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• A numerical investigation of an evaporator of a diffusion-absorption-refrigeration system using computational fluid dynamics (CFD). • The CFD modelling is conducted by CONVERGE CFD software and was experimentally validated. • The study provides a deeper understanding of the evaporation process in DAR systems. • The study examined also the impact of ammonia presence at the hydrogen inlet on temperature distribution and overall, the accuracy of the CFD model. • The present study emphasizes the significance of utilizing CFD simulation to analyse and improve numerous processes, thus boosting the overall performance of the DAR system. The evaporation process has a considerable impact on the operation of a diffusion absorption refrigeration system (DAR). However, there have been few studies that have focused on this specific issue. In this paper, a numerical investigation of the evaporator region in a DAR system was conducted using CONVERGE CFD software and the RANS approach. The aim of this study is to validate an accurate CFD model by analysing the flow behaviour and thermal parameters within the evaporator. The computational results show high agreement with the experimental data, with slight deviations often remaining under 3 %. The current study additionally investigated the effect of ammonia presence at the hydrogen inlet, specifically at 5 % and 10 % ratios. The results demonstrate that the average deviation is less than 1 % when using 5 % ammonia. This study sheds light on the evaporation process, which is important for enhancing the design and operational efficiency of DAR systems. For this purpose, the validated numerical model will be of great use. [ABSTRACT FROM AUTHOR]

The imbalance of oxidation system and antioxidant system can lead to oxidative stress. Exercise is an important source of oxidative stress, which is closely related to the occurrence and development of exercise fatigue and sports injury. Molecular hydrogen has a good prevention and treatment effect on oxidative stress-related diseases, and has a good application prospect in the field of exercise. However, the effect of hydrogen on exercise-induced oxidative stress and its mechanism are still unclear. Therefore, the purpose of this study is to explore the protective mechanism of hydrogen on exercise-induced injury through the effects of hydrogen on oxidative stress and intestinal flora. The 24 healthy SD male rats were randomly divided into control (Ctrl) group, exercise (Exe) group and hydrogen-inhaled exercise (Hydro) group. The rats in group Exe were trained on the treadmill 5 times a week for 4 weeks, and the rats in group Hydro were treated by 1% hydrogen after each exercise. Except for the second week of exercise, the body weight of group Exe was significantly lower than that of group Ctrl (p < 0.05), while the weight of group Hydro was not significantly different from that of group Ctrl. Compared with the group Ctrl, the levels of ROS, MDA, T-AOC, SOD, CAT and Nrf2 in the group Exe were significantly increased, while those in group Hydro had no significant changes except MDA and Nrf2. The ROS, CAT and Nrf2 levels in group Hydro were significantly lower than those in group Exe. In terms of intestinal barrier, compared with group Ctrl, the level of D-lactate in group Hydro was not significantly changed, but significantly increased in group Exe(p < 0.05); Compared with group Exe, serum D-lactate level in group Hydro had a downward trend, and the gene expression of ZO-1 and occludin increased significantly (p < 0.01). In addition, the abundance of beneficial bacteria in Group Exe was significantly decreased (p < 0.05), such as Ruminococcacea, Romboutsia , Ruminococcaceae_UCG-014 and Peptostreptococcaceae. While the abundance of some beneficial bacteria in group Hydro was significantly increased. Long term hydrogen supplement can effectively improve the exercise-induced oxidative stress injury, and its mechanism may be related to clearing excessive free radicals, increasing the expression of intestinal barrier related proteins, increasing the number of beneficial bacteria and promoting the balance of microecology. [ABSTRACT FROM AUTHOR]

• Selection of cooling system for superconducting machines requires a series of high-level considerations. • Different components of cooling system are discussed based on the prerequisites of a machine engineer and designer. • Technical and economic aspects of choosing a cryogenic fluid and the related system were discussed. • Specific considerations for aerospace, marine, and wind applications of superconducting machines were discussed. • Hydrogen and Turbo Brayton cryocoolers are discussed as future of cooling systems for superconducting machine in aviation. In this paper, general considerations for selecting a cryogenic cooling system for superconducting machine in different applications were explained with respect to the design, operation, and condition monitoring constraints. These considerations are explained so that they help electric machine engineers and designers to get familiar with cryogenic aspects of selecting and using cryogenic cooling system of superconducting machines. In fact, the main questions are: what are the important factors that one should take into account when selecting a cooling system for a superconducting machine application? Also, which one of these factors could later affect the performance of the cooling system so that it can efficiently cope with the expected heat load withoutfacing a thermal breakdown? To adress these questions, common cooling system structures, different cryogenic fluids, the associated parameters with the value of heat loads, and safety margins were discussed to help the machine engineers to choose the most appropriate cryogenic cooling system that adjusts better with their superconducting machine and the specific considerations that they might have. Some considerations regarding the auxiliary devices such as heat exchangers and pumps, were explained as the next priority in selecting a cooling system. Special challenges and considerations imposed to the cooling systems of superconducting machines in aerospace applications such as electric- and hydrogen-powered aircraft, naval applications, and wind energy application were also discussed. Although all of these applications share similar concerns like weight, cost, and specific mass of cooling systems, each one of them have their specific concerns and constraints which come with higher priority. [ABSTRACT FROM AUTHOR]

La transition énergétique est devenue un défi majeur voire une urgence et une réelle volonté sociétale. Aujourd'hui et demain, nous devons imaginer les besoins et les utilisations futures d'énergies alternatives telles que l'hydrogène pourrait nous apporter. Pour cela, nous devons définir et concevoir des services innovants qui répondront aux attentes futures des utilisateurs de demain. Mais comment imaginer et évaluer des produits et des services quand ils n'existent pas encore ? Comment analyser des activités et usages qui ne se manifestent pas encore ? Comment faire une ergonomie de ce qui adviendra ? Pour aborder ces questions, il est nécessaire d'introduire la prospective dans les approches ergonomiques, appelée encore ergonomie prospective. Aussi, dans le cadre d'une recherche sur les futurs usages de l'hydrogène comme énergie avons-nous organisé trois focus groups d'experts de l'hydrogène (dans les secteurs de la production, du transport et de la distribution d'énergie) et nous avons fait une analyse automatique et thématique de leurs échanges. Cet article restitue cette recherche en mettant en avant les grandes classes de discours, des thèmes regroupant des besoins humains et finalement des descriptions de futurs utilisateurs grâce à la méthodologie des personas. Le rôle principal de ces représentations est de faciliter l'idéation afin de permettre aux professionnels de l'hydrogène de stimuler la conception de produits et services innovants à partir de représentations d'utilisateurs futurs. The energy transition has become a major challenge, even an emergency and a real societal will. Today and tomorrow, we must imagine the needs and future uses of alternative energies such as hydrogen could bring us. To achieve this, we must define and design innovative services that will meet the future expectations of tomorrow's users. But how can we imagine and evaluate products and services when they do not yet exist? How to analyze activities and uses that do not yet exist either? How to work with ergonomics on what will be? To address these issues, it is necessary to introduce prospective in ergonomic approaches, called prospective ergonomics. Therefore, in the context of research on the future uses of hydrogen as energy, we have organized three focus groups of hydrogen experts (in the sectors of production, transport and distribution of energy) and we did an automatic and thematic analysis of their verbal exchanges. This article describes this research by highlighting the major classes of the verbal exchanges, themes gathering human needs and finally descriptions of future users on the basis of the methodology of the personas. The main role of these representations is to facilitate ideation in order to allow hydrogen professionals to design new products and innovative services. [ABSTRACT FROM AUTHOR]

Abstract: A diffusion absorption refrigeration (DAR) cycle is driven by heat and has no moving parts. These systems are both quiet and reliable and therefore often used in hotel rooms and offices. The disadvantage of these systems is a very low COP. Therefore, the configuration of the generator and bubble pump is of great importance. In order to increase the COP, it must utilize minimum heat as possible and desorb as much refrigerant as possible from the solution. In this work, a previous thermodynamic model was modified and validated by an experimental system. Detailed thermodynamic models for three generator and bubble pump configurations were developed: (a) heat input into the rich solution with no heat transfer to the poor solution; (b) heat input into the rich solution with heat transfer to the poor solution in the annular; and (c) heat input into the rich solution through the poor solution, thus also desorbing refrigerant from the poor solution, with heat transfer to the poor solution in the annular (a configuration which is used in commercial systems). The performance of three DAR systems, which differ in their generator and bubble pump configuration, was studied numerically. It was found that for the same heat input, the second configuration desorbed the highest amount of refrigerant and the first configuration desorbed the lowest. The third configuration proved to be less efficient compared to the second configuration in terms of COP. The first configuration resulted in the lowest performance, although heat is supplied directly to the rich solution. [Copyright &y& Elsevier]

Abstract: A thermodynamic model was developed for an ammonia–water diffusion absorption refrigeration (DAR) cycle with hydrogen or helium as the auxiliary inert gas, manufactured by Electrolux Sweden (currently known as Dometic). The performance of the system was examined parametrically by computer simulation. Mass and energy conservation equations were developed for each component of the cycle and solved numerically. The model was validated by comparison with previously published experimental data for DAR systems. Investigation of cycle performance under different conditions indicated that the best performance was obtained for a concentration range of the rich solution of 0.2–0.3 ammonia mass fraction and that the recommended concentration of the weak solution was 0.1. It was also found that as the degree of rectification decreased, the performance of the DAR cycle decreased. Finally, the study showed that helium was superior to hydrogen as the inert gas: the coefficient of performance of a DAR unit working with helium was higher by up to 40% than a cycle working with hydrogen. [Copyright &y& Elsevier]