To address hydrogen separation from hydrogen-blended natural gas, this work develops a mathematical model for a novel thermal-transpiration-effect-based circulating-flow gas separator according to the Navier-Stokes equations, following the joint modification with velocity-slip and temperature-jump boundary conditions, and a binary gas diffusion model derived from the Maxwell-Stefan equations. The model is then used to investigate the component transport and flow of a CH4-H-2 mixture at the slip flow regime. The average hydrogen mole fraction in the component enrichment zone increases monotonically as the temperature difference increases, reaching 0.429 at a hot channel temperature of 400 K. An optimum inlet gas velocity of 0.93 m/s is identified to achieve the maximum average hydrogen mole fraction in the enrichment zone. In addition, decreasing the microchannel diameter enhances the hydrogen enrichment performance, with the average hydrogen mole fraction reaching 0.578 at a microchannel diameter of 1 mu m whereas increasing the microchannel diameter improves the product gas flow rate, indicating a trade-off between separation performance and processing capacity. These insights provide guidance for understanding the component transport mechanism and for the preliminary design of this type of gas separator for hydrogen separation applications.

During the marine transport of liquid hydrogen, heat ingress leads to the generation of boil-off gas (BOG), which increases the pressure in the liquid hydrogen storage tanks. Effective BOG management is therefore essential to ensure tank safety and minimize hydrogen loss. This study develops a cryogenic compression recovery and storage system for BOG generated during the marine transport of 160,000 m3 liquid hydrogen. The core process involves compressing a portion of the BOG and subsequently utilizing the BOG’s inherent cold energy to cool the compressed hydrogen, ultimately enabling the storage of the final cryogenic compressed hydrogen product. ASPEN-PLUS software was employed to analyze the proposed system’s specific energy consumption (SEC) and ψ (hydrogen density/SEC) for producing cryogenic compressed hydrogen (CcH2) across a temperature range of 53 to 110 K and a pressure range of 40 to 100 MPa. Seven optimal sets of state parameters were identified for the cryogenic compressed hydrogen product. Based on a specified optimal parameter set of 80 K and 50 MPa, a simulation of the proposed system’s performance yielded a SEC of 2.25 kWh/kg CcH2 and an exergy efficiency of 87.88% with BOG feed at 53 K and 0.1 MPa, along with the exergy loss and exergy efficiency for each component. Compared to a BOG re-liquefaction system and a MRJT CcH2 system under identical conditions, the proposed system achieves 31.81% and 64.9% reduction, respectively, in SEC and 17.32% and 94.6% improvement, respectively, in exergy efficiency. Furthermore, the effects of feed temperature and cryogenic compressed hydrogen product mass flow rate on the proposed system’s SEC and exergy efficiency were investigated.

Strategically integrating anti-freezing flexible segments with rigid carriers provides an innovative paradigm for a wide temperature range of carbon capture, expanding the thermodynamics-kinetics equilibrium window in extremely cold-temperature environments. In this study, an entropy-compensated antifreeze carbon sink cage (EACSC) was developed by strategically integrating a rigid framework network, CO2 molecular capture units, and cold-temperature antifreeze entropy-compensating molecular bridges. The anti-freezing flexible segments of polyethylene glycol in EACSC endowed the anti-freezing performance under cold-temperature conditions through enhancing bonding water of a rigid-flexible network. Consequently, the capture units of EACSC with high amino density possessed an ideal adsorption capacity above 3.73 mmol/g in a wide adsorption temperature window of-15 degrees C to 55 degrees C. Interestingly, the antifreeze molecular bridges can expand the thermodynamics-kinetics equilibrium window through compensating for the reduction in molecular movement caused by cold temperature conditions, while suppressing the loss of adsorption capacity caused by adsorption kinetics. Consequently, the EACSC exhibited an optimal adsorption capacity of 8.79 mmol/g at-5 degrees C by the entropy compensation effect, expanding the thermodynamics-kinetics equilibrium window in cold-temperature environments. Notably, the EACSC successfully prolonged the lifespan of mice by 70.73% owing to its ability to maintain low concentrations of carbon dioxide. Moreover, the EACSC maintained a regeneration efficiency of over 90% even after 85 days of adsorption-desorption cycles. This study broadens the temperature adaptation range for life-support systems by unraveling the entropy-compensated mechanism while providing insights into extreme-environment carbon management and innovation in enclosed systems.

Using biomass for the production of low-energy regenerative carbon capture materials represents an effective strategy to advance carbon dioxide capture and storage technologies. In this study, a low-energy regenerative bagasse-based CO2 capture material is synthesized through a one-step, rapid crosslinking strategy. In this method, epichlorohydrin is used to crosslink bagasse with temperature sensitive Pluronic® F-127 and polyethyleneimine, thereby addressing the challenge of simultaneously incorporating multiple functional groups into the biomass matrix. The resulting material with abundant amino adsorption sites demonstrates a high adsorption capacity of 4.52 mmol/g. Interestingly, the temperature-sensitive response of the material facilitates the grafted amine chain segments on bagasse to stretch and shrink reversibly within a narrow temperature range of 25 °C for adsorption and 55 °C for desorption. The shrinkage state is conducive to the CO2 desorption process, resulting in an ultralow regeneration temperature of 55 °C. Additionally, the water contained in the material enhances its cyclic stability in extreme environments, such as pure CO2 atmosphere at high temperature. Overall, this research not only provides new ideas for enhancing the long-term stability and economic viability of CO2 capture materials but also offers feasible solutions for combating climate change and promoting sustainable development.

Laser powder bed fusion (LPBF) of titanium alloys has demonstrated significant potential in high-value-added fields such as aerospace and biomedical. However, the highly non-stationary thermal history and inherent limitations of the LPBF process lead to critical challenges associated with LPBF Ti–6Al–4V components. This severely constrains the application and advancement of LPBF Ti–6Al–4V alloys. This paper focuses on the recent research progress on microstructure, mechanical properties and post-machining performance of LPBF Ti–6Al–4V alloys. Firstly, the influence of key process parameters and laser scanning strategies on forming properties of LPBF Ti–6Al–4V alloys is systematically overviewed. Subsequently, influenced by highly localised heat flow input, extremely high cooling rate and steep temperature gradient, the formation of common defects, non-equilibrium metallurgical structures and mechanical properties, and tensile residual stresses in as-built LPBF parts are analysed in-depth. Finally, the comprehensive machining performance of SLMed Ti–6Al–4V alloys is emphasised in terms of cutting force, surface morphology and roughness, subsurface microstructure evolution, variation of residual stress, and features of tool wear.

Strategically coupling nanoparticle hybrids and internal thermosensitive molecular switches establishes an innovative paradigm for constructing micro/nanoscale-reconfigurable robots, facilitating energy-efficient CO2 management in life-support systems of confined space. Here, a micro/nano-reconfigurable robot is constructed from the CO2 molecular hunters, temperature-sensitive molecular switch, solar photothermal conversion, and magnetically-driven function engines. The molecular hunters within the molecular extension state can capture 6.19 mmol g−1 of CO2 to form carbamic acid and ammonium bicarbonate. Interestingly, the molecular switch of the robot activates a molecular curling state that facilitates CO2 release through nano-reconfiguration, which is mediated by the temperature-sensitive curling of Pluronic F127 molecular chains during the photothermal desorption. Nano-reconfiguration of robot alters the amino microenvironment, including increasing surface electrostatic potential of the amino group and decreasing overall lowest unoccupied molecular orbital energy level. This weakened the nucleophilic attack ability of the amino group toward the adsorption product derivatives, thereby inhibiting the side reactions that generate hard-to-decompose urea structures, achieving the lowest regeneration temperature of 55 °C reported to date. The engine of the robot possesses non-contact magnetically-driven micro-reconfiguration capability to achieve efficient photothermal regeneration while avoiding local overheating. Notably, the robot successfully prolonged the survival time of mice in the sealed container by up to 54.61

The welding quality of industrial pipelines directly impacts structural safety. X-ray non-destructive testing (NDT), known for its non-invasive and efficient characteristics, is widely used for weld defect detection. However, challenges such as low contrast between defects and background, as well as large variations in defect scales, reduce the accuracy of existing object detection models. To address these, an optimized detection model based on You Only Look Once (YOLO) v5 is proposed. Firstly, the Efficient Multi-Scale Attention (EMA) attention mechanism is integrated into the first Cross Stage Partial (C3) module of the backbone to enhance the model’s receptive field and the initial feature extraction. Secondly, the Efficient Channel Attention (ECA) attention mechanism is embedded before the Spatial Pyramaid Pooling Fast (SPPF) layer to enhance the model’s ability to extract small targets and key features. Finally, the Complete Intersection over Union (CIoU) loss is replaced with Wise Intersection over Union (WIoU) to improve localization accuracy and multi-scale detection performance. The experimental results show that the optimized model achieves a precision of 94.1%, a recall of 89.2%, and an mAP@0.5 of 94.6%, representing improvements by 11.5%, 5.4%, and 6.9%, respectively, over the original YOLOv5. The optimized model also outperforms several mainstream object detection models in weld defect detection. In terms of mAP@0.5, the optimized YOLOv5 model shows improvements of 14.89%, 13.02%, 6.1%, 19.37%, 7.1%, 7.5%, and 10.7% compared with the Faster-RCNN, SSD, RT-DETR, YOLOv3, YOLOv8, YOLOv9, and YOLOv10 models, respectively. This optimized model significantly enhances X-ray weld defect detection accuracy, meeting industrial application requirements and offering another high-precision solution for weld defect detection.

Designing an energy-saving carbon breathing paper offers the substantial potential for life support systems owing to its effective removal of low-level CO2. Here, an energy-saving carbon breathing paper was tailored by the rigid-flexible interlocking of cellulose molecules with polyethyleneimine and poly-N-isopropylacrylamide. Abundant amino groups (14.98 mmol/g) on paper could capture CO2 (6.47 mmol/g) to form carbamic acid, which further generated the difficult-to-decompose urea through dehydration and nucleophilic addition reactions, leading to higher regeneration temperature. Interestingly, the excellent temperature sensitivity of the paper endows stretch-to-shrink molecular state transitions, increased the amino surface electrostatic potential, passivated nucleophilic addition activity and regulated carbamic acid towards thermal decomposition, effectively reduced regeneration temperature to 55 degrees C. More encouragingly, water, which is rich in paper, prevented the formation of urea, improving the cycle stability in extreme environments, such as high temperatures and pure CO2 atmosphere. The result of 30.67 % life extension in mice in confined spaces indicates that the TCBP is a promising candidate for cost-effective carbon removal of life support systems.

Photocatalytic regeneration of nicotinamide adenine dinucleotide (NADH) is indispensable for the sustainability of enzyme-driven industrial processes. In this study, we developed a Z-scheme heterogeneous photocatalyst consisting of CdS and g-C3N4, which markedly enhanced visible-light absorption and photogenerated charge separation efficiency, and applied it to an in situ visible-light-driven NADH regeneration system. The synthesized catalyst afforded an exceptional NADH regeneration yield of 97.88

An energy analysis model and several evaluation indexes are established for a novel gas separator employing molecular exchange flow as working principle. The influences of several important factors on energy consumption and thermal efficiency are investigated. As temperature difference increases, both energy consumption and thermal efficiency rise linearly. As Knudsen number increases, total work decreases while minimum separation work and thermal efficiency initially increase and subsequently decrease. When inlet velocity increases, total work increases but minimum separation work and thermal efficiency go down. Furthermore, both energy consumption and thermal efficiency initially rise and then decline with an increasing mole fraction of the lighter molecular weight component. The results indicate that energy consumption and separation performance should be taken into consideration when selecting temperature differences. In addition, it is preferable to choose the Knudsen number corresponding to optimal separation performance and the intermediate value for component mole fraction. Moreover, it had better employ a lower inlet velocity as long as the separation requirements are satisfied. This study presents a method to optimize the performance of the novel separator based on molecular exchange flow from the perspective of energy conversion and utilization.

In this study, the process of catalytic oxidation of methane considering radiative heat transfer was simulated using FLUENT computational software to study the effect of thermal radiation on the oxidation performance of the simulated device, and to investigate the extent to which radiative heat transfer affects the oxidation performance of the device under different operating conditions. The results show that the extent to which thermal radiation affects the oxidative performance of the equipment increases with increasing inlet temperature. When the intake temperature reaches 900K, its proportion is close to 45%. At the same time, as the inlet gas temperature increases, the maximum reaction temperature of the oxidation unit is 1154 K, and the methane conversion rate reaches up to 89%. The main factor affecting the oxidation performance of the unit at this time is radiation heat transfer. The extent to which thermal radiation affects the oxidative performance of the device diminishes with increasing inlet velocity. When the wind speed reaches 2 m/s, the proportion of radiative heat transfer is only 10%, the maximum reaction temperature of the plant falls to 993 K, and the methane conversion rate drops to 68%. At this time, the main factor affecting the oxidation performance of the plant is convective heat transfer. The influence of thermal radiation on oxidation performance gradually diminishes with an increase in intake velocity, and the proportion of radiative heat transfer decreases continuously. At methane concentrations above 1 %, the proportion of radiative heat transfer is less than 25 per cent, the maximum reaction temperature of the unit increases to 1087 K, and the methane conversion rises to 88 %. At this point, the main factor affecting the oxidation performance of the plant is convective heat transfer.

This review aims to summarize the recent advancements and prevailing challenges within the realm of hydrogen storage and transportation, thereby providing guidance and impetus for future research and practical applications in this domain. Through a systematic selection and analysis of the latest literature, this study highlights the strengths, limitations, and technological progress of various hydrogen storage methods, including compressed gaseous hydrogen, cryogenic liquid hydrogen, organic liquid hydrogen, and solid material hydrogen storage, as well as the feasibility, efficiency, and infrastructure requirements of different transportation modes such as pipeline, road, and seaborne transportation. The findings reveal that challenges such as low storage density, high costs, and inadequate infrastructure persist despite progress in high-pressure storage and cryogenic liquefaction. This review also underscores the potential of emerging technologies and innovative concepts, including metal–organic frameworks, nanomaterials, and underground storage, along with the potential synergies with renewable energy integration and hydrogen production facilities. In conclusion, interdisciplinary collaboration, policy support, and ongoing research are essential in harnessing hydrogen’s full potential as a clean energy carrier. This review concludes that research in hydrogen storage and transportation is vital to global energy transformation and climate change mitigation.

Based on the performance test data of the 136 samples for bagasse boiler in Guangxi Zhuang Autonomous Region, China, the energy analysis of bagasse boilers is performed. The results show that the average thermal efficiency was estimated to be 86.75%, and 39.71% of samples did not meet the limited value requirements, only 1.47% in quantity met the target value, and the energy saving potential is very large. The heat loss of bagasse boilers is dominated by the heat loss of flue gases. Therefore, the effects of bagasse moisture content, excess air ratio and oxygen concentration on flow rate of flue gas and thermal efficiency were further simulated. The average thermal efficiency of bagasse sample boiler will increase obviously, when the moisture content of bagasse and excess air ratio decrease and oxygen concentration increases. In addition, the average value of carbon dioxide emission was 131 kg/GJ. If the thermal efficiency of the substandard boilers reaches the target level, bagasse consumption and carbon dioxide emissions will be reduced by 526 kt and 466 kt per year, respectively. This will be of great significance to energy conservation and emission reduction.

An improved model to calculate the length of the mixing chamber of the ejector was proposed on the basis of the Fano flow model, and a method to optimize the structures of the mixing chamber and diffuser of the ejector was put forward. The accuracy of the model was verified by comparing the theoretical results calculated using the model to experimental data reported in literature. Variations in the length of the mixing chamber Lm and length of the diffuser Ld with respect to variations in the outlet temperature of the ejector Tc, outlet pressure of the ejector pc, and the expansion ratio of the pressure of the primary flow to that of the secondary flow pg/pe were investigated. Moreover, variations in Lm and Ld with respect to variations in the ratio of the diameter of the throat of the motive nozzle to the diameter of the mixing chamber dg0/dc3 and ratio of the outlet diameter of the diffuser to the diameter of the mixing chamber dc/dc3 were investigated. The distribution of flow fields in the ejector was simulated. Increasing Lm and dc3 reduced Tc and pc. Moreover, reducing pg/pe or dg0/dc3 reduced Tc and pc. The length of the mixed section Lm2, which was determined on the basis of the Fano flow model, increased as pg increased and decreased as dc3 increased. The mixing length Lm1, which was considered the primary flow expansion, showed the opposite trend with that of Lm2. Moreover, Ld increased as pg/pe and dc/dc3 increased. When the value of dc was 1.8 to 2.0 times as high as that of dc3, the semi-cone angle of the diffuser ranged between 6° and 12°. At a constant dc/dc3, decreasing Tc and pc increased Ld.

基于特征线法利用有限差分法建立CO2两相引射器主动流超音速膨胀模型.通过模拟主动流喷嘴出口激波链的发展过程,分析了不同工况与结构参数对膨胀角的影响.研究表明,同一喷嘴距(NXP)下,较大的主动流压力、引射系数和膨胀比,会产生较大的膨胀角.而较大的截面比和引射流压力,会减小膨胀角度.一定范围内的较大膨胀角会增加膨胀波长度,减小引射器出口压力.此外,拟合获得了膨胀角和喷嘴距计算关联式,为预测引射器结构与性能参数间关系提供参考.

The special flow phenomenon in microflow, molecular exchange flow, can be used for gas separation. The mathematic models to describe principles of molecular exchange flow are established by illustrating a novel gas separator with similar structure to the Knudsen pump based on thermal transpiration effect. The ratio of temperature gradient to pressure gradient is employed to determine the characteristics of molecular exchange flow. Taking binary gas mixtures of He–Ne, He-Ar and Ne–Ar as examples, the construct conditions and influence factors on flow behaviors are investigated on negative/ideal/positive molecular exchange flows. The limiting ratios of temperature gradient to pressure gradient are sensitive to Knudsen number. The intensity of molecular exchange flow is greatly affected by not only mole fractions of gas components but also Knudsen number. The temperature difference and implicitly corresponding pressure difference should be carefully chosen since they are the driving forces for molecular exchange flow phenomena. The intensities and construct conditions of molecular exchange flows are closely related to the properties of species in gas mixtures.

目前蔗渣锅炉存在服役年限较长、燃烧不充分、效率低下、燃料浪费严重以及污染物排放高等问题,对其原因分析欠缺大量现场数据.为了解决这一问题,本文对121台蔗渣锅炉进行能效测试,得出锅炉热效率达到标准限定值和目标值的数量分别仅占51.24％和0.83％;热损失最大的排烟热损失达10％,其中所含水分的热损失占到将近1/4;二氧化碳排放量平均值达到131.54kg/GJ.深入分析各影响因素与热效率的关系,得出了主要影响因素为烟气温度、过量空气系数和飞灰含碳量.并针对这些因素提出了能效提升措施.若能效均能达到限定值或目标值,每年的蔗渣消耗量将分别减少157kt或568kt,二氧化碳排放量将分别减少160kt或522kt,其他污染物排放同样会减少,推及到全国的蔗渣锅炉,节能减排潜力更巨大.