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Research Papers: Evaporation, Boiling, and Condensation

Flow Boiling in a Heat Sink Embedded With Hexagonally Linked Minichannels

[+] Author and Article Information
Shubhankar Chakraborty

Department of Mechanical Engineering,
Indian Institute of Technology, Kharagpur,
Kharagpur 721302, India
e-mail: shubhankar@mech.iitkgp.ernet.in

Omprakash Sahu

Department of Mechanical Engineering,
Indian Institute of Technology, Kharagpur,
Kharagpur 721302, India
e-mail: rajuom.11@gmail.com

Prasanta Kr. Das

Department of Mechanical Engineering,
Indian Institute of Technology, Kharagpur,
Kharagpur 721302, India
e-mail: pkd@mech.iitkgp.ernet.in

1Corresponding author.

Contributed by the Heat Transfer Division of ASME for publication in the JOURNAL OF HEAT TRANSFER. Manuscript received December 3, 2015; final manuscript received April 1, 2016; published online May 3, 2016. Assoc. Editor: Amy Fleischer.

J. Heat Transfer 138(8), 081504 (May 03, 2016) (8 pages) Paper No: HT-15-1759; doi: 10.1115/1.4033354 History: Received December 03, 2015; Revised April 01, 2016

The thermal hydraulic performance of a miniature heat sink during flow boiling of distilled water is presented in this article. The unique design of the heat sink contains a number of microchannels of 1 mm × 1 mm cross section arranged in a regular hexagonal array. The design facilitates repeated division and joining of individual streams from different microchannels and thereby can enhance heat transfer. Individual slug bubble experiences a typical route of break up, coalescence, and growth. The randomness of these processes enhances the transport of heat. With the increase of vapor quality the heat transfer coefficient increases, reaches the maximum value, and then drops. The maximum heat transfer coefficient occurs at an exit vapor quality much higher than that observed in conventional parallel microchannel heat sinks. Repeated redistribution of the coolant in the interlinked channels and the restricted growth of the slug bubbles may be responsible for this trend.

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References

Figures

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Fig. 2

Exploded view of the heat sink (4) assembly with heaters (7) in a copper block (5), top and bottom flanges (1 and 8), gasket (3), quartz plate (2), and insulation (6)

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Fig. 1

Schematic representation of the experimental facility

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Fig. 4

Bubble merging and breakup during adiabatic two phase flow (air–water) through the heat sink: (a) visualization and (b) process

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Fig. 3

Variation of confinement number

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Fig. 5

Process of bubble growth through the linked channels

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Fig. 6

Typical growth of single bubble during boiling

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Fig. 9

Pressure drop across the heat sink during flow boiling

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Fig. 7

Increase of diameter and length of a vapor bubble with time

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Fig. 8

(a) Dry out in the heat sink and (b) scale formation during the boiling of tap water

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Fig. 10

Temperature reading from all the thermocouple during single-phase cooling of the heat sink

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Fig. 11

Variation of heat transfer coefficient for single phase flow (no preheat at inlet and power supplied = 14.8 W)

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Fig. 12

Repeatability of the heat transfer coefficient estimated for the heat sink (mass flux = 1.25 × 10−4 kg/s, inlet temperature = 75 °C)

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Fig. 13

Variation of heat transfer coefficient with the exit vapor quality (inlet temperature = 75 °C)

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Fig. 14

Effect of inlet temperature on the heat transfer coefficient during flow boiling (mass flux = 1.25 × 10−4 kg/s)

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