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Helium-xenon Brayton cycle systems have significant potential as the energy conversion system for small-scale reactors in remote land, deep-sea, and space applications due to a range of advantages, including high cycle efficiency, compact system structures, and chemical stability. The objective of this review is to provide a comprehensive understanding of the helium-xenon Brayton cycle system based on the projects and researches. First, the basic information and development history are introduced, and a series of typical designs are summarized. Then, the system configurations, cycle parameter analysis and optimization are discussed. Next, the key components are classified, such as turbine, compressor, and heat exchanger. Moreover, the dynamic processes and control strategies are introduced in different conditions. Finally, the deficiency and prospect of current research are presented. The review covers the representative helium-xenon Brayton cycle systems, which could provide a reference for promoting the development of energy conversion systems.

Micro reactors, typically with power below 15 MW, are designed in a modular fashion, allowing for flexible and maneuverable deployment, enabling independent operation away from the grid. They can meet energy demands in various scenarios such as remote areas, isolated islands, and desert regions. These reactors hold potential application value and strategic significance in scientific. Supercritical carbon dioxide (SCO2) Brayton cycle, with its high cycle efficiency, high capacity-to-power ratio, and compact structure, has excellent prospects in the field of nuclear power. It is well suited as an energy conversion system for micro reactors. Scholars both domestically and internationally have conducted extensive research on this topic. In this study, different configurations of SCO2 Brayton cycle systems were investigated. The system-component combined design method was applied, which combined the cycle thermodynamic model with the component design method to iteratively correct the cycle thermodynamic calculations and component design results. Equipment models and overall system analysis models were established, and key components were selected and thermally designed. Optimization of system parameters for different configurations was carried out using various evaluation criteria, resulting in the identification of the optimal configuration and parameter settings for different optimization objectives. The results indicate that for the SCO2 Brayton cycle in micro reactors, the system design scheme including heat pipe reactors, centrifugal turbines, centrifugal compressors, shell-and-tube main heat exchangers with heat pipes, printed circuit board recuperator, and flat finned-tube coolers is deemed reasonable. When maximizing power generation efficiency as the optimization objective, the optimal cycle configuration is the recompression-heating-reheating cycle (RHRC), achieving a maximum power generation efficiency of 47.5%. When maximizing power density as the optimization objective, the optimal cycle configuration is the recompression cycle (RC), with a maximum power density of 282.42 kW/m3. When maximizing power-to-mass ratio as the optimization objective, the optimal cycle configuration is also RC, with a maximum power-to-mass ratio of 98.81 kW/t. Through a comparison of different configurations, it is found that the RHRC configuration exhibits higher efficiency, but it also has a larger system volume and mass. The RC configuration has efficiency close to the RHRC configuration while possessing higher power density and power-to-mass ratio. It effectively balances efficiency and compactness, making it more suitable as a mobile micro reactor energy conversion system.

Supercritical carbon dioxide(S-CO2) Brayton cycle has great development potential in the field of efficient utilization of clean energy represented by fourth-generation nuclear energy and solar energy. A reasonable and reliable control strategy is the key to ensure the safe, stable, efficient and flexible operation of the S-CO2 Brayton cycle system. This paper summarized the characteristics of S-CO2 Brayton cycle control, and summarized and compared the S-CO2 Brayton cycle control strategies under different application scenarios. The results show that the key control strategies of S-CO2 Brayton cycle include running state control, impeller machine control, heat source control, etc. The variable load control strategies mainly include volume control, turbine bypass control, turbine inlet throttle control, compressor speed control, etc. The analysis results provide a reference for the selection of S-CO2 Brayton cycle control strategies in related power generation fields.

This research studied the performance of a spindle‐controlled steam ejector using models such as ideal gas and wet steam under various operating conditions based on computational fluid dynamics (CFD). A wet steam model incorporating nonequilibrium condensation was employed to simulate the complex flow phenomena within the ejector. The structure of the flow, entrainment ratio (Er), and shock wave characteristics of the steam ejector were examined in two different models. Results indicate that the spindle position has a substantial impact on steam ejector performance. For the ideal gas and wet steam models, the optimal spindle position (SP‐5) at a .1 MPa motive pressure achieves the highest entrainment ratios (Er) of 1.01 and 1.042, respectively. However, an ejector with a fixed geometry achieves Er values of only .517 and .549 for the ideal gas and wet steam models, under identical working conditions. This represents a substantial improvement of 89.8% over the fixed‐geometry ejector. The wet steam model consistently predicts 2%–4% higher Er values compared with the ideal gas model across all spindle positions. The study also reveals that increasing the motive pressure from .1 to .3 MPa reduces Er by up to 45.8% at the optimal spindle position, with the shock train length extending to 35% of the mixing chamber at .3 MPa. These findings offer insights for improving the design and optimization of variable‐geometry steam ejectors, potentially increasing efficiency in industrial applications. [ABSTRACT FROM AUTHOR]

Backgrounds: A deep neck space abscess (DNSA) is a critical condition resulting from infection of deep neck fascia and soft issue, leading to high morbidity and mortality. Therefore, intensive care can be very significant for patients with DNSA. This study aimed to develop models to predict the need for postoperative intensive care in patients with DNSA. Methods: We retrospectively analyzed the records of 332 patients with DNSA who received drainage operation between 2015 and 2020. Multivariate logistic regression analysis and the eXtrem Gradient Boosting (XGBoost) algorithm were used to develop predictive models. Results: We developed two predictive models, the nomogram and the XGBoost model. The area under the curve (AUC) of the nomogram was 0.911 and of the XGBoost model was 0.935. Conclusion: We developed two predictive models for guiding clinical decision making for postoperative ICU admission for DNSA patients, which may help improve prognosis and optimize intensive care resource allocation. [ABSTRACT FROM AUTHOR]