Evaluation of Hydrodynamic Performance of New Random Packing Structure Using CFD

Abstract

This study demonstrates the use of computational fluid dynamics (CFD) to evaluate the hydraulic properties of a new/complicated random packing structure, including flooding point, interfacial area, and liquid holdup. A standard Raschig ring and an extremely complex helical ring were employed as representative traditional and new structures. The combination of Green-Gauss node-based method with polyhedral meshing was presented to improve the hydraulic predictions. The CFD models were adopted to extend the liquid-to-gas ratio, L/G to the flooding points for hydraulic evaluation. The combination to calculate the gradient is essential for correctly evaluating the hydrodynamics of the complex helical ring. The predicted hydrodynamics for the helical ring were in good agreement with the experimental data. The helical ring has a wider operating range of L/G than the Raschig ring. Furthermore, we observed that the gas-liquid interface changed during the flooding and found that the inverted interfacial area was caused due to the flooding affecting the generation of the gas-liquid interface. The hydrodynamics of the Raschig ring and helical ring were compared based on CFD simulations; notably, the helical ring exhibited a wider range of L/G ratios and a better hydraulic performance. Finally, the flooding behaviors of the Raschig ring and the helical ring were investigated through volume fraction contours in CFD. We found that a part of the liquid was blown away, leading to the gas-liquid mixing area increasing at the flooding point. A severe flooding state can be investigated due to a large volume of liquid leaving the upper outlet which could be found when over the flooding point.