Influence of slat attack angle and pitch ratio on turbulent hydrothermal characteristics in a louvered two-pass square channel

•An innovative design of 3-D louver-type turbulator is proposed.•Detailed PIV and IRT measurements of flow and temperature fields are conducted.•The effects of slat attack angle and pitch ratio on Nu, f, and TPF are revealed.•A compilation of Nu-f data for both previous and present designs is presen...

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Bibliographic Details
Published in:International journal of heat and mass transfer 2019-11, Vol.143, p.118527, Article 118527
Main Authors: Liou, Tong-Miin, Wang, Chun-Sheng, Tseng, Jui-Cheng, Hsieh, I-Ming, Chen, Chieh-Chu
Format: Article
Language:English
Subjects:
Angle of attack
Core flow
Fluid dynamics
Fluid flow
Friction factor
Impingement
Infrared imagery
Infrared imaging
Infrared thermography
Louver-type turbulator
Particle image velocimetry
Pitch ratio
Pressure loss
Reynolds number
Slat attack angle
Stress concentration
Temperature distribution
Thermography
Turbulent flow
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Summary:•An innovative design of 3-D louver-type turbulator is proposed.•Detailed PIV and IRT measurements of flow and temperature fields are conducted.•The effects of slat attack angle and pitch ratio on Nu, f, and TPF are revealed.•A compilation of Nu-f data for both previous and present designs is presented. This study reports an innovative design of 3-D louver-type turbulator based on previous ribs, baffles, and 2-D louver-type turbulators. Its effects on turbulent flow field, detailed temperature distribution, and pressure loss in a two-pass channel with square cross-section are investigated by Particle Image Velocimetry (PIV), Infrared Thermography (IRT), and pressure transducer. Four pitch ratios (Pi/DH), namely 1, 2, 3, and ∞, are explored, and the slat attack angle (α) of the louver-type turbulator ranges from −40° to 30°. The Reynolds number (Re) for PIV and IRT measurement is fixed at 10,000 and in the range of 5000–20,000, respectively. It is found that the present turbulators with Pi/DH = ∞ not only disturb the core flow and degenerate wake zone behind the turbulator but also induce four pairs of Dean-like counter-rotating vortices which result in strong impingement on the bottom and top walls. The main contributions of this study are twofold: (1) the present design fills the blank at moderate friction factor ratio (f‾/f∞ ≤100) compared with previous ribs and baffles; (2) it attains much higher Nusselt number ratio (Nu‾/Nu∞ up to 4.4) at that f‾/f∞ region or for the same value of Nu‾/Nu∞ the value of f‾/f∞ is 44.1% lower.
ISSN:0017-9310
1879-2189
DOI:10.1016/j.ijheatmasstransfer.2019.118527