Abstract
Open-cell foams as structured catalyst supports are promising candidates for the design of high throughput catalytic processes. In this contribution, we employ a coupled numerical and experimental approach to assess the pressure losses in foams. Large discrepancies between experimental results and predictions by empirical/analytical correlations are present in the literature, mainly due to the structural differences between adopted models and real foams. To exclude such structural differences, we explore virtually-generated foam models and their 3D printed replicas for a combined CFD and experimental study of fluid dynamics in foams. In particular, we focus our analysis on the low Reynolds number regime (Re < 50), where deviations between the existing correlation and experimental data are more pronounced. We find a very good agreement between CFD simulations and experimental measurements in evaluating the pressure drop of gas flows across foams. The effect of porosity, cell sizes and strut shape are studied, leading to the derivation of an engineering correlation for the pressure drop in open-cell foams. Subsequently, the derived correlation is used to evaluate the trade-off between the external transport rate and the pressure drop, which is a pivotal aspect in most environmental catalytic processes: results show that open-cell foams can outperform honeycomb monoliths in the range of low Reynolds numbers.
Highlights
Open-cell foams are considered attractive structured catalyst supports for the intensification of catalytic processes limited by the external transport, such as automotive after-treatment systems [1], and environmental/chemical catalysis applications like partial oxidations [2], catalytic oxidation of methane [3], CO and methanol [4,5], methanol-to-propylene (MTP) reactions [6,7,8]
We assume that the deviation in porosity between the CAD file of the virtual reconstruction and the printed sample is insignificant in the comparative study of pressure drop of this work
We have performed a comprehensive analysis of pressure drops in open-cell foams using a combined numerical (CFD)/experimental method, which is based on virtual reconstruction and additive manufacturing
Summary
Open-cell foams are considered attractive structured catalyst supports for the intensification of catalytic processes limited by the external transport, such as automotive after-treatment systems [1], and environmental/chemical catalysis applications like partial oxidations [2], catalytic oxidation of methane [3], CO and methanol [4,5], methanol-to-propylene (MTP) reactions [6,7,8]. The choice of characteristic length introduces peculiar dependencies of the inertial and viscous coefficients on the morphological properties of foams usually based on empirical assumptions rather than on theoretical derivations. Among these correlations, the ones proposed by Dietrich et al [18] and Inayat et al [19] have been validated against the widest set of available literature data and are considered the most adequate estimates for pressure drops in open cell foams. Inayat et al [19] developed a theoretically grounded model for the prediction of pressure drops in open cell foams accounting for the effect of the different morphological properties of foams assuming the hydraulic diameter as characteristic length and proposing a dependence of the Ergun coefficient from the tortuosity
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