Mechanisms of the Self-Organization of Tornado-Like Jets Flowing Past Three-Dimensional Concave Reliefs

Кикнадзе, Г. И.; Gachechiladze, I. A.; Oleinikov, V. G.; Алексеев, В. В.

doi:10.1615/heattransres.v37.i6.10

Cited by 13 publications

(10 citation statements)

References 0 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…Large-scale dynamic vortex structures observed in a wide range of flow regimes are formed inside the dimples and in their vicinity. Despite a large number of publications dealing with using surfaces with dimples, however, some disputable issues have not been resolved (hypothesis of the tornado-like mechanism of heat-transfer enhancement [7,8], role of dimples in flows with high turbulence levels [9, 10], and determining the boundary between the domains of existence of separated and non-separated flows past spherical cavities [11,12]). This is explained by the complexity of the phenomenon, which is affected not only by the flow velocity, but also by the dimple size, shapes of its edges, character and thickness of the boundary layer at the dimple entrance, and channel height.…”

mentioning

confidence: 99%

See 2 more Smart Citations

Flow regimes in a single dimple on the channel surface

Kovalenko

Терехов

Халатов

2010

J Appl Mech Tech Phy

View full text Add to dashboard Cite

The boundaries of the domains of existence of flow regimes past single dimples made as spherical segments on a flat plate are determined with the use of available experimental results. Regimes of a diffuser-confuser flow, a horseshoe vortex, and a tornado-like vortex in the dimple are considered. Neither a horseshoe vortex nor a tornado-like vortex is observed in dimples with the relative depth smaller than 0.1. Transformations from the diffuser-confuser flow regime to the horseshoe vortex regime and from the horseshoe vortex flow to the tornado-like vortex flow are found to depend not only on the Reynolds number, but also on the relative depth of the spherical segment. Dependences for determining the boundaries of the regime existence domains are proposed, and parameters at which the experimental results can be generalized are given.Key words: dimple, vortex structures, horseshoe and tornado-like vortices, enhancement of heat transfer. Introduction.A large amount of experimental data on specific features of the flow structure and heat transfer in the flow past surfaces with spherical cavities (dimples) has been accumulated. There are some summary papers where numerous aspects of vortex formation in dimples under the action of a large number of factors were considered [1-6]. It was found in the first experiments that the increase in heat transfer in the flow past a surface with dimples made as spherical segments is accompanied by an insignificant relative increase in hydraulic resistance [7]. Large-scale dynamic vortex structures observed in a wide range of flow regimes are formed inside the dimples and in their vicinity. Despite a large number of publications dealing with using surfaces with dimples, however, some disputable issues have not been resolved (hypothesis of the tornado-like mechanism of heat-transfer enhancement [7,8], role of dimples in flows with high turbulence levels [9, 10], and determining the boundary between the domains of existence of separated and non-separated flows past spherical cavities [11,12]). This is explained by the complexity of the phenomenon, which is affected not only by the flow velocity, but also by the dimple size, shapes of its edges, character and thickness of the boundary layer at the dimple entrance, and channel height.Here, we make an attempt to determine the boundaries of the domains of existence of flow regimes in the dimple, depending on the external flow velocity and on the geometric characteristics of the dimple, by means of analyzing available experimental data. Similar studies were performed previously (see, e.g., [11,13]), but the previous results can now be refined because a large amount of new data appeared.Regimes of the Flow Past Dimples. The following flow regimes past a surface with a dimple can be identified. As low velocities, the flow has a diffuser-confuser character. The streamlines passing close to the dimple become curved. As the flow velocity is increased, the flow becomes separated near the leading edge of the dimple, forming a recirculation zone,...

show abstract

mentioning

confidence: 99%

“…1b) [7,10,12,15]. A pair of symmetric vortices is seen in the projection of the dimple wall onto a plane.…”

mentioning

confidence: 99%

See 1 more Smart Citation

Flow regimes in a single dimple on the channel surface

Kovalenko

Терехов

Халатов

2010

J Appl Mech Tech Phy

View full text Add to dashboard Cite

show abstract

“…But they focused on the effect produced by the system of annular protrusions formed at the same time on the inner surface of the tube [2]. Initiators of dimpled surfaces [3] used for the enhancement of heat transfer system of dimples on the outer surface. Its formation on the inner surface using initially round smooth tubes would be a difficult task.…”

Section: Brief Review Of Previous Researchs Concerning Dimpling Effectsmentioning

confidence: 99%

“…Such situation takes place both for bundles of plain tubes and finned tubes. This opinion is implemented in formulas (3,4). We have seen data of CFD calculations (figure 4) where opposite results were obtained.…”

Section: Figure 7 Illustration Of Colborn Number Dependence On Re Numentioning

confidence: 99%

Ways of dimpling use for efficiency improvement of shell and tube heat exchangers with finned tubes

Gotovsky¹,

Kolpakov²,

Mikhailov³

et al. 2017

IJHT

View full text Add to dashboard Cite

To date, accumulated large amount of experimental and theoretical data on the thermal hydraulics dimpled surfaces that demonstrate their high efficiency. However, the extent of the use of these surfaces in the industry far below their potential. This paper discusses the idea of using these surfaces to increase the efficiency of heat exchangers with a high coefficient of fins (e.g., air coolers). This makes it possible to achieve good results with minimal pressure loss increase and admit to widen practical use of such artificial roughness. Importantly, these reliefs provide heat transfer enhancement both on the side with dimples and on the side with protrusions. Most practically suitable for industrial implementation are tube-and-plate heat exchangers with continuous fins and new type of finned tubes − flat-oval tubes with partial finning. When using plane fins with dimples we can substantially increase efficiency if heat transfer intensity on shell side is not high. So we can bring the level of compactness of shell-and-tube heat exchangers up to values characteristic for the plate heat exchangers. Results of calculations showed a possibility of efficiency increase due to dimples to 60-70%.

show abstract