Luminescence technique for the measurement of local concentration distribution in thin liquid films

Experimental data of the concentration field with high spatiotemporal resolution is required for the comprehension of mass transfer increasing kinetic phenomena in falling liquid films. For this purpose a non-invasive measuring method based on luminescence indicators is developed. It is used to determine the concentration distribution and the local film thickness simultaneously. First results are presented for the oxygen absorption into a laminar-wavy water film flowing down a plane with an inclination angle of 4° and a liquid side Reynolds number of 177. With the measured concentration distributions the effective diffusion coefficients are calculated at three points in a single wave of the film.