Effect on heat transfer augmentation by some geometric shapes of a turbulence promoter in a rectangular duct.

Oyakawa, Kenyu; Shinzato, Takao; Mabuchi, Ikuo

doi:10.1299/kikaib.52.860

Cited by 4 publications

(5 citation statements)

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“…The local heat transfer coefficient distribution of the heated wall can be calculated from the whole-field coolant temperature distribution provided by the LW intaferograms and is shown in The above dependence of Nit/Nu, on H/De was also found by Sparrow and Tao (1984) for Sherwood number in a duct with attached circular ribs.…”

Section: Results and Discussion Local Nusselt Numbermentioning

confidence: 75%

“…They found that the pitch to cylinder diameter ratios(Pi/H) of 12.5 and 25 for the range of 6.25 < < co investigated resulted in the optimum thermal performance. Oyakawa et al (1986) investigated how the rib shapes(different shapes of band plate) and detached distances affect the heat transfer from the wall in the fully developed region of a rectangular duct with staggered ribs using thermocouples. The band plate with I shape was found to provide best thermal performance and the optimal clearance ratio(C/H=detached distance/rib height) was about 0.3.…”

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confidence: 99%

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Effect of Rib Height and Pitch on the Thermal Performance of a Passage Disturbed by Detached Solid Ribs

Liou

Shuy

Tsao

1996

Volume 4: Heat Transfer; Electric Power; Industrial and Cogeneration

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Laser holographic interferometry and pressure measurements are presented for the effects of rib-to-duct height ratio (H/2B), rib pitch-to-height ratio (Pi/H), and Reynolds number (Re) on the spatially periodic-fully developed turbulent heat transfer and friction in a rectangular duct of width-to-height ratio of 4:1 with an array of ribs detached from one wall at a clearance to rib-height ratio of 0.38. The range of H/2B, Pi/H, and Re examined were 0.13 to 0.26, 7 to 13, and 5×103 to 5×104, respectively. The difference in the H/2B dependence of the thermal performance between the detached and attached solid-rib array is documented. H/2B=0.17 and Pi/H=10 are found to provide the best thermal performance for the range of parameters tested. Compact heat transfer and friction correlations are developed. Additionally, it is found that heat transfer augmentation with a detached solid-rib array is superior to with a detached perforated-rib array, and the mechanism responsible for the difference is revealed by the complementary flow visualization results.

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Section: Results and Discussion Local Nusselt Numbermentioning

confidence: 75%

mentioning

confidence: 99%

Effect of Rib Height and Pitch on the Thermal Performance of a Passage Disturbed by Detached Solid Ribs

Liou

Shuy

Tsao

1996

Volume 4: Heat Transfer; Electric Power; Industrial and Cogeneration

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“…Most of the above studies investigated the flow aspect but not the heat transfer aspect of the problems. Oyakawa et al (1986) studied the effect of inserting different geometric shapes in rectangular ducts on the heat transfer characteristics. Also, Oyakawa et al (1995) studied experimentally the effect of using jet discharge on the reattachment heat transfer in the region downstream of a backward facing step.…”

Section: Introductionmentioning

confidence: 99%

Using localized wall discharge to control the fluid flow and heat transfer for the flow over a backward facing step

Kiwan

2008

International Journal of Numerical Methods for Heat &Amp; Fluid Flow

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PurposeStudying the effect of localized wall discharge on the fluid flow and heat transfer for a flow over backward facing step is the main purpose of this paper. Jet is used to control the reattachment length which controls the fluid flow and heat transfer downstream the step. Several parameters are to be investigated: geometric; expansion ratio, location of the jet, and jet angle flow; Reynolds number, jet velocity.Design/methodology/approachNumerical simulation using both the standard K−ε and renormalized group turbulence theory (RNG) K−ε models are used to model flow in the computational domain. The energy equation is also used to model the heat transfer characteristics of the flow. The model equations are solved numerically using a finite volume code.FindingsIt is found that the presence of the wall jet at a proper location can significantly influence the flow and heat characteristics of the problem. Furthermore, varying the ratio of the jet velocity to the main stream velocity could play an important role in controlling the size of the circulating bubble and, therefore, the fluid and heat transfer characteristics of the flow, whereas, the expansion ratio has less influence. It is also found that increasing Reynolds number increases the value of maximum heat transfer but has less influence on either its location or the reattachment length.Research limitations/implicationsThe range of the Reynolds number considered in this research covers only the turbulent regime. The research does not cover laminar flows. The results and conclusions cover only three values of expansion ratios. Namely (expansion ratio (ER)=1.67, 1.8 and 2). Conclusions should not be read beyond these values of ER.Practical implicationsThis work gives designers of similar flows a new method of controlling the fluid flow and heat transfer by varying jet angle.Originality/valueThis work has not been done before and it can initiate additional research projects as investigating the effect of applying wall jets in combustors.

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“…Oyakawa et al [3] studied the effect of geometric shape (a straight band plate, an angled band plate, and a T band plate) and clearance of the turbulence promoters, which were set in staggered arrangement on the heat transfer augmentation in the fully developed region of a rectangular duct. Some shapes of turbulence promoters were found to provide a marked improvement in thermal performance as compared with the previously reported cylinder case.…”

Section: Introductionmentioning

confidence: 99%

Effect of Aspect Ratio, Channel Orientation, Rib Pitch-to-Height Ratio, and Number of Ribbed Walls on Pressure Drop Characteristics in a Rotating Channel with Detached Ribs

Arun

Prabhu

2007

International Journal of Rotating Machinery

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The present work involves experimental investigation of the effects of aspect ratio, channel orientation angle, rib pitch-to-height ratio (P/e), and number of ribbed walls on friction factor in orthogonally rotating channel with detached ribs. The ribs are separated from the base wall to provide a small region of flow between the base wall and the ribs. Experiments have been conducted at Reynolds number ranging from 10000-17000 with rotation numbers varying from 0-0.38. Pitch-to-rib height ratios (P/e) of 5 and 10 at constant rib height-to-hydraulic diameter ratio (e/D) of 0.1 and a clearance ratio (C/e) of 0.38 are considered. The rib angle of attack with respect to mainstream flow is 90 • . The channel orientation at which the ribbed wall becomes trailing surface (pressure side on which the Coriolis force acts) is considered as the 0 • orientation angle. For one-wall ribbed case, channel is oriented from 0 • to 180 • about its axis in steps of 30 • to change the orientation angle. For two-wall ribbed case, the orientation angle is changed from 0 • to 90 • in steps of 30 • . Friction factors for the detached ribbed channels are compared with the corresponding attached ribbed channel. It is found that in one-wall detached ribbed channel, increase in the friction factor ratio with the orientation angle is lower for rectangular channel compared to that of square channel for both the pitch-to-rib height ratios of 5 and 10 at a given Reynolds number and rotation number. Friction factor ratios of two-wall detached ribbed rectangular channel are comparable with corresponding two-wall detached ribbed square channel both under stationary and rotating conditions.

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Effect on heat transfer augmentation by some geometric shapes of a turbulence promoter in a rectangular duct.

Cited by 4 publications

References 0 publications

Effect of Rib Height and Pitch on the Thermal Performance of a Passage Disturbed by Detached Solid Ribs

Effect of Rib Height and Pitch on the Thermal Performance of a Passage Disturbed by Detached Solid Ribs

Using localized wall discharge to control the fluid flow and heat transfer for the flow over a backward facing step

Effect of Aspect Ratio, Channel Orientation, Rib Pitch-to-Height Ratio, and Number of Ribbed Walls on Pressure Drop Characteristics in a Rotating Channel with Detached Ribs

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