Heat Transfer to a Pvd Rotor Blade at High Subsonic Passage Throat Mach Numbers

1978 ◽  
Vol 192 (1) ◽  
pp. 225-235 ◽  
Author(s):  
B. W. Martin ◽  
A. Brown ◽  
S. E. Garrett
Keyword(s):  
Heat Transfer ◽  
Rotor Blade ◽  
Local Heat Transfer ◽  
Reynolds Numbers ◽  
Local Heat ◽  
Transfer Coefficients ◽  
Suction Surface ◽  
Pressure Surface ◽  
Air Stream ◽  
Mach Numbers

This paper reports heat-transfer measurements round a PVD rotor blade using a transient method. Instrumented syndanio-asbestos blades forming part of a cascade are suddenly introduced into a heated air stream, the temperature-time response of surface thermocouples attached to copper inserts in the blades then being used to determine local heat-transfer coefficients for (a) passage throat Mach numbers between 0.79 and 0.94 (b) turbulence intensities from 4.15 to 9.05 per cent (c) blade chord Reynolds numbers from 7.8 times 105 to 8.9 times 105. Measured transition lengths on the suction surface, over which the heat transfer nearly trebles, are somewhat short in relation to other measurements. The onset of transition, which is downstream of predictions for the higher Reynolds numbers but accords with the trends of existing correlations, is little influenced by turbulence intensity variations in the above range. Over the pressure surface the heat transfer is less than for a fully-turbulent boundary layer. Comparisons with other high Mach-number measurements suggest that much further work is needed before the effects of scale of turbulence are fully understood.

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.

Experimental Investigation of Local Heat Transfer Distribution on Smooth and Roughened Surfaces Under an Array of Angled Impinging Jets

2001 ◽  
Author(s):  
Lamyaa A. El-Gabry ◽  
Deborah A. Kaminski
Keyword(s):  
Heat Transfer ◽  
Reynolds Number ◽  
Cross Flow ◽  
Local Heat Transfer ◽  
Reynolds Numbers ◽  
Local Heat ◽  
Impinging Jets ◽  
Transfer Coefficients ◽  
Heat Transfer Coefficients ◽  
Roughened Surface

Abstract Measurements of the local heat transfer distribution on smooth and roughened surfaces under an array of angled impinging jets are presented. The test rig is designed to simulate impingement with cross-flow in one direction which is a common method for cooling gas turbine components such as the combustion liner. Jet angle is varied between 30, 60, and 90 degrees as measured from the impingement surface, which is either smooth or randomly roughened. Liquid crystal video thermography is used to capture surface temperature data at five different jet Reynolds numbers ranging between 15,000 and 35,000. The effect of jet angle, Reynolds number, gap, and surface roughness on heat transfer efficiency and pressure loss is determined along with the various interactions among these parameters. Peak heat transfer coefficients for the range of Reynolds number from 15,000 to 35,000 are highest for orthogonal jets impinging on roughened surface; peak Nu values for this configuration ranged from 88 to 165 depending on Reynolds number. The ratio of peak to average Nu is lowest for 30-degree jets impinging on roughened surfaces. It is often desirable to minimize this ratio in order to decrease thermal gradients, which could lead to thermal fatigue. High thermal stress can significantly reduce the useful life of engineering components and machinery. Peak heat transfer coefficients decay in the cross-flow direction by close to 24% over a dimensionless length of 20. The decrease of spanwise average Nu in the crossflow direction is lowest for the case of 30-degree jets impinging on a roughened surface where the decrease was less than 3%. The decrease is greatest for 30-degree jet impingement on a smooth surface where the stagnation point Nu decreased by more than 23% for some Reynolds numbers.

Numerical and Experimental Study of Turbulent Heat Transfer and Fluid Flow in Longitudinal Fin Arrays

1986 ◽  
Vol 108 (1) ◽  
pp. 16-23 ◽  
Author(s):  
D. S. Kadle ◽  
E. M. Sparrow
Keyword(s):  
Heat Transfer ◽  
Local Heat Transfer ◽  
Base Plate ◽  
Local Heat ◽  
Turbulent Heat Transfer ◽  
Turbulent Heat ◽  
Transfer Coefficients ◽  
Numerical Work ◽  
Model Average ◽  
Air Stream

Heat transfer from an array of parallel longitudinal fins to a turbulent air stream passing through the interfin spaces has been investigated both analytically/numerically and experimentally. The fins were integrally attached to a heated base plate, while the fin tips were shrouded to avoid leakage. In the analytical/numerical work, a conjugate problem was solved which encompassed turbulent flow and heat transfer in the air stream and heat conduction in the fins and in the base plate. The turbulence model and computational scheme were verified by comparison with experiment. It was found that the local heat transfer coefficients varied along the fins and along the surface of the base plate, with the lowest values in the corners formed by the fin/base plate intersections and the fin/shroud intersections. The numerically determined fin efficiencies did not differ appreciably from those calculated from the conventional pure-conduction fin model. Average Nusselt numbers, evaluated from the experimental data in conjunction with the numerically determined fin efficiencies (for derating the fin surface area), agreed well with those for fully developed heat transfer in a uniformly heated circular tube.

Effect of Variation of Local Film Coefficients on Fin Performance

1969 ◽  
Vol 91 (1) ◽  
pp. 21-26 ◽  
Author(s):  
J. W. Stachiewicz
Keyword(s):  
Heat Transfer ◽  
Local Heat Transfer ◽  
Reynolds Numbers ◽  
Local Heat ◽  
Single Equation ◽  
Transfer Coefficients ◽  
Base Surface ◽  
Heat Transfer Coefficients ◽  
Local Coefficients ◽  
Film Coefficient

Local heat-transfer coefficients on the surface of a longitudinal, constant area fin were measured experimentally. Turbulent flow was maintained in all tests and the range of fin spacing-to-height ratios from 0.25 to 0.5 was covered. The film coefficients do not increase monotonically from the base of the fin as suggested by an earlier investigation, but increase to a maximum at about 50 percent of fin height, then dip, and then increase again near the tip. The distribution of local coefficients along the height of the fin was similar at all Reynolds numbers and fin spacings investigated. This distribution yields lower fin efficiencies than those computed assuming a constant film coefficient, but, taking advantage of the fact that the distribution is remarkably similar at all fin spacings and all Reynolds numbers, a simple correction factor can be applied to the conventional, constant “h” efficiency to allow for the effect of variation of h. The integrated average heat-transfer coefficients on the surface of the fin were correlated at all fin spacings by a single equation. The coefficients along the base surface between fins were also measured.

Heat Transfer Measurements on a Turbine Airfoil With Pressure Side Separation

2009 ◽  
Author(s):  
Helge Ladisch ◽  
Achmed Schulz ◽  
Hans-Jo¨rg Bauer
Keyword(s):  
Heat Transfer ◽  
Free Stream ◽  
Separation Bubble ◽  
Local Heat Transfer ◽  
Reynolds Numbers ◽  
Boundary Layer Separation ◽  
Local Heat ◽  
Free Stream Turbulence ◽  
Pressure Surface ◽  
Low Pressure Turbine

Heat transfer measurements on a highly loaded low-pressure turbine airfoil with a separation bubble on the pressure surface are presented. The experiments were conducted in a linear cascade at various free-stream turbulence intensities (Tu1 = 1.6% to 10%) and Reynolds numbers of the inflow. The effect of both quantities on heat transfer, separation and laminar-turbulent transition is quantified. Particle-Image-Velocimetry has been performed to study the characteristics of the separation bubble. The results reveal a considerable influence of the boundary layer separation on the local heat transfer. The size of the separation region is strongly influenced by free-stream turbulence level and Reynolds number.

Detailed Heat Transfer Distributions in Engine Similar Cooling Channels for a Turbine Rotor Blade With Different Rib Orientations

2012 ◽  
Vol 135 (1) ◽  
Author(s):  
Christopher LeBlanc ◽  
Srinath V. Ekkad ◽  
Tony Lambert ◽  
Veera Rajendran
Keyword(s):  
Heat Transfer ◽  
Reynolds Number ◽  
Rotor Blade ◽  
Color Change ◽  
Leading Edge ◽  
Local Heat Transfer ◽  
Local Heat ◽  
Channel Inlet ◽  
Transfer Coefficients ◽  
Edge Channel

Detailed Nusselt number distributions are presented for a gas turbine engine similar internal channel geometry used for cooling a modern first stage rotor blade. The cooling design has one leading edge channel and a three-pass channel that covers the rest of the blade. The simulated model, generated from the midspan section of an actual cooling circuit, was studied for wall heat transfer coefficient measurements using the transient liquid crystal technique. The model wall inner surfaces were sprayed with thermochromic liquid crystals, and a transient test was used to obtain the local heat transfer coefficients from the measured color change. Results are presented for a nominal channel inlet leading edge channel Reynolds number of 10,700 and a channel inlet three-pass channel Reynolds number of 25,500. Detailed heat transfer measurements are presented for the simulated leading edge, first pass, second pass and third pass interior walls for different rib configurations. The channels were studied for smooth, 90 deg ribs, and angled ribs geometries in addition to ribs on the divider walls between adjacent passages. Overall pressure drop measurements were also obtained for each passage. Some of these results are compared with the predicted heat transfer from standard correlations used in design practices. Results show very complicated heat transfer behavior in these realistic channels compared to results obtained in simplistic geometry channels from published studies. In some cases, the Nusselt numbers predicted by correlations are 50–60% higher than obtained from the current experiments.

Comparison of Trip-Strip/Impingement/Dimple Cooling Concepts at High Reynolds Numbers

2003 ◽  
Author(s):  
Yong W. Kim ◽  
Leonel Arellano ◽  
Mark Vardakas ◽  
Hee-Koo Moon ◽  
Kenneth O. Smith
Keyword(s):  
Heat Transfer ◽  
Film Cooling ◽  
Engine Performance ◽  
Jet Impingement ◽  
Local Heat Transfer ◽  
Reynolds Numbers ◽  
Local Heat ◽  
Transfer Coefficients ◽  
Strip Surface ◽  
Number Range

Modern industrial combustor liners employ various cooling schemes such as, but not limited to, impingement arrays, trip-strips, and film cooling. With an increasing demand for a higher turbine inlet temperatures and lower emissions, there is less air available to cool the combustor liner. To ensure the required liner durability without compromising engine performance more innovative cooling schemes are required. In the present work, three different cooling concepts, i.e., strip-strips, jet array impingement and dimples, operating at unusually high flow conditions were investigated. There is very little data available in the open literature for the aforementioned cooling schemes in the indicated Reynolds Number range (ReDh>60,000). The wall flow friction characteristics as well as the local heat transfer were measured. The heat transfer coefficients were obtained using a transient liquid crystal technique. The test configurations consisted of a 90° trip-strip surface (only one side turbulated), a fixed staggered array with varying impingement hole sizes, and a fixed staggered dimple pattern. For the Reynolds numbers investigated (26,000< ReDh <360,000), the jet-impingement cooling provided the highest average heat transfer enhancement followed by the trip-strip channel, and then by the dimpled channel. In terms of the overall thermal performance, the dimpled channel tends to stand out as the most effective cooling scheme. This is consistent with findings from other investigators at lower Reynolds numbers.

Heat Transfer of Slug Air-Water Flow in a Slightly Upward Inclined Tube

2001 ◽  
Author(s):  
Jae-yong Kim ◽  
Steve Trimble ◽  
Afshin J. Ghajar
Keyword(s):  
Heat Transfer ◽  
Water Flow ◽  
Inclination Angle ◽  
Local Heat Transfer ◽  
Reynolds Numbers ◽  
Local Heat ◽  
Transfer Coefficients ◽  
Two Phase ◽  
Flux Boundary Condition ◽  
Inclined Tube

Abstract This paper presents a preliminary study on the heat transfer in slug air-water flow in a slightly upward inclined tube, which is a widely appeared pattern in the inclined two-phase flow regime. Local heat transfer coefficients and flow parameters have been measured for slug air-water flow in a pipe [1.097 in (2.79 cm) I.D. and L/D = 100] at slightly upward inclination angles of 2° and 5°. The heat transfer data with slug air-water flow pattern were measured under a uniform wall heat flux boundary condition. The change on the heat transfer with inclination angle compared to the horizontal case is discussed in terms of the change in the overall heat transfer coefficient with respect to the superficial gas and liquid Reynolds numbers. For these data, the superficial Reynolds number ranged from about 3700 to 28000 for the water and from about 540 to 6500 for the air. The results indicate that there is an increase in the heat transfer with only slight increases in the inclination angle. However, the amount of increase is strongly dependent on the magnitudes of superficial liquid and gas Reynolds numbers.

Detailed Heat Transfer Distributions in Engine Similar Cooling Channels for a Turbine Rotor Blade With Different Rib Orientations

2011 ◽  
Author(s):  
Christopher LeBlanc ◽  
Srinath V. Ekkad ◽  
Tony Lambert ◽  
Veera Rajendran
Keyword(s):  
Heat Transfer ◽  
Reynolds Number ◽  
Rotor Blade ◽  
Color Change ◽  
Leading Edge ◽  
Local Heat Transfer ◽  
Local Heat ◽  
Channel Inlet ◽  
Transfer Coefficients ◽  
Edge Channel

Detailed Nusselt number distributions are presented for a gas turbine engine similar internal channel geometry used for cooling a modern first stage rotor blade. The cooling design has one leading edge channel and a three-pass channel that covers the rest of the blade. The simulated model, generated from the midspan section of an actual cooling circuit, was studied for wall heat transfer coefficient measurements using the transient liquid crystal technique. The model wall inner surfaces were sprayed with thermochromic liquid crystals, and a transient test was used to obtain the local heat transfer coefficients from the measured color change. Results are presented for a nominal channel inlet leading edge channel Reynolds number of 10700 and a channel inlet three-pass channel Reynolds number of 25500. Detailed heat transfer measurements are presented for the simulated leading edge, first pass, second pass and third pass interior walls for different rib configurations. The channels were studied for smooth, 90° ribs, and angled ribs geometries in addition to ribs on the divider walls between adjacent passages. Overall pressure drop measurements were also obtained for each passage. Some of these results are compared with the predicted heat transfer from standard correlations used in design practices. Results show very complicated heat transfer behavior in these realistic channels compared to results obtained in simplistic geometry channels from published studies. In some cases, the Nusselt numbers predicted by correlations are 50–60% higher than obtained from the current experiments.

Influence of High Mainstream Turbulence on Leading Edge Heat Transfer

1991 ◽  
Vol 113 (4) ◽  
pp. 843-850 ◽  
Author(s):  
A. B. Mehendale ◽  
J. C. Han ◽  
S. Ou
Keyword(s):  
Heat Transfer ◽  
Turbulence Intensity ◽  
Leading Edge ◽  
Local Heat Transfer ◽  
Reynolds Numbers ◽  
Local Heat ◽  
Transfer Coefficients ◽  
Heat Transfer Coefficients ◽  
Turbulence Decay ◽  
High Turbulence

The influence of high mainstream turbulence on leading edge heat transfer was studied. High mainstream turbulence was produced by a bar grid (Tu = 3.3–5.1 percent), passive grid (Tu = 7.6–9.7 percent), and jet grid (Tu = 12.9–15.2 percent). Experiments were performed using a blunt body with a semicylinder leading edge and flat sidewalls. The mainstream Reynolds numbers based on leading edge diameter were 25,000, 40,000, and 100,000. Spanwise and streamwise distributions of local heat transfer coefficients on the leading edge and flat sidewall were obtained. The results indicate that the leading edge heat transfer increases significantly with increasing mainstream turbulence intensity, but the effect diminishes at the end of the flat sidewall because of turbulence decay. Stagnation point heat transfer results for high turbulence intensity flows agree with the Lowery and Vachon correlation, but the overall heat transfer results for the leading edge quarter-cylinder region are higher than their overall correlation for the entire circular cylinder region. High mainstream turbulence tends not to shift the location of the separation-reattachment region. The reattachment heat transfer results are about the same regardless of mainstream turbulence levels and are much higher than the turbulent flat plate correlation.

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