Heat Transfer and Flow Resistance Characteristics of the Horizontal Semi-cylindrical Vortex Generators and Analysis with Field Synergy Theory

2016 ◽  
Vol 52 (2) ◽  
pp. 166
Author(s):  
Zhiming XU
Keyword(s):  
Heat Transfer ◽  
Flow Resistance ◽  
Vortex Generators ◽  
Field Synergy ◽  
Cylindrical Vortex

Numerical Investigation of Heat Transfer Enhancement Inside the Pipes Filled With Radial Pore-Size Gradient Porous Materials

2018 ◽  
Vol 10 (5) ◽  
Author(s):  
Peiyong Ma ◽  
Baogang Wang ◽  
Shuilin Chen ◽  
Xianwen Zhang ◽  
Changfa Tao ◽  
...  
Keyword(s):  
Heat Transfer ◽  
Porous Materials ◽  
Pore Size ◽  
Flow Resistance ◽  
Heat Transfer Performance ◽  
Evaluation Criteria ◽  
Field Synergy ◽  
Transfer Enhancement ◽  
Size Gradient ◽  
Opening Up

The gradient porous materials (GPMs)-filled pipe structure has been proved to be effective in improving the heat transfer ability and reducing pressure drop of fluid. A GPMs-filled pipe structure in which radial pore-size gradient increased nonlinearly has been proposed. The field synergy theory and tradeoff analysis on the efficiency of integrated heat transfer has been accomplished based on performance evaluation criteria (PEC). It was found that the ability of heat transfer was enhanced considerably, based on the pipe structure, in which the pore-size of porous materials increased as a parabolic opening up. The flow resistance was the lowest and the integrated heat transfer performance was the highest when radial pore-size gradient increasing as a parabolic opening down.

Mass/Heat Transfer in a Ribbed Passage With Cylindrical Vortex Generators: The Effect of Generator-Rib Spacing

1999 ◽  
Vol 122 (4) ◽  
pp. 641-652 ◽  
Author(s):  
S. Acharya ◽  
R. G. Hibbs ◽  
Y. Chen ◽  
D. E. Nikitopoulos
Keyword(s):  
Heat Transfer ◽  
Shear Layer ◽  
Sherwood Number ◽  
Vortex Generator ◽  
Vortex Generators ◽  
Single Element ◽  
Cylindrical Vortex ◽  
Study Results ◽  
Lower Heat ◽  
Layer Development

The effect of vortex generators on the heat transfer from internally ribbed passages is studied experimentally using a mass transfer technique. Cylindrical vortex generators placed directly above the ribs have been used in this study. Results are reported on the effect of the spacing between the vortex generator and the ribs. Detailed distributions of the Sherwood number contours and the centerline Sherwood number distributions are presented. Reynolds number values of 5000, 10,000, and 30,000 are studied and three generator-rib-spacing/rib-height (s/e) values of 0.55, 1, and 1.5 are considered. It is shown that at small generator-rib spacings (s/e=0.55), the two act as a single element, and lead to a retardation of the shear layer development past the reattachment point. This is generally associated with lower heat transfer. At a larger generator-rib spacing (s/e=1.5), the generator wake and the rib shear layer interact with each other to promote mixing and heat transfer. [S0022-1481(00)02103-4]

The Effects of Arrangement of Longitudinal Vortex Generators on the Flow and Heat Transfer in the Rectangular Channel

2014 ◽  
Vol 694 ◽  
pp. 205-210
Author(s):  
Nan Cai ◽  
Li Ting Tian ◽  
Chun Hua Min ◽  
Cheng Yin Qi
Keyword(s):  
Heat Transfer ◽  
Flow Resistance ◽  
Heat Transfer Performance ◽  
Rectangular Channel ◽  
Vortex Generator ◽  
Vortex Generators ◽  
Longitudinal Vortex ◽  
Flow And Heat Transfer ◽  
Rectangular Channels ◽  
Flow Drag

In this paper, the heat transfer performance and flow resistance characteristics of the asymmetric arrangement of the rectangular winglet longitudinal vortex generators in the rectangular channels are numerically studied. Results show that at Re=500~2000, comparing with the symmetric arrangement of the longitudinal vortex generator, the Nusselt number of the asymmetric arrangement of the longitudinal vortex generator only decreased by 4% ~ 6%,while,the friction factor f decreases by 11% ~ 22%,the effect of flow drag reduction is very obvious. The asymmetric arrangements of the longitudinal vortex generators show the better overall thermal performance with the increase of j/f by 5% ~ 20%.

Detailed Mass Transfer Distribution in Rotating, Two-Pass Ribbed Coolant Channels With Vortex Generators

1999 ◽  
Author(s):  
V. Eliades ◽  
D. E. Nikitopoulos ◽  
S. Acharya
Keyword(s):  
Heat Transfer ◽  
Mass Transfer ◽  
Vortex Generator ◽  
Reynolds Numbers ◽  
Vortex Generators ◽  
Recirculation Region ◽  
Height Ratio ◽  
Cylindrical Vortex ◽  
Rotation Numbers ◽  
High Reynolds

Local and global effects of cylindrical vortex generators on the mass transfer distributions over the four active walls of a square, rib-roughened rotating duct with a sharp 180° bend are investigated. Cylindrical vortex generators (rods) are placed above, and parallel to, every other rib on the leading and trailing walls of the duct so that their wake can interact with the shear layer and recirculation region formed behind the ribs, as well as the rotation-generated secondary flows. Local increases in near-wall turbulence intensity resulting from these interactions give rise to local enhancement of mass (heat) transfer. Measurements are presented for duct Reynolds numbers (Re) in the range 5000–30,000, and for rotation numbers in the range 0 to 0.3. The rib height-to-hydraulic diameter ratio (e/Dh) is fixed at 0.1, while the rib pitch-to-rib height ratio (P/e) is 10.5. The vortex generator rods have a diameter-to-rib height ratio (d/e) of 0.78, and the distance separating them from the ribs relative to the rib height (s/e) is 0.55. Mass transfer measurements of naphthalene sublimation have been carried out using an automated acquisition system and are correlated with heat transfer using the heat/mass transfer analogy. The results indicate that the vortex generators tend to enhance overall mass transfer in the duct, compared to the case where only ribs are present, both before and after the bend at high Reynolds and Rotation numbers. Local enhancements of up to 30% are observed on all four walls of the duct. At low Reynolds numbers (e.g. 5,000) the insertion of the rods often leads to degradation. At high Reynolds numbers (e.g. 30,000) the enhancement due to the rods occurs on the surfaces stabilized by rotation (trailing edge on the inlet pass and leading edge on the outlet pass) and the side walls.. The enhancement is more pronounced as the Rotation number is increased. The detailed measurements in a ribbed duct with vortex-generator rods clearly show localized regions of enhanced mass (heat) transfer at Reynolds and Rotation numbers within the envelope of practical interest for gas-turbine blade cooling applications.

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