Effect of liquid temperature on wave characteristics in falling film based on PLIF

Falling film is widely applied in many industries, such as evaporation, condensation, chemical reaction and distillation. In order to investigate the influence of the liquid temperature on the wave characteristics in the free-falling film that is subjected to the sensible heating, instantaneous measurements of the film thickness using planar laser-induced fluorescence are performed. Experiments are carried out at liquid temperature that ranges from 24 °C to 52 °C. The spatiotemporal flow structure of falling film is reconstructed and analyzed at different temperatures. It is found that the frequency and the amplitudes of the large waves change with the temperature simultaneously, and the substrate regions become more smoother and wider with the temperature rising. The profiles of film thickness probability density function and the power spectrum density function are presented and discussed.