Direct Liquid Jet-Impingment Cooling With Micron-Sized Nozzle Array and Distributed Return Architecture

We demonstrate submerged single-phase direct liquid-jet-impingement cold plates that use arrays of jets with diameters in the range of 31 to 126 mum and cell pitches from 100 to 500 mum for high power-density microprocessor cooling applications. Using parallel inlet and outlet manifolds, a distributed return concept for easy scaling to 40,000 cells on an area of 4 cm was implemented. Pressure drops < 0.1 bar at 2.5 1/min flow rate have been reached with a hierarchical tree-like double-branching manifold. Experiments were carried out with water jets having Reynolds numbers smaller than 900 at nozzle to heater gaps ranging between 3 to 300 mum. We identified four flow regimes, namely, pinch-off, transition, impingement, and separation, with different influences on heat-removal and pressure-drop characteristics. Parametric analysis resulted in an optimal heat-removal rate of 420 W/cm² using water as a coolant. For a near optimal design with a gap to inlet diameter ratio of 1.2, we measured a heat-transfer coefficient of 8.7 W/cm² K and a junction to inlet fluid unit thermal resistance of 0.17 Kcm² /W (720 mum chip), which is equivalent to a 370 W/cm² cooling performance at a junction to inlet fluid temperature rise of 63 degC, a pressure drop of 0.35 bar, and a flow rate of 2.5 1/min