Numerical Predictions of Flow Structure and Local Nusselt Number Ratios Along and Above Dimpled Surfaces With Different Dimple Depths in a Channel

Won, Se Youl; Ligrani, Phillip M.

doi:10.1080/10407780490487830

Cited by 57 publications

(20 citation statements)

References 10 publications

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“…In fact, the realizable k model has been employed as the turbulence model in some studies on dimpled channel flow [17,18], because of its improved predictive capabilities compared to the standard k model and its ability to resolve portions of separated flows and flows with complex secondary circulation which are located very close to solid wall. This model also satisfies some constraints related to the Reynolds normal stress, including positive normal stress magnitudes, and Schwarz's inequality consistent with the physics of recirculating flows [17].…”

Section: Selection Of Turbulence Modelmentioning

confidence: 99%

Numerical Study on Heat Transfer Enhancement in a Receiver Tube of Parabolic Trough Solar Collector with Dimples, Protrusions and Helical Fins

Zhen

et al. 2015

Energy Procedia

104

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Vacuum tubular receiver is the core component of parabolic trough solar collectors (PTCs). To enhance the heat transfer rate from solar radiation to heat transfer fluid (HTF), one of the effective techniques is to improve the convective heat transfer inside the inner tube. In this study, we focus the heat transfer of the HTF side. A numerical simulation on the fully developed turbulent flow and heat transfer in the inner tube with and without helical fins, protrusions and dimples has been investigated. The results show that the receiver tubes with dimples have superior performance of heat transfer augmentation compared with that with protrusions or helical fins. Then, the effects of the geometry sizes and arrangements of dimples on the convective heat transfer performance are further studied. The performance evaluation plot of heat transfer enhancement techniques show that dimples with deeper depth, narrower pitch and more numbers in the circumference direction is benefit for improving the performance of heat transfer enhancement while the varied arrangements have no obvious influence.

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Section: Selection Of Turbulence Modelmentioning

confidence: 99%

Numerical Study on Heat Transfer Enhancement in a Receiver Tube of Parabolic Trough Solar Collector with Dimples, Protrusions and Helical Fins

Zhen

et al. 2015

Energy Procedia

104

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show abstract

“…Mahmood et al [9] describe the mechanisms responsible for local and spatially-averaged heat transfer augmentations on flat channel surfaces with an array of dimples on one wall for one channel height equal to 50 percent of the dimple print diameter. Other recent investigations consider flow and heat transfer in single spherical cavities [10], effects of dimples and protrusions on opposite channel walls [11,12], the effects of dimple depth on vortex structure and surface heat transfer [13,14], the effects of deep dimples on local surface Nusselt number distributions [15], the combined influences of aspect ratio, temperature ratio, Reynolds number, and flow structure [16], and the flow structure due to dimple depressions on a channel surface [17].…”

Section: Dimpled Test Surfacementioning

confidence: 99%

Flow characteristics along and above dimpled surfaces with three different dimple depths within a channel

Won

Ligrani

2007

J Mech Sci Technol

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The effects of dimples in altering time-averaged flow behavior occur mostly within one-half of one dimple print diameter from the surface, and the dimples within the arrays periodically eject a primary vortex pair from each dimple, which exists in conjunction with edge vortex pairs that form along the spanwise edges of staggered dimples regardless of three dimple depths. As the dimple depth increases, deeper dimples eject stronger primary vortex pairs, with hig her levels of turbulence transport due to larger deficits of time-averaged, normalized total pressure and streamw ise velocity as the surfaces with deeper dimples are approached. Primary vortex pair ejection frequencies range about 7-9 Hz, and edge vortex pair oscillation frequencies range about 5-7 Hz for RelJ=20,OOO, regardless of dimple depths.

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“…They reported that the large scale unsteadiness related to these vortices was strongly correlated to the Reynolds normal stress and flow mixing. In addition to this study, Ligrani and his co-workers conducted many other studies [4][5][6][7][8][9] for the characteristics of pressure drop and heat transfer according to various geometries of the dimpled surface. Wang et al [10] carried out the research for the turbulent flow in the dimpled channels at Re s = 180 based on the wall shear velocity.…”

Section: Introductionmentioning

confidence: 96%

Study on improvement of compactness of a plate heat exchanger using a newly designed primary surface

Doo

Yoon

2010

International Journal of Heat and Mass Transfer

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Numerical Predictions of Flow Structure and Local Nusselt Number Ratios Along and Above Dimpled Surfaces With Different Dimple Depths in a Channel

Cited by 57 publications

References 10 publications

Numerical Study on Heat Transfer Enhancement in a Receiver Tube of Parabolic Trough Solar Collector with Dimples, Protrusions and Helical Fins

Numerical Study on Heat Transfer Enhancement in a Receiver Tube of Parabolic Trough Solar Collector with Dimples, Protrusions and Helical Fins

Flow characteristics along and above dimpled surfaces with three different dimple depths within a channel

Study on improvement of compactness of a plate heat exchanger using a newly designed primary surface

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