FMP Technology (Germany)

The use of the dibenzyltoluene/perhydro‐dibenzyltoluene (H18–DBT) system as a liquid organic hydrogen carrier (LOHC) enables the safe and loss‐free storage of hydrogen. The release of hydrogen from the LOHC is a catalytic reaction and requires ≈27% of the lower heating value of the released hydrogen in the form of heat neglecting heat losses. The high heat requirement makes it necessary to design chemical conversion units that both provide good heat input and accommodate the high gas release. Up to 1200 L of hydrogen is released from 1 L of LOHC under reaction conditions. In this work, a cuboid reactor for the release of hydrogen from H18–DBT is demonstrated. In the experiments, it is shown that evaporation has a significant effect on the reaction rate and thus the amount of hydrogen releases. Therefore, a kinetic model capable of accounting for the release rate and evaporation in the reactor is developed. The model is successfully validated and shows deviations of less than 15% between measured and modeled hydrogen flow in the entire range considered. Since the model considers this important interaction between evaporation and hydrogen release for the first time, it is suitable for optimizing the reactor used.

Abstract In this first chapter, introductory remarks about fluid mechanics are provided and the importance of fluid flows in physical sciences, engineering and medicine is stressed. Flows in our natural and technical environment are summarized to underline that our entire life depends on fluid flows. Technical equipment and processes utilize fluid flows and it is therefore understandable that fluid mechanics education should be an essential part of the university education of students. This also should include the historical developments of fluid mechanics, also covered in this chapter.

Abstract The general properties of wave motions are presented and plane, spherical and cylindrical waves and their mathematical descriptions are explained. The “full continuity and momentum equations” are used to derive the wave equation. For gaseous flows, the sound velocity is derived and surface waves are considered. Plane standing waves and plane progressive waves are treated as examples of interesting but simple wave motions. References are given for complex waves in fluids, so that the reader can easily find treatments of such waves in the literature.

Abstract Another way to treat fluid flows in an integral way is the introduction of stream and potential functions to simplify the equation for treatments of rotational flows. The simplified treatment of two-dimensional flows becomes possible in this way. The Cauchy–Riemann differential equations are derived for the stream function Φ and the potential function ψ. Both functions are used to introduce the complex potential of the velocity field. The latter permits “potential flows” to be treated, such as flows around corners or in angled sectors, sink and source flows, dipole-generated flows and flows around spheres. Through the treatments of these different potential flows, interesting insights into some simple, but still very interesting, flows are obtained.

Similarity considerations are carried out and order of magnitude calculations to show that the characteristics of high Reynolds numberReynolds number flows are boundary layers. They are characterized by the convective transport of flow properties in the flow direction and diffusive transport in the cross-flow direction. The boundary-layer forms of the basic fluid flow equations are derived and are solved for wall boundary-layer flows. The Blasius form and the von Mises form of the boundary-layer equation are presented and their solutions are explained. TheBoundary conditionsBlasius solution Blasius solutionBlasius solution is elaborated and integral properties of the Blasius wall boundary layer are derived. The boundary-layer thicknessBoundary layer thickness is introduced, and also the displacement thicknessDisplacement thickness and the momentum loss thicknessBoundary layer thickness. Boundary-layer solutions are also presented for a laminar, two-dimensional free jetFlowsjet and the corresponding freeFlowswake wake flowFree wake flow.

Article Max Weber, Max Weber-Gesamtausgabe. Bd. III, Teil 2: Praktische Nationalökonomie. Vorlesungen 1895–1899. Hrsg. von Hauke Janssen in Zusammenarbeit mit Cornelia Meyer-Stoll und Ulrich Rummel. Tübingen, Mohr Siebeck 2020 was published on October 1, 2021 in the journal Historische Zeitschrift (volume 313, issue 2).

Analytical simulation is a powerful tool for the optimization of the convective drying of continuous thin film coatings. Knowledge of the heat transfer coefficient is a prerequisite for applying such simulations. In this work, the heat transfer coefficient distributions in industrial dryers with oblique twin nozzles is investigated. Convergent nozzles show higher heat transfer than divergent nozzles. The results are used as boundary condition for a dryer simulation, which is in good agreement with experimental data. An alternative nozzle design, using a wider outlet area and a lower velocity is also investigated. A more homogeneous local Nusselt number is observed.

Physical and mental well-being during the COVID-19 pandemic is typically assessed via surveys, which might make it difficult to conduct longitudinal studies and might lead to data suffering from recall bias. Ecological momentary assessment (EMA) driven smartphone apps can help alleviate such issues, allowing for in situ recordings. Implementing such an app is not trivial, necessitates strict regulatory and legal requirements, and requires short development cycles to appropriately react to abrupt changes in the pandemic. Based on an existing app framework, we developed Corona Health, an app that serves as a platform for deploying questionnaire-based studies in combination with recordings of mobile sensors. In this paper, we present the technical details of Corona Health and provide first insights into the collected data. Through collaborative efforts from experts from public health, medicine, psychology, and computer science, we released Corona Health publicly on Google Play and the Apple App Store (in July 2020) in eight languages and attracted 7290 installations so far. Currently, five studies related to physical and mental well-being are deployed and 17,241 questionnaires have been filled out. Corona Health proves to be a viable tool for conducting research related to the COVID-19 pandemic and can serve as a blueprint for future EMA-based studies. The data we collected will substantially improve our knowledge on mental and physical health states, traits and trajectories as well as its risk and protective factors over the course of the COVID-19 pandemic and its diverse prevention measures.