Tailoring bubble dynamics in 3D-printed graded porous lattices for enhanced conjugate pool boiling heat transfer

Two-phase immersion cooling offers promising thermal management capacity for AI-driven data centers with escalating power densities, for which sustaining efficient nucleate boiling across varying operating temperatures and power densities is essential. This work demonstrates that graded BCC porous lattice structures fabricated via laser powder bed fusion (L-PBF) enable enhanced pool boiling heat transfer compared with matched uniform lattices over the investigated superheat range. At a representative wall superheat of approximately 14 K, the graded lattice with an average porosity of 80% exhibited an HTC approximately 137% higher than that of its matched uniform counterpart. This enhancement arises because the graded porosity accommodates progressive vapor bubble growth along the height direction, while transverse interconnected pores enable timely liquid replenishment without compromising vertical bubble detachment. Quantitative high-speed visualization directly reveals distributed nucleation over the lattice height and shows that, unlike a flat copper surface following classical trends, the lattice structures exhibit increasing bubble departure diameter and a two-stage departure frequency response with increasing superheat. The graded lattice design provides robust heat transfer performance across varying operating conditions, with a large effective heating area that is directly comparable to CPU/GPU cooling demands. The synergistic combination of three-dimensional heat spreading, capillary-driven liquid supply, optimized graded porosity, and regulated vapor–liquid pathways offers a scalable approach for next-generation two-phase immersion cooling of high-power-density electronics.