A technique using a thermochromic liquid crystal coating to measure film cooling effectiveness (η) and heat transfer coefficient $hf$ 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 $hf$ 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 $M$ 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 $hf$ are presented. [S0889-504X(00)01403-3]

1.
,
S. V.
,
Zapata
,
D.
, and
Han
,
J. C.
,
1997
, “
Heat Transfer Coefficients Over a Flat Surface With Air and CO2 Injection Through Compound Angle Holes Using a Transient Liquid Crystal Image Method
,”
ASME J. Turbo-mach.
,
119
, pp.
580
586
.
2.
Vedula, R. J., and Metzger, D. E., 1991, “A Method for the Simultaneous Determination of Local Effectiveness and Heat Transfer Distribution in Three-Temperature Convection Situations,” ASME Paper No. 91-GT-345.
3.
Yu
,
Y.
, and
Chyu
,
M. K.
,
1998
, “
Influence of Gap Leakage Downstream of the Injection Holes on Film Cooling Performance
,”
ASME J. Turbomach.
,
120
, pp.
541
548
.
4.
Chyu, M. K., and Hsing Y. C., 1996, “Use of Thermographic Phosphor Fluorescence Imaging System for Simultaneous Measurement of Film Cooling Effectiveness and Heat Transfer Coefficient,” ASME Paper No. 96-GT-430.
5.
Licu, D. N., 1998, “Heat Transfer Characteristics in Film Cooling Applications,” Ph.D. thesis, Dept. Mech. Eng., The University of British Columbia, Vancouver, BC, Canada.
6.
Findlay, M. J., 1998, “Experimental and Computational Investigation of Inclined Jets in a Crossflow,” Ph.D. thesis, Dept. Mech. Eng., The University of British Columbia, Vancouver, BC, Canada.
7.
Thermax—Thermographic Measurements Ltd., 1998, http://www.thermax.com/.
8.
Pitas, I., 1993, Digital Image Processing, Prentice Hall, Englewood Cliffs, NJ.
9.
Wang
,
Z.
,
Ireland
,
P. T.
,
Jones
,
T. V.
, and
Davenport
,
R.
,
1996
, “
A Color Image Processing System for Transient Liquid Crystal Heat Transfer Experiments
,”
ASME J. Turbomach.
,
118
, pp.
421
427
.
10.
Carslaw, H. S., and Jaeger J. C., 1959, Conduction of Heat in Solids, Oxford University Press, New York, 2nd ed.
11.
Ajersch, P., 1995, “Detailed Measurements on a Row of Jets in a Crossflow—With Applications,” M.A.Sc. Thesis, Department of Mechanical Engineering, The University of British Columbia, Vancouver, BC, Canada.
12.
Haven
,
B. A.
, and
Kurosaka
,
M.
,
1997
, “
Kidney and Anti-kidney Vortices in Crossflow Jets
,”
ASME J. Fluid Mech.
,
352
, pp.
27
64
.
13.
Metzger
,
D. E.
, and
Larson
,
D. E.
,
1986
, “
Use of Melting Point Surface Coatings for Local Convection Heat Transfer Measurements in Rectangular Channel Flows With 90-deg Turns
,”
ASME J. Heat Transfer
,
108
, pp.
48
54
.
14.
Salcudean
,
M.
,
Gartshore
,
I. S.
,
Zhang
,
K.
, and
McLean
,
I.
,
1994
, “
An Experimental Study of Film Cooling Effectiveness Near the Leading Edge of a Turbine Blade
,”
ASME J. Turbomach.
,
116
, pp.
71
79
.
15.
Sun, Y., 1995, “An Experimental and Numerical Investigation of Heat Transfer Downstream of a Normal Film Cooling Injection Slot,” Ph.D. thesis, Department of Mechanical Engineering, The University of British Columbia, Vancouver, BC, Canada.
16.
Kays, W. M., and Crawford, M. E., 1980, Convective Heat and Mass Transfer, McGraw-Hill, New York, 2nd ed.
17.
Abernethy
,
R. B.
,
Benedict
,
R. P.
, and
Dowdell
,
R. B.
,
1985
, “
ASME Measurement Uncertainty
,”
ASME J. Fluids Eng.
,
107
, pp.
161
163
.
18.
Eckert
,
E. R. G.
,
1984
, “
Analysis of Film Cooling and Full-Coverage Film Cooling of Gas Turbine Blades
,”
ASME J. Eng. Gas Turbines Power
,
106
, pp.
206
213
.