Effects of Corrugation Angle on Local Heat/Mass Transfer in Wavy Duct of Heat Exchanger

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.

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Local Heat/Mass Transfer Phenomena in Rotating Passage, Part 2: Angled Ribbed Passage

Journal of Thermophysics and Heat Transfer ◽

10.2514/1.14912 ◽

2006 ◽

Vol 20 (2) ◽

pp. 199-210 ◽

Cited By ~ 15

Author(s):

Kyung Min Kim ◽

Yun Young Kim ◽

Dong Hyun Lee ◽

Dong Ho Rhee ◽

Hyung Hee Cho

Keyword(s):

Mass Transfer ◽

Heat Mass Transfer ◽

Local Heat

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Local Heat/Mass Transfer Characteristics on a Rotating Blade With Flat Tip in a Low-Speed Annular Cascade—Part II: Tip and Shroud

Journal of Turbomachinery ◽

10.1115/1.2098767 ◽

2005 ◽

Vol 128 (1) ◽

pp. 110-119 ◽

Cited By ~ 30

Author(s):

Dong-Ho Rhee ◽

Hyung Hee Cho

Keyword(s):

Heat Transfer ◽

Mass Transfer ◽

Flow Velocity ◽

Rotational Speed ◽

Heat Mass Transfer ◽

Local Heat ◽

Incoming Flow ◽

Transfer Coefficients ◽

Low Speed ◽

Annular Cascade

The local heat/mass transfer characteristics on the tip and shroud were investigated using a low speed rotating turbine annular cascade. Time-averaged mass transfer coefficients on the tip and shroud were measured using a naphthalene sublimation technique. A low speed wind tunnel with a single stage turbine annular cascade was used. The turbine stage is composed of sixteen guide plates and blades. The chord length of blade is 150 mm and the mean tip clearance is about 2.5% of the blade chord. The tested Reynolds number based on inlet flow velocity and blade chord is 1.5×105 and the rotational speed of the blade is 255.8 rpm at design condition. The results were compared with the results for a stationary blade and the effects of incidence angle of incoming flow were examined for incidence angles ranging from −15 to +7deg. The off-design test conditions are obtained by changing the rotational speed with a fixed incoming flow velocity. Flow reattachment on the tip near the pressure side edge dominates the heat transfer on the tip surface. Consequently, the heat/mass transfer coefficients on the blade tip are about 1.7 times as high as those on the blade surface and the shroud. However, the heat transfer on the tip is about 10% lower than that for the stationary case due to reduced leakage flow with the relative motion. The peak regions due to the flow reattachment are reduced and shifted toward the trailing edge and additional peaks are formed near the leading edge region with decreasing incidence angles. But, quite uniform and high values are observed on the tip with positive incidence angles. The time-averaged heat/mass transfer on the shroud surface has a level similar to that of the stationary cases.

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

ASME 1997 Turbo Asia Conference ◽

10.1115/97-aa-126 ◽

1997 ◽

Cited By ~ 2

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.

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Effects of Fin Shapes and Arrangements on Heat Transfer for Impingement/Effusion Cooling With Crossflow

Volume 3: Turbo Expo 2005, Parts A and B ◽

10.1115/gt2005-68684 ◽

2005 ◽

Cited By ~ 1

Author(s):

Sung Kook Hong ◽

Dong-Ho Rhee ◽

Hyung Hee Cho

Keyword(s):

Mass Transfer ◽

Heat Mass Transfer ◽

Flow Characteristics ◽

Local Heat ◽

Wall Jet ◽

Transfer Coefficients ◽

Mass Transfer Coefficients ◽

Blowing Ratio ◽

Transfer Characteristics ◽

Sublimation Method

The present paper has investigated the effects of fin on the flow and heat/mass transfer characteristics for the impingement/effusion cooling with crossflow. The fins of circular or rectangular shape are installed between two perforated plates and the crossflow passes between these two plates. The blowing ratio is changed from 0.5 to 1.5 for a fixed jet Reynolds number of 10,000. A naphthalene sublimation method is used to obtain the local heat/mass transfer coefficients on the effusion plate. A numerical calculation is also performed to investigate the flow characteristics. Flow and heat/mass transfer characteristics are changed significantly due to installation of fins. In the injection region, wall jet spreads more widely than the case without fins because fin prevents the wall jet from being swept away by the crossflow. In the effusion region, higher heat/mass transfer coefficient is obtained due to the flow disturbance and acceleration by the fin. As the blowing ratio increases, the effects of fin against the crossflow become more significant and then the higher average heat/mass transfer coefficients are obtained. Especially, the cases with rectangular fins have about 40%∼45% enhancement at the high blowing ratio of M = 1.5. However, the increase of blockage effect gives more pressure loss in the channel.

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Local heat/mass transfer measurements on effusion plates in impingement/effusion cooling with rotation

International Journal of Heat and Mass Transfer ◽

10.1016/j.ijheatmasstransfer.2009.12.022 ◽

2010 ◽

Vol 53 (7-8) ◽

pp. 1373-1379 ◽

Cited By ~ 5

Author(s):

Sung Kook Hong ◽

Dong Hyun Lee ◽

Hyung Hee Cho ◽

Dong-Ho Rhee

Keyword(s):

Mass Transfer ◽

Heat Mass Transfer ◽

Local Heat

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

Journal of Heat Transfer ◽

10.1115/1.2824323 ◽

1998 ◽

Vol 120 (3) ◽

pp. 624-632 ◽

Cited By ~ 34

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.

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Local Heat/Mass Transfer Measurement on the Effusion Plate in Impingment/Effusion Cooling System

Volume 3: Heat Transfer; Electric Power; Industrial and Cogeneration ◽

10.1115/2000-gt-0252 ◽

2000 ◽

Author(s):

Hyung Hee Cho ◽

Dong Ho Rhee

Keyword(s):

Mass Transfer ◽

Heat Mass Transfer ◽

Cooling System ◽

Perforated Plate ◽

Local Heat ◽

Impinging Jets ◽

Transfer Coefficients ◽

Stagnation Region ◽

Perforated Plates ◽

Flow Acceleration

The present study is conducted to investigate the local heat/mass transfer characteristics for flow through perforated plates. A naphthalene sublimation method is employed to determine the local heat/mass transfer coefficients on the effusion plate. Two parallel perforated plates are arranged in two different configurations: staggered and shifted in one direction. The experiments are conducted for hole pitch-to-diameter ratios of 6.0, for gap distance between the perforated plates of 0.33 to 10 hole diameters, and for Reynolds numbers of 5,000 to 12,000. The result shows that the high transfer region is formed at stagnation region and at the mid-line of the adjacent impinging jets due to secondary vortices and flow acceleration to the effusion hole. For flows through the perforated plates, the mass transfer rates on the surface of the effusion plate are about six to ten times higher than for effusion cooling alone (single perforated plate). In general, higher heat/mass transfer is obtained with smaller gap distance between two perforated plates.

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