Improvements in the determination of convective transfers from infrared thermography

In wind tunnel tests, the use of an infrared camera associated with a numerical analysis of the images performed by a computer makes it possible to rapidly determine maps of convective transfer coefficients. The number of points making up the thermographic images to be processed amounting to several thousands, the algorithms to be used must be limited to those leading to computer times as short as possible. That is why the modelling of a semiinfinite plane wall is generally used. It may however lead to erroneous results because of the effects of local curvature or lateral conduction, or because of the finite thickness of the model wall. This latter type of error is investigated in the paper. Correlations are proposed between the error entailed by the use of the semiinfinite model and nondimensional groupings formed from the Fourier and Biot numbers relative to the model wall thickness. A correction is then made possible, which without altering the order of magnitude of computing times, improves the precision of the method and enlarges its domain of application.