Determination of local heat transfer coefficient based on bulk mean temperature using a transient liquid crystals technique

Chyu, M. K.; Ding, Hui; Downs, J. P.; Soechting, F. O.

doi:10.1016/s0894-1777(98)10016-x

Cited by 56 publications

(5 citation statements)

References 6 publications

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“…Instead, it has to be determined after the test by either approximation or applying the principle of energy balance over the test channel. Chyu et al (1997) have recently compared several different approaches in converting the heat transfer coefficient based conveniently on the inlet temperature, t to that based on T r,,. The present study uses one of the most effective techniques, the so-called "invariant heat flux" method, which is based on local energy balance with time marching.…”

Section: Experimental Apparatus and Proceduresmentioning

confidence: 99%

Concavity Enhanced Heat Transfer in an Internal Cooling Passage

Chyu

Ding

et al. 1997

Volume 3: Heat Transfer; Electric Power; Industrial and Cogeneration

134

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The present study evaluates an innovative approach for enhancement of surface heat transfer in a channel using concavities, rather than protruding elements. Serving as a vortex generator, a concavity is expected to promote turbulent mixing in the flow bulk and enhance the heat transfer. Using a transient liquid crystal imaging system, local heat transfer distribution on the surface roughened by an staggered array based on two different shapes of concavities, i.e. hemispheric and tear-drop shaped, have been obtained, analyzed and compared. The results reveal that both concavity configurations induce a heat transfer enhancement similar to that of continuous rib turbulators, about 2.5 times their smooth counterparts 10,000 ≤ Re ≤ 50,000. In addition, both concavity arrays reveal remarkably low pressure losses that are nearly one-half the magnitudes incurred with protruding elements. In turbine cooling applications, the concavity approach is particularly attractive in reducing system weight and ease of manufacturing.

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Section: Experimental Apparatus and Proceduresmentioning

confidence: 99%

Concavity Enhanced Heat Transfer in an Internal Cooling Passage

Chyu

Ding

et al. 1997

Volume 3: Heat Transfer; Electric Power; Industrial and Cogeneration

134

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“…Heat transfer investigations using the transient TLC technique for a row of delta-shaped VG pairs have been reported by Chyu et al (1998) where the trailing edges of the VGs were closely aligned. The channel cross section was oval-shaped with a channel width (bottom) to height ratio of 2:1.…”

Section: Introductionmentioning

confidence: 99%

Flow and heat transfer characteristics behind vortex generators – A benchmark dataset

Henze

Wolfersdorf

Weigand

et al. 2011

International Journal of Heat and Fluid Flow

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“…To resolve the heat transfer characteristics for the endwall, the current measurement approach is based on an established technique that is well documented by Chyu et al [21]. Most of the results presented in this paper are in the form of a dimensionless heat transfer coefficient, the Nusselt number, Nu, which is defined as…”

Section: Test Section and Experimental Approachmentioning

confidence: 99%

Heat Transfer and Pressure Loss Characteristics of Zig-Zag Channel With Rib-Turbulators

Siw

Chyu

Alvin

2013

Volume 3A: Heat Transfer

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This paper describes a detailed experimental study of ribturbulators in a novel four-pass channel with 110 degree turns that exhibits a "zig-zag" pattern, and hence the name. The rectangular cross-sectional channel has the cross-section of 63.5mm by 25.4mm, corresponding to the aspect ratio of 2.5:1. This specific design with several turns will generate additional secondary vortices, while providing longer flow path that allows coolant to remove a greater heat load before being discharged downstream. Heat transfer is further enhanced by the presence of rib-turbulators. Four test cases with different rib-configurations are explored and compared to the baseline case, the smooth zig-zag channel. For the first three cases, the rib pitch-to-height (p/e) ratio is 10 and height-to-hydraulic diameter (e/Dh) of 0.044. Larger ribs are used in the fourth case, giving the p/e ratio of 5, and e/Dh of 0.088. The local heat transfer coefficient of the entire zig-zag channel is determined using the transient liquid crystal technique. The Reynolds number is based on the hydraulic diameter of the channel and bulk mean velocity ranges from 15,000 up to 30,000. The heat transfer in the zig-zag channel is enhanced due to the additional vortices and bulk flow mixing induced by the presence of turns and ribs in the entire channel. The highest heat transfer is observed along each rib-turbulator, followed by the region immediately behind the rib-turbulators. However, the heat transfer at the corner of each turn remains low and unaffected by the presence of rib-turbulators. The zigzag channel with larger rib-turbulators exhibits the highest heat transfer enhancement at approximately 4.0-4.8 times higher than that of the smooth channel, followed by the other test cases with the heat transfer enhancement ranging from 2.5-3.5. In each zig-zag channel test case, although ribturbulators have profound impact toward the heat transfer enhancement, with rather minimal increment in pressure loss within the tested Reynolds number.

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Determination of local heat transfer coefficient based on bulk mean temperature using a transient liquid crystals technique

Cited by 56 publications

References 6 publications

Concavity Enhanced Heat Transfer in an Internal Cooling Passage

Concavity Enhanced Heat Transfer in an Internal Cooling Passage

Flow and heat transfer characteristics behind vortex generators – A benchmark dataset

Heat Transfer and Pressure Loss Characteristics of Zig-Zag Channel With Rib-Turbulators

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