• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.13 no.5
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• pp.341-347
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• 2001

A comparison of fully developed heat transfer and friction factor characteristics has been made in rectangular ducts with ones roughened by five different shapes. The effects of rib shape geometries and Reynolds number are examined. The rib height-to-duct hydraulic diameter, pitch-to height ratio, and aspect ratio of channel width to height are fixed at $e$/De=0.0476, P/$e$=8, and W/H=2.33, respectively. To understand the mechanisms of the heat transfer enhancements, the measurements of the friction factors are also conducted in the smooth and rough channels. The data indicates that the triangular type rib has a substantially higher heat transfer performance than any other ones in the range we studied.

• Journal of Mechanical Science and Technology
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• v.16 no.4
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• pp.549-556
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• 2002

An investigation on the fully developed heat transfer and friction factor characteristics has been made in rectangular ducts with one-side roughened by five different shapes. The effects of rib shape geometries as well as Reynolds numbers are examined. The rib height-to-duct hydraulic diameter, pitch-to-height ratio, and aspect ratio of channel width to height are fixed at e/De=0.0476, P/e=8, and W/H=2.33, respectively. To understand the characteristics of heat transfer enhancements, the friction factors are also measured. The data indicates that the triangular type rib has a substantially higher heat transfer performance than any other ones.

• Journal of Advanced Marine Engineering and Technology
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• v.26 no.6
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• pp.646-652
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• 2002

The influence of reciprocating frequency and radius on heat transfer in the roughened rectangular channel is experimentally investigated. The aspect ratio (width/height) of the duct is 2.33 and the rib height is one fifteenth of the duct height. And the ratio of rib-to-rib distance to rib height is 10. The discrete ribs were periodically attached to the button wall of the duct with a parallel orientation. The parametric test matrix involves Reynolds number, reciprocating, and reciprocating radius, in the ranges, 1,000∼6,000, 1.7∼2.5 HB and 7∼15cm, respectively. The combined effects of reciprocating frequency and reciprocating radius have considerable influence on the heat transfer due to the modified vortex flow structure.

• Proceedings of the KSME Conference
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• 2001.11b
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• pp.241-247
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• 2001

A comparison of fully developed heat transfer and friction factor characteristics has been made in rectangular ducts with ones roughened by five different shapes. The effects of rib shape geometries and Reynolds number are examined. The rib height-to-duct hydraulic diameter, pitch-to-height ratio, and aspect ratio of channel width to height are fixed at e/De=0.0476, P/e=8, and W/H=2.33, respectively. To understand the mechanisms of the heat transfer enhancements, the measurements of the friction factors are also conducted in the smooth and rough channels. The data indicates that the triangular type rib has a substantially higher heat transfer performance than any other ones in the range we studied.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.22 no.4
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• pp.530-541
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• 1998

Heat transfer augmentation in a rib-roughened duct is affected by the rib configurations, such as rib height, angle of attack, shape, rib to rib pitch, and aspect ratio of a duct. These have been the main subjects in studying the average heat transfer and the friction loss of the fully developed flow. Investigating distributions of local heat transfer coefficients and flow patterns in a duct with the rib turbulators is necessary to find the characteristics of heat transfer augmentation and to decide the optimal configurations of ribs. In the present study the numerical analyses and the mass transfer experiments are performed to understand the flow through a rib roughened duct and the heat transfer characteristics with various angles of attack of ribs. A pair of counter-rotating secondary flow in a duct has a main effect on the lateral distributions of local mass transfer coefficients. Downwash of the rotating secondary flow, reattachment of main flow between ribs and the vortices near ribs and wall enhanced the mass transfer locally up to 8 times of that in case of the duct without ribs.

• Journal of Power System Engineering
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• v.5 no.2
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• pp.30-35
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• 2001

A comparison of fully developed heat transfer and friction factor characteristics has been made in rectangular ducts with one wall roughened by five different shapes. The effects of rib shape geometries and Reynolds number are examined. The rib height-to-duct hydraulic diameter, pitch-to-height ratio, and aspect ratio of channel width to height are fixed at $e/D_e=0.0476$, P/e=8, and W/H=2.33, respectively. To understand the mechanisms of the heat transfer enhancements, the measurements of the friction factors are also conducted in the smooth and rough channels. The data indicate that the triangular type rib has a substantially higher efficiency index than any other ones in the range we studied.

• Journal of Advanced Marine Engineering and Technology
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• v.24 no.2
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• pp.17-23
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• 2000

Experimental investigations were conducted to study the forced convection of fully-developed turbulent flow in horizontal equilateral duct fabricated with the same length and equivalent diameter, but different surface roughness pitch ratio(P/e) of 4, 8 and 16 on the one side wall only. The experiments were performed with the hydraulic diameter based Reynolds number ranged from 70,000 to 10,000. The entire bottom wall of the duct was heated uniformly and the other surfaces were thermally insulated. To understand the mechanisms of the heat transfer enhancement, measurements of the heat transfer were done to investigate the contributive factor of heat transfer promotion, namely, the fin effect. And the results were compared with those of previous investigations for similarly configured channels, at which they were roughened by regularly spaced transverse ribs in the rectangular and circular channels.

• Proceedings of the KSME Conference
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• 2000.04b
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• pp.65-70
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• 2000

Experimental investigations were conducted to study the forced convection of fully-developed turbulent f)on· in horizontal equilateral duct fabricated with the same length and equivalent diameter, but different surface roughness Pitch ratio(P/e) of 4, 8 and 16 on the one side wall only The experiments were performed with the hydraulic diameter based Reynolds number ranged from 70.000 to 10,000 The entire bottom wall of the duct was heated uniformly and the other surfaces were thermally insulated. To understand the mechanisms of the heat transfer enhancement. measurements of the heat transfer were done to investigate the contributive factor of heat transfer promotion. namely the fin effect. And the results were compared with those of Previous investigations for similarly configured channels, at which they were roughened by regularly spaced transverse ribs in the rectangular and circular channels.

• Proceedings of the KSME Conference
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• 2001.11b
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• pp.280-287
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• 2001

The present study investigates convective heat/mass transfer and flow characteristics inside the rib-roughened cooling passage of the gas turbine blades. A square duct with rectangular ribs is used and $\wedge-$ and V-shape ribs with $60^{\circ}$ attack angle are installed on the test plate surfaces. Naphthalene sublimation technique is employed to determine the detailed local heat transfer coefficients using the heat and mass transfer analogy. The ribs disturb the main flow resulting in the recirculation and secondary flows near the ribbed wall and the vortices near the side-wall. The local heat transfer and the secondary flow in the duct are changed largely according to the rib orientation. A square duct with $\wedge$ and V-shape ribs has two pairs of secondary flow because of the rib arrangement. So, the duct has complex heat/mass transfer distribution. The average heat/mass transfer coefficient and pressure drop of $\wedge-$ and V-shape ribs are higher than those with $90^{\circ}$ and $60^{\circ}$ attack angles. The average heat/mass transfer coefficient on the $\wedge-shape$ ribs is higher than that on the V-shape ribs. Also, the uniformity of heat/mass transfer coefficient on discrete ribs is higher than that on continuous rib.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.26 no.11
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• pp.1542-1551
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• 2002

The present study investigates the convective heat/mass transfer characteristics and pressure drop inside the rib-roughened cooling passage of gas turbine blades. The internal cooling passage is simulated using a square duct with h- and V-shaped rectangular ribs which have a 60。attack angle. A naphthalene sublimation technique is employed to determine the detailed local heat/mass transfer coefficients using the heat and mass transfer analogy. The ribs disturb the main flow resulting in the recirculation and secondary flows near the ribbed wail. The secondary flow patterns and the local heat transfer in the duct are changed significantly according to the rib orientation. A square duct with ∧ - and V-shaped ribs have two pairs of secondary flow due to the rib arrangement. Therefore, the average heat/mass transfer coefficients and pressure drop of ∧ - and V-shaped ribs are higher than those of the continuous ribs with 90$^{\circ}$ and 60$^{\circ}$attack angles. The ∧-shaped ribs have higher heat/mass transfer coefficients than the V-shaped ribs, and the uniformity of heat/mass transfer coefficient are increased with the discrete ribs due to the flow leakage and acceleration near the surface.