Evaluation of viewing-angle effect on determination of local heat transfer coefficients on a curved surface using transient and heated-coating liquid-crystal methods

This paper presents the effect of viewing-angle variations on the accuracy of transient and heated-coating liquid-crystal methods for determining the local heat transfer coefficients on a curved surface. A developed liquid-crystal calibration technique using a true-color image processing system has been used to alleviate the effect of viewing angle on oblique/curved surfaces. The accuracy of heat transfer coefficients improved significantly with careful correction of the viewing-angle effect on the surface geometry. It is crucial to ensure the implementation of the suggested calibration technique to be used in wideband thermochromic liquid-crystal applications on the non-orthogonal surface. Received: 26 January 2001/Accepted: 29 May 2001