Research Papers

Microfeature Heat Exchanger Using Variable-Density Arrays for Near-Isothermal Cold-Plate Operation

[+] Author and Article Information
Noris Gallandat, Danielle Hesse

The George W. Woodruff School
of Mechanical Engineering,
Georgia Institute of Technology,
Atlanta, GA 30332

J. Rhett Mayor

Associate Professor
The George W. Woodruff School
of Mechanical Engineering,
Georgia Institute of Technology,
Atlanta, GA 30332
e-mail: rhett.mayor@me.gatech.edu

1Corresponding author.

Contributed by the Electronic and Photonic Packaging Division of ASME for publication in the JOURNAL OF ELECTRONIC PACKAGING. Manuscript received September 25, 2015; final manuscript received December 8, 2015; published online March 10, 2016. Assoc. Editor: Xiaobing Luo.

J. Electron. Packag 138(1), 010908 (Mar 10, 2016) (6 pages) Paper No: EP-15-1096; doi: 10.1115/1.4032347 History: Received September 25, 2015; Revised December 08, 2015

The purpose of this paper is to demonstrate the possibility to selectively tune the convective heat transfer coefficient in different sections of a heat sink by varying the density of microfeatures in order to minimize temperature gradients between discrete heat sources positioned along the flow path. Lifetime of power electronics is strongly correlated to the thermal management of the junction. Therefore, it is of interest to have constant junction temperatures across all devices in the array. Implementation of microfeature enhancement on the convective side improves the heat transfer due to an increase in surface area. Specific shapes such as micro-hydrofoils offer a reduced pressure drop allowing for combined improvement of heat transfer and flow performance. This study presents experimental results from an array of three discrete heat sources (20 × 15 mm) generating 100 W/cm2 and positioned in line along the flow path with a spacing of 10 mm between each of the sources. The heat sink was machined out of aluminum 6061, and micro-hydrofoils with a characteristic length of 500 μm were embedded in the cold plate. The cooling medium used is water at a flow rate of 3.6–13.4 g/s corresponding to a Reynolds number of 420–1575. It is demonstrated that the baseplate temperature can be maintained below 90 °C, and the difference between the maximum temperatures of each heat source is less than 6.7 °C at a heat flux of 100 W/cm2 and a water flow rate of 4.8 g/s.

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Fig. 1

Definition of the characteristic length (lc), the longitudinal pitch (sl), and the transversal pitch (st) for micro-hydrofoil arrays (from Ref. [29])

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Fig. 2

Cold-plate temperature and water temperature along the flow path. In the case with a constant feature density, the heat exchanger is overdesigned and maintains the first and second heat sources well below the required operating temperature.

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Fig. 3

Package considered with three discrete devices producing 300 W each with a contact surface of 15 × 20 mm

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Fig. 4

Flowchart summarizing the heat sink design process

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Fig. 5

Physical setup (a) and computational domain for the design of the heat exchanger(b)

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Fig. 6

Heat exchanger with the three graded arrays of micro-hydrofoils machined out of aluminum 6061

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Fig. 7

Schematic of the custom test bench to characterize the thermofluidic performance of the heat exchanger

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Fig. 8

Location of the thermocouples and pressure sensors

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Fig. 9

Plate and water temperature at a water flow rate of 12.82 g/s and a heat flux of 100 W/cm2

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Fig. 10

Plate and water temperature at a water flow rate of 7.91 g/s and a heat flux of 100 W/cm2

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Fig. 11

Plate and water temperature at a water flow rate of 4 g/s and a heat flux of 100 W/cm2




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