| description abstract | Abstract. This study experimentally investigates the thermal–hydraulic performance of ultraconfined two-phase jet-impingement cooling using a distributed inlet–outlet nozzle manifold, a configuration that has received limited attention in prior work. It addresses a critical knowledge gap by providing the first experimental characterization of a confined two-phase distributed inlet–outlet jet architecture operating at an ultraconfinement height (z) of 0.33 mm (z/d = 0.66), representative of practical chip-level cooling constraints. Simultaneous measurements of critical heat flux (CHF), pressure drop, and local impingement cavity pressure enable direct evaluation of thermal–hydraulic tradeoffs under strong confinement. Experiments were conducted with the low-global warming potential (GWP) refrigerant R1233zd(E) overflow rates from 0.15 to 1.25 lpm and jet-array densities corresponding to nondimensional jet-to-jet spacing of s/d = 4.0–10.0. The results show that CHF and thermal–hydraulic efficiency are governed by jet-array density in the ultraconfined regime, where liquid momentum, vapor evacuation, and confinement-induced flow resistance are tightly coupled. Maximum CHF values approaching 270 W/cm2 are achieved at ultralow pumping powers below 0.4 W. Direct impingement cavity pressure measurements reveal a transition in the CHF-limiting mechanism from thermally dominated dryout at low flow rates to hydrodynamically constrained operation at higher flow rates. A scaling relationship linking CHF to jet Reynolds number and jet-array spacing is established, providing quantitative design guidance for compact, high-performance ultraconfined two-phase jet-impingement cooling systems. | |
