ABSTRACT
The heat transfer characteristics of liquid crystal coated rotating surfaces can be easily observed from a stationary frame of reference. Temperature/heat transfer measurement methods based on the calibration of liquid crystal hue in function of local temperature have been developed in the past; see Kim (1991), Camci et al. (1992), Camci et al. (1993), Wiedner and Camci (1993a, 1993b), Wilson et al. (1993), Farina et al. (1993), and Rizzo and Camci (1994). When the liquid crystal coated heat transfer surface is illuminated by white light, a selective reflection of a specific wavelength occurs in the helical structure of the liquid crystal. This can be explained by the “interference of light reflected from the helical layers so that the optical wavelength in the material actually equals the helical pitch”; see Jones et al. (1992), Collings (1990), and de Gennes (1974). The pitch of the crystal helix is very sensitive to temperature and hence the selectively reflected color may be used to indicate temperature. Most of the past work in liquid crystal thermography is reported under stationary conditions. There are limited numbers of measurements obtained from the rotating frames of thermal systems, mainly for rotating machinery applications. However, a quantitative investigation of hue response to temperature in the rotating environment does not exist.
