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research-article

Application of the Transient Heat Transfer Measurement Technique Using TLC in a Network Configuration with Intersecting Circular Passages

[+] Author and Article Information
Anika Steurer

Institute of Aerospace Thermodynamics (ITLR), University of Stuttgart, Pfaffenwaldring 31, Stuttgart, 70569, Germany
anika.steurer@itlr.uni-stuttgart.de

Rico Poser

Institute of Aerospace Thermodynamics (ITLR), University of Stuttgart, Pfaffenwaldring 31, Stuttgart, 70569, Germany
rico.poser@itlr.uni-stuttgart.de

Jens Vonwolfersdorf

Institute of Aerospace Thermodynamics (ITLR), University of Stuttgart, Pfaffenwaldring 31, Stuttgart, 70569, Germany
jens.vonwolfersdorf@itlr.uni-stuttgart.de

Stefan Retzko

Ansaldo Energia Switzerland AG, Römerstrasse 36, Baden, 5400, Switzerland
stefan.retzko@ansaldoenergia.com

1Corresponding author.

ASME doi:10.1115/1.4041807 History: Received September 21, 2018; Revised October 17, 2018

Abstract

This study deals with the application of the transient thermochromic liquid crystal (TLC) technique in a flow network of intersecting circular passages as a potential internal turbine component cooling geometry. The investigated network consists of six circular passages with a diameter d=20mm that intersect at an angle ?=40° , the innermost in three, the outermost in one intersection level. Two additional non-intersecting passages serve as references. Such a network entails specific characteristics associated with the transient TLC method that have to be accounted for in the evaluation process: the strongly curved surfaces, the mixing and mass flow redistribution at each intersection, and the resulting gradients between the wall and passage centerline temperatures. All this impedes the choice of a representative fluid reference temperature, which results in deviations using established evaluation methods. An alternative approach is introduced, which is supported by computational results obtained from steady-state three-dimensional RANS simulations using the SST turbulence model. The presented analysis uncouples local heat transfer coefficients from actually measured local temperatures but uses the time information of the thermocouples instead that represents the fluid temperature step change and evolution along the passages. This experimental time information is transferred to the steady-state numerical bulk temperatures, which are finally used as local references to evaluate the transient TLC experiments. As effective local mass flow rates in the passage sections are considered, the approach allows for a conclusion whether heat transfer is locally enhanced due to higher mass flow rates or intersection effects.

Copyright (c) 2018 by ASME
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