Numerical and experimental research on thickness fluctuation and Marangoni effect of falling film heat&mass transfer: A comprehensive review
Songning Yu, Chuanshuai Dong, Ronghui Qi
Abstract
Low-Re liquid falling film plays an important role in heat and mass transfer applications. Film instability, manifested as interface waves, and the resulting Marangoni effect determine the liquid/gas contact performance. This review summarized experimental/theoretical approaches for characterizing film thickness and uneven temperature distributions , as well as methods for calculating Marangoni effect of falling film. Non-intrusive measurements such as planar laser-induced fluorescence are recommended as they do not affect film flow pattern and have a higher precision. Analytical theoretical solutions present wave characteristics without iteration, while numerical studies can illustrate the details of local fluctuations and internal physical fields. The choice of the appropriate scale (molecular, droplet, wave or falling film) is important for simulations; thereby, lattice Boltzmann method has received attentions. As it exhibits apparent randomness, an accurate theoretical description of film rupture remains challenging. This study helps to identify the research progress and bottleneck of liquid/gas falling film systems.