Application of thermochromic liquid crystal mixtures for transient heat transfer measurements

Authors

C. Waidmann, R. Poser, J. von Wolfersdorf - University of Stuttgart, Germany

Abstract

An approach to use mixtures of thermochromic liquid crystals (TLCs) in transient heat transfer experiments is presented. Multiple TLC indications in a single experiment increase measuring accuracy for experiments where the range of indication times would be too wide when using only a single TLC-type or by providing additional measurement information [Talib et al. (2004)]. For this study, five types of narrowband TLCs with indication temperatures between 30 °C and 50 °C have been used. TLC-mixtures and single TLCs were calibrated simultaneously and repeatedly to investigate possible aging effects. For comparison purposes a single-jet impingement plate test setup has been used. Transient experiments were then conducted for a generic turbine blade internal cooling channel configuration with a 180°-turn and ribbed walls. A technique to filter and process the signals of the green-channel and to match the intensity peaks to the respective sort of TLCs is presented in relation to Poser et al. (2009) and the results with respect to heat transfer coefficient evaluations for the cooling configuration are given. The results indicate the possibility to detect via the TLC-indications regions of unsteady heat transfer in complex flow situations