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Effects of 2-D and 3-D helical inserts on the turbulent flow in pipes

Marco Virgilio (UGent) , I. Mayo, Jens Dedeyne (UGent) , Kevin Van Geem (UGent) , Guy Marin (UGent) and T. Arts
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Abstract
A constant search for more efficient heat exchangers motivates the use of innovative turbulators. Original flowfield measurements were performed with S-PIV to gain a better understanding of the role of 3-D wall obstacles in pipe flows. Such effects are compared with those of 2-D helically corrugated tubes, which are already provided in the literature. This work further investigates the impact of both continuous (2-D corrugation) and discontinuous (3-D corrugation) obstructions on the surrounding velocity field. The analysis of the flow structures is made by comparing two types of helicoidal turbulators. The continuous geometry has a pitch-to-diameter-ratio of p/ D = 11 and an inclination angle of 80°. An obstacle height-to-diameter-ratio of e/D = 3.6% is used, which is constant throughout the helix-wise direction. The discontinuous geometry is equivalent to the continuous one except that it has a varying obstacle height throughout the helix. The reattachment and redevelopment of the flow are determined by time-averaged velocity analysis, at Re = 20,000. Notably, the aim of this study is to examine the effects of the discontinuity in the tube corrugation on the flow separation/reattachment, turbulence statistics, vorticity (ω) and strain-rate ( ) Sxy of the flow particles, and compare them with a previously studied continuous turbulator. As a result, the discontinuous rib has a lower impact on the pressure losses, on the azimuthal swirl, and on the turbulent kinetic energy generation. In the field close to the wall, the changing height of the discontinuous rib generates a turbulent kinetic energy and an azimuthal velocity, respectively, 50% and 35% lower than the continuous configuration. The irregularity of the discontinuous obstacles provides a reduced skin friction coefficient (Cf) which is 0.57 times the one given by the continuous 2-D helical turbulator. On the other hand, the observed less intense wall-bounded turbulence levels associated with the 3-D helical turbulator suggest a lower local heat transfer enhancement.
Keywords
Mechanical Engineering, Nuclear Energy and Engineering, General Chemical Engineering, Fluid Flow and Transfer Processes, Aerospace Engineering

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MLA
Virgilio, Marco, et al. “Effects of 2-D and 3-D Helical Inserts on the Turbulent Flow in Pipes.” EXPERIMENTAL THERMAL AND FLUID SCIENCE, vol. 110, 2020.
APA
Virgilio, M., Mayo, I., Dedeyne, J., Van Geem, K., Marin, G., & Arts, T. (2020). Effects of 2-D and 3-D helical inserts on the turbulent flow in pipes. EXPERIMENTAL THERMAL AND FLUID SCIENCE, 110.
Chicago author-date
Virgilio, Marco, I. Mayo, Jens Dedeyne, Kevin Van Geem, Guy Marin, and T. Arts. 2020. “Effects of 2-D and 3-D Helical Inserts on the Turbulent Flow in Pipes.” EXPERIMENTAL THERMAL AND FLUID SCIENCE 110.
Chicago author-date (all authors)
Virgilio, Marco, I. Mayo, Jens Dedeyne, Kevin Van Geem, Guy Marin, and T. Arts. 2020. “Effects of 2-D and 3-D Helical Inserts on the Turbulent Flow in Pipes.” EXPERIMENTAL THERMAL AND FLUID SCIENCE 110.
Vancouver
1.
Virgilio M, Mayo I, Dedeyne J, Van Geem K, Marin G, Arts T. Effects of 2-D and 3-D helical inserts on the turbulent flow in pipes. EXPERIMENTAL THERMAL AND FLUID SCIENCE. 2020;110.
IEEE
[1]
M. Virgilio, I. Mayo, J. Dedeyne, K. Van Geem, G. Marin, and T. Arts, “Effects of 2-D and 3-D helical inserts on the turbulent flow in pipes,” EXPERIMENTAL THERMAL AND FLUID SCIENCE, vol. 110, 2020.
@article{8628734,
  abstract     = {A constant search for more efficient heat exchangers motivates the use of innovative turbulators. Original flowfield measurements were performed with S-PIV to gain a better understanding of the role of 3-D wall obstacles in
pipe flows. Such effects are compared with those of 2-D helically corrugated tubes, which are already provided in
the literature. This work further investigates the impact of both continuous (2-D corrugation) and discontinuous
(3-D corrugation) obstructions on the surrounding velocity field. The analysis of the flow structures is made by
comparing two types of helicoidal turbulators. The continuous geometry has a pitch-to-diameter-ratio of p/
D = 11 and an inclination angle of 80°. An obstacle height-to-diameter-ratio of e/D = 3.6% is used, which is
constant throughout the helix-wise direction. The discontinuous geometry is equivalent to the continuous one
except that it has a varying obstacle height throughout the helix. The reattachment and redevelopment of the
flow are determined by time-averaged velocity analysis, at Re = 20,000. Notably, the aim of this study is to
examine the effects of the discontinuity in the tube corrugation on the flow separation/reattachment, turbulence
statistics, vorticity (ω) and strain-rate ( ) Sxy of the flow particles, and compare them with a previously studied
continuous turbulator. As a result, the discontinuous rib has a lower impact on the pressure losses, on the
azimuthal swirl, and on the turbulent kinetic energy generation. In the field close to the wall, the changing
height of the discontinuous rib generates a turbulent kinetic energy and an azimuthal velocity, respectively, 50%
and 35% lower than the continuous configuration. The irregularity of the discontinuous obstacles provides a
reduced skin friction coefficient (Cf) which is 0.57 times the one given by the continuous 2-D helical turbulator.
On the other hand, the observed less intense wall-bounded turbulence levels associated with the 3-D helical
turbulator suggest a lower local heat transfer enhancement.},
  articleno    = {109923},
  author       = {Virgilio, Marco and Mayo, I. and Dedeyne, Jens and Van Geem, Kevin and Marin, Guy and Arts, T.},
  issn         = {0894-1777},
  journal      = {EXPERIMENTAL THERMAL AND FLUID SCIENCE},
  keywords     = {Mechanical Engineering,Nuclear Energy and Engineering,General Chemical Engineering,Fluid Flow and Transfer Processes,Aerospace Engineering},
  language     = {eng},
  title        = {Effects of 2-D and 3-D helical inserts on the turbulent flow in pipes},
  url          = {http://dx.doi.org/10.1016/j.expthermflusci.2019.109923},
  volume       = {110},
  year         = {2020},
}

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