Single-Phase and Boiling Cooling of Small Pin Fin Arrays by Multiple Nozzle Jet Impingement

Copeland, David

doi:10.1115/1.2792122

Cited by 31 publications

(19 citation statements)

References 6 publications

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“…Rau and Garimella [1], and the current experiments. Empty symbols for the current data set correspond to overshoot at boiling incipience and those for de Brún et al [23] correspond to critical heat flux. Figure 12.…”

Section: List Of Figuresmentioning

confidence: 99%

Development and validation of a semi-empirical model for two-phase heat transfer from arrays of impinging jets

Mira-Hernández

Clark

Weibel

et al. 2018

International Journal of Heat and Mass Transfer

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Two-phase jet impingement is a compact cooling technology that provides high-heat-flux dissipation at manageable pressure drop, with applications in cooling power electronics and server modules. The extensive set of geometrical parameters and operating conditions that determine the heat transfer behavior of jet impingement systems provide an attractive level of design flexibility. In the present study, a semiempirical approach is developed to predict heat transfer from arrays of jets of liquid that undergoes phase change upon impingement. In the modeling approach developed, the jet array is divided into unit cells centered on each orifice that are assumed to behave identically. Based on prior experimental observations, the impingement surface in each unit cell is divided into two distinct regions: a single-phase heat transfer region directly under the jet, and a surrounding boiling heat transfer region along the periphery. Singlephase convection and boiling heat transfer correlations available in the literature are used to estimate the heat transfer coefficient distribution in each region, and the mean surface temperature of the unit cell is estimated via area-averaging. An analysis is performed to show that the model outputs are sensitive to the heat transfer coefficient correlations used as inputs, with the choice depending on the heat flux input and the expected operating regime. Experiments are performed to validate the area-averaged thermal performance predictions. The model results are also compared against experimental data in the literature.The semi-empirical modeling approach developed in this work successfully represents the different heat transfer modes and transitions that occur during two-phase jet impingement. The location of transition to boiling predicted by the model is consistent with prior experimental observations of an inward-creeping boiling front with increasing heat flux. The predicted temperature difference between the surface and the jet inlet across all experimental comparisons has a mean absolute percentage error of 3.88%. The proposed modeling approach is demonstrated to be a practical tool in the development of two-phase jet array impingement devices, allowing for parametric exploration across the expansive design space.

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Section: List Of Figuresmentioning

confidence: 99%

Development and validation of a semi-empirical model for two-phase heat transfer from arrays of impinging jets

Mira-Hernández

Clark

Weibel

et al. 2018

International Journal of Heat and Mass Transfer

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“…As a potential cooling technology, two-phase jet impingement has a number of advantages over single-phase forced convection and passive boiling approaches. The added change of phase offers significant enhancement in heat transfer compared to single-phase jets, and active purging of vapor by the impinging flow can extend critical heat flux (CHF) significantly compared to pool boiling [3,4].…”

Section: Introductionmentioning

confidence: 99%

Local two-phase heat transfer from arrays of confined and submerged impinging jets

Rau

Garimella

2013

International Journal of Heat and Mass Transfer

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a b s t r a c tLocal heat transfer distributions at high spatial resolution are obtained under two-phase transport conditions in confined and submerged impingement from arrays of miniature jets. The dielectric liquid HFE-7100 is investigated to enable direct cooling of electronic components. Three round orifice geometries with the same total orifice open area are investigated, including a single orifice of 3.75 mm diameter, a 3 Â 3 array of 1.25 mm diameter orifices, and a 5 Â 5 array of 0.75 mm diameter orifices. A thin-foil heat source backed by a magnesium-fluoride window is fabricated to allow detailed mapping of the heated surface temperature via infrared (IR) thermography. The rigorous experimental calibration procedures employed, and correction for heat spreading within the thermally conductive IR-transparent window, yield low-uncertainty local heat transfer coefficient distributions. Each of the three orifice geometries is characterized at volumetric flow rates of 450 ml/min, 900 ml/min, and 1800 ml/min, resulting in a Reynolds number range of 1920-39400. Pressure drop across the confined jets is measured for all experimental cases. The test facility and measurement techniques employed are validated against heat transfer and pressure drop correlations in the literature for single-phase jet impingement from a single round orifice. Spatially resolved temperature contour maps, along with local heat transfer coefficient and boiling curves, are presented as a function of applied heat flux. Boiling is shown to coexist with single-phase convection under the impinging liquid jets. Two-phase enhancement is exhibited at large radial distances from the single jet axis, and in regions between neighboring jets within the arrays. The arrays of jets result in higher area-averaged heat transfer than a single jet at a fixed flow rate; however, the arrays display larger relative nonuniformity in local two-phase heat transfer coefficient and surface temperature. While the 5 Â 5 array resulted in a higher (and the 3 Â 3 a lower) pressure drop than the single jet, all orifices displayed pressure drop that is independent of the applied heat flux and vapor generation.

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“…In one example case tested, a nine-jet array provided similar area-averaged heat transfer coefficients to that of a single jet but with a 36 times lower pressure drop. Arrays of jets are advantageous in two-phase operation as well, extending CHF and area-averaged heat transfer coefficients relative to single jets [6,7].…”

Section: Introductionmentioning

confidence: 99%

Boiling Heat Transfer From an Array of Round Jets With Hybrid Surface Enhancements

Rau

Garimella

Dede³

et al. 2015

Journal of Heat Transfer

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The effect of a variety of surface enhancements on the heat transfer achieved with an array of impinging jets is experimentally investigated using the dielectric fluid HFE-7100 at different volumetric flow rates. The performance of a 5 × 5 array of jets, each 0.75 mm in diameter, is compared to that of a single 3.75 mm diameter jet with the same total open orifice area, in single-and two-phase operation. Four different target copper surfaces are evaluated: a baseline smooth flat surface, a flat surface coated with a microporous layer, a surface with macroscale area enhancement (extended square pin–fins), and a hybrid surface on which the pin–fins are coated with the microporous layer; area-averaged heat transfer and pressure drop measurements are reported. The array of jets enhances the single-phase heat transfer coefficients by 1.13–1.29 times and extends the critical heat flux (CHF) on all surfaces compared to the single jet at the same volumetric flow rates. Additionally, the array greatly enhances the heat flux dissipation capability of the hybrid coated pin–fin surface, extending CHF by 1.89–2.33 times compared to the single jet on this surface, with a minimal increase in pressure drop. The jet array coupled with the hybrid enhancement dissipates a maximum heat flux of 205.8 W/cm2 (heat input of 1.33 kW) at a flow rate of 1800 ml/min (corresponding to a jet diameter-based Reynolds number of 7800) with a pressure drop incurred of only 10.9 kPa. Compared to the single jet impinging on the smooth flat surface, the array of jets on the coated pin–fin enhanced surface increased CHF by a factor of over four at all flow rates.

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Single-Phase and Boiling Cooling of Small Pin Fin Arrays by Multiple Nozzle Jet Impingement

Cited by 31 publications

References 6 publications

Development and validation of a semi-empirical model for two-phase heat transfer from arrays of impinging jets

Development and validation of a semi-empirical model for two-phase heat transfer from arrays of impinging jets

Local two-phase heat transfer from arrays of confined and submerged impinging jets

Boiling Heat Transfer From an Array of Round Jets With Hybrid Surface Enhancements

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