“…A virtually generated foam model and 3D printed replicas. [93] As it can be seen from Figure 7, while the differences between the outlet temperatures of 100% alumina and aluminum foams of both gas and solid phase are almost the same, a significant reduction in the difference between 100% alumina and aluminium foams is obtained in the gas phase compared to the solid phase. Indeed, a higher porosity value, meaning of a higher exchange area, resulted in an enhancement of tortuosity and gas-solid heat exchange area.…”
“…Otaru et al [92] compared experimental measurements of the pressure drops across porous aluminum foams with computational fluid dynamics simulations, finding a reliably prediction of the pressure drops behaviour within the Forchheimer regime. Also, Bracconi et al [93], due to the presence of large discrepancies in the literature between experimental results and predictions by models, developed a virtually-generated foam model and 3D printed replicas, in order to diminish the structural differences between the CFD models and the real foams. The results of the study pointed out the effect of the geometrical properties (e.g., cell size, porosity and strut shape) on the pressure drop; in particular, they found that an increase of the cell diameter or of the void fraction lower the pressure drop across the support, and moreover, the average strut size is the key factor affecting the pressure losses.…”
The water-gas shift reaction plays a key role in hydrogen production processes from fossil sources and renewable biomass feedstock and can be considered as the first purification process of syngas. The water gas shift process is normally carried out in two adiabatic stages, of high and low temperature with an intersystem cooling. The two stages use two different catalytic systems, which present some critical issues, thus making extremely attractive the designing and implementing of new configurations. Innovative and highly active catalytic formulations along with more efficient reactor systems could provide the basis for the design of a single-stage process, resulting in a noticeable process intensification. In the last decades, much attention has been paid to the use of structured catalysts, which have numerous advantages, related to both fluid dynamics and heat transfer phenomena. Numerous papers have been published in which the competitive performances of structured catalysts have been shown with respect to conventional catalytic systems. In this brief review, we provide an overview of the most recent developments in the preparation of structured catalysts and use in the water gas shift reaction.
“…A virtually generated foam model and 3D printed replicas. [93] As it can be seen from Figure 7, while the differences between the outlet temperatures of 100% alumina and aluminum foams of both gas and solid phase are almost the same, a significant reduction in the difference between 100% alumina and aluminium foams is obtained in the gas phase compared to the solid phase. Indeed, a higher porosity value, meaning of a higher exchange area, resulted in an enhancement of tortuosity and gas-solid heat exchange area.…”
“…Otaru et al [92] compared experimental measurements of the pressure drops across porous aluminum foams with computational fluid dynamics simulations, finding a reliably prediction of the pressure drops behaviour within the Forchheimer regime. Also, Bracconi et al [93], due to the presence of large discrepancies in the literature between experimental results and predictions by models, developed a virtually-generated foam model and 3D printed replicas, in order to diminish the structural differences between the CFD models and the real foams. The results of the study pointed out the effect of the geometrical properties (e.g., cell size, porosity and strut shape) on the pressure drop; in particular, they found that an increase of the cell diameter or of the void fraction lower the pressure drop across the support, and moreover, the average strut size is the key factor affecting the pressure losses.…”
The water-gas shift reaction plays a key role in hydrogen production processes from fossil sources and renewable biomass feedstock and can be considered as the first purification process of syngas. The water gas shift process is normally carried out in two adiabatic stages, of high and low temperature with an intersystem cooling. The two stages use two different catalytic systems, which present some critical issues, thus making extremely attractive the designing and implementing of new configurations. Innovative and highly active catalytic formulations along with more efficient reactor systems could provide the basis for the design of a single-stage process, resulting in a noticeable process intensification. In the last decades, much attention has been paid to the use of structured catalysts, which have numerous advantages, related to both fluid dynamics and heat transfer phenomena. Numerous papers have been published in which the competitive performances of structured catalysts have been shown with respect to conventional catalytic systems. In this brief review, we provide an overview of the most recent developments in the preparation of structured catalysts and use in the water gas shift reaction.
“…Moreover, it should be taken into account that metals in small particles require special handling and storage due to the high sensitivity to oxidation. 31 In order to overcome many of these limitations, a valuable approach reported in literature consists in the combination of 3D printing and replica techniques: accordingly, first, a polymeric template is produced by additive manufacturing; the use of stereolithography (SLA) can be exploited to produce high-resolution resin structures 32 (with details up to 25 μm and fibers in the range 200-500 μm).…”
Additive manufacturing by 3D printing comprises a set of methods for production of 3D objects starting from a CAD file. Advantages of additive manufacturing combine high manufacturing resolution, a reduction of waste material, and the possibility of computer-aided design (CAD). When applied to the manufacturing
“…Recent studies have explored the use of additive manufacturing (e.g., selective metal laser or electron beam melting) [35][36][37][38][39] and metal casting [40,41] to produce non-stochastic cellular materials. This has the advantage of allowing in situ geometric and dimensional control, thus, they are able to display tailored properties [42].…”
Cellular structures are a classic route to obtain high values of specific mechanical properties. This characteristic is advantageous in many fields, from diverse areas such as packaging, transportation industry, and/or medical implants. Recent studies have employed additive manufacturing and casting techniques to obtain non-stochastic cellular materials, thus, generating an in situ control on the overall mechanical properties. Both techniques display issues, such as lack of control at a microstructural level in the additive manufacturing of metallic alloys and the difficulty in casting thin-rib cellular materials (e.g., metallic scaffolds). To mitigate these problems, this study shows a combination of additive manufacturing and investment casting, in which vacuum is used to assist the filling of thin-rib and high aspect-ratio scaffolds. The process uses 3D printing to produce the investment model. Even though, vacuum is fundamental to allow a complete filling of the models, the temperatures of both mold and casting are important to the success of this route. Minimum temperatures of 250 °C for the mold and 700 °C for the casting must be used to guarantee a successful casting. Cast samples shown small deviations relatively to the initial CAD model, mainly small expansions in rib length and contraction in rib thickness may be observed. However, these changes may be advantageous to obtain higher values of aspect ratio in the final samples.
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