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Research Papers: Evaporation, Boiling, and Condensation

Confined Jet Impingement With Boiling on a Variety of Enhanced Surfaces

[+] 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

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 June 24, 2014; published online July 29, 2014. Assoc. Editor: Jim A. Liburdy.

J. Heat Transfer 136(10), 101503 (Jul 29, 2014) (12 pages) Paper No: HT-14-1039; doi: 10.1115/1.4027942 History: Received January 24, 2014; Revised June 24, 2014

Confined jet impingement with boiling offers unique and attractive performance characteristics for thermal management of high heat flux components. Two-phase operation of jet impingement has been shown to provide high heat transfer coefficients while maintaining a uniform temperature over a target surface. This can be achieved with minimal increases in pumping power compared to single-phase operation. To investigate further enhancements in heat transfer coefficients and increases in the maximum heat flux supported by two-phase jet impingement, an experimental study of surface enhancements is performed using the dielectric working fluid HFE-7100. The performance of a single, 3.75 mm-diameter jet orifice is compared across four distinct copper target surfaces of varying enhancement scales: 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. The heat transfer performance of each surface is compared in single- and two-phase operation at three volumetric flow rates (450 ml/min, 900 ml/min, and 1800 ml/min); area-averaged heat transfer parameters and pressure drop are reported. The mechanisms resulting in enhanced performance for the different surfaces are identified, with a special focus on the coated pin fins. This hybrid surface showed the best enhancement of all those tested, and resulted in an extension of critical heat flux (CHF) by a maximum of 2.42 times compared to the smooth flat surface at the lowest flow rate investigated; no increase in the overall pressure drop was measured.

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References

Figures

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Fig. 1

Flow loop schematic diagram

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Fig. 2

Cross-sectional illustration of the jet impingement test section with copper heat source installed

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Fig. 3

Exploded view of the heater assembly (hardware, seals, and loose-fill fiberglass insulation not shown)

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Fig. 4

(a) Illustration of the surface designs, and photographs of the (b) baseline smooth surface, (c) uncoated pin fins, (d) coated flat surface, (e) coated pin fins, and (f) SEM image of the microporous coating

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Fig. 5

Area-averaged single-phase heat transfer coefficient plotted as a function of jet velocity for all four surfaces at the heat flux just prior to the onset of boiling

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Fig. 6

Boiling curves for all surface enhancements at a flow rate of (a) 450 ml/min, (b) 900 ml/min, and (c) 1800 ml/min; arrows indicate CHF

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Fig. 7

High-speed images (right) of jet impingement on the coated pin-fin surface at 900 ml/min at the points highlighted (solid symbols) in the boiling curve (left); arrows indicate CHF. Supplementary video provided online [51].

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Fig. 8

Surface efficiency of the pin-fin and coated pin-fin surfaces for the single jet at all flow rates

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Fig. 9

Boiling curves at all flow rates for the (a) flat surfaces and (b) pin-fin surfaces; arrows indicate CHF

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Fig. 10

Pressure drop for all flow rates and surfaces as a function of heat flux

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