| 1. |
- Jareteg, Adam, 1989, et al.
(författare)
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Detailed simulations of heterogeneous reactions in porous media using the Lattice Boltzmann Method
- 2018
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- Flows though porous media are commonly found in many systems, both natural and manmade. A few examples from nature include petroleum reservoirs, soil and solid biomass where industrial applications include fuel cells, foams and packed beds. Most of these areas are still subject to both scientific and engineering challenges ranging from basic understanding to detailed optimization. A non-trivial part of the remaining challenges includes the interaction between macro-scale performance and micro-scale characteristics. For some systems, it is possible to control and tune micro-scale properties to optimize the overall performance of the application. This scenario typically manifests in the design of packed beds, especially when reactions occur within the bed. In such situations, particle shape and size distribution will affect not only the pressure drop (and hence the preferential flow paths), but also local reaction rates and thereby efficiency and selectivity. This work aims to understand and identify key design parameters that influences reactions within a packed bed, and ultimately, the overall performance of the pack- ing. Representative microstructures of packed beds are generated with a Discrete Element Method. Flow, temperature and concentration fields (cf. Figure 1) are then fully resolved using the Lattice Boltzmann Method with a first order reaction scheme at the boundaries. Residence time, flow structures and permeability of the systems are correlated to conversion and selectivity of the chemical reactions in the system. Comparisons between packings of different particle shapes and spacing serve to eluci- date phenomena involved in the process and implies design directions for macro-scale optimization.
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| 2. |
- Jareteg, Adam, 1989, et al.
(författare)
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Finely resolved numerical simulations of reactive flow in porous media
- 2018
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- A wide variety of scientific and engineering challenges involve flows through porous media. Applications range from flow through natural porous systems, such as petroleum reservoirs, soil and biomass char particles, to flows through artificially created porous systems such as packed beds, fuel cells, foams and membranes. In both natural and artificial systems, the microscale characteristics of the media can often, to different degrees, be controlled to optimize the macroscale performance of the application. The problem is then to find the optimal configuration of the porous system. This works aims to increase the understanding of which design parameters of a packed bed that influence the performance of homo-and heterogeneous reactions inside the bed.The flow, temperature and concentration fields in representative microstructures of various packed bed configurations are fully resolved in numerical simulations employing the Lattice Boltzmann Method (LBM), where homo-and heterogeneous chemistry is simultaneously accounted for. Detailed information about the flow structures, permeability and flow paths through the system is retrieved and correlated to the conversion and selectivity of the chemical reactions in the system. The dependence of a reactive porous system on different packing parameters, such as particle shape, spacing, and packing inhomogeneities is elucidated, and the implications for achieving optimal performance in a variety of different porous media are discussed.
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| 3. |
- Maggiolo, Dario, 1985, et al.
(författare)
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Two-phase flow patterns and condensation on wetted surfaces for innovative self-cleaning heat exchangers: experiments and numerics
- 2018
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- Fouling is a common and pervasive problem in industrial processes that involve the cooling of hydrocarbon-rich gas mixtures and and it is considered responsible for 1%÷2.5% of the global anthropogenic emissions of CO2. One of the major drawbacks related to fouling is that it impedes heat recovery and thereby it considerably limits the efficiency of many industrial processes. We experimentally and numerically have investigated whether self-cleaning surfaces of heat exchangers represent a possible solution to overcome this technological bottleneck. Hydrophilically and hydrophobically treated corrugated plates of heat exchangers have been experimentally tested in a 2 MW th research-gasifier and their capabilities to resist fouling have been evaluated. Results revealed that hydrophobically treated surfaces exhibit good anti-fouling and self-cleaning properties. By means of numerical Lattice-Boltzmann-based simulations we then unveiled the self-cleaning phenomenon induced by the wetted surfaces: with a similar mechanism to lotus-leaves, small and motile condensed water droplets are able to collect and remove impurities present in the gas and prevent surfaces fouling. Condensation, two-phase flows patterns formation and droplets coalescence all contribute to promote or weaken the self-cleaning effects. Therefore, numerical simulations have been finally used to identify the main mass and heat transport mechanisms that affect self-cleaning and the optimal operative conditions of the heat exchangers.
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