Effect of Channel Orientation of Local Heat (Mass) Transfer Distributions in a Rotating Two-Pass Square Channel With Smooth Walls

1998 ◽  
Vol 120 (3) ◽  
pp. 624-632 ◽  
Author(s):  
C. W. Park ◽  
S. C. Lau
Keyword(s):  
Mass Transfer ◽  
Coriolis Force ◽  
Heat Mass Transfer ◽  
Control Volume ◽  
Local Heat ◽  
Local Mass ◽  
Square Channel ◽  
Sharp Turn ◽  
Local Mass Transfer ◽  
Channel Orientation

Naphthalene sublimation experiments have been conducted to study the effects of channel orientation, rotational Coriolis force, and a sharp turn, on the local heat (mass) transfer distributions in a two-pass square channel with a sharp turn and smooth walls, rotating about a perpendicular axis. The test channel was oriented so that the direction of rotation was perpendicular to or at a 45 deg angle to the leading and trailing walls. The Reynolds number was kept at 5,500 and the rotation number ranged up to 0.24. For the radial outward flow in the first straight pass of the diagonally oriented channel, rotation-induced Coriolis force caused large monotonic spanwise variations of the local mass transfer on both the leading and trailing walls, with the largest mass transfer along the outer edges of both walls. Rotation did not lower the spanwise average mass transfer on the leading wall and did not increase that on the trailing wall in the diagonally oriented channel as much as in the normally oriented channel. The combined effect of the channel orientation, rotation, and the sharp turn caused large variations of the local mass transfer distributions on the walls at the sharp turn and immediately downstream of the sharp turn. The velocity fields that were obtained with a finite difference control-volume-based computer program helped explain how rotation and channel orientation affected the local mass transfer distributions in the rotating two-pass channel.

Heat (Mass) Transfer in a Diagonally Oriented Rotating Two-Pass Channel With Rib-Roughened Walls

1999 ◽  
Vol 122 (1) ◽  
pp. 208-211 ◽  
Author(s):  
C. W. Park ◽  
C. Yoon ◽  
S. C. Lau
Keyword(s):  
Mass Transfer ◽  
Heat Mass Transfer ◽  
Turbine Blades ◽  
Local Heat ◽  
Secondary Flows ◽  
Test Channel ◽  
Square Channel ◽  
Sharp Turn ◽  
Channel Orientation ◽  
Rib Roughened

Naphthalene sublimation experiments have been conducted to examine the effects of channel orientation, rotational Coriolis force, ad a sharp turn, on the local heat (mass) transfer distributions in a two-pass square channel with rib-roughened walls, rotating about a perpendicular axis. The test channel was oriented so that the direction of rotation was perpendicular or at a 45 deg angle to the leading and trailing walls. In the two straight passes of the test channel, there were parallel 90 or 60 deg ribs on the leading and trailing walls. The test channel modeled serpentine cooling passages in modern gas turbine blades. The results showed that the heat (mass) transfer was very low on the leading wall of the first pass when the channel was oriented with the rotating direction normal to the leading and trailing walls. There were regions of very low heat (mass) transfer on both the leading and trailing walls in the turn, especially on the trailing wall in the turn when the channel with transverse ribs was oriented diagonally. For the given diagonal channel orientation, rotational Coriolis forces caused the leading and trailing wall heat (mass) transfer to be high near the outer edges of the walls in the channel with transverse ribs; rotation-induced secondary flows dominated near wall rib-induced secondary flows in the channel with angled ribs, since the heat (mass) transfer was generally higher near the outer edges of the walls than near the inner edges in the first and second straight passes. [S0022-1481(00)00201-2]

Effects of Bleed Flow on Heat/Mass Transfer in a Rotating Rib-Roughened Channel

2006 ◽  
Vol 129 (3) ◽  
pp. 636-642 ◽  
Author(s):  
Yun Heung Jeon ◽  
Suk Hwan Park ◽  
Kyung Min Kim ◽  
Dong Hyun Lee ◽  
Hyung Hee Cho
Keyword(s):  
Mass Transfer ◽  
Heat Mass Transfer ◽  
Local Heat Transfer ◽  
Local Heat ◽  
Main Flow ◽  
Hydraulic Diameter ◽  
Transfer Coefficients ◽  
Square Channel ◽  
Rib Turbulators ◽  
Sublimation Method

The present study investigates the effects of bleed flow on heat/mass transfer and pressure drop in a rotating channel with transverse rib turbulators. The hydraulic diameter (Dh) of the square channel is 40.0mm. 20 bleed holes are midway between the rib turburators on the leading surface and the hole diameter (d) is 4.5mm. The square rib turbulators are installed on both leading and trailing surfaces. The rib-to-rib pitch (p) is 10.0 times of the rib height (e) and the rib height-to-hydraulic diameter ratio (e∕Dh) is 0.055. The tests were conducted at various rotation numbers (0, 0.2, 0.4), while the Reynolds number and the rate of bleed flow to main flow were fixed at 10,000 and 10%, respectively. A naphthalene sublimation method was employed to determine the detailed local heat transfer coefficients using the heat/mass transfer analogy. The results suggest that for a rotating ribbed passage with the bleed flow of BR=0.1, the heat/mass transfer on the leading surface is dominantly affected by rib turbulators and the secondary flow induced by rotation rather than bleed flow. The heat/mass transfer on the trailing surface decreases due to the diminution of main flow. The results also show that the friction factor decreases with bleed flow.

scholarly journals Heat (Mass) Transfer Distributions in a Rotating Two-Pass Channel with Angled Ribs

1999 ◽  
Vol 5 (1) ◽  
pp. 1-16 ◽  
Author(s):  
C. W. Park ◽  
S. C. Lau ◽  
R. T. Kukreja
Keyword(s):  
Mass Transfer ◽  
Heat Mass Transfer ◽  
Local Heat ◽  
Test Model ◽  
Turbine Blade Cooling ◽  
Blade Cooling ◽  
Twin Peaks ◽  
Smooth Channel ◽  
Sharp Turn ◽  
The Difference

Experiments have been conducted to study the local heat (mass) transfer distributions in a two-pass test model of internal turbine blade cooling passages, with 60 ribs on the leading and trailing walls. For radial outward flow in the first pass, rotation did not significantly increase the local nor the overall heat (mass) transfer between consecutive ribs on the trailing wall. Rotation-induced Coriolis force lowered the relative overall heat (mass) transfer on the leading wall less in the rib-roughened channel than in a smooth channel. When the rotation number was high, there were twin peaks in the local heat (mass) transfer distribution between ribs on the leading wall. For radial inward flow in the second pass, the sharp turn reduced the difference between the heat (mass) transfer.on the leading wall and that on the trailing wall.

scholarly journals Local Heat/Mass Transfer Distribution Around Sharp 180 Degree Turn in MultiPass Rib-Roughened Channels

1986 ◽  
Author(s):  
J. C. Han ◽  
P. R. Chandra ◽  
S. C. Lau
Keyword(s):  
Mass Transfer ◽  
Heat Mass Transfer ◽  
Outer Wall ◽  
Local Heat ◽  
Test Channel ◽  
Square Channel ◽  
Naphthalene Sublimation Technique ◽  
Smooth Channel ◽  
Naphthalene Sublimation ◽  
Rib Roughened

The detailed heat/mass transfer distributions in and around the sharp 180 degree turn of a three-pass square channel were determined by using the naphthalene sublimation technique. The top, bottom, inner (divider) and outer walls of the test channel were naphthalene plates. For the case of rib-roughened tests, the ribs of square cross section were glued periodically in-line on the top and bottom walls of the naphthalene channel in a required distribution. The rib height-to-hydraulic diameter ratios (e/D) were 0.063 and 0.094, whereas the rib pitch-to-height ratios (P/e) were 10 and 20, respectively. The channel Reynolds numbers varied from 30,000 to 60,000. The results showed that, for both the smooth and the ribbed channels, the Sherwood numbers after the sharp 180 degree turn were higher than that before the sharp 180 degree turn; after the turn the Sherwood numbers of the inner wall were higher than that of the outer wall. The results also indicated that the Sherwood numbers on the top, outer and inner walls of the rib roughened channel were higher than that of the smooth channel.

scholarly journals Heat (Mass) Transfer in a Rotating Two-Pass Square Channel — Part II: Local Transfer Coefficient, Smooth Channel

1998 ◽  
Vol 4 (1) ◽  
pp. 1-15 ◽  
Author(s):  
R. T. Kukreja ◽  
C. W. Park ◽  
S. C. Lau
Keyword(s):  
Mass Transfer ◽  
Heat Mass Transfer ◽  
Local Heat ◽  
Coriolis Forces ◽  
Square Channel ◽  
Naphthalene Sublimation Technique ◽  
Smooth Channel ◽  
Naphthalene Sublimation ◽  
Flow Through ◽  
Rotating Channel

Naphthalene sublimation technique and the heat/mass transfer analogy are used to determine the detailed local heat/mass transfer distributions on the leading and trailing walls of a twopass square channel with smooth walls that rotates about a perpendicular axis. Since the variation of density is small in the flow through the channel, buoyancy effect is negligible. Results show that, in both the stationary and rotating channel cases, very large spanwise variations of the mass transfer exist in he turn and in the region immediately downstream of the turn in the second straight pass. In the first straight pass, the rotation-induced Coriolis forces reduce the mass transfer on the leading wall and increase the mass transfer on the trailing wall. In the turn, rotation significantly increases the mass transfer on the leading wall, especially in the upstream half of the turn. Rotation also increases the mass transfer on the trailing wall, more in the downstream half of the turn than in the upstream half of the turn. Immediately downstream of the turn, rotation causes the mass transfer to be much higher on the trailing wall near the downstream corner of the tip of the inner wall than on the opposite leading wall. The mass transfer in the second pass is higher on the leading wall than on the trailing wall. A slower flow causes higher mass transfer enhancement in the turn on both the leading and trailing walls.

Effect of Rib-Angle Orientation on Local Mass Transfer Distribution in a Three-Pass Rib-Roughened Channel

1991 ◽  
Vol 113 (1) ◽  
pp. 123-130 ◽  
Author(s):  
J. C. Han ◽  
P. Zhang
Keyword(s):  
Mass Transfer ◽  
Internal Cooling ◽  
Combined Effects ◽  
Cooling Channel ◽  
Transfer Coefficients ◽  
Mass Transfer Coefficients ◽  
Local Mass ◽  
Square Channel ◽  
Local Mass Transfer ◽  
Turbulent Air Flow

In this experimental investigation of the heat transfer characteristics of turbulent air flow in a three-pass square channel, the test section consisted of three straight square channels jointed by two 180 deg turns, modeling the internal cooling passages of gas turbine airfoils. Naphthalene-coated ribs were attached to the top and bottom walls of the naphthalene-coated, three-pass channel. The rib height-to-hydraulic diameter ratio was 0.063; the rib pitch-to-height ratio was 10; the rib angles were 90 and 60 deg. For α = 60 deg, both the crossed ribs (on two opposite walls of the cooling channel) and the parallel ribs (on two opposite walls of the cooling channel) were investigated. The combined effects of the two sharp 180 deg turns and the rib orientations on the distributions of the local mass transfer coefficient in the entire three-pass channel were determined. The rib angle, the rib orientation, and the sharp 180 deg turn significantly affect the local mass transfer distributions. The combined effects of these parameters can increase or decrease the mass transfer coefficients after the sharp 180 deg turns. The angled ribs, in general, provide higher mass transfer coefficients than the transverse ribs; the parallel ribs give higher mass transfer than the crossed ribs.

Effect of Rib-Angle Orientation on Local Mass Transfer Distribution in a Three-Pass Rib-Roughened Channel

1989 ◽  
Author(s):  
J. C. Han ◽  
P. Zhang
Keyword(s):  
Mass Transfer ◽  
Internal Cooling ◽  
Combined Effects ◽  
Cooling Channel ◽  
Transfer Coefficients ◽  
Mass Transfer Coefficients ◽  
Local Mass ◽  
Square Channel ◽  
Local Mass Transfer ◽  
Turbulent Air Flow

In this experimental investigation of the heat transfer characteristics of turbulent air flow in a three-pass square channel, the test section consisted of three straight square channels jointed by two 180° turns, modeling the internal cooling passages of gas turbine airfoils. Naphthalene-coated ribs were attached to the top and the bottom walls of the naphthalene-coated, three-pass channel. The rib height-to-hydraulic diameter ratio was 0.063; the rib pitch-to-height ratio was 10; the rib angles were 90° and 60°. For α = 60°, both the crossed ribs (on two opposite walls of the cooling channel) and the parallel ribs (on two opposite walls of the cooling channel) were investigated. The combined effects of the two sharp 180° turns and the rib orientations on the distributions of the local mass transfer coefficient in the entire three-pass channel were determined. The rib angle, the rib orientation, and the sharp 180° turn significantly affect the local mass transfer distributions. The combined effects of these parameters can increase or decrease the mass transfer coefficients after the sharp 180° turns. The angled ribs, in general, provide higher mass transfer coefficients than the transverse ribs; the parallel ribs give higher mass transfer than the crossed ribs.

Effects of Bleed Flow on Heat/Mass Transfer in a Rotating Rib-Roughened Channel

2006 ◽  
Author(s):  
Yun Heung Jeon ◽  
Suk Hwan Park ◽  
Kyung Min Kim ◽  
Dong Hyun Lee ◽  
Hyung Hee Cho
Keyword(s):  
Mass Transfer ◽  
Heat Mass Transfer ◽  
Local Heat Transfer ◽  
Local Heat ◽  
Main Flow ◽  
Hydraulic Diameter ◽  
Transfer Coefficients ◽  
Square Channel ◽  
Rib Turbulators ◽  
Sublimation Method

The present study investigates the effects of bleed flow on heat/mass transfer and pressure drop in a rotating channel with transverse rib turbulators. The hydraulic diameter (Dh) of the square channel is 40.0 mm. The bleed holes are located between the rib turburators on the leading surface and the hole diameter (d) is 4.5 mm. The square rib turbulators are installed on both leading and trailing surface. The rib-to-rib pitch (p) is 10.0 times of the rib height (e) and the rib height-to-hydraulic diameter ratio (e/Dh) is 0.055. The tests were conducted at various rotation numbers (0, 0.2, 0.4), while the Reynolds number and the rate of bleed flow to main flow were fixed at 10,000 and 10%, respectively. A naphthalene sublimation method was employed to determine the detailed local heat transfer coefficients using the heat/mass transfer analogy. The results suggest that for a rotating ribbed passage with bleed flow of BR = 0.1, the heat/mass transfer on the leading surface is dominantly affected by rib turbulators and the secondary flow induced by rotation rather than bleed flow. The heat/mass transfer on the trailing surface decreases due to the diminution of main flow. The results also show that the friction factor decreases with bleed flow.

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