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Research Papers

Microchannels With Manufacturing Roughness Levels

[+] Author and Article Information
S. A. Weaver

Department of Mechanical and Nuclear Engineering, The Pennsylvania State University, University Park, PA 16802sweaver@sandia.gov

M. D. Barringer

Department of Mechanical and Nuclear Engineering, The Pennsylvania State University, University Park, PA 16802mbarringer@psu.edu

K. A. Thole

Department of Mechanical and Nuclear Engineering, The Pennsylvania State University, University Park, PA 16802kthole@psu.edu

J. Turbomach 133(4), 041014 (Apr 21, 2011) (8 pages) doi:10.1115/1.4002991 History: Received July 01, 2010; Revised July 08, 2010; Published April 21, 2011; Online April 21, 2011

There are heat transfer advantages to reducing the size of channels used for internal cooling gas turbine components. As channel sizes decrease, however, there are concerns as to how manufacturing surface roughness may affect the channels’ expected pressure drop and heat transfer. For microchannel size scales, in particular, there is relatively little data indicating the effect of manufacturing roughness levels. The focus of this paper is to describe the development and validation of a testing method for microchannels as well as to determine the effect of manufacturing roughness levels on these small channels. Convective heat transfer coefficients and friction factors were deduced based on measured flow conditions and known boundary conditions. It was shown that at an average roughness height of 6.1μm, which corresponded to 2.2% of the channel height, heat transfer was augmented by 1.1–1.2, while the friction factor was augmented significantly more by 2.1–2.6 over a smooth channel.

Copyright © 2011 by American Society of Mechanical Engineers
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References

Figures

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Figure 1

Schematic of the microchannel test apparatus designed in this study

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Figure 2

Axial view of the heat transfer test chamber and internal components

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Figure 3

Photograph of the foam insulation used to surround the test coupon and heat sinks

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Figure 4

Axial view of the pressure drop test chamber and internal components

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Figure 5

Drawing of the measurement locations within the test apparatus

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Figure 6

Photograph of thermocouples installed at channel exit

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Figure 7

Diagram of test coupon assembly process and overall dimensions

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Figure 8

Coupon C three-dimensional profilometry surface plot

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Figure 9

Schematic of a cross-sectional view of the test stack (foam to air)

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Figure 10

Three-dimensional ansys simulation of copper heat sinks and test coupon temperatures

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Figure 11

Copper midplane horizontal temperature distribution

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Figure 12

Copper and test coupon midplane vertical temperature distribution

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Figure 13

Test coupon energy balance percent as a function of Reynolds number

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Figure 14

Individual parameter contributions to overall heat transfer coefficient uncertainty

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Figure 15

Individual parameter contributions to overall friction factor uncertainty

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Figure 16

Test coupon Nusselt number as a function of Reynolds number

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Figure 17

Test coupon Nusselt number augmentation as a function of Reynolds number

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Figure 18

Test coupon friction factor as a function of Reynolds number

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Figure 19

Test coupon friction factor augmentation as a function of Reynolds number

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