Transient Heat Transfer Experiments in Complex Passages

Poser, Rico; Wolfersdorf, Jens von; Semmler, Klaus

doi:10.1115/ht2005-72260

Cited by 13 publications

(6 citation statements)

References 7 publications

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“…All tests were carried out at mass flow rate of 0.095 kg/s or at an according Reynolds number of 75,000. The sudden temperature step was chosen to 40 K. For tests conducted to acquire TLC data the temperature step had to be reduced to 30 K. This was necessary to enlarge the time period needed for the TLCs color change and thus to enhance their evaluation quality as described in [3] and [13].…”

Section: Experiments and Resultsmentioning

confidence: 99%

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Experimental Study of Heat Transfer in Gas Turbine Blades Using a Transient Inverse Technique

Heidrich

Wolfersdorf

Schnieder

2009

Heat Transfer Engineering

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To enhance specific power output and thermal efficiency of gas turbine engines, industry searches for ways to increase the turbine inlet temperatures. Therefore, temperatures of turbine blades increase as well and necessitate active cooling of these components. Experimental design work on such internal cooling schemes is carried out to find acceptable compromises between heat transfer and pressure losses. It is often carried out by using transient thermochromic liquid crystal techniques in combination with Plexiglas models. However, for real turbine blades this experimental technique is inappropriate due to the lack of optical access. Therefore, to study actual turbine blades there is need for development of noninvasive, nondestructive methodologies. This article describes a measurement technique that allows determination of internal heat transfer coefficients of real turbine blades experimentally. Thus, a test rig with a rapidly responding heater was designed to fulfill the requirement of a sudden increase in the air temperature within the cooling passages. The outer surface temperatures were measured using infrared thermography. To estimate the spatial distribution of internal heat transfer coefficients from transient surface temperatures the inverse heat transfer problem was solved. As optimization algorithm the Levenberg-Marquardt method was chosen. Outer surface temperature data was measured for a rectangular reference model with rib turbulators and compared with simultaneously acquired data using the thermochromic liquid crystal technique. It is concluded that the new experimental measurement technique could be used to quantitatively determine internal heat transfer coefficients.

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Section: Experiments and Resultsmentioning

confidence: 99%

“…The evaluation of the TLC data was done with the program ProTeIn developed at the Institute of Aerospace Thermodynamics (ITLR). References [13] and [14] give further information on this program and its accuracy.…”

Section: Measurement Methods and Equipmentmentioning

confidence: 99%

Experimental Study of Heat Transfer in Gas Turbine Blades Using a Transient Inverse Technique

Heidrich

Wolfersdorf

Schnieder

2009

Heat Transfer Engineering

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“…For the evaluation of the measured temperature and video data, an advanced evaluation algorithm described by Poser et al [31,32] was applied. The in-house code ProTeIn evaluated the video data in order to determine the green maximum time for which the TLC indication temperature was calibrated and numerically solved equation ( 6) for the heat transfer coefficient.…”

Section: Heat Transfer Measurementsmentioning

confidence: 99%

Experimental investigations of pressure loss and heat transfer in a 180° bend of a ribbed two-pass internal cooling channel with engine-similar cross-sections

Schüler

Neumann

2009

Proceedings of the Institution of Mechanical Engineers, Part A:

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In the present study, the pressure loss and heat transfer of a two-pass internal cooling channel with engine-similar cross-sections were investigated experimentally. This channel consisted of a trapezoidal leading edge pass, a sharp 180° bend, and a nearly rectangular outlet pass. The investigations focused on the influence of tip-to-web distance and rib configuration on pressure loss and heat transfer. The channel was equipped with skewed ribs (α=45°, P/ e=10, e/ dh=0.1) in an inline and a staggered configuration. The dimensionless tip-to-web distance Wel/ dS was varied from 0.6 to 1.2. The investigated Reynolds number ranged from 15 000 up to 100 000. The experimental results showed a strong increase in pressure loss with decreasing tip-to-web distance, while heat transfer was only slightly increasing. Both rib configurations showed nearly the same heat transfer enhancement in the bend region.

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“…The analysis by Yan and Owen [6] might still be used to value the experimental conditions using the fluid flow temperature at the inlet of a test section, but higher uncertainties are to be expected for very short indication times related to high heat transfer coefficients [7]. With a single type of liquid crystal and therefore a fixed wall temperature, it can be inevitable to reach areas, where the uncertainties become intolerable (e.g., Poser et al [8]), especially for more downstream positions with slower fluid temperature transients. Different approaches can be taken to solve this issue.…”

Section: Introductionmentioning

confidence: 99%

Heat Transfer Measurements Using Multiple Thermochromic Liquid Crystals in Symmetric Cooling Channels

Krille

Retzko²,

Poser

et al. 2021

Journal of Turbomachinery

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The transient Thermochromic Liquid Crystal (TLC) method is applied to determine the distribution of the local heat transfer coefficients using a configuration with parallel cooling channels at an engine relevant Reynolds number. The rectangular channels with a moderate aspect ratio and a high length-to-diameter ratio are equipped with one-sided oblique ribs with high blockage, which is a promising configuration for turbine near wall cooling applications. In this arrangement, the three inner channels should experience same flow and thermal conditions. Numerical simulations are performed to substantiate this assumption. The symmetric single channels are sprayed with narrowband TLC with various indication temperatures. Multiple experiments were conducted. All start at ambient conditions before the fluid is heated up to several temperatures between 46°C and 73°C. The results show that the determined local heat transfer coefficients and therefore the Nusselt numbers vary significantly for the different experimental conditions especially at locations of high heat transfer coefficient behind the ribs. A simplified procedure with respect to measurement uncertainties is applied to enable an easy and fast valuation on the data quality. This might be used within the data reduction analysis for such experiments directly. The approach is illustrated using the obtained experimental data.

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Transient Heat Transfer Experiments in Complex Passages

Cited by 13 publications

References 7 publications

Experimental Study of Heat Transfer in Gas Turbine Blades Using a Transient Inverse Technique

Experimental Study of Heat Transfer in Gas Turbine Blades Using a Transient Inverse Technique

Experimental investigations of pressure loss and heat transfer in a 180° bend of a ribbed two-pass internal cooling channel with engine-similar cross-sections

Heat Transfer Measurements Using Multiple Thermochromic Liquid Crystals in Symmetric Cooling Channels

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