Development and application of a visual observation device for measuring bubble migration characteristics

Gas-liquid two-phase flow is a widespread problem in the fields of the petrochemical industry, energy power, and biopharmaceuticals. The shape, size, migration trajectory, and velocity of bubbles in the liquid phase have an important influence on the gas-liquid distribution, mass transfer, and heat transfer efficiency of the device. Limited by the complexity of gas-liquid two-phase flow problems, the migration characteristics of bubbles in the gas-liquid reverse are difficult to describe. To explore the problem of bubble migration in countercurrent flow, analyze the influence of different factors on bubble migration characteristics and morphological changes, and then provide a theoretical basis for establishing a bubble morphology and velocity prediction model, a set of visual observation devices was developed for bubble migration characteristics.

The experimental device includes a pipeline, power, and data acquisition modules. The experimental device can meet the bubble migration test under three flow conditions: static liquid phase, gas-liquid coflow, and gas-liquid reverse flow. The inclination angle of the pipe can be adjusted, and the annular flow channel can be changed into a circular pipe by removing the inner pipe. First, the reliability of the experimental device was verified, and bubble migration experiments under different liquid phase displacements, pipeline inclinations, and liquid phase viscosities in the annulus were performed. A high-speed camera was used to record the bubble migration process, and MATLAB was used to process the video to obtain changes in the bubble migration speed, shape, and size during the migration process.

The test results show the following: ① The migration trajectory of small bubbles presents an S shape and a zigzag shape, and the degree of jitter increases with the countercurrent liquid velocity. As the viscosity of the liquid phase increases, the trajectory shape tends to be linear. ② The rising mode of small bubbles is affected by the liquid viscosity, velocity, and pipe inclination. On increasing the liquid viscosity, pipe inclination angle, and liquid velocity, the bubble migration velocity decreases, and the interaction between the bubbles increases. In particular, in the nonviscous liquid phase, with an increase in liquid velocity and pipe inclination angle, the front and rear bubbles interact and collide, the entanglement rises, and the bubbles gather into groups to rise. After the liquid phase thickens, with an increase in the liquid velocity and pipe inclination angle, the bubbles connect and coalesce into large bubbles.

Through the established visual observation device of bubble migration characteristics, the migration trajectory and state of bubbles in different liquid phase environments are clearly observed and recorded, and the velocity variation law of bubbles is obtained. The experimental results are intuitive and reliable. Furthermore, the device is simple to operate and has various functions. It can be used to solve the problem of complex bubble migration characteristics, several influencing factors, and difficulty in obtaining intuitive data. It is of great significance to study the related problems in the field of gas-liquid two-phase flow and bubble dynamics, which can be popularized and applied in several fields.