Differential infrared thermography (DIT) in a flashing jet: a feasibility study

This paper discusses the feasibility of differential infrared thermography (DIT) for performing quantitative temperature measurements in a flashing jet. In the literature, the technique has been previously applied to map temperature distributions in diesel sprays. Thanks to the differential operation, DIT enables the local determination of the spray emissivity, independently from a detailed knowledge of the drop size distribution. Temperatures can then be determined through application of the Planck’s radiation law. As a first step, we revised DIT constitutive equations in the framework of the theory of radiative heat transfer in particulate media. The objective is twofold: First, to identify the quantity actually measured by DIT and the limits of applicability of the method; Second, all factors, which may hamper quantitative data interpretation, are carefully reviewed. The analysis includes the choice of the background temperature, multiple scattering effects and the spatial resolution of the optical sys...