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Research Papers: Heat and Mass Transfer

Measurement of Local Mass Transfer and the Resulting Roughness in a Large Diameter S-Bend at High Reynolds Number

[+] Author and Article Information
D. Wang, D. Ewing, T. Le

Department of Mechanical Engineering,
McMaster University,
Hamilton, ON L8S 4L7, Canada

C. Y. Ching

Department of Mechanical Engineering,
McMaster University,
Hamilton, ON L8S 4L7, Canada
e-mail: chingcy@mcmaster.ca

1Corresponding author.

Contributed by the Heat Transfer Division of ASME for publication in the JOURNAL OF HEAT TRANSFER. Manuscript received September 10, 2015; final manuscript received February 23, 2016; published online March 30, 2016. Assoc. Editor: Wilson K. S. Chiu.

J. Heat Transfer 138(6), 062001 (Mar 30, 2016) (7 pages) Paper No: HT-15-1591; doi: 10.1115/1.4032985 History: Received September 10, 2015; Revised February 23, 2016

The local mass transfer and the resulting roughness in a 203 mm diameter back-to-back bend arranged in an S-configuration were measured at a Reynolds number of 300,000. A dissolving wall method using gypsum dissolution to water at 40 °C was used, with a Schmidt number of 660. The topography of the unworn and worn inner surface was quantified using nondestructive X-ray computed tomography (CT) scans. The local mass transfer rate was obtained from the local change in radius over the flow time. Two regions of high mass transfer were present: (i) along the intrados of the first bend near the inlet and (ii) at the exit of the extrados of the first bend that extends to the intrados of the second bend. The latter was the region of highest mass transfer, and the scaling of the maximum Sherwood number with Reynolds number followed that developed for lower Reynolds numbers. The relative roughness distribution in the bend corresponded to the mass transfer distribution, with higher roughness in the higher mass transfer regions. The spacing of the roughness elements in the upstream pipe and in the two regions of high mass transfer was approximately the same; however, the spacing-to-height ratio was very different with values of 20, 10, and 6, respectively.

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Figures

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Fig. 1

(a) Example of typical CT scan image, (b) point cloud of edges detected from CT scan images after 3D reconstruction, and (c) cross section of reconstructed 3D CT scan image

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Fig. 2

Local Sherwood number contours over the entire test section viewed along (a) the intrados of the first bend and (b) the extrados of the first bend

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Fig. 3

Azimuthal profiles of Sherwood number at typical streamwise locations

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Fig. 4

Variation of the local maximum and upstream Sherwood number with Reynolds number in S-bend

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Fig. 5

(a) The entire 3D reconstructed worn surface contour from CT scan and (b) view of ①: Upstream pipe (−1.4 < z/D < −0.4, −90 < θ < 90 deg), ②: High mass transfer region I in the first bend (0 < φ1 < 40 deg, −180 < θ < 0 deg), and ③: High mass transfer region II in the second bend (0 < φ2 < 40 deg, 0 < θ < 180 deg)

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Fig. 6

Azimuthal profiles of local deviation on the worn rough surface at three typical streamwise locations: (a) z/D = −1, (b) φ1 = 15 deg, and (c) φ2 = 10 deg

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Fig. 7

Relative roughness (e/D) contours over the entire test section viewed along (a) the intrados of the first bend and (b) the extrados of the first bend

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Fig. 8

Enlarged view of surface roughness in (a) upstream pipe, (b) high mass transfer region I in the first bend, and (c) high mass transfer region II in the second bend for illustration of streamwise and circumfirential spacing distributions of peak to valley roughness

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