Double‐slit model for partially wetted trickle flow hydrodynamics

Abstract

A double-slit model de®eloped can predict the frictional two-phase pressure drop, external liquid holdup, pellet-scale external wetting efficiency, and gas ᎐ liquid interfacial area in cocurrent downflow trickle-bed reactors operated under partially wetted condi-( tions in the trickle flow regime. The model, an extension of the Holub et al. 1992, ) 1993 mechanistic pore-scale phenomenological approach, was designed to mimic the actual bed ®oid by two inclined and interconnected slits: wet and dry slit. The external wetting efficiency is linked to both the pressure drop and external liquid holdup. The model also predicts gas ᎐ liquid interfacial areas in partially wetted conditions. An exten-si®e trickle-flow regime database including o®er 1,200 measurements of two-phase pressure drop, liquid holdup, gas ᎐ liquid interfacial area and wetting efficiency, published in 1974 ᎐ 1998 on the partial-wetted conditions, was used to ®alidate the modeling approach. Two new impro®ed slip-factor functions were also de®eloped using dimensional analysis and artificial neural networks. High-pressure and -temperature wetting efficiency, liquid holdup, pressure drop, and gas ᎐ liquid interfacial area data from the literature on the trickle-flow regime using con®entional monosized beds and catalyst bed-dilution conditions were successfully forecasted by the model.

Modification of Ergun equation for application in trickle bed reactors randomly packed with trilobe particles using computational fluid dynamics technique

“…Among various approaches that have been adopted to calculate the drag force term in momentum balance equation, four distinct and important models can be identified. The relative permeability model [9,16], single slit model [17,18], double slit model [19] and finally, the two-fluid model [20][21][22][23][24] which drag exchange coefficients are obtained from the fluid-fluid interfacial force. In slit models the local flow of liquid and gas around the particles is modeled by assuming the flow between two parallel inclined plates that their gap is related to void fraction of the medium.…”

Numerical simulation of reactive pulsing flow for the catalytic wet oxidation in TBR using a VOF technique

“…Attou and Ferschneider 10 presented simulations for the first rank of solvers without accounting for radial variation in bed porosity. Conversely, Jiang et al 11 have developed a two-dimensional CFD model able to capture some of the key features of hydrodynamics of trickle beds, whereas Iliuta et al 12 and Souadnia and Latafi 13 have used the CFD model for predicting hydrodynamics characteristics over a wide range of operating parameters. Gunjal et al 14 have used a similar CFD model for studying liquid phase mixing and liquid distribution.…”

Applications of tomography in bubble column and trickle bed reactors

“…For example, in a recent MRI study, simultaneous measurements of the gas and liquid velocity distribution in a trickle bed reactor have been presented (Sankey, Holland, et al, 2009). Such measurements will provide a means for testing directly the assumptions that underpin the closure models used for gaseliquid interaction in trickle bed reactors (Attou, Boyer, & Ferschneider, 1999;Iliuta, Larachi, & Al-Dahhan, 2000;Iliuta, Larachi, & Grandjean, 1998;S aez & Carbonell, 1985). Future developments of numerical models of bubble column and trickle bed reactors will depend on detailed experimental investigations, such as those described above, in order to establish the correct methods for modelling these complex systems.…”