A Comparison of Radiation Versus Convection Calibration of Thin-Film Heat Flux Gauges

1999 ◽  
Author(s):  
D. E. Smith ◽  
J. V. Bubb ◽  
O. Popp ◽  
T. E. Diller ◽  
Stephen J. Hevey
Keyword(s):  
Thin Film ◽  
Heat Flux ◽  
Surface Temperature ◽  
Temperature Response ◽  
Turbine Rotor ◽  
Separate Experiment ◽  
Measured Temperature ◽  
Conduction Model ◽  
Time Resolved ◽  
Turbine Rotor Blade

Abstract A transient, in-situ method was examined for calibrating thin-film heat flux gauges using experimental data generated from both convection and radiation tests. Also, a comparison is made between this transient method and the standard radiation substitution calibration technique. Six Vatell Corporation HFM-7 type heat flux gauges were mounted on the surface of a 2-D, first-stage turbine rotor blade. These gauges were subjected to radiation from a heat lamp and in a separate experiment to a convective heat flux generated by flow in a transonic cascade wind tunnel. A second set of convective tests were performed using jets of cooled air impinging on the surface of the gauges. Direct measurements were simultaneously taken of both the time-resolved heat flux and surface temperature on the blade. The heat flux input was used to predict a surface temperature response using a one-dimensional, semi-infinite conduction model into a substrate with known thermal properties. The sensitivities of the gauges were determined by correlating the semi-infinite predicted temperature response to the measured temperature response. A finite-difference code was used to model the penetration of the heat flux into the substrate in order to estimate the time for which the semi-infinite assumption was valid. The results from these tests showed that the gauges accurately record both the convection and radiation modes of heat transfer. The radiation and convection tests yielded gauge sensitivities which agreed to within ±11%.

Comparison of Time-Resolved Turbine Rotor Blade Heat Transfer Measurements and Numerical Calculations

1991 ◽  
Author(s):  
R. S. Abhari ◽  
G. R. Guenette ◽  
A. H. Epstein ◽  
M. B. Giles
Keyword(s):  
Heat Transfer ◽  
Rotor Blade ◽  
Pressure Ratio ◽  
Time History ◽  
Turbine Rotor ◽  
Numerical Calculations ◽  
Test Facility ◽  
Time Resolved ◽  
Turbine Rotor Blade ◽  
History Of

Time-resolved turbine rotor blade heat transfer data are compared with ab initio numerical calculations. The data was taken on a transonic, 4-to-1 pressure ratio, uncooled, single-stage turbine in a short duration turbine test facility. The data consists of the time history of the heat transfer distribution about the rotor chord at midspan. The numerical calculation is a time accurate, 2-D, thin shear layer, multiblade row code known as UNSFLO. UNSFLO uses Ni’s Lax-Wendroff algorithm, conservative boundary conditions, and a time tilting algorithm to facilitate the calculation of the flow in multiple blade rows of arbitrary pitch ratio with relatively little computer time. The version used for this work had a simple algebraic Baldwin-Lomax turbulence model. The code is shown to do a good job of predicting the quantitative time history of the heat flux distribution. The wake/boundary layer and transonic interaction regions for suction and pressure surfaces are identified and the shortcomings of the current algebraic turbulence modelling in the code are discussed. The influence of hardware manufacturing tolerance on rotor heat transfer variation is discussed. A physical reasoning explaining the discrepancies between the unsteady measurement and the calculations for both the suction and pressure surfaces are given, which may be of use in improving future calculations and design procedures.

Inverse Heat Conduction Errors From Temperature Bias in Thin Film Sensors: Effect of Contact Resistance

2011 ◽  
Author(s):  
Keith A. Woodbury ◽  
Jonathan W. Woolley
Keyword(s):  
Thin Film ◽  
Heat Flux ◽  
Heat Conduction ◽  
Contact Resistance ◽  
Surface Temperature ◽  
Temperature Error ◽  
Lead Wire ◽  
Inverse Heat Conduction ◽  
Detailed Model ◽  
Thin Film Sensors

Thin platinum resistance thermometers (herein called thin film sensors) are often used in applications where rapid measurements of surface temperature are required. These gages are typically vapor deposited onto a non-conducting substrate surface and electrically connected with small wires through access holes to the surface. The time response of the gage is measured in milliseconds and surface temperature data obtained with this gage is often combined with a pseudo-inverse heat conduction algorithm to provide information about the surface heat flux. However, the thermal mass of the connecting wires, though small in absolute terms, is large compared to that of the thin film, and the capacitive effect of this mass gives rise to distortions in the temperature field in the area of the gage, resulting in a small error in the sensed temperature. This temperature error, when used in the inversion for heat flux, also results in an error. In this report, a detailed model of a particular thin film gage is used to compute the response of the sensor to supposed heating conditions. The effect of contact resistance between the parent material and the lead wire connections is investigated. The response of the sensor, with and without the contact resistance, and the undisturbed surface temperature are compared to estimate the temperature error. Finally, the error in the computed heat flux is determined. A simple approximate technique based on superposition is applied to account for the sensor dynamics and correct the error in the estimated heat flux.

Approach to Heat Transfer Mechanism Beneath Boiling Bubble With MEMS Sensor

2009 ◽  
Author(s):  
Tomohide Yabuki ◽  
Osamu Nakabeppu
Keyword(s):  
Thin Film ◽  
Heat Transfer ◽  
Heat Flux ◽  
Heated Surface ◽  
Bubble Nucleation ◽  
Temperature Data ◽  
Heated Wall ◽  
Measured Temperature ◽  
Back Side ◽  
Mems Sensor

Temperature variation beneath isolated bubble during saturated boiling of water was measured with a MEMS (Micro-Electro-Mechanical Systems) sensor having high temporal and spatial resolution. Then, local heat transfer from the heated surface was evaluated by a transient heat conduction analysis of the wall with measured temperature data as a boundary condition. The MEMS sensor on a 20 × 20 mm2 silicon substrate includes an electrolysis trigger and eight thin film thermocouples on the top side, and two thin film heaters on the back side. The thin film thermocouple was calibrated with a thermal scan method using two alloy samples with different melting point. The condition of the sensor was smoothly controlled with the heater. The bubble is initiated with electrolysis at a gap of the trigger electrode, where slight hydrogen gasses are supplied as bubble nuclei. Then, local and fast temperature variations in wide region are measured with the thermocouples with cutoff frequency of 100 kHz arranged in a line at 40 – 2000 μm far from the trigger gap. Measured temperature data presents formation of microlayer and expansion of dryout area in bubble growth process and rewetting in bubble departure process. The numerical analysis showed that average heat flux beneath the bubble indicated the maximum value of 19 W/cm2 during the microlayer evaporation, and then after hitting a bottom slightly lower than a heat flux at the bubble nucleation, recovers to the nucleation level. The contribution of the heat transfer from the heated wall was evaluated to approximately one-fourth of latent heat in the bubble at departure.

Heat-Flux Measurements for the Rotor of a Full-Stage Turbine: Part II—Description of Analysis Technique and Typical Time-Resolved Measurements

1986 ◽  
Vol 108 (1) ◽  
pp. 98-107 ◽  
Author(s):  
M. G. Dunn ◽  
W. K. George ◽  
W. J. Rae ◽  
S. H. Woodward ◽  
J. C. Moller ◽  
...  
Keyword(s):  
Thin Film ◽  
Heat Flux ◽  
Design Flow ◽  
Suction Surface ◽  
Stagnation Region ◽  
Time Resolved ◽  
Analysis Technique ◽  
Typical Time ◽  
Flux Measurements ◽  
Dominant Frequencies

This paper presents a detailed description of an analysis technique and an application of this technique to obtain time-resolved heat flux for the blade of a Garrett TFE 731-2 hp full-stage rotating turbine. A shock tube is used as a short-duration source of heated air and platinum thin-film gages are used to obtain the heat-flux measurements. To obtain the heat-flux values from the thin-film gage temperature histories, a finite-difference procedure has been used to solve the heat equation, with variable thermal properties. The data acquisition and the data analysis procedures are described in detail and then their application is illustrated for three midspan locations on the blade. The selected locations are the geometric stagnation point, 32.7 percent wetted distance on the suction surface, and 85.5 percent wetted distance on the suction surface. For these measurements, the turbine was operating at the design flow function and very near 100 percent corrected speed. The vane–blade axial spacing was consistent with the engine operating configuration. The results demonstrate that the magnitude of the heat-flux fluctuation resulting from the vane–blade interaction is large by comparison with the time-averaged heat flux at all locations investigated. The magnitude of the fluctuation is greatest in the stagnation region and decreases with increasing wetted distance along the surface. A Fourier analysis by FFT of a portion of the heat-flux record illustrates that the dominant frequencies occur at the wake-cutting frequency and its harmonics.

Comparison of Time-Resolved Turbine Rotor Blade Heat Transfer Measurements and Numerical Calculations

1992 ◽  
Vol 114 (4) ◽  
pp. 818-827 ◽  
Author(s):  
R. S. Abhari ◽  
G. R. Guenette ◽  
A. H. Epstein ◽  
M. B. Giles
Keyword(s):  
Heat Transfer ◽  
Rotor Blade ◽  
Pressure Ratio ◽  
Time History ◽  
Turbine Rotor ◽  
Numerical Calculations ◽  
Test Facility ◽  
Time Resolved ◽  
Turbine Rotor Blade ◽  
History Of

Time-resolved turbine rotor blade heat transfer data are compared with ab initio numerical calculations. The data were taken on a transonic, 4-to-1 pressure ratio, uncooled, single-stage turbine in a short-duration turbine test facility. The data consist of the time history of the heat transfer distribution about the rotor chord at midspan. The numerical calculation is a time accurate, two-dimensional, thin shear layer, multiblade row code known as UNSFLO. UNSFLO uses Ni’s Lax-Wendroff algorithm, conservative boundary conditions, and a time tilting algorithm to facilitate the calculation of the flow in multiple blade rows of arbitrary pitch ratio with relatively little computer time. The version used for this work had a simple algebraic Baldwin-Lomax turbulence model. The code is shown to do a good job of predicting the quantitative time history of the heat flux distribution. The wake/boundary layer and transonic interaction regions for suction and pressure surfaces are identified and the shortcomings of the current algebraic turbulence modeling in the code are discussed. The influence of hardware manufacturing tolerance on rotor heat transfer variation is discussed. A physical reasoning explaining the discrepancies between the unsteady measurement and the calculations for both the suction and pressure surfaces are given, which may be of use in improving future calculations and design procedures.

scholarly journals Methodology for High-Accuracy Infrared Calibration in Environments with Through-Wall Heat Flux

2020 ◽  
Vol 4 ◽  
pp. 1-13
Author(s):  
Mathias Michaud ◽  
Francesco Ornano ◽  
Nafiz Chowdhury ◽  
Thomas Povey
Keyword(s):  
Heat Flux ◽  
Surface Temperature ◽  
Guide Vane ◽  
Measurement Techniques ◽  
Wall Heat Flux ◽  
New Technique ◽  
Measured Temperature ◽  
Additional Advantage ◽  
Ir Calibration

This paper describes a new method for accurate in situ infrared (IR) calibration in environments with significant through-wall heat flux and surface temperature non-uniformity. In the context of turbine research environments, conventional approaches for in situ IR calibrations rely on thermocouples embedded in the surface or bonded to the surface using an adhesive layer. A review of the literature points to lack of emphasis on the uncertainty in the calibration arising from the effect of the adhesive substrate and paint on the temperature measured by the thermocouple, namely that under diabatic conditions (i.e. with through-wall heat flux) the measured temperature deviates from the true surface temperature. We present a systematic study of the sensitivity of the thermocouple temperature to installation conditions seen in typical laboratory IR calibration arrangements, and under realistic conditions of through-wall heat flux. A new technique is proposed that improves the calibration accuracy by reducing the difference between the thermocouple measurement and the external wall temperature seen by the infrared camera. The new technique has the additional advantage of reducing the uncertainty associated with selecting an appropriate pixel in the IR image, by providing a region with greater temperature uniformity especially in environments with significant underlying lateral surface temperature variation. The new approach is experimentally demonstrated and compared to more conventional measurement techniques on a heavily film-cooled nozzle guide vane assembly operated at highly engine-representative conditions. The proposed technique is demonstrated to significantly improve the measurement accuracy for IR in situ calibrations in environment with through-wall heat flux and surface temperature non-uniformity.

Tool Heat Fluxes During Cutting of A360 Using Beck’s Method

2009 ◽  
Author(s):  
Sean C. McCarty ◽  
Keith A. Woodbury ◽  
Y. Kevin Chou
Keyword(s):  
Heat Flux ◽  
Temperature Response ◽  
Heat Fluxes ◽  
Temperature History ◽  
Measured Temperature ◽  
Detailed Model ◽  
Sensitivity Coefficients ◽  
Metal Chips ◽  
Cutting Zone ◽  
Mechanical Cutting

The energy released during mechanical cutting is carried away by the metal chips and conduction into the tool. This report focuses on determination of the heat fluxes into the tool during cutting using Beck’s method. A small thermocouple is used to measure the temperature rise on the surface of a cutting tool during turning of aluminum A360 cylinders. A detailed model of the tool in FLUENT is used to compute the sensitivity coefficients for the temperature response at the sensor location due to a unit heat flux disturbance at the cutting zone. These sensitivity coefficients are used in Beck’s method along with the measured temperature history, to determine the heat flux history at the cutting zone.

Effects of Wake Passing on Stagnation Region Heat Transfer

1990 ◽  
Vol 112 (3) ◽  
pp. 522-530 ◽  
Author(s):  
J. E. O’Brien
Keyword(s):  
Thin Film ◽  
Heat Transfer ◽  
Heat Flux ◽  
Windward Side ◽  
Stagnation Region ◽  
Time Resolved ◽  
Stagnation Line ◽  
Test Cylinder ◽  
Hot Film ◽  
Wake Passing

An experimental study is described in which both time-averaged and time-resolved effects of wake passing were measured in a cylinder stagnation region. The experiments were carried out in an annular-flow wind tunnel, which was fitted with a spoked-wheel wake generator. The cylindrical spokes produce wakes that simulate those shed from a turbine inlet guide vane. Time-averaged heat transfer results indicate an asymmetric distribution of heat transfer coefficient about the stagnation line, with higher heat transfer coefficients on the windward side (with respect to the bar-passing direction), which corresponds to the suction side of a turbine blade. This asymmetry is also reflected in the time-resolved heat transfer results, which were obtained using a test cylinder instrumented with platinum thin-film gages. Unsteady heat flux records reveal very large positive excursions (as much as a factor of three) in instantaneous heat flux during wake passing on the windward side of the cylinder and much smaller effects on the leeward side. Hot-film records in the cylinder stagnation region were also obtained by operating the thin-film gages in the constant-temperature mode. Spectra of these hot-film records indicate that vortex shedding is a major contributor to the unsteady buffeting of the test-cylinder boundary layer at circumferential stations located at both + 60 deg and − 60 deg from the stagnation line, but makes a very small contribution on the stagnation line itself.

Time-Averaged and Time-Resolved Heat Flux Measurements on a Turbine Stator Blade Using Two-Layered Thin-Film Gauges

2004 ◽  
Author(s):  
V. Iliopoulou ◽  
R. De´nos ◽  
N. Billiard ◽  
T. Arts
Keyword(s):  
Thin Film ◽  
Heat Flux ◽  
Numerical Algorithm ◽  
Temperature History ◽  
Layered System ◽  
Time Resolved ◽  
Flux Measurements ◽  
Stator Blade ◽  
Original Procedure ◽  
Layered Thin Film

This paper describes the steps undertaken to measure heat flux in a turbine tested in a blowdown windtunnel when using a two-layered thin film gauge array. The sensor consists of a nickel thermo resistor deposited onto a flexible polymide sheet that can be easily bounded on a substrate using double sided adhesive. The assembly constitutes a two-layered system. First, a numerical algorithm is proposed to extract the wall heat flux from the surface temperature history measured by the thin film gauge. It is very flexible and handles multi-layered systems. Then, an original procedure is proposed to determine the thermal properties and the thickness of the different layers. It uses the above numerical algorithm coupled with a minimization routine. The repeatability of the procedure is assessed. Finally, tests are processed according to the proposed method. The results are successfully compared with measurements performed with single-layered thin film gauges.

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