CFD simulation and experimental validation of fluid flow in liquid distributors

The uniform distribution of liquid above structured packings is important for their performance. Consequently, liquid distributors play a major role. The outflow through the orifices depends on a number of parameters like liquid height and orifice area. The influence of the lateral fluid velocity on the orifice coefficient is important in this context and is difficult to quantify unless the flow field is known. Therefore, the outflow through the orifices of liquid distributors has been investigated numerically using computational fluid dynamics (CFD). The local liquid height is an important parameter regarding the outflow through orifices as mentioned above. Accordingly, the free surface is modelled using the volume-of-fluid (VOF) scheme. As a first part of the project, the flow through a single orifice was investigated and compared with experiments. In a second part of the project, the flow through multiple orifices of a single channel was analysed. Considering the long simulation times, a two-step approach was developed based on the different time scales of the more macroscopic quasi-steady state flow within the single channel and the more microscopic outflow through the orifices. These results were validated by experimental results, too. As a third part of the project, the flow rates through the orifices of an arbitrary part of a complete channel distributor including pre-distributor were simulated. The above mentioned two-step approach was applied which allows the detailed quantification of local flow rates through orifices of large devices in a feasible expenditure of time. To validate the CFD-simulation the corresponding channel distributor was tested with water on the distributor test rig. The outflow was determined by area measurements.