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Research Papers: Evaporation, Boiling, and Condensation

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

[+] Author and Article Information
Matthew J. Rau

School of Mechanical Engineering,
Purdue University,
585 Purdue Mall,
West Lafayette, IN 47907

Suresh V. Garimella

School of Mechanical Engineering,
Purdue University,
585 Purdue Mall,
West Lafayette, IN 47907
e-mail: sureshg@purdue.edu

Ercan M. Dede, Shailesh N. Joshi

Electronics Research Department,
Toyota Research Institute of North America,
1555 Woodridge Avenue,
Ann Arbor, MI 48105

1Corresponding author.

Contributed by the Heat Transfer Division of ASME for publication in the JOURNAL OF HEAT TRANSFER. Manuscript received January 24, 2014; final manuscript received March 2, 2015; published online March 24, 2015. Assoc. Editor: Keith Hollingsworth.

J. Heat Transfer 137(7), 071501 (Jul 01, 2015) (9 pages) Paper No: HT-14-1040; doi: 10.1115/1.4029969 History: Received January 24, 2014; Revised March 02, 2015; Online March 24, 2015

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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References

Figures

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Fig. 1

(a) A photograph of the jet impingement test section, and (b) plan views of the single jet orifice from Ref. [16] (right) and current 5 × 5 jet orifice array (left) overlaid on a dashed, 25.4 mm × 25.4 mm, outline of the heat source. The diameters of the orifices in the 5 × 5 array are chosen such that the total open area of the array is equal to that of the single orifice.

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Fig. 2

(a) Schematic drawing of the flat and pin–fin surfaces with an overlay of the 5 × 5 jet array orifices, and photographs of (b) the uncoated flat surface, (c) uncoated pin–fin surface, (d) coated flat surface, and (e) coated pin–fins

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Fig. 3

SEM images of the coated pin–fins (a) before testing and (b) after boiling from the surface for approximately 64 hr

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Fig. 4

Area-averaged single-phase heat transfer coefficient plotted as a function of jet velocity for the single jet [16] (open markers) and the array of impinging jets (closed markers) on all four surfaces considered

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Fig. 5

Boiling curves for the single jet [16] (open markers) and the array of impinging jets (closed markers) on all four surfaces considered at a flow rate of 1800 ml/min; arrows indicate the point at which CHF occurs

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Fig. 6

Boiling curves for the array of impinging jets on all four surfaces at total flow rates of (a) 450 ml/min and (b) 900 ml/min; arrows indicate the point at which CHF occurs

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Fig. 7

Surface efficiency of the pin–fin (closed markers) and coated pin–fin (open markers) surfaces for the array of impinging jets at all flow rates, along with the single jet [16] results at 1800 ml/min

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Fig. 8

(a) CHF for the single jet [16] (open markers) and 5 × 5 jet array (closed markers) and (b) CHF normalized with the single jet on the flat surface, as a function of jet velocity

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Fig. 9

(a) High-speed photograph of the single jet impinging at 1800 ml/min at a heat flux of 85.7 W/cm2, and schematic drawings of the liquid distribution resulting from the (b) single jet [16] and (c) 5 × 5 array of jets. Orifice position shown in black.

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Fig. 10

Pressure drop as a function of heat input for the jet array on all surfaces at all flow rates

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