Christian Leithäuser

This paper presents an overview about the state of the art in the development of structured packings for distillation applications. The focus is on highlighting different approaches, including heuristic development cycles, the development of new packing structures, 3D printing as a tool for manufacturing, and computational fluid dynamics to determine the packings’ performance through use of simulations. Special attention is given to the recently upcoming application of shape optimization algorithms to improve structured packings. It is evaluated how this approach fits into the conventional development process, what the limitations of current shape optimization approaches are, and how they can impact the performance of structured packings. Finally, an opinion about the next steps in the development of shape optimization algorithms for packing development is given.

This article presents an overview about the state of the art in the development of structured packings for distillation applications. The focus is on highlighting different approaches including heuristic development cycles, the development of new packing structures, 3D-printing as tool for manufacturing, and computational-fluid-dynamics to determine the packings’ performance through use of simulations. Special attention is given to the recently upcoming application of shape optimization algorithms to improve structured packings. It is evaluated how this approach fits into the conventional development process, what the limitation of current shape optimization approaches are, and how they can impact the performance of structured packings. Finally, an opinion about the next steps in the development of shape optimization algorithms for packing development is given.

Topology optimization problems usually feature multiple local minimizers. To guarantee convergence to local minimizers that perform best globally, or to find local solutions that are desirable for practical applications due to easy manufacturability or aesthetic designs, it is important to compute multiple local minimizers of topology optimization problems. In this paper, we introduce a novel deflation approach to systematically find multiple local minimizers of general topology optimization problems. The approach is based on a penalization of previously found local solutions in the objective. We validate our approach on the so-called five-holes double-pipe example. Finally, we introduce a model for the topology optimization of bipolar plates of hydrogen electrolysis cells and demonstrate that our deflation approach enables the discovery of novel designs for such plates.

Diazo compounds are gathering interest for their potential in promoting greener synthesis routes. We investigate, at a lab‐scale, the continuous synthesis of diazo acetonitrile (DAN) using a micro‐structured flow reactor and a flow reaction calorimeter. Data concerning DAN formation in the former, and relative to reaction heat and gas flow rate in the latter, are collected. We present a physical and a grey‐box model, both of which are calibrated to our data. Compared to the physical model, the grey‐box approach allows to better incorporate the complex chemical reaction pathways of DAN.

A novel reactor concept for ammonia decomposition utilizing tail gas from a purification unit as heat supply is presented. The designed micro‐structured reactor integrates both endothermic ammonia decomposition and exothermic tail gas combustion. The reactor and corresponding process are simulated using a mathematical multi‐scale model, which combines the results of multiple detailed computational fluid dynamics simulations into a fast surrogate model. The latter is coupled with a process simulation software via a so‐called container to simulate the entire process. The efficiency of the presented reactor concept is determined and benefits over alternative approaches are highlighted.

Summary: We investigate the transmission of aerosol particles in an airplane cabin with a joint approach using experiments and simulation. Experiments were conducted in a realistic aircraft cabin with heated dummies acting as passengers. A Sheffield head with an aerosol generator was used to emulate an infected passenger and particle numbers were measured at different locations throughout the cabin to quantify the exposure of other passengers. The same setting was simulated with a computational fluid dynamics model consisting of a Lagrange continuous phase for capturing the air flow, coupled with a Lagrange suspended discrete phase to represent the aerosols. Virtual measurements were derived from the simulation and compared with the experiments. Our main results are: the experimental setup provides good measurements well suited for model validation, the simulation does correctly reproduce the fundamental mechanisms of aerosol dispersion and simulations can help to improve the understanding of aerosol transmission for example by visualizing particle distributions. Furthermore, with findings from the simulation it was possible to crucially improve the experimental setup, proving that feedback between the numerical and the hardware world is indeed beneficial.

Objectives To evaluate tissue expansion during cryoablation, the displacement of markers in ex vivo kidney tissue was determined using computed tomographic (CT) imaging. Methods CT-guided cryoablation was performed in nine porcine kidneys over a 10 min period. Markers and fiber optic temperature probes were positioned perpendicular to the cryoprobe shaft in an axial orientation. The temperature measurement was performed simultaneously with the acquisitions of the CT images in 5 s intervals. The distance change of the markers to the cryoprobe was determined in each CT image and equated to the measured temperature at the marker. Results The greatest increase in the distance between the markers and the cryoprobe was observed in the initial phase of cryoablation. The maximum displacement of the markers was determined to be 0.31±0.2 mm and 2.8±0.02 %, respectively. Conclusions The mean expansion of ex vivo kidney tissue during cryoablation with a single cryoprobe is 0.31±0.2 mm. The results can be used for identification of basic parameters for optimization of therapy planning.

We want to investigate whether temperature measurements obtained from MR thermometry are accurate and reliable enough to aid the development and validation of simulation models for Laser-induced in...