The steady rise in cooling requirements of commercial computer products mandates the development of aggressive thermal management techniques, as well as accurate design and analysis methodologies. Single phase direct liquid jet impingement, offers a controlled high performance alternative, by eliminating the need for a thermal interface, and by delivering the coolant directly to the surface of the chip. This paper characterizes the thermal performance of a specific direct liquid jet impingement scheme in which the hot fluid exhausts via return vents located in the immediate vicinity of the jet. The study also quantifies the error associated with using the average heat transfer coefficient as a thermal performance metric for the non-uniform cooling boundary condition that occurs in such jet impingement solutions. The thermal performance of the direct liquid jet impingement designs are characterized and studied, via CFD (Computational Fluid Dynamics) models constructed using a commercial numerical solver. The hydraulic performance is analytically estimated using a simple loss coefficient based model. A square 10×10×0.75 mm3 chip, dissipating 400W, and cooled by water at 32°C, is considered as the representative example for the analysis. The effect of jet density on thermal performance is characterized for 1–400 jets/cm2, and for several feasible flow parameters, i.e. inlet jet velocities (5–10 m/s) and volumetric flow rates (946–1893 liters/minute). For the configurations explored, the optimal jet density was found to be 100 jets/cm2. An engineering cut-off point for the use of the 1-D average heat transfer coefficient metric, was identified as 10 jets/cm2. The error associated with use of a 1-D average heat transfer coefficient was shown to be in excess of 5% when the jet density is less than 10 jets/cm2, as high as 20% for the single jet case, and less than 0.7% for jet densities greater than 36 jets/cm2.

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