-phase cooling technologies. These results demonstrate the potential of DCEC as a scalable, actively pumped two-phase cooling solution for future high power density data center systems.

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