A technique using a thermochromic liquid crystal coating to measure film cooling effectiveness (η) and heat transfer coefficient has been developed so that both of these important parameters can be obtained, as a function of time, from a single transient test. The technique combines a real-time, true color (24 bit) imaging system with the use of a wide-band liquid crystal coating and multiple event sampling for the simultaneous determination of η and from the single test. To illustrate and validate this technique, the flow from compound-angle square jets in a crossflow is examined. The tests, in which the jet air was suddenly heated to about 40°C, lasted 30 seconds. The measured η is compared with measurements made in the same flow under steady-state conditions in a totally different way, using a mass/heat analogy and a flame ionization detector. Good agreement is obtained. Three different blowing ratios of 0.5, 1.0, and 1.5 are investigated with a constant jet Reynolds number of about 5000. Detailed quantitative comparisons of the η measured in both ways are made for all blowing ratios, and plots of η and are presented. [S0889-504X(00)01403-3]
Transient Heat Transfer Measurements Using a Single Wide-Band Liquid Crystal Test
Contributed by the International Gas Turbine Institute and based on a paper presented at the 44th International Gas Turbine and Aeroengine Congress and Exhibition, Indianapolis, Indiana, June 7–10, 1999. Manuscript received by the International Gas Turbine Institute February 1999. Paper No. 99-GT-167. Review Chair: D. C. Wisler.
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Licu, D. N., Findlay, M. J., Gartshore , I. S., and Salcudean, M. (February 1, 1999). "Transient Heat Transfer Measurements Using a Single Wide-Band Liquid Crystal Test ." ASME. J. Turbomach. July 2000; 122(3): 546–552. https://doi.org/10.1115/1.1303819
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