A study on the behaviour of bubbles of a 2D gas–solid fluidized bed using digital image analysis

Bubble characteristics (shape factor, , and aspect ratio, β) are very important in the design of fluidized beds since they have a strong influence on its hydrodynamics. Although several experimental techniques have been used to measure bubble parameters, in this work, experimental data were obtained using digital image analysis from two-dimensional (2D) fluidized beds. Digital image analysis is susceptible to supplying a great quantity of information; it is none-intrusive, it is capable of securing several properties simultaneously and it is cost saving. The distribution of these two bubble characteristics (shape factor, , and aspect ratio, β) as a function of the gas velocity is presented. Moreover, several experiments were performed where the influence of particle diameter, relative humidity, column width and bed height on the bubble characteristics was studied. The results show that the bubble parameters, and β, follow a normal distribution which allows to perform a statistical treatment of the data obtained.