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Heat Transfer Research
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ISSN Print: 1064-2285
ISSN Online: 2162-6561

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Heat Transfer Research

DOI: 10.1615/HeatTransRes.v42.i2.60
pages 181-197

Liquid Crystal Thermography for Transient Heat Transfer Measurements in Complex Internal Cooling Systems

Rico Poser
Institute of Aerospace Thermodynamics (ITLR), Universitüt Stuttgart, Germany
Jens von Wolfersdorf
Institute of Aerospace Thermodynamics, University of Stuttgart, Germany

ABSTRACT

Thermochromic Liquid Crystals (TLCs) are frequently applied as optical temperature sensors for transient heat transfer measurements. Typical examples include the investigation of heat transfer characteristics for cooled gas turbine components using models manufactured from optical-transparent materials. By applying a suddenly changing fluid temperature to a test specimen, a delayed wall temperature response occurs that is monitored on the surface using TLCs and observed with a digital color video camera. Common evaluation techniques associate a calibrated temperature to a unique TLC hue value or peak intensity and detect the corresponding surface response time. Assuming one-dimensional heat conduction in a semi-infinite medium with a convective boundary condition, the analytical solution of Fourier's equation can be applied to calculate local heat transfer distributions. Besides the application of this measurement technique to large-scaled models of simplified representative parts of cooling systems, the investigation of full complex cooling configurations requires special considerations. To account for engine relevant conditions, these models need to represent the actual machine geometry including different surface curvature conditions, individual coolant flow distributions, flow extraction locations and small scale features. The paper presents some new developments associated with the application of the transient heat transfer measurement technique for such complex cooling systems.