Direct Measurement of Heat Transfer Coefficient Augmentation at Multiple Density Ratios

2014 ◽  
Author(s):  
Emily J. Boyd ◽  
John W. McClintic ◽  
Kyle F. Chavez ◽  
David G. Bogard
Keyword(s):  
Heat Transfer ◽  
Heat Flux ◽  
Heat Transfer Coefficient ◽  
Transfer Coefficient ◽  
Film Cooling ◽  
Heated Surface ◽  
Density Ratio ◽  
Adiabatic Wall ◽  
Density Ratios ◽  
The Heat Transfer Coefficient

Knowing the heat transfer coefficient augmentation is imperative to predicting film cooling performance on turbine components. In the past, heat transfer coefficient augmentation was generally measured at unit density ratio to keep measurements simple and uncertainty low. Some researchers have measured heat transfer coefficient augmentation while taking density ratio effects into account, but none have made direct temperature measurements of the wall and adiabatic wall to calculate hf/h0 at higher density ratios. This work presents results from measuring the heat transfer coefficient augmentation downstream of shaped holes with a 7° forward and lateral expansion at DR = 1.0, 1.2, and 1.5 on a flat plate using a constant heat flux surface. The results showed that the heat transfer coefficient augmentation was low while the jets were attached to the surface and increased when the jets started to separate. At DR = 1.0, hf/h0 was higher for a given blowing ratio than at DR = 1.2 and DR = 1.5. However, when velocity ratios are matched, better correspondence was found at the different density ratios. Surface contours of hf/h0 showed that the heat transfer was initially increased along the centerline of the jet, but was reduced along the centerline at distances farther downstream. The decrease along the centerline may be due to counter-rotating vortices sweeping warm air next to the heat flux plate toward the center of the jet, where they sweep upward and thicken the thermal boundary layer. This warming of the core of the coolant jet over the heated surface was confirmed with thermal field measurements.

Direct Measurement of Heat Transfer Coefficient Augmentation at Multiple Density Ratios

2016 ◽  
Vol 139 (1) ◽  
Author(s):  
Emily J. Boyd ◽  
John W. McClintic ◽  
Kyle F. Chavez ◽  
David G. Bogard
Keyword(s):  
Heat Transfer ◽  
Heat Flux ◽  
Heat Transfer Coefficient ◽  
Transfer Coefficient ◽  
Film Cooling ◽  
Heated Surface ◽  
Density Ratio ◽  
Adiabatic Wall ◽  
Density Ratios ◽  
The Heat Transfer Coefficient

Knowing the heat transfer coefficient augmentation is imperative to predicting film cooling performance on turbine components. In the past, heat transfer coefficient augmentation was generally measured at unit density ratio to keep measurements simple and uncertainty low. Some researchers have measured heat transfer coefficient augmentation while taking density ratio effects into account, but none have made direct temperature measurements of the wall and adiabatic wall to calculate hf/h0 at higher density ratios. This work presents results from measuring the heat transfer coefficient augmentation downstream of shaped holes with a 7 deg forward and lateral expansion at DR = 1.0, 1.2, and 1.5 on a flat plate using a constant heat flux surface. The results showed that the heat transfer coefficient augmentation was low while the jets were attached to the surface and increased when the jets started to separate. At DR = 1.0, hf/h0 was higher for a given blowing ratio than at DR = 1.2 and DR = 1.5. However, when velocity ratios are matched, better correspondence was found at the different density ratios. Surface contours of hf/h0 showed that the heat transfer was initially increased along the centerline of the jet, but was reduced along the centerline at distances farther downstream. The decrease along the centerline may be due to counter-rotating vortices sweeping warm air next to the heat flux plate toward the center of the jet, where they sweep upward and thicken the thermal boundary layer. This warming of the core of the coolant jet over the heated surface was confirmed with thermal field measurements.

Heat Transfer Measurements Downstream of Trenched Film Cooling Holes Using a Novel Optical Two-Layer Measurement Technique

2015 ◽  
Vol 138 (3) ◽  
Author(s):  
Peter Schreivogel ◽  
Michael Pfitzner
Keyword(s):  
Heat Transfer ◽  
Heat Flux ◽  
Heat Transfer Coefficient ◽  
Transfer Coefficient ◽  
Film Cooling ◽  
Slight Reduction ◽  
Superposition Method ◽  
Cooling Effectiveness ◽  
Cylindrical Holes ◽  
The Heat Transfer Coefficient

A new approach for steady-state heat transfer measurements is proposed. Temperature distributions are measured at the surface and a defined depth inside the wall to provide boundary conditions for a three-dimensional heat flux calculation. The practical application of the technique is demonstrated by employing a superposition method to measure heat transfer and film cooling effectiveness downstream of two different 0.75D deep narrow trench geometries and cylindrical holes. Compared to the cylindrical holes, both trench geometries lead to an augmentation of the heat transfer coefficient supposedly caused by the highly turbulent attached cooling film emanating from the trenches. Areas of high heat transfer are visible, where recirculation bubbles or large amounts of coolant are expected. Increasing the density ratio from 1.33 to 1.60 led to a slight reduction of the heat transfer coefficient and an increased cooling effectiveness. Both trenches provide a net heat flux reduction (NHFR) superior to that of cylindrical holes, especially at the highest momentum flux ratios.

Heat Flux Reduction From Film Cooling and Correlation of Heat Transfer Coefficients From Thermographic Measurements at Engine Like Conditions

2002 ◽  
Author(s):  
S. Baldauf ◽  
M. Scheurlen ◽  
A. Schulz ◽  
S. Wittig
Keyword(s):  
Heat Transfer ◽  
Heat Flux ◽  
Heat Transfer Coefficient ◽  
Transfer Coefficient ◽  
Film Cooling ◽  
Transfer Coefficients ◽  
Average Heat ◽  
Heat Transfer Coefficients ◽  
New Correlation ◽  
The Heat Transfer Coefficient

Heat transfer coefficients and the resulting heat flux reduction due to film cooling on a flat plate downstream a row of cylindrical holes are investigated. Highly resolved two dimensional heat transfer coefficient distributions were measured by means of infrared thermography and carefully corrected for local internal testplate conduction and radiation effects [1]. These locally acquired data are processed to lateral average heat transfer coefficients for a quantitative assessment. A wide range variation of the flow parameters blowing rate and density ratio as well as the geometrical parameters streamwise ejection angle and hole spacing is examined. The effects of these dominating parameters on the heat transfer augmentation from film cooling are discussed and interpreted with the help of highly resolved surface results of effectiveness and heat transfer coefficients presented earlier [2]. A new method of evaluating the heat flux reduction from film cooling is presented. From a combination of the lateral average of both the adiabatic effectiveness and the heat transfer coefficient, the lateral average heat flux reduction is processed according to the new method. The discussion of the total effect of film cooling by means of the heat flux reduction reveals important characteristics and constraints of discrete hole ejection. The complete heat transfer data of all measurements are used as basis for a new correlation of lateral average heat transfer coefficients. This correlation combines the effects of all the dominating parameters. It yields a prediction of the heat transfer coefficient from the ejection position to far downstream, including effects of extreme blowing angles and hole spacing. The new correlation has a modular structure to allow for future inclusion of additional parameters. Together with the correlation of the adiabatic effectiveness it provides an immediate determination of the streamwise heat flux reduction distribution of cylindrical hole film cooling configurations.

scholarly journals The Effect of Density Ratio on the Heat Transfer Coefficient From a Film Cooled Flat Plate

1989 ◽  
Author(s):  
H. D. Ammari ◽  
N. Hay ◽  
D. Lampard
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Coefficient ◽  
Transfer Coefficient ◽  
Flat Plate ◽  
Strong Dependence ◽  
Density Ratio ◽  
Polymer Surface ◽  
Operating Conditions ◽  
Density Ratios ◽  
The Heat Transfer Coefficient

The effect of density ratio of cooling films on the heat transfer coefficient on a flat plate is investigated using a heat-mass transfer analogy. The experimental technique employed uses a swollen polymer surface and laser holographic interferometry. A density ratio of 1.0 was achieved using air as the injectant. Density ratios of 1.38 and 1.52, representative of turbine operating conditions, were obtained by using foreign gases. The coolant fluids were injected at various blowing rates through a single normal hole or through a row of holes spaced at three-diameter intervals, and inclined at 35° or 90° to the mainstream direction. The experiments were conducted under isothermal conditions in a subsonic, zero mainstream pressure gradient turbulent boundary layer. The results indicated large differences in behaviour between the two injection angles. For normal injection, the heat transfer coefficient at a fixed blowing parameter was insensitive to the variation of density ratio, whereas for 35° injection strong dependence was observed. Scaling parameters for the heat transfer data have been proposed so that use can be made of data obtained at density ratios not representative of gas turbine practice. In addition, a correlation for normal injection data has been formulated.

Heat Flux Reduction From Film Cooling and Correlation of Heat Transfer Coefficients From Thermographic Measurements at Enginelike Conditions

2002 ◽  
Vol 124 (4) ◽  
pp. 699-709 ◽  
Author(s):  
S. Baldauf ◽  
M. Scheurlen ◽  
A. Schulz ◽  
S. Wittig
Keyword(s):  
Heat Transfer ◽  
Heat Flux ◽  
Heat Transfer Coefficient ◽  
Transfer Coefficient ◽  
Film Cooling ◽  
Transfer Coefficients ◽  
Average Heat ◽  
Heat Transfer Coefficients ◽  
New Correlation ◽  
The Heat Transfer Coefficient

Heat transfer coefficients and the resulting heat flux reduction due to film cooling on a flat plate downstream a row of cylindrical holes are investigated. Highly resolved two-dimensional heat transfer coefficient distributions were measured by means of infrared thermography and carefully corrected for local internal testplate conduction and radiation effects. These locally acquired data are processed to lateral average heat transfer coefficients for a quantitative assessment. A wide range variation of the flow parameters blowing rate and density ratio as well as the geometrical parameters streamwise ejection angle and hole spacing is examined. The effects of these dominating parameters on the heat transfer augmentation from film cooling are discussed and interpreted with the help of highly resolved surface results of effectiveness and heat transfer coefficients presented earlier. A new method of evaluating the heat flux reduction from film cooling is presented. From a combination of the lateral average of both the adiabatic effectiveness and the heat transfer coefficient, the lateral average heat flux reduction is processed according to the new method. The discussion of the total effect of film cooling by means of the heat flux reduction reveals important characteristics and constraints of discrete hole ejection. The complete heat transfer data of all measurements are used as basis for a new correlation of lateral average heat transfer coefficients. This correlation combines the effects of all the dominating parameters. It yields a prediction of the heat transfer coefficient from the ejection position to far downstream, including effects of extreme blowing angles and hole spacing. The new correlation has a modular structure to allow for future inclusion of additional parameters. Together with the correlation of the adiabatic effectiveness it provides an immediate determination of the streamwise heat flux reduction distribution of cylindrical hole film-cooling configurations.

Experimental Investigation of Double Rows Film Cooling on Vane Pressure Side

2012 ◽  
Author(s):  
T. Elnady ◽  
I. Hassan ◽  
L. Kadem ◽  
T. Lucas
Keyword(s):  
Heat Transfer ◽  
Experimental Investigation ◽  
Heat Transfer Coefficient ◽  
Transfer Coefficient ◽  
Film Cooling ◽  
Density Ratio ◽  
Radius Of Curvature ◽  
Pressure Side ◽  
Cooling Effectiveness ◽  
The Heat Transfer Coefficient

An experimental investigation has been performed to study the effect of hole shape and position on the cooling performance of a gas turbine stator. Two rows of laid-back fan-shaped holes are placed on the pressure side of a scaled vane in a two-dimensional cascade and compared with two identical rows of standard cylindrical exit. Both hole shapes have the same base diameter and were investigated at three different blowing ratios (1, 1.35, and 1.7) with the same coolant flow rate used in each case. The experiments are conducted for the first row of holes only, then for the second row only, and finally for both two rows together at a 0.9 density ratio. The mainstream inlet Reynolds number based on the true chord is 1.4E5 and the exit Mach number is 0.23. The local distributions of the heat transfer coefficient and film cooling effectiveness are obtained using a transient TLC technique. The second row of holes, with by a higher local radius of curvature, shows a 40% decrease in the cooling effectiveness as well as a 10% increase in the heat transfer coefficient near downstream of the hole compared with that obtained by the first hole. The double injection provides a slight increase in the cooling effectiveness and a lower heat transfer coefficient due to the favorable interaction between both injections.

scholarly journals The Effects of Hole Arrangement and Density Ratio on the Heat Transfer Coefficient Augmentation of Fan-Shaped Film Cooling Holes

Energies ◽  
2021 ◽  
Vol 14 (1) ◽  
pp. 186
Author(s):  
Young Seo Kim ◽  
Jin Young Jeong ◽  
Jae Su Kwak ◽  
Heeyoon Chung
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Coefficient ◽  
Transfer Coefficient ◽  
Film Cooling ◽  
Density Ratio ◽  
Blowing Ratio ◽  
The One ◽  
Film Cooling Holes ◽  
The Given ◽  
The Heat Transfer Coefficient

An experimental study was performed to investigate the effects of the arrangement of fan-shaped film cooling holes and density ratio (DR) on heat transfer coefficient augmentation. Both single- and multi-row fan-shaped film cooling holes were considered. For the multi-row fan-shaped holes, the heat transfer coefficient was measured at DRs of 1 and 2, and both staggered and inline arrangements of holes were considered. For the single-row fan-shaped holes, DR = 1.0, 1.5, 2.0, and 2.5 and M = 1.0 and 2.0 conditions were tested. The mainstream velocity was 20 m/s, and the turbulence intensity and boundary layer thickness were 3.6% and 6 mm, respectively. The heat transfer coefficient was measured using the one-dimensional transient infrared thermography method. The results show that an increased heat transfer coefficient augmentation is observed between film cooling holes for the case with a smaller hole pitch and higher blowing ratio. For the given fan-shaped hole parameters, the effects of the row-to-row distance and hole arrangement are not significant. In addition, as the velocity difference between the mainstream and coolant increases, the heat transfer coefficient ratio increases.

scholarly journals Computation of Full-Coverage Film-Cooled Airfoil Temperatures by Two Methods and Comparison With High Heat Flux Data

1987 ◽  
Author(s):  
H. J. Gladden ◽  
F. C. Yeh ◽  
P. J. Austin
Keyword(s):  
Heat Transfer ◽  
Heat Flux ◽  
Heat Transfer Coefficient ◽  
Transfer Coefficient ◽  
Film Cooling ◽  
Convective Heat Transfer Coefficient ◽  
Superposition Method ◽  
High Heat Flux ◽  
Adiabatic Wall ◽  
Full Coverage

Two methods were used to calculate the heat flux to full-coverage film cooled airfoils and, subsequently, the airfoil wall temperatures. The calculated wall temperatures were compared to measured temperatures obtained in the Hot Section Facility operating at real engine conditions. Gas temperatures and pressures up to 1900 K and 18 atm with a Reynolds number up to 1.9 million were investigated. Heat flux was calculated by the convective heat transfer coefficient adiabatic wall method and by the superposition method which incorporates the film injection effects in the heat transfer coefficient. The results of the comparison indicate the first method can predict the experimental data reasonably well. However, superposition overpredicted the heat flux to the airfoil without a significant modification of the turbulent Prandtl number. The results of this research suggests that additional research is required to model the physics of full-coverage film cooling where there is significant temperature/density differences between the gas and coolant.

Film Cooling and Heat Transfer Performance of a Fully-Cooled Turbine Vane at Varied Density Ratios and Mass Flow Ratios

2020 ◽  
Author(s):  
Chun-yi Yao ◽  
Hui-ren Zhu ◽  
Cun-liang Liu ◽  
Bo-lun Zhang ◽  
Xin-lei Li
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Coefficient ◽  
Transfer Coefficient ◽  
Mass Flow ◽  
Film Cooling ◽  
Density Ratio ◽  
Cooling Effectiveness ◽  
Film Cooling Effectiveness ◽  
Turbine Vane ◽  
Density Ratios

Abstract A number of experimental studies have been performed to study the effect of geometric and aerodynamic parameters on the film cooling performance on the flat plate and turbine blade, however, the experimental investigations on a fully-cooled turbine vane is limited, especially at different density ratios. Consequently, an experiment on a fully-cooled turbine vane with multi-row film cooling holes was carried out to investigate the effect of mass flow ratio and density ratio on the film cooling performance, in which the film cooling effectiveness and heat transfer coefficient was measured by transient liquid crystal. The mainstream inlet Reynolds number based on the inlet velocity and the true chord length is 120000 and the mainstream turbulence intensity is 15%, three mass flow ratios of 5.5%, 8.4% and 11% and two density ratios of 1.0 and 1.5 were tested. The air was selected as the mainstream, the air and carbon dioxide were independently selected as secondary flow to produce two density ratios of 1.0 and 1.5. The test vane is similar in geometry to a first stage turbine vane of a normal aeroengine. Two cavities were manufactured in the test vane to feed 18 rows of film cooling holes. Results show that with the mass flow ratio increasing for DR = 1.0 and 1.5, the film cooling effectiveness on pressure side gradually increases, however, that on the suction side gradually decreases. Generally, increased density ratio produces higher film cooling effectiveness because the injection momentum was reduced, however, the film cooling effectiveness on the suction side for DR = 1.5 is lower than that for DR = 1.0. The coolant outflow significantly enhances the surface heat transfer coefficient for 0 < S/C < 0.5 and S/C < −0.5. The heat transfer coefficient in the leading edge is less affected by the density ratio, however, the increase in density ratio reduces the heat transfer coefficient ratio in other regions, especially for large mass flow ratios.

Heat transfer characteristics analysis on a fully cooled vane with varied density ratios

2021 ◽  
pp. 1-19
Author(s):  
Chunyi Yao ◽  
Zheng Zhang ◽  
Bo-lun Zhang ◽  
Hui Ren Zhu ◽  
Cun Liang Liu
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Coefficient ◽  
Transfer Coefficient ◽  
Film Cooling ◽  
Density Ratio ◽  
Pressure Side ◽  
Cooling Effectiveness ◽  
Film Cooling Effectiveness ◽  
Coolant Injection ◽  
Density Ratios

Abstract The objective of this experimental investigation was to determine the cooling performance of a fully cooled vane with 18 rows of cylinder cooling holes. The exit Reynolds number in the wind tunnel normalized by the true chord was 500,000 with a turbulence intensity of 15%. The film cooling effectiveness and heat transfer coefficient distribution were obtained by the transient liquid crystal technology, three mass flow ratios (MFR=7.0%, 9.9%, 11%) and two density ratios (DR=1.0, 1.5) were tested. The results show that the film cooling effectiveness distribution on the suction side is more uniform and the coolant injection trajectory is much longer than that on the pressure side. As the density ratio increasing to 1.5, the more laterally uniform film cooling effectiveness contour on the pressure side is observed and the spatially averaged film cooling effectiveness is increased by 11%∼43%. For the MFR=7.0%, the coolant injection with low momentum thickens the boundary layer and reduces the heat transfer coefficient in the mid-chord region of the pressure side. Both the increased mass flow ratio and decreased density ratio result in a higher heat transfer coefficient, while do not alter the distribution trend. By calculating the heat flux ratio, the reduction in the heat flux at DR=1.5 is found to be within 20% in most areas than that of DR=1.0 on the vane surface.

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