Paper presented at the 9th International Conference on Heat Transfer, Fluid Mechanics and Thermodynamics, Malta, 16-18 July, 2012.
Optical techniques have a long tradition in flow visualization, allowing both qualitative and quantitative analysis. In particular, speckle photography, introduced in 1968, has been extensively used and applied to many heat and mass transfer problems. The aim of this work is to compare white-light speckle photography and laser speckle photography techniques in the evaluation of liquid diffusion coefficients. White-light speckle photography (WLSP), recently proposed in natural convection heat transfer problems, has several advantages with respect to laser speckle photography, which makes it a more robust method. Basic theory as well as some experimental results are given. A comparison of the data provided by the two speckle photography techniques, processed with the same algorithms, with values available in literature shows a satisfactory agreement.