A comparison between transient heat transfer measurements using TLC and IR thermography

Abstract

Narrowband thermochromic liquid crystals (TLCs) and infrared thermography (IRT) are compared in the context of spatially resolved and transient heat transfer measurements. For accurate measurements the TLC coating was calibrated with a stationary method before the experiment. The IRT-camera was in-situ calibrated with a surface thermocouple. A good agreement on temperature was achieved for both methods. The TLC data as a single point measurement was evaluated for a time-independent heat transfer coefficient ℎTLC. The surface temperature history measured with the IRT-camera enables an additional evaluation for a time-dependent ℎCF(t). In the case of one-dimensional heat conduction situations and late TLC indications ℎTLC and ℎCF(t) agree well after the first 10 s of the experiment. An investigation of the heat transfer in the wake region of a vortex generator illustrated the influence of lateral conduction. This effect is not taken into account by any method and leads to greater differ-ences between ℎTLC and ℎCF(t).