Heat Transfer and Pressure Losses of W-Shaped Small Ribs at High Reynolds Numbers for Combustor Liner

2011 ◽  
Vol 133 (9) ◽  
Author(s):  
Tomoko Hagari ◽  
Katsuhiko Ishida ◽  
Takeo Oda ◽  
Yasushi Douura ◽  
Yasuhiro Kinoshita
Keyword(s):  
Heat Transfer ◽  
Reynolds Number ◽  
Flat Plate ◽  
Pressure Loss ◽  
Reynolds Numbers ◽  
High Reynolds Numbers ◽  
High Reynolds ◽  
Cooling Passage ◽  
Combustor Liner ◽  
Rib Roughened

The present study investigates the heat transfer performance of W-shaped ribs in a rectangular channel with typical geometries and flow conditions for a combustor liner cooling passage. In order to assess the Reynolds number dependence on heat transfer enhancement by the ribs for the combustor cooling passage, experiments were conducted with channel Reynolds number ranging from 40,000 to 550,000. The ribs were located on one side of the channel and the rib height-to-hydraulic diameter ratio (e/Dh) was 0.006–0.014, which simulate the combustor liner cooling configurations. Rib pitch-to-height ratio (P/e) was 10. Rib-roughened copper plates with constant temperature were used to measure the averaged heat transfer coefficients. Measured results show that the heat transfer enhancements of about 3 were obtained over that of a flat plate at high Reynolds numbers for all cases. The slope of heat transfer coefficient becomes constant with increasing Reynolds number because of the laminar-turbulent transition around the ribs, which is considered to occur at Reynolds number based on rib height of about 1000. Pressure loss measurements showed that the friction coefficients are constantly 3–4.5 times higher than those of a flat plate for a fully turbulent flow such as a combustor cooling passage. Pressure loss by ribs seems not to have a significant impact to the overall combustor performance. Numerical calculations were conducted additionally for all test cases. Predicted amount of heat released from the ribs contributes about 40% of the overall heat release even for low ribs. Heat transfer on the rib surface is essential in the evaluation of the rib-roughened cooling passage.

Heat Transfer and Pressure Losses of W-Shaped Small Ribs at High Reynolds Numbers for Combustor Liner

2010 ◽  
Author(s):  
Tomoko Hagari ◽  
Katsuhiko Ishida ◽  
Takeo Oda ◽  
Yasushi Douura ◽  
Yasuhiro Kinoshita
Keyword(s):  
Heat Transfer ◽  
Reynolds Number ◽  
Flat Plate ◽  
Pressure Loss ◽  
Reynolds Numbers ◽  
High Reynolds Numbers ◽  
High Reynolds ◽  
Cooling Passage ◽  
Combustor Liner ◽  
Rib Roughened

The present study investigates the heat transfer performance of W-shaped ribs in a rectangular channel with typical geometries and flow conditions for a combustor liner cooling passage. In order to assess the Reynolds number dependence on heat transfer enhancement by the ribs for the combustor cooling passage, experiments were conducted with channel Reynolds number ranging from 40,000 to 550,000. The ribs were located on one side of the channel and the rib height-to-hydraulic diameter ratio (e/Dh) was 0.006 to 0.014, which simulate the combustor liner cooling configurations. Rib pitch-to-height ratio (P/e) was 10. Rib-roughened copper plates with constant temperature were used to measure the averaged heat transfer coefficients. Measured results show that the heat transfer enhancements of about 3 were obtained over that of a flat plate at high Reynolds numbers for all cases. The slope of heat transfer coefficient becomes constant with increasing Reynolds number because of the laminar-turbulent transition around the ribs, which is considered to occur at Reynolds number based on rib height of about 1,000. Pressure loss measurements showed that the friction coefficients are constantly 3–4.5 times higher than those of a flat plate for a fully turbulent flow such as a combustor cooling passage. Pressure loss by ribs seems not to have a significant impact to the overall combustor performance. Numerical calculations were conducted additionally for all test cases. Predicted amount of heat released from the ribs contributes about 40% of overall heat release even for low ribs. Heat transfer on the rib surface is essential in the evaluation of the rib-roughened cooling passage.

Heat Transfer and Pressure Drop Correlations for Square Channels With V-Shaped Ribs at High Reynolds Numbers

2011 ◽  
Vol 133 (11) ◽  
Author(s):  
Nawaf Y. Alkhamis ◽  
Akhilesh P. Rallabandi ◽  
Je-Chin Han
Keyword(s):  
Heat Transfer ◽  
Reynolds Number ◽  
Friction Factor ◽  
Thermal Performance ◽  
Reynolds Numbers ◽  
Transfer Coefficients ◽  
Heat Transfer Coefficients ◽  
High Reynolds Numbers ◽  
High Reynolds ◽  
Rib Roughened

Heat transfer coefficients and friction factors are measured in a 45 deg V-shaped rib roughened square duct at high Reynolds numbers, pertaining to internal passages of land-based gas turbine engines. Reynolds numbers in this study range from 30,000 to 400,000, which is much higher than prior studies of V-shaped rib roughened channels. The dimensions of the channel are selected to ensure that the flow is in the incompressible regime. Blockage ratio e/D ranges from 0.1 to 0.18 and the spacing ratio P/e ranges from 5 to 10. Reported heat transfer coefficients are regionally averaged, measured by isothermal copper plates. Results show that the heat transfer enhancement decreases with increasing Reynolds number. The friction factor is found to be independent of the Reynolds number. The thermal performance decreases when the Reynolds number increases. 45 deg V-shaped ribs show a higher thermal performance than corresponding 45 deg angled ribs, consistent with the trend established in literature. Correlations for the Nusselt number and the friction factor as function of Re, e/D, and P/e are developed. Also developed are correlations for R and G (friction and heat transfer roughness functions, respectively) as a function of the roughness Reynolds number (e+).

An Experimental and Numerical Study of Heat Transfer and Pressure Loss in a Rectangular Channel With V-Shaped Ribs

2006 ◽  
Author(s):  
Michael Maurer ◽  
Jens von Wolfersdorf ◽  
Michael Gritsch
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Enhancement ◽  
Thermal Performance ◽  
Pressure Loss ◽  
Numerical Study ◽  
Rectangular Channel ◽  
Reynolds Numbers ◽  
Transfer Enhancement ◽  
High Reynolds Numbers ◽  
High Reynolds

An experimental and numerical study was conducted to determine the thermal performance of V-shaped ribs in a rectangular channel with an aspect ratio of 2:1. Local heat transfer coefficients were measured using the steady state thermochromic liquid crystal technique. Periodic pressure losses were obtained with pressure taps along the smooth channel sidewall. Reynolds numbers from 95,000 to 500,000 were investigated with V-shaped ribs located on one side or on both sides of the test channel. The rib height-to-hydraulic diameter ratios (e/Dh) were 0.0625 and 0.02, and the rib pitch-to-height ratio (P/e) was 10. In addition, all test cases were investigated numerically. The commercial software FLUENT™ was used with a two-layer k-ε turbulence model. Numerically and experimentally obtained data were compared. It was determined that the heat transfer enhancement based on the heat transfer of a smooth wall levels off for Reynolds numbers over 200,000. The introduction of a second ribbed sidewall slightly increased the heat transfer enhancement whereas the pressure penalty was approximately doubled. Diminishing the rib height at high Reynolds numbers had the disadvantage of a slightly decreased heat transfer enhancement, but benefits in a significantly reduced pressure loss. At high Reynolds numbers small-scale ribs in a one-sided ribbed channel were shown to have the best thermal performance.

Temperature Control of Blow-Down, Supersonic Tunnels

1956 ◽  
Vol 60 (541) ◽  
pp. 67-70
Author(s):  
T. A. Thomson
Keyword(s):  
Heat Transfer ◽  
Boundary Layer ◽  
Reynolds Number ◽  
Mach Number ◽  
Reynolds Numbers ◽  
Stagnation Temperature ◽  
Blow Down ◽  
High Reynolds Numbers ◽  
Experimental Errors ◽  
High Reynolds

The blow-down type of intermittent, supersonic tunnel is attractive because of its simplicity and because relatively high Reynolds numbers can be obtained for a given size of test section. An adverse characteristic, however, is the fall of stagnation temperature during runs, which can affect experiments in several ways. The Reynolds number varies and the absolute velocity is not constant, even if the Mach number and pressure are; heat-transfer cannot be studied under controlled conditions and the experimental errors arising from the effect of heat-transfer on the boundary layer vary in time. These effects can become significant in quantitative experiments if the tunnel is large and the variation of temperature very rapid; the expense required to eliminate them might then be justified.

Heat Transfer Coefficient Distribution of W and Broken W Turbulators At High Reynolds Numbers

2021 ◽  
pp. 1-29
Author(s):  
Sam Ghazi-Hesami ◽  
Dylan Wise ◽  
Keith Taylor ◽  
Étienne Robert ◽  
Peter Ireland
Keyword(s):  
Heat Transfer ◽  
Reynolds Number ◽  
Heat Transfer Coefficient ◽  
Transfer Coefficient ◽  
Thermal Performance ◽  
Reynolds Numbers ◽  
High Reynolds Numbers ◽  
Smooth Channel ◽  
Wide Range ◽  
High Reynolds

Abstract An experimental and numerical study of the convective heat transfer enhancement provided by two rib families (W and Broken W) is presented, covering Reynolds numbers (Re) between 300,000 to 900,000 in a straight channel with a rectangular cross section (AR=1.29). These high Reynolds numbers were selected for the current study since most data in the available literature typically pertain to investigations at lower Reynolds numbers. The objective of this study is to assess the local heat transfer coefficient (HTC) enhancement (compared with a smooth channel) and the overall thermal performance, taking into account the effect of increased roughness on the friction factor, of a group of W shaped turbulators over a wide range of Reynolds numbers. Furthermore, the effects of increasing the rib spacing on the thermal performance of the Broken W configuration are presented and discussed. The numerical results are compared against heat transfer measurements obtained using the Transient Liquid Crystal (TLC) method. The research shows that for the Broken W turbulators, increasing the Reynolds number is associated with an overall decrease of the thermal performance while the thermal performance of the W configuration is relatively insensitive to Reynolds number. Nevertheless, the Broken W configuration delivers higher thermal performance and heat transfer compared with the W configuration for the range of Re investigated. The Broken W configuration with a pitch spacing of 10 times the rib height was shown to provide the optimal thermal performance in the configurations investigated here.

An Experimental and Numerical Study of Heat Transfer and Pressure Loss in a Rectangular Channel With V-Shaped Ribs

2006 ◽  
Vol 129 (4) ◽  
pp. 800-808 ◽  
Author(s):  
Michael Maurer ◽  
Jens von Wolfersdorf ◽  
Michael Gritsch
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Enhancement ◽  
Thermal Performance ◽  
Pressure Loss ◽  
Numerical Study ◽  
Rectangular Channel ◽  
Reynolds Numbers ◽  
Transfer Enhancement ◽  
High Reynolds Numbers ◽  
High Reynolds

An experimental and numerical study was conducted to determine the thermal performance of V-shaped ribs in a rectangular channel with an aspect ratio of 2:1. Local heat transfer coefficients were measured using the steady state thermochromic liquid crystal technique. Periodic pressure losses were obtained with pressure taps along the smooth channel sidewall. Reynolds numbers from 95,000 to 500,000 were investigated with V-shaped ribs located on one side or on both sides of the test channel. The rib height-to-hydraulic diameter ratios (e∕Dh) were 0.0625 and 0.02, and the rib pitch-to-height ratio (P∕e) was 10. In addition, all test cases were investigated numerically. The commercial software FLUENT™ was used with a two-layer k-ε turbulence model. Numerically and experimentally obtained data were compared. It was determined that the heat transfer enhancement based on the heat transfer of a smooth wall levels off for Reynolds numbers over 200,000. The introduction of a second ribbed sidewall slightly increased the heat transfer enhancement whereas the pressure penalty was approximately doubled. Diminishing the rib height at high Reynolds numbers had the disadvantage of a slightly decreased heat transfer enhancement, but benefits in a significantly reduced pressure loss. At high Reynolds numbers small-scale ribs in a one-sided ribbed channel were shown to have the best thermal performance.

Rib Turbulator Heat Transfer Enhancements at Very High Reynolds Numbers

2019 ◽  
Vol 11 (6) ◽  
Author(s):  
Mingyang Zhang ◽  
Prashant Singh ◽  
Srinath V. Ekkad
Keyword(s):  
Heat Transfer ◽  
Reynolds Number ◽  
Gas Turbines ◽  
Turbine Blades ◽  
Reynolds Numbers ◽  
Geometrical Parameters ◽  
High Reynolds Numbers ◽  
Rib Turbulators ◽  
High Reynolds ◽  
Very High

High-pressure stage gas turbine blades feature serpentine passages where rib turbulators are installed to enhance heat transfer between the relatively colder air bled off from the compressor and the hot internal walls. Most of the prior studies have been restricted to Reynolds number of 90,000 and several studies have been carried out to determine geometrically optimized parameters for achieving high levels of heat transfer in this range of Reynolds number. However, for land-based power generation gas turbines, the Reynolds numbers are significantly high and vary between 105 and 106. The present study is targeted toward these high Reynolds numbers where traditional rib turbulator shapes and prescribed optimum geometrical parameters have been investigated experimentally. A steady-state liquid crystal thermography technique is employed for measurement of detailed heat transfer coefficient. Five different rib configurations, viz., 45 deg, V-shaped, inverse V-shaped, W-shaped, and M-shaped have been investigated for Reynolds numbers ranging from 150,000 to 400,000. The ribs were installed on two opposite walls of a straight duct with an aspect ratio of unity. For very high Reynolds numbers, the heat transfer enhancement levels for different rib shapes varied between 1.4 and 1.7 and the thermal hydraulic performance was found to be less than unity.

Heat Transfer Measurements on a Cooled Flat Plate Simulating Actual Size Turbine Hardware

1999 ◽  
Author(s):  
J. Lepicovsky ◽  
T. J. Bencic
Keyword(s):  
Heat Transfer ◽  
Reynolds Number ◽  
Mach Number ◽  
Flat Plate ◽  
Boundary Layers ◽  
Local Heat Transfer ◽  
Reynolds Numbers ◽  
Local Heat ◽  
Transfer Rates ◽  
Cooling Passage

Application of thin-film thermocouples and temperature sensitive paint to surface temperature and heat transfer rate measurement on a flat plate with internal cooling is described in this paper. The test arrangement was designed to model flow and heat transfer conditions in terms of gas (external) and coolant (internal) Reynolds numbers that are typical for cooled turbine components. The test article is geometrically simple; however, from the heat transfer point of view it represents a fairly complex case. For both flows, internal and external, the hydrodynamic boundary layers start well ahead of the thermal boundary layers. The thermally active surface is preceded by an adiabatic starting length. Also, the heat transfer occurs under nonisothermal wall conditions and nonuniform heat flux conditions. The heat transfer experiments were carried out for a range of Mach number and Reynolds number on the gas side from 0.17 to 0.53 and from 135 000 to 580 000, respectively. On the coolant side, the corresponding ranges were from 0.3 to 0.52 for the flow Mach number, and from 20 000 to 65 000 for the Reynolds number. Measured bulk heat transfer rates demonstrated expected trends as functions of external (gas) and internal (coolant) Reynolds numbers. Local heat transfer rates measured along the mid-span line behaved as expected in relation to the internal (coolant) Reynolds number. However, they seem to be insensitive to changes in the external (gas) Reynolds number — at least for the particular test arrangement. Local heat transfer rates, however, strongly depend on the location with respect to the width of the cooling passage. These results were not expected; they may be caused by three dimensional nature of heat convection and conduction in this test arrangement.

Heat Transfer and Pressure Drop Correlations for Square Channels With 45 Deg Ribs at High Reynolds Numbers

2009 ◽  
Vol 131 (7) ◽  
Author(s):  
Akhilesh P. Rallabandi ◽  
Huitao Yang ◽  
Je-Chin Han
Keyword(s):  
Heat Transfer ◽  
Local Heat Transfer ◽  
Reynolds Numbers ◽  
Local Heat ◽  
Transfer Coefficients ◽  
Turbine Blade Cooling ◽  
Square Channel ◽  
Heat Transfer Coefficients ◽  
High Reynolds ◽  
Cooling Passage

Systematic experiments are conducted to measure heat transfer enhancement and pressure loss characteristics on a square channel (simulating a gas turbine blade cooling passage) with two opposite surfaces roughened by 45 deg parallel ribs. Copper plates fitted with a silicone heater and instrumented with thermocouples are used to measure regionally averaged local heat transfer coefficients. Reynolds numbers studied in the channel range from 30,000 to 400,000. The rib height (e) to hydraulic diameter (D) ratio ranges from 0.1 to 0.18. The rib spacing (p) to height ratio (p/e) ranges from 5 to 10. Results show higher heat transfer coefficients at smaller values of p/e and larger values of e/D, though at the cost of higher friction losses. Results also indicate that the thermal performance of the ribbed channel falls with increasing Reynolds numbers. Correlations predicting Nusselt number (Nu) and friction factor (f¯) as a function of p/e, e/D, and Re are developed. Also developed are correlations for R and G (friction and heat transfer roughness functions, respectively) as a function of the roughness Reynolds number (e+), p/e, and e/D.

Jet-to-Plate Distance Effect on Heat Transfer From a Flat Plate to an Impinging Jet at Various Reynolds Numbers

2012 ◽  
Author(s):  
Patricia Streufert ◽  
Terry X. Yan ◽  
Mahdi G. Baygloo
Keyword(s):  
Heat Transfer ◽  
Experimental Data ◽  
Reynolds Number ◽  
Flat Plate ◽  
Numerical Solutions ◽  
Stokes Equations ◽  
Local Heat Transfer ◽  
Reynolds Numbers ◽  
Air Jet ◽  
Plate Distance

Local turbulent convective heat transfer from a flat plate to a circular impinging air jet is numerically investigated. The jet-to-plate distance (L/D) effect on local heat transfer is the main focus of this study. The eddy viscosity V2F turbulence model is used with a nonuniform structured mesh. Reynolds-Averaged Navier-Stokes equations (RANS) and the energy equation are solved for axisymmetric, three-dimensional flow. The numerical solutions obtained are compared with published experimental data. Four jet-to-plate distances, (L/D = 2, 4, 6 and 10) and seven Reynolds numbers (Re = 7,000, 15,000, 23,000, 50,000, 70,000, 100,000 and 120,000) were parametrically studied. Local and average heat transfer results are analyzed and correlated with Reynolds number and the jet-to-plate distance. Results show that the numerical solutions matched experimental data best at low jet-to-plate distances and lower Reynolds numbers, decreasing in ability to accurately predict the heat transfer as jet-to-plate distance and Reynolds number was increased.

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