Encapsulated thermochromic liquid crystal (TLC) can be used to measure the surface temperature of stationary or rotating bodies. However, some research workers have reported a “rotational shift”: When the temperature of a rotating body is measured by thermocouples and TLC, there is a difference between the two sets of temperatures, and this difference increases with increasing rotational speed. Two research groups (Camci and Glezer in the USA, and Owen, Pilbrow, and Syson in the UK) have independently examined the effect of speed on TLC applied to the surfaces of rotating disks. The USA group used narrow-band TLC on a disk of 305 mm diameter rotating up to 7500 rpm measuring the surface temperature using an infrared (IR) sensor. The UK group used wide-band TLC on a disk of 580 mm diameter rotating up to 7000 rpm, measuring the temperature with an IR thermal imager. Both groups used the so-called hue technique to evaluate the temperature of the TLC and concluded that, even for centripetal accelerations in excess of 104 g, there is no significant effect of rotational speed on either narrow-band or wide-band TLC. It is suggested that the “rotational shift” observed by some researchers was probably caused by thermal-disturbance errors, which affected the thermocouples, rather than by changes in the TLC.

Issue Section:
Research Papers
Topics:
Liquid crystals, Temperature, Disks, Rotating bodies, Thermocouples, Errors, Rotating disks, Sensors
1.
Blair, M. F., Wagner, J. H., and Steuber, G. D., 1991, “New Applications of Liquid Crystal Thermography in Rotating Turbomachinery Heat Transfer Research,” ASME Paper No. 91-GT-354.
2.
Camci
C.
,
Kim
K.
, and
Hippensteele
S. A.
,
1992
, “
A New Hue Capturing Technique for the Quantitative Interpretation of Liquid-Crystal Images Used in Convective Heat Transfer Studies
,”
ASME JOURNAL OF TURBOMACHINERY
, Vol.
114
, pp.
765
–
775
.
3.
Camci
C.
,
Kim
K.
,
Hippensteele
S. A.
, and
Poinsatte
P. E.
,
1993
, “
Evaluation of a Hue Capturing Based Transient Liquid Crystal Method for High Resolution Mapping of Convective Heat-Transfer on Curved Surfaces
,”
ASME JOURNAL OF HEAT TRANSFER
, Vol.
115
, pp.
311
–
318
.
4.
Camci
C.
, and
Glezer
B.
,
1997
, “
Liquid Crystal Thermography on the Fluid Solid Interface of Rotating Systems
,”
ASME JOURNAL OF HEAT TRANSFER
, Vol.
119
, pp.
20
–
29
.
5.
Farina, D. J., Hacker, J. M., Moffat, R. J., and Eaton, J., 1993, “Illuminant Invariant Calibration of Thermochromic Liquid Crystals,” ASME HTD-Vol. 252, Visualization of Heat Transfer Processes.
6.
Kim, K., 1991, “A New Hue Capturing Technique for the Quantitative Interpretation of Liquid Crystal Images Used in Convective Heat Transfer Studies,” PhD Thesis, The Pennsylvania State University, USA.
7.
Metzger
D. E.
,
Bunker
R. S.
, and
Bosch
G.
,
1991
, “
Transient Liquid-Crystal Measurement of Local Heat Transfer on a Rotating Disk With Jet Impingement
,”
ASME JOURNAL OF TURBOMACHINERY
, Vol.
113
, pp.
52
–
59
.
8.
Rizzo, D., and Camci, C., 1994, “The Effects of a Boundary Layer Fence on the Aerodynamic Flowfield and Endwall Heat Transfer in a 90° Turning Square Duct,” presented at ASME Winter Annual Meeting, Session: Heat Transfer In Gas Turbines, Chicago, IL.
9.
Syson
B. J.
,
Pilbrow
R. G.
, and
Owen
J. M.
,
1996
, “
Effect of Rotation on Temperature Response of Thermochromic Liquid Crystal
,”
Int. J. Heat Fluid Flow
, Vol.
17
, No.
5
, pp.
491
–
499
.
10.
Wilson, M., Syson, B. J., and Owen, J. M., 1993, “Image Processing Techniques Applied to Wide-Band Thermochromic Liquid Crystals,” presented at Eurotherm 32: Heat Transfer in Single Phase Flows, Oxford, UK, July.
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