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Complementary Orifice and Surface Enhancement Geometries for Jet Impingement Boiling Heat Transfer
Keywords: Two-phase jet impingement, Surface enhancement, Microporous coating
Boiling heat transfer offers a means of augmenting the heat dissipation capabilities of liquid jet impingement. This two-phase operation of jet impingement has been shown to provide high heat transfer coefficients with only minimal increases in pumping power compared to single-phase operation, making two-phase jet impingement an attractive cooling technology for high-power-density electronic systems. To investigate further enhancements in the heat transfer coefficient and critical heat flux (CHF) of this technology, an experimental study of hybrid surface enhancement structures, which complement the impinging flow from an array of jets, is performed using the dielectric working fluid HFE-7100 at volumetric flow rates of 450, 900, and 1800 ml/min. The cooling performance is evaluated for a 5 × 5 array of jets (d = 0.75 mm) impinging on four different target copper surfaces: a baseline smooth flat surface, a flat surface coated with a microporous layer, a surface with macroscale area enhancement (extended square pin fins), and the hybrid surface on which the pin fins are coated with the microporous layer. The performance of the jet array is compared to that of a single jet (d = 3.75 mm) of equivalent orifice area on each surface. The jet array coupled with the hybrid enhancement dissipates a maximum heat flux of 206 W/cm2 (heat input of 1.3 kW) at a flow rate of 1800 ml/min with a pressure drop of only 10.9 kPa incurred. Compared to the single jet impinging on this hybrid surface, the impinging flow from the jet array provides a 2.3 times enhancement in CHF. As an overall enhancement scheme, the array of jets coupled with the hybrid surface design results in CHF enhancements of over 4 times, while incurring a pressure drop increase of less than 1.8 times, at all flow rates investigated compared to the baseline surface with the single jet.
Matthew J. Rau,
Purdue University
West Lafayette, IN

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