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.

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.

High Rotation Number Heat Transfer of Rotating Trapezoidal Duct With 45-deg Staggered Ribs and Bleeds From Apical Side Wall

2007 ◽  
Author(s):  
Shyy Woei Chang ◽  
Tong-Minn Liou ◽  
Shyr Fuu Chiou ◽  
Shuen Fei Chang
Keyword(s):  
Heat Transfer ◽  
Rotation Number ◽  
Density Ratio ◽  
Side Wall ◽  
Local Heat Transfer ◽  
Local Heat ◽  
Turbine Rotor ◽  
Practical Applications ◽  
Turbine Rotor Blade ◽  
Apical Side

An experimental study of heat transfer in a radially rotating trapezoidal duct with two opposite walls roughened by 45° staggered ribs and mid-rib bleeds from the apical side wall is performed. Centerline heat transfer variations on two rib-roughened surfaces are measured for radially outward flows with and without bleeds at test conditions of Reynolds number (Re), rotation number (Ro) and density ratio (Δρ/ρ) in the ranges of 15000–30000, 0–0.8 and 0.04–0.31, respectively. Geometrical configurations and rotation numbers tested have considerably extended the previous experiences that offer practical applications to the trail edge cooling of a gas turbine rotor blade. A selection of experimental data illustrates the individual and interactive influences of Re, Ro and buoyancy number (Bu) on local heat transfer with and without bleeds. Local heat transfer results are generated with the influences of sidewall bleeds examined to establish heat transfer correlations with Re, Ro and Bu as the controlling flow parameters for design applications.

Numerical Study on Local Heat Transfer in a Rotating Cooling Channel

2018 ◽  
Author(s):  
Min Ren ◽  
Xueying Li ◽  
Jing Ren ◽  
Hongde Jiang
Keyword(s):  
Heat Transfer ◽  
Rotation Number ◽  
Numerical Study ◽  
Density Ratio ◽  
Local Heat Transfer ◽  
Local Heat ◽  
Hydraulic Diameter ◽  
Internal Cooling ◽  
Cooling Channel ◽  
Channel Diameter

Effect of rotation on turbine blade internal cooling is an important factor in gas turbine cooling systems. To obtain the distribution of the heat transfer and the flow field in a rotating cooling channel, a series of computational simulations using the realizable k-ε model are utilized. The channel Reynolds number based on the channel diameter is 25000. The rotation number ranges from 0 to 0.20. The investigated density ratio Δρ/ρ ranges from 0.05 to 0.33 and the range of radius-to-passage hydraulic diameter r/D is from 10 to 40. The results show that the heat transfer on the trailing side shows an overall augmentation while that on the leading side decreases in the cooling channel. When the channel is stationary, the density ratio has little effect on the thermal performance. And for the rotating channel, the heat transfer on the trailing side and leading side both increases when the density ratio increases. The heat transfer both on the trailing side and leading side decreases when the radius-to-passage hydraulic diameter (r/D) increase. And the radius has a greater effect when the rotation number is higher.

Heat Transfer in High-Speed Rotating Trapezoidal Duct With Rib-Roughened Surfaces and Air Bleeds From the Wall on the Apical Side

2008 ◽  
Vol 130 (6) ◽  
Author(s):  
Shyy Woei Chang ◽  
Tong-Minn Liou ◽  
Shyr Fuu Chiou ◽  
Shuen Fei Chang
Keyword(s):  
Heat Transfer ◽  
High Speed ◽  
Density Ratio ◽  
Side Wall ◽  
Local Heat Transfer ◽  
Local Heat ◽  
Turbine Rotor ◽  
Practical Applications ◽  
Apical Side ◽  
Rib Roughened

An experimental study of heat transfer in a radially rotating trapezoidal duct with two opposite walls roughened by 45deg staggered ribs and bleed from the apical side wall is performed. Centerline heat transfer variations on two rib-roughened surfaces are measured for radially outward flows with and without bleeds at test conditions of Reynolds number (Re), rotation number (Ro), and density ratio (Δρ∕ρ) in the ranges of 15,000–30,000, 0–0.8, and 0.04–0.31, respectively. Geometrical configurations and rotation numbers tested have considerably extended the previous experiences that offer practical applications to the trailing edge cooling of a gas turbine rotor blade. A selection of experimental data illustrates the individual and interactive influences of Re, Ro, and buoyancy number (Bu) on local heat transfer with and without bleeds. Local heat transfer results are generated with the influences of bleeds on the apical side examined to establish heat transfer correlations with Re, Ro, and Bu as the controlling flow parameters for design applications. The rotation of present trapezoidal duct with rib-roughened surfaces and air bleeds on the apical side worsens the impairing heat transfer impacts due to bleeds. Within the Ro range of 0.1–0.8, bleeds on the apical side of the rotating channel respectively produce 25–50% and 25–40% of heat transfer reductions from the rotational no-bleed references along the leading and trailing centerlines. Such heat transfer reductions due to the combined bleeds and Ro-Bu impacts need design precautions for turbine rotor blades.

Local Heat Transfer Distribution in a Rotating Serpentine Rib-Roughened Flow Passage

1993 ◽  
Vol 115 (3) ◽  
pp. 560-567 ◽  
Author(s):  
N. Zhang ◽  
J. Chiou ◽  
S. Fann ◽  
W.-J. Yang
Keyword(s):  
Heat Transfer ◽  
Reynolds Number ◽  
Heat Transfer Performance ◽  
Local Heat Transfer ◽  
Local Heat ◽  
Transfer Performance ◽  
Height Ratio ◽  
Nusselt Numbers ◽  
Rayleigh Numbers ◽  
Rib Roughened

Experiments are performed to determine the local heat transfer performance in a rotating serpentine passage with rib-roughened surfaces. The ribs are placed on the trailing and leading walls in a corresponding posited arrangement with an angle of attack of 90 deg. The rib height-to-hydraulic diameter ratio, e/Dh, is 0.0787 and the rib pitch-to-height ratio, s/e, is 11. The throughflow Reynolds number is varied, typically at 23,000, 47,000, and 70,000 in the passage both at rest and in rotation. In the rotation cases, the rotation number is varied from 0.023 to 0.0594. Results for the rib-roughened serpentine passages are compared with those of smooth ones in the literature. Comparison is also made on results for the rib-roughened passages between the stationary and rotating cases. It is disclosed that a significant enhancement is achieved in the heat transfer in both the stationary and rotating cases resulting from an installation of the ribs. Both the rotation and Rayleigh numbers play important roles in the heat transfer performance on both the trailing and leading walls. Although the Reynolds number strongly influences the Nusselt numbers in the rib-roughened passage of both the stationary and rotating cases, Nuo and Nu, respectively, it has little effect on their ratio Nu/Nuo.

Effects of Rib Arrangements on Pressure Drop and Heat Transfer in a Rib-Roughened Channel With a Sharp 180 deg Turn

1997 ◽  
Vol 119 (3) ◽  
pp. 610-616 ◽  
Author(s):  
S. Mochizuki ◽  
A. Murata ◽  
M. Fukunaga
Keyword(s):  
Heat Transfer ◽  
Pressure Drop ◽  
Secondary Flow ◽  
Flow Direction ◽  
Local Heat Transfer ◽  
Local Heat ◽  
Diameter Ratio ◽  
Equivalent Diameter ◽  
Before And After ◽  
Rib Roughened

The objective of this study was to investigate, through experiments, the combined effects of a sharp 180 deg turn and rib patterns on the pressure drop performance and distributions of the local heat transfer coefficient in an entire two-pass rib-roughened channel with a 180 deg turn. The rib pitch-to-equivalent diameter ratio P/de was 1.0, the rib-height-to-equivalent diameter ratio e/de was 0.09, and the rib angle relative to the main flow direction was varied from 30 ∼ 90 deg with an interval of 15 deg. Experiments were conducted for Reynolds numbers in the range 4000 ∼ 30,000. It was disclosed that, due to the interactions between the bend-induced secondary flow and the rib-induced secondary flow, the combination of rib patterns in the channel before and after the turn causes considerable differences in the pressure drop and heat transfer performance of the entire channel.

Local Heat Transfer in Rotating Smooth and Ribbed Two-Pass Square Channels With Three Channel Orientations

1996 ◽  
Vol 118 (3) ◽  
pp. 578-584 ◽  
Author(s):  
S. Dutta ◽  
J.-C. Han
Keyword(s):  
Heat Transfer ◽  
Rotation Number ◽  
Local Heat Transfer ◽  
Local Heat ◽  
Transfer Coefficients ◽  
Channel Changes ◽  
Square Channel ◽  
Heat Transfer Coefficients ◽  
Experimental Heat ◽  
Channel Orientation

This paper presents experimental heat transfer results in a two-pass square channel with smooth and ribbed surfaces. The ribs are placed in a staggered half-V fashion with the rotation orthogonal to the channel axis. The channel orientation varies with respect to the rotation plane. A change in the channel orientation about the rotating frame causes a change in the secondary flow structure and associated flow and turbulence distribution. Consequently, the heat transfer coefficient from the individual surfaces of the two-pass square channel changes. The effects of rotation number on local Nusselt number ratio distributions are presented. Heat transfer coefficients with ribbed surfaces show different characteristics in rotation number dependency from those with smooth surfaces. Results show that staggered half-V ribs mostly have higher heat transfer coefficients than those with 90 and 60 deg continuous ribs.

Effects of Pin Detached Space on Heat Transfer in a Rib Roughened Channel

2012 ◽  
Vol 135 (2) ◽  
Author(s):  
Sin Chien Siw ◽  
Minking K. Chyu ◽  
Mary Anne Alvin
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Coefficient ◽  
Transfer Coefficient ◽  
Local Heat Transfer ◽  
Local Heat ◽  
Local Heat Transfer Coefficient ◽  
Hybrid Technique ◽  
Pin Fins ◽  
Cooling Passage ◽  
Rib Roughened

An experimental study is performed to investigate the heat transfer characteristics and frictional losses in a rib roughened channel combined with detached pin-fins. The overall channel geometry (W = 76.2 mm, E = 25.4 mm) simulates an internal cooling passage of wide aspect ratio (3:1) in a gas turbine airfoil. With a given pin diameter, D = 6.35 mm = [1/4]E, three different pin-fin height-to-diameter ratios, H/D = 4, 3, and 2, were examined. Each of these three cases corresponds to a specific pin array geometry of detachment spacing (C) between the pin-tip and one of the endwalls, i.e., C/D = 0, 1, 2, respectively. The rib height-to-channel height ratio is 0.0625. Two newly proposed cross ribs, namely the broken rib and full rib are evaluated in this effort. The broken ribs are positioned in between two consecutive rows of pin-fins, while the full ribs are fully extended adjacent to the pin-fins. The Reynolds number, based on the hydraulic diameter of the unobstructed cross section and the mean bulk velocity, ranges from 10,000 to 25,000. The experiment employs a hybrid technique based on transient liquid crystal imaging to obtain distributions of the local heat transfer coefficient over all of the participating surfaces, including the endwalls and all pin elements. The presence of ribs enhances local heat transfer coefficient on the endwall substantially by approximately 20% to 50% as compared to the neighboring endwall. In addition, affected by the rib geometry, which is a relatively low profile as compared to the overall height of the channel, the pressure loss seems to be insensitive to the presence of the ribs. However, from the overall heat transfer enhancement standpoint, the baseline cases (without ribs) outperform cases with broken ribs or full ribs.

Heat Transfer in a Two-Pass Rectangular Channel (AR=1:4) Under High Rotation Numbers

2008 ◽  
Vol 130 (8) ◽  
Author(s):  
Yao-Hsien Liu ◽  
Michael Huh ◽  
Je-Chin Han ◽  
Sanjay Chopra
Keyword(s):  
Heat Transfer ◽  
Rotation Number ◽  
Rectangular Channel ◽  
Density Ratio ◽  
Leading Edge ◽  
First Passage ◽  
Test Channel ◽  
Sharp Bend ◽  
Buoyancy Parameter ◽  
Sharp Turn

This paper experimentally investigated the rotational effects on heat transfer in a two-pass rectangular channel (AR=1:4), which is applicable to the channel near the leading edge of the gas turbine blade. The test channel has radially outward flow in the first passage through a redirected sharp-bend entrance and radially inward flow in the second passage after a 180deg sharp turn. In the first passage, rotation effects on heat transfer are reduced by the redirected sharp-bend entrance. In the second passage, under rotating conditions, both leading and trailing surfaces experienced heat transfer enhancements above the stationary case. Rotation greatly increased heat transfer enhancement in the tip region up to a maximum Nu ratio (Nu∕Nus) of 2.4. The objective of the current study is to perform an extended parametric study of the low rotation number (0–0.3) and low buoyancy parameter (0–0.2) achieved previously. By varying the Reynolds numbers (10,000–40,000), the rotational speeds (0–400rpm), and the density ratios (inlet density ratio=0.10–0.16), the increased range of the rotation number and buoyancy parameter reached in this study are 0–0.67 and 0–2.0, respectively. The higher rotation number and buoyancy parameter have been correlated very well to predict the rotational heat transfer in the two-pass, 1:4 aspect ratio flow channel.

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