Experiments and modeling of pressure drop for the droplet flow system in a tubular packed bed

In droplet flow systems, pressure drop is a critical parameter reflecting energy dissipation, which directly impacts the droplet dynamics and consequently guides the equipment design and optimization. Most modeling studies on droplet flow pressure drop primarily focus on the frictional pressure drop under the homogeneous fluid flow assumption. The contribution of interfacial drag to the pressure drop is overlooked, which leads to a lack of deeper mechanistic understanding of pressure drop and the limited predictive accuracy of current models. In this work, the droplet flow experiments in a tubular packed bed were performed to systematically quantify the interfacial drag. The coupling of interfacial drag with droplet size was characterized and a pressure drop model integrating both frictional and interfacial contributions was developed. First, the variation in droplet size was captured using a microphotography technique. Subsequently, the pressure drop was measured with varying flow velocity, dispersed phase holdup, and packed bed diameter. The contribution of interfacial drag to pressure drop was discussed by analyzing droplet dynamics. Finally, the correlation between interfacial drag and droplet size was established. A model combining the frictional and interfacial pressure drop was proposed, achieving a mean relative error of 2.08%. Furthermore, validation experiments confirmed that the developed model precisely captures the contribution of interfacial drag mechanisms and substantially enhances the accuracy of pressure drop prediction in droplet flow systems.