scholarly journals Measurements of Heat Transfer Coefficients on Gas Turbine Components: Part I — Description, Analysis and Experimental Verification of a Technique for Use in Hostile Environments

1982 ◽  
Author(s):  
B. Barry ◽  
A. E. Forest ◽  
A. J. White
Keyword(s):  
Heat Transfer ◽  
Gas Turbine ◽  
Wall Temperature ◽  
Experimental Verification ◽  
Companion Paper ◽  
Transfer Coefficients ◽  
Flow Environment ◽  
Heat Transfer Coefficients ◽  
Internally Cooled ◽  
Hostile Environments

A method of determining local connective heat transfer coefficients around internally cooled components in a hostile flow environment is described. The method involves the measurement of the response of the wall temperature to perturbations in the coolant flow. A companion paper includes results obtained in cascades of turbine aerofoils using refined versions of the method.

scholarly journals Measurements of Heat Transfer Coefficients on Gas Turbine Components: Part II — Applications of the Technique Described in Part I and Comparisons With Results From a Conventional Measuring Technique and Predictions

1982 ◽  
Author(s):  
R. J. Beacock ◽  
F. G. Horton ◽  
T. J. Kirker ◽  
A. J. White
Keyword(s):  
Heat Transfer ◽  
Gas Turbine ◽  
Design Methods ◽  
Transfer Coefficients ◽  
High Pressure And Temperature ◽  
Heat Transfer Coefficients ◽  
Internally Cooled ◽  
Current Design ◽  
Thin Walled ◽  
Convective Heat Transfer Coefficients

An experimental technique, described in Part I, for the measurement of local, convective heat transfer coefficients around hollow, thin walled, internally cooled components has been applied to gas turbine aerofoils operating at high pressure and temperature. Both experimental technioques provide data for use in improving design methods and comparisons with predictions using current design methods are presented.

Heat Transfer Coefficients and Film Cooling Effectiveness on the Squealer Tip of a Gas Turbine Blade

2003 ◽  
Vol 125 (4) ◽  
pp. 648-657 ◽  
Author(s):  
Jae Su Kwak ◽  
Je-Chin Han
Keyword(s):  
Heat Transfer ◽  
Gas Turbine ◽  
Turbine Blade ◽  
Film Cooling ◽  
Rotor Blade ◽  
Transfer Coefficients ◽  
Cooling Effectiveness ◽  
Film Cooling Effectiveness ◽  
Heat Transfer Coefficients ◽  
Blowing Ratio

Experimental investigations were performed to measure the detailed heat transfer coefficients and film cooling effectiveness on the squealer tip of a gas turbine blade in a five-bladed linear cascade. The blade was a two-dimensional model of a first stage gas turbine rotor blade with a profile of the GE-E3 aircraft gas turbine engine rotor blade. The test blade had a squealer (recessed) tip with a 4.22% recess. The blade model was equipped with a single row of film cooling holes on the pressure side near the tip region and the tip surface along the camber line. Hue detection based transient liquid crystals technique was used to measure heat transfer coefficients and film cooling effectiveness. All measurements were done for the three tip gap clearances of 1.0%, 1.5%, and 2.5% of blade span at the two blowing ratios of 1.0 and 2.0. The Reynolds number based on cascade exit velocity and axial chord length was 1.1×106 and the total turning angle of the blade was 97.9 deg. The overall pressure ratio was 1.2 and the inlet and exit Mach numbers were 0.25 and 0.59, respectively. The turbulence intensity level at the cascade inlet was 9.7%. Results showed that the overall heat transfer coefficients increased with increasing tip gap clearance, but decreased with increasing blowing ratio. However, the overall film cooling effectiveness increased with increasing blowing ratio. Results also showed that the overall film cooling effectiveness increased but heat transfer coefficients decreased for the squealer tip when compared to the plane tip at the same tip gap clearance and blowing ratio conditions.

scholarly journals Effect of Discrete Ribs on Heat Transfer and Friction Inside Narrow Rectangular Cross Section Cooling Passage of Gas Turbine Blade

2021 ◽  
Vol 10 (6) ◽  
pp. 192-209
Author(s):  
Karthik Krishnaswamy ◽  
◽  
Srikanth Salyan ◽  
Keyword(s):  
Heat Transfer ◽  
Gas Turbine ◽  
Turbine Blade ◽  
Turbine Blades ◽  
Local Heat Transfer ◽  
Local Heat ◽  
Hydraulic Diameter ◽  
Transfer Coefficients ◽  
Heat Transfer Coefficients ◽  
Cooling Passage

The performance of a gas turbine during the service life can be enhanced by cooling the turbine blades efficiently. The objective of this study is to achieve high thermohydraulic performance (THP) inside a cooling passage of a turbine blade having aspect ratio (AR) 1:5 by using discrete W and V-shaped ribs. Hydraulic diameter (Dh) of the cooling passage is 50 mm. Ribs are positioned facing downstream with angle-of-attack (α) of 30° and 45° for discrete W-ribs and discerte V-ribs respectively. The rib profiles with rib height to hydraulic diameter ratio (e/Dh) or blockage ratio 0.06 and pitch (P) 36 mm are tested for Reynolds number (Re) range 30000-75000. Analysis reveals that, area averaged Nusselt numbers of the rib profiles are comparable, with maximum difference of 6% at Re 30000, which is within the limits of uncertainty. Variation of local heat transfer coefficients along the stream exhibited a saw tooth profile, with discrete W-ribs exhibiting higher variations. Along spanwise direction, discrete V-ribs showed larger variations. Maximum variation in local heat transfer coefficients is estimated to be 25%. For experimented Re range, friction loss for discrete W-ribs is higher than discrete-V ribs. Rib profiles exhibited superior heat transfer capabilities. The best Nu/Nuo achieved for discrete Vribs is 3.4 and discrete W-ribs is 3.6. In view of superior heat transfer capabilities, ribs can be deployed in cooling passages near the leading edge, where the temperatures are very high. The best THPo achieved is 3.2 for discrete V-ribs and 3 for discrete W-ribs at Re 30000. The ribs can also enhance the power-toweight ratio as they can produce high thermohydraulic performances for low blockage ratios.

Effect of Uneven Wall Temperature on Local Heat Transfer in a Rotating Square Channel With Smooth Walls and Radial Outward Flow

1992 ◽  
Vol 114 (4) ◽  
pp. 850-858 ◽  
Author(s):  
J.-C. Han ◽  
Y. M. Zhang
Keyword(s):  
Heat Transfer ◽  
Wall Temperature ◽  
Local Heat Transfer ◽  
Local Heat ◽  
Surface Heat ◽  
Transfer Coefficients ◽  
Surface Heat Transfer ◽  
Square Channel ◽  
Heat Transfer Coefficients ◽  
Rotation Numbers

The influence of uneven wall temperature on the local heat transfer coefficient in a rotating square channel with smooth walls and radial outward flow was investigated for Reynolds numbers from 2500 to 25,000 and rotation numbers from 0 to 0.352. The square channel, composed of six isolated copper sections, has a length-to-hydraulic diameter ratio of 12. The mean rotating radius to the channel hydraulic diameter ratio is kept at a constant value of 30. Three cases of thermal boundary conditions were studied: (A) four walls uniform temperature, (B) four walls uniform heat flux, and (C) leading and trailing walls hot and two side walls cold. The results show that the heat transfer coefficients on the leading surface are much lower than that of the trailing surface due to rotation. For case A of four walls uniform temperature, the leading surface heat transfer coefficient decreases and then increases with increasing rotation numbers, and the trailing surface heat transfer coefficient increases monotonically with rotation numbers. The decreased (or increased) heat transfer coefficients on the leading (or trailing) surface are due to the cross-stream and centrifugal buoyancy-induced flows from rotations. However, the trailing surface heat transfer coefficients, as well as those for the side walls, for case B are higher than for case A and the leading surface heat transfer coefficients for cases B and C are significantly higher than for case A. The results suggest that the local uneven wall temperature creates the local buoyancy forces, which change the effect of the rotation. Therefore, the local heat transfer coefficients on the leading, trailing, and side surfaces are altered by the uneven wall temperature.

Cooling of a Finned Cylinder by a Jet Flow of Air

2003 ◽  
Author(s):  
F. Gori ◽  
M. Borgia ◽  
A. Doro Altan
Keyword(s):  
Heat Transfer ◽  
Temperature Distribution ◽  
Wall Temperature ◽  
Experimental Tests ◽  
Jet Flow ◽  
Heat Transfer Characteristics ◽  
Transfer Coefficients ◽  
Electric System ◽  
Heat Transfer Coefficients ◽  
Convective Heat Transfer Coefficients

Experimental tests have been carried out to evaluate the heat transfer characteristics on an externally finned cylinder impinged by a jet flow of air. The cylinder is internally heated with an electric system. Thermocouples located inside the cylinder allow to evaluate the wall temperature distribution, in order to calculate the local and average convective heat transfer coefficients.

Thermoreflectance Wall Temperature Measurement in Annular Two-Phase Flow

2019 ◽  
Author(s):  
Jason Chan ◽  
Brian E. Fehring ◽  
Roman W. Morse ◽  
Kristofer M. Dressler ◽  
Gregory F. Nellis ◽  
...  
Keyword(s):  
Heat Transfer ◽  
Wall Temperature ◽  
Annular Flow ◽  
High Heat ◽  
High Heat Flux ◽  
Phase Flow ◽  
Transfer Coefficients ◽  
Two Phase ◽  
Heat Transfer Coefficients ◽  
Dry Out

Abstract A thermoreflectance method to measure wall temperature in two-phase annular flow is described. In high heat flux conditions, momentary dry-out occurs as the liquid film vaporizes, resulting in dramatic decreases in heat transfer coefficient. Simultaneous liquid and vapor thermoreflectance measurements allow calculations of instantaneous and time-averaged heat transfer coefficients. Validation, calibration and uncertainty of the technique are discussed.

Uneven Wall Temperature Effect on Local Heat Transfer in a Rotating Two-Pass Square Channel With Smooth Walls

1993 ◽  
Vol 115 (4) ◽  
pp. 912-920 ◽  
Author(s):  
J.-C. Han ◽  
Y.-M. Zhang ◽  
Kathrin Kalkuehler
Keyword(s):  
Heat Transfer ◽  
Wall Temperature ◽  
Local Heat Transfer ◽  
Local Heat ◽  
Diameter Ratio ◽  
Transfer Coefficients ◽  
Square Channel ◽  
Heat Transfer Coefficients ◽  
Buoyancy Forces ◽  
Flow Heat

The influence of uneven wall temperature on the local heat transfer coefficient in a rotating, two-pass, square channel with smooth walls is investigated for rotation numbers from 0.0352 to 0.352 by varying Reynolds numbers from 25,000 to 2500. The two-pass square channel, composed of 12 isolated copper sections, has a length-to-hydraulic diameter ratio of 12. The mean rotating radius to the channel hydraulic diameter ratio is kept at a constant value of 30. Three cases of thermal boundary conditions are studied: (A) four walls at the same temperature, (B) four walls at the same heat flux, and (C) trailing wall hotter than leading with side walls unheated and insulated. The results for case A of four walls at the same temperature show that the first channel (radial outward flow) heat transfer coefficients on the leading surface are much lower than that of the trailing surface due to the combined effect of Coriolis and buoyancy forces. The second channel (radial inward flow) heat transfer coefficients on the leading surface are higher than that of the trailing surface. The difference between the heat transfer coefficients for the leading and trailing surface in the second channel is smaller than that in the first channel due to the opposite effect of Coriolis and buoyancy forces in the second channel. However, the heat transfer coefficients on each wall in each channel for cases B and C are higher than case A because of interactions between rotation-induced secondary flows and uneven wall temperatures in cases B and C. The results suggest that the effect of uneven wall temperatures on local heat transfer coefficients in the second channel is greater than that in the first channel.

Laminar and Transitional Boundary Layer Structures in Accelerating Flow With Heat Transfer

1986 ◽  
Vol 108 (1) ◽  
pp. 116-123 ◽  
Author(s):  
K. Rued ◽  
S. Wittig
Keyword(s):  
Heat Transfer ◽  
Boundary Layer ◽  
Gas Turbine ◽  
Turbine Blades ◽  
Pressure Gradients ◽  
Transfer Coefficients ◽  
Gas Turbine Blades ◽  
Heat Transfer Coefficients ◽  
Layer Structures ◽  
Flow Heat

The accurate prediction of heat transfer coefficients on cooled gas turbine blades requires consideration of various influence parameters. The present study continues previous work with special efforts to determine the separate effects of each of several parameters important in turbine flow. Heat transfer and boundary layer measurements were performed along a cooled flat plate with various freestream turbulence levels (Tu = 1.6−11 percent), pressure gradients (k = 0−6 × 10−6), and cooling intensities (Tw/T∞ = 1.0−0.53). Whereas the majority of previously available results were obtained from adiabatic or only slightly heated surfaces, the present study is directed mainly toward application on highly cooled surfaces as found in gas turbine engines.

Simplified method for estimating heat transfer coefficients: constant wall temperature case

2015 ◽  
Vol 51 (7) ◽  
pp. 1041-1047 ◽  
Author(s):  
M. A. Alves ◽  
A. Baptista ◽  
P. M. Coelho
Keyword(s):  
Heat Transfer ◽  
Wall Temperature ◽  
Transfer Coefficients ◽  
Constant Wall Temperature ◽  
Heat Transfer Coefficients ◽  
Simplified Method
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