Abstract
The experimental technique presented is designed to obtain detailed local heat transfer data on both stationary as well as rotating disc-cavity surfaces applicable to gas turbines. The method employed utilizes thin coatings of thermochromic liquid crystals (TLC) as surface temperature indicators under aerodynamically steady but thermally transient experimental conditions. The color display of the liquid crystals is monitored by a video camera. The video signals are captured in real time by a computer-based color recognition system to extract areal temperature and heat transfer information. Some typical results are presented and compared with-literature data to illustrate the potential of the system.
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Abbreviations
- a :
-
m2/s thermal diffusivity
- B :
-
- blue color signal
- G :
-
- green color signal
- G :
-
- rotor/stator spacing ratio z/r o
- Nu ro :
-
- Nusselt number αr o/λ
- r :
-
m radial location
- r o :
-
m disc radius
- R :
-
- red color signal
- Re m :
-
- mass flow Reynolds number V/2πzv
- Re ro :
-
- rotational Reynolds number ωr o 2/v
- t :
-
s time
- T o :
-
K initial temperature
- T ref :
-
K convecting fluid temperature
- T s :
-
K disc surface temperature
- U :
-
- color difference signal
- V :
-
- color difference signal
- Y :
-
- luminance signal
- z :
-
m rotor/stator spacing
- α :
-
- spectral weight factor
- α :
-
W/m2 K local heat transfer coefficient
- β :
-
1/K volumetric expansion coefficient
- β :
-
- spectral weight factor
- δ :
-
- scaling factor
- δ ij :
-
- Kronecker-Delta
- ε :
-
- scaling factor
- γ :
-
- spectral weight factor
- λ :
-
W/m K thermal conductivity
- v :
-
m2/s fluid kinematic viscosity
- ρ :
-
kg/m3 fluid density
References
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Platzer, K.H., Hirsch, C., Metzger, D.E. et al. Computer-based areal surface temperature and local heat transfer measurements with thermochromic liquid crystals (TLC). Experiments in Fluids 13, 26–32 (1992). https://doi.org/10.1007/BF00208071
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DOI: https://doi.org/10.1007/BF00208071