Study of multiphase flow in bubble - and packed columns using low-intrusive measuring methods

Multiphase contactors are the most important apparatuses for reaction and separation in chemical engineering. Limited by the measuring methods, the analysis of their hydrodynamic behavior is usually done using superficial liquid and gas flow velocities. Several new measuring techniques for the investigation of multiphase flows in vessel cross sections have been developed in the last decades. Especially the use of tomographic visualization techniques is of great interest since these are noninvasive and thus non-intrusive methods, and enable the visualization of phase distributions.
However, currently developed nonintrusive methods have considerable drawbacks. The computer tomography methods can obtain high spatial resolution. In comparison, the temporal resolution is relative low. For the application of topographic measurement techniques in multiphase flows, especially with fast changing flow patterns, a high temporal resolution is essential. Electrical tomography has a high temporal resolution. However, reconstruction algorithm is very complex and the electrical field lines are not linear, therefore spatial resolution rate is relative low. Therefore, no exact mass balance could be established and the resulting phase fractions cannot be applied for model developments.
In this research, Wire-Mesh Sensor (WMS) is used for the study of phase distribution in multiphase contactors. The WMS comprises two planes, in each plane there are sensing wires. Wires from different planes are orthogonally arranged. Since water and air have different electrical permittivity values and thus, produce different capacitances in the sensing points of the WMS, images of phase distributions can be generated from the measurements of the local capacitance.
Phase distribution in multiphase contactor, e.g. bubble column and packed column, were studied with a WMS. It was shown that the flow regime in bubble column at various gas superficial velocity ((a) uG=8.4 cm/s; (b) uG=16.8 cm/s). Gas-liquid phase distribution in packed column measured with WMS and that measured with gamma-tomography can be characterized.
Measurements of phase distribution with WMS could supply more accurate information of spatial phase distribution to update the theoretical models used in multiphase flow.