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Entropy 2018, 20(5), 379; https://doi.org/10.3390/e20050379

Flow and Heat Transfer in the Tree-Like Branching Microchannel with/without Dimples

1
Key Laboratory of NC Machine Tools and Integrated Manufacturing Equipment of the Education Ministry & Key Laboratory of Manufacturing Equipment of Shaanxi Province, Xi’an University of Technology, Xi’an 710048, China
2
Xi’an Aerospace Composite Materials Research Institute, Xi’an 710025, China
*
Author to whom correspondence should be addressed.
Received: 2 April 2018 / Revised: 10 May 2018 / Accepted: 16 May 2018 / Published: 18 May 2018
(This article belongs to the Special Issue Non-Equilibrium Thermodynamics of Micro Technologies)
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Abstract

This work displays a numerical and experimental investigation on the flow and heat transfer in tree-like branching microchannels and studies the effects of dimples on the heat transfer enhancement. The numerical approach is certified by a smooth branching microchannel experiment. The verification result shows that the SSG turbulence model can provide a reasonable prediction. Thus, further research on the convective heat transfer in dimpled branching microchannels is conducted with the SSG turbulence model. The results indicate that the dimples can significantly improve the averaged heat transfer performance of branching microchannels, and the heat transfer increment of the branch segment increases with the increase in the branching level. However, the flow dead zones in some dimples at bifurcations and bends suppress the turbulent flow and heat transfer. Furthermore, the Nu number ratio (Nua/Nus) and thermal enhancement factor (η) both monotonously decrease as the Re number increases, while the friction factor ratio (fa/fs) changes nonlinearly. The entropy generation rates of S ˙ t and S ˙ p in all dimpled cases are lower than those in the smooth case, and the dimpled case with the streamwise spacing to diameter ratio s/D = 3 obtains the lowest value of augmentation entropy generation (Ns) under the high Re number conditions. Nua/Nus, fa/fs, and η decline with the increase in the streamwise spacing to diameter ratio (s/D) from 3 to 9; therefore, the dimpled case with s/D = 3 shows the best overall thermal performance. View Full-Text
Keywords: gas turbine cooling; tree-like branching microchannel; dimple; heat transfer enhancement; friction factor gas turbine cooling; tree-like branching microchannel; dimple; heat transfer enhancement; friction factor
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This is an open access article distributed under the Creative Commons Attribution License which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited (CC BY 4.0).
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Shui, L.; Sun, J.; Gao, F.; Zhang, C. Flow and Heat Transfer in the Tree-Like Branching Microchannel with/without Dimples. Entropy 2018, 20, 379.

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