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]

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.

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.

Local Heat/Mass Transfer Distributions Around Sharp 180 deg Turns in Two-Pass Smooth and Rib-Roughened Channels

1988 ◽  
Vol 110 (1) ◽  
pp. 91-98 ◽  
Author(s):  
J. C. Han ◽  
P. R. Chandra ◽  
S. C. Lau
Keyword(s):  
Mass Transfer ◽  
Reynolds Numbers ◽  
Local Heat ◽  
Test Channel ◽  
Transfer Data ◽  
Ribbed Channel ◽  
Smooth Channel ◽  
Sharp Turn ◽  
Coated Surfaces ◽  
Rib Roughened

The detailed mass transfer distributions around the sharp 180 deg turns in a two-pass, square, smooth channel and in an identical channel with two rib-roughened opposite walls were determined via the napthalene sublimation technique. The top, bottom, inner (divider), and outer walls of the test channel were napthalene-coated surfaces. For the ribbed channel tests, square, transverse, brass ribs were attached to the top and bottom walls of the channel in alignment. The rib height-to-hydraulic diameter ratios (e/D) were 0.063 and 0.094; the rib pitch-to-height ratios (P/e) were 10 and 20. Experiments were conducted for three Reynolds numbers of 15,000, 30,000, and 60,000. Results show that the Sherwood numbers on the top, outer, and inner walls around the turn in the rib-roughened channel are higher than the corresponding Sherwood numbers around the turn in the smooth channel. For both the smooth and the ribbed channels, the Sherwood numbers after the sharp turn are higher than those before the turn. The regional averages of the local Sherwood numbers are correlated and compared with published heat transfer data.

scholarly journals Heat/Mass Transfer Distribution in a Rotating Two-Pass Square Channel Part I: Regional Heat Transfer, Smooth Channel

1998 ◽  
Vol 4 (3) ◽  
pp. 175-188 ◽  
Author(s):  
C. W. Park ◽  
M. Kandis ◽  
S. C. Lau
Keyword(s):  
Mass Transfer ◽  
Reynolds Number ◽  
Rotation Number ◽  
Heat Mass Transfer ◽  
Turbine Blades ◽  
Square Channel ◽  
Smooth Channel ◽  
Sharp Turn ◽  
First Pass ◽  
Rotating Channel

Naphthalene sublimation experiments have been conducted to examine the effect of rotation on the regional heat]mass transfer distribution for turbulent air flow in a rotating smooth two-pass square channel that has a 180 turn with sharp corners. The Reynolds number ranges from 5,500 to 14,500 and the rotation number goes up to 0.24. The test channel models the first two passes of serpentine internal cooling passages of gas turbine blades. Flow around a sharp turn causes larger heat]mass transfer increase in the turn and in the second pass than flow around a smooth turn. In the first pass with radially outward flow, rotation increases the heat]mass transfer on the trailing wall and decreases the heat/mass transfer on the leading wall. The reversed trend in the second pass with radially inward flow is evident only after four hydraulic diameters downstream of the turn exit. With rotation, there is an abrupt increase of the regional heat]mass transfer in the upstream portion of the turn on the leading wall. The regional heat]mass transfer on the trailing wall, however, increases along the streamwise direction in the turn, as in the stationary channel case. In the turn and immediately downstream of the turn, the shape of the heat/mass transfer distribution in a rotating channel is invariant over the range of rotation number studied. In a rotating channel, decreasing the Reynolds number increases the heat]mass transfer on the trailing wall and decreases that on the leading wall in the first pass, and increases the heat/mass transfer on both walls in the turn and immediately downstream of the turn.

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.

Heat Transfer in a Radially Rotating Square-Sectioned Duct With Two Opposite Walls Roughened by 45Deg Staggered Ribs at High Rotation Numbers

2006 ◽  
Vol 129 (2) ◽  
pp. 188-199 ◽  
Author(s):  
Shyy Woei Chang ◽  
Tong-Minn Liou ◽  
Jui-Hung Hung ◽  
Wen-Hsien Yeh
Keyword(s):  
Heat Transfer ◽  
Rotation Number ◽  
Coriolis Force ◽  
Density Ratio ◽  
Inertial Force ◽  
Local Heat Transfer ◽  
Local Heat ◽  
Secondary Flows ◽  
Test Channel ◽  
Rib Roughened

This paper describes an experimental study of heat transfer in a radially rotating square duct with two opposite walls roughened by 45deg staggered ribs. Air coolant flows radially outward in the test channel with experiments to be undertaken that match the actual engine conditions. Laboratory-scale heat transfer measurements along centerlines of two rib-roughened surfaces are performed with Reynolds number (Re), rotation number (Ro), and density ratio (Δρ∕ρ) in the ranges of 7500–15,000, 0–1.8, and 0.076–0.294. The experimental rig permits the heat transfer study with the rotation number considerably higher than those studied in other researches to date. The rotational influences on cooling performance of the rib-roughened channel due to Coriolis forces and rotating buoyancy are studied. A selection of experimental data illustrates the individual and interactive impacts of Re, Ro, and buoyancy number on local heat transfer. A number of experimental-based observations reveal that the Coriolis force and rotating buoyancy interact to modify heat transfer even if the rib induced secondary flows persist in the rotating channel. Local heat transfer ratios between rotating and static channels along the centerlines of stable and unstable rib-roughened surfaces with Ro varying from 0.1 to 1.8 are in the ranges of 0.6–1.6 and 1–2.2, respectively. Empirical correlations for periodic flow regions are developed to permit the evaluation of interactive and individual effects of ribflows, convective inertial force, Coriolis force, and rotating buoyancy on heat transfer.

Effect of Rib Size on Heat (Mass) Transfer Distribution in a Rotation Channel

1997 ◽  
Author(s):  
C. W. Park ◽  
R. T. Kukreja ◽  
S. C. Lau
Keyword(s):  
Mass Transfer ◽  
Rotation Number ◽  
Heat Mass Transfer ◽  
Reynolds Numbers ◽  
Local Heat ◽  
Test Channel ◽  
Turbine Blade Cooling ◽  
Blade Cooling ◽  
Rotation Numbers ◽  
Better Than

Experiments have been conducted to study the effect of rib size on the local heat (mass) transfer distribution for radial outward flow in a rotating channel with transverse ribs on the leading and trailing walls. The test channel modeled internal turbine blade cooling passages. Results were obtained for Reynolds numbers of 5,500 and 10,000, rotation numbers of 0.09 and 0.24, and for a fixed rib pitch that was equal to the channel hydraulic diameter. For a fixed rib configuration on the leading wall, increasing the size of the ribs on the trailing wall increased the heat (mass) transfer on the leading wall. Ribs with D/e = p/e = 16 on the trailing wall performed better than ribs with D/e = p/e = 10. When the rotation number was large, the heat (mass) transfer on the leading wall was quite low, regardless of the sizes of the ribs on the leading and trailing walls. There was very little spanwise variation of the local heat (mass) transfer between the transverse ribs on the trailing wall. When the rotation number was large, however, there was a significant spanwise variation of the local heat (mass) transfer between ribs on the leading wall.

Heat Transfer in a Radially Rotating Square-Sectioned Duct With Two Opposite Walls Roughened by 45° Staggered Ribs

2006 ◽  
Author(s):  
Shyy Woei Chang ◽  
Tong-Minn Liou ◽  
Wen-Hsien Yeh ◽  
Jui-Hung Hung
Keyword(s):  
Heat Transfer ◽  
Rotation Number ◽  
Coriolis Force ◽  
Density Ratio ◽  
Inertial Force ◽  
Local Heat Transfer ◽  
Local Heat ◽  
Secondary Flows ◽  
Test Channel ◽  
Rib Roughened

This paper describes an experimental study of heat transfer in a radially rotating square duct with two opposite walls roughened by 45° staggered ribs. Air coolant flows radially outward in the test channel with experiments to be undertaken that match the actual engine conditions. Laboratory-scale heat transfer measurements along centerlines of two rib-roughened surfaces are performed with Reynolds number (Re), rotation number (Ro) and density ratio (Δρ/ρ) in the ranges of 7500–15000, 0–1.8 and 0.076–0.294. The experimental rig permits the heat transfer study with the rotation number considerably higher than those studied in other researches to date. The rotational influences on cooling performance of the rib-roughened channel due to Coriolis forces and rotating buoyancy are studied. A selection of experimental data illustrates the individual and interactive impacts of Re, Ro and buoyancy number on local heat transfer. A number of experimental-based observations reveal that the Coriolis force and rotating buoyancy interact to modify heat transfer even if the rib induced secondary flows persist in the rotating channel. Local heat transfer ratios between rotating and static channels along the centerlines of stable and unstable rib-roughened surfaces with Ro varying from 0.1 to 1.8 are in the ranges of 0.6–1.6 and 1–2.2 respectively. Empirical correlations for periodic flow regions are developed to permit the evaluation of interactive and individual effects of rib-flows, convective inertial force, Coriolis force and rotating buoyancy on heat transfer.

Effect of Trailing-Edge Ejection on Local Heat (Mass) Transfer in Pin Fin Cooling Channels in Turbine Blades

1994 ◽  
Vol 116 (1) ◽  
pp. 159-168 ◽  
Author(s):  
R. D. McMillin ◽  
S. C. Lau
Keyword(s):  
Mass Transfer ◽  
Gas Turbine ◽  
Heat Mass Transfer ◽  
Turbine Blades ◽  
Local Heat ◽  
Transfer Coefficients ◽  
Pin Fin ◽  
Flow Through ◽  
Straight Flow ◽  
Cooling Air

Experiments are conducted to study the local heat transfer distribution and pressure drop in a pin fin channel that models the cooling passages in modern gas turbine blades. The detailed heat/mass transfer distribution is determined via the naphthalene sublimation technique for flow through a channel with a 16-row, staggered 3 × 2 array of short pin fins (with a height-to-diameter ratio of 1.0, and streamwise and spanwise spacing-to-diameter ratios of 2.5) and with flow ejection through holes in one of the side walls and at the straight flow exit (to simulate ejection through holes along the trailing edges and through tip bleed holes of turbine blades). The pin fin heat/mass transfer and the channel wall heat/mass transfer are obtained for the straight-flow-only and the ejection-flow cases. The results show that the regional pin heat/mass transfer coefficients are generally higher than the corresponding regional wall heat/mass transfer coefficients in both cases. When there is side wall flow ejection, a portion of the flow turns to exit through the ejection holes and the rate of heat/mass transfer decreases in the straight flow direction as a result of the reducing mass flow rate along the channel. The rate of cooling air flow through a pin fin channel in a gas turbine blade must be increased to compensate for the “loss” of the cooling air through trailing edge ejection holes, so that the blade tip is cooled sufficiently.

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