Search Results (435)

Hydrogen energy is considered a crucial clean energy carrier for replacing fossil fuels in the future. Liquid hydrogen (LH₂), with its economic advantages and high purity, is central to the development of future hydrogen refueling stations (HRSs). However, leakage poses significant fire and explosion risks, challenging its safe industrial use. In this study, a numerical model of LH₂ leakage at an HRS in Chongqing was established using Computational Fluid Dynamics (CFD) software. The diffusion law of a flammable gas cloud (FGC) was examined under the synergistic effect of the leakage direction, rate, and wind speed of an LH₂ storage tank in an HRS. The phase transition of LH₂ presents dual risks of combustion and frostbite owing to the spatial overlap between low-temperature areas and FGCs. The findings revealed that the equivalent stoichiometric gas cloud volume (Q9) reached 685 m³ in the case of crosswind leakage, with the superimposed effect of reflected waves from the LH₂ transport vehicle resulting in a peak explosion overpressure of 0.61 bar. The low-temperature hazard area and the FGC (with a concentration of 30–75%) show significant spatial overlap. These research outcomes offer crucial theoretical underpinning for enhancing equipment layout optimization and safety protection strategies at HRSs. Full article

Emergency diesel is prone to degradation during long-term storage, and experimental evaluations are costly and slow. Three-dimensional computational fluid dynamics (CFD) simulations were employed to model the diesel conditioning process. A physical model based on the actual dimensions of the storage tank was constructed. The volume of fraction (VOF) model tracked the gas–liquid interface, and the species transport model handled mixture transport. A UDF then recorded inlet and outlet flow rates and velocities in each cycle. The study focused on the effects of different baffle structures and numbers on conditioning efficiency. Results showed that increasing the baffle flow area significantly delays the mixing time but reduces the cycle time. Openings at the bottom of baffles effectively mitigate the accumulation of high-concentration conditioning oil caused by density differences. Increasing the number of baffles decreases the effective volume of the tank and amplifies density differences across the baffles, which shortens the mixing time. However, excessive baffle numbers diminish these benefits. These findings provide essential theoretical guidance for optimizing baffle design in practical diesel tanks, facilitating rapid achievement of emergency diesel quality standards while reducing costs and improving efficiency. Full article

In the context of the current global transition toward low-carbon energy, the issue of $C{O}_2$ utilization has become increasingly important. One of the most promising natural targets for $C{O}_2$ sequestration is the terrigenous sedimentary formations found in oil, gas, and coal basins. It is generally assumed that $C{O}_2$ injected into such formations can be stored indefinitely in a stable form. However, the dissolution of $C{O}_2$ into subsurface water leads to a reduction in pH, which may cause partial dissolution of the host formation, altering the structure of the subsurface in the injection zone. This process is relatively slow, potentially unfolding over decades or even centuries, and its long-term consequences require careful investigation through mathematical modeling. The geological formation is treated as a partially soluble porous medium, where the dissolution rate is governed by surface chemical reactions occurring at the pore boundaries. In this study, we present an applied mathematical model that captures the coupled processes of mass transport, surface chemical reactions, and the resulting microscopic changes in the pore structure of the formation. To ensure the model remains grounded in realistic geological conditions, we based it on exploration data characterizing the composition and microstructure of the pore space typical of the Cenomanian suite in northern Western Siberia. The model incorporates the dominant geochemical reactions involving calcium carbonate (calcite, $CaC{O}_3$), characteristic of Cenomanian reservoir rocks. It describes the dissolution of $C{O}_2$ in the pore fluid and the associated evolution of ion concentrations, specifically $H^{+}$, $C{a}^{2+}$, and $HC{O}_3^{-}$. The input parameters are derived from experimental data. While the model focuses on calcite-based formations, the algorithm can be adapted to other mineralogies with appropriate modifications to the reaction terms. The simulation domain is defined as a cubic region with a side length of 1 $\mathsf{\mu }$m, representing a fragment of the geological formation with a porosity of 0.33. The pore space is initially filled with a mixture of liquid $C{O}_2$ and water at known saturation levels. The mathematical framework consists of a system of diffusion–reaction equations describing the dissolution of $C{O}_2$ in water and the subsequent mineral dissolution, coupled with a model for surface evolution of the solid phase. This model enables calculation of surface reaction rates within the porous medium and estimates the timescales over which significant changes in pore structure may occur, depending on the relative saturations of water and liquid $C{O}_2$. Full article

Hydrofluorocarbons (HFC) are today widely used as refrigerants, solvents, or aerosols for fire protection. Due to their non-negligible environmental impact, there exists an increasing interest towards their effective separation and recovery, which still remains a major challenge. This work presents a comprehensive thermodynamic and transport modeling approach able to describe HFC sorption and transport in different amorphous polymers, including glassy, rubbery, and copolymers, as well as in supported Ionic Liquid membranes (SILMs). In particular, the literature solubility data for refrigerants such as R-32, R-125, R-134a, and R-152a is analyzed by means of the Sanchez–Lacombe Equation of State (SL-EoS), and its non-equilibrium extension (NELF), to predict gas uptake in complex polymeric materials. The Standard Transport Model (STM) is then employed to describe permeability behaviors, incorporating concentration-dependent diffusion using a mobility coefficient and thermodynamic factor. Results demonstrate that fluorinated gases exhibit strong affinity to fluorinated and high free-volume polymers, and that solubility is primarily governed by gas condensability, molecular size, and polymer structure. The combined EoS–STM approach accurately predicts both solubility and permeability across different pressures in all polymers, including SILM. The thorough study of HFC transport in polymer membranes provided both systematic insights and predictive capabilities to guide the design of next-generation materials for refrigerant recovery and low-GWP separation processes. Full article

Digestate valorization is essential for sustainable waste management and circular economy strategies, yet large-scale adoption faces technical, economic, and environmental challenges. Beyond waste-to-energy conversion, digestate is a valuable soil amendment, enhancing soil structure and reducing reliance on synthetic fertilizers. However, its agronomic benefits depend on feedstock characteristics, treatment processes, and application methods. This study reviews digestate composition, treatment technologies, regulatory frameworks, and environmental impact assessment through Life Cycle Assessment. It analyzes the influence of functional unit selection and system boundary definitions on Life Cycle Assessment outcomes and the effects of feedstock selection, pretreatment, and post-processing on its environmental footprint and fertilization efficiency. A review of 28 JCR-indexed articles (2018–present) analyzed LCA studies on digestate, focusing on methodologies, system boundaries, and impact categories. The findings indicate that Life Cycle Assessment methodologies vary widely, complicating direct comparisons. Transportation distances, nutrient stability, and post-processing strategies significantly impact greenhouse gas emissions and nutrient retention efficiency. Techniques like solid–liquid separation and composting enhance digestate stability and agronomic performance. Digestate remains a promising alternative to synthetic fertilizers despite market uncertainty and regulatory inconsistencies. Standardized Life Cycle Assessment methodologies and policy incentives are needed to promote its adoption as a sustainable soil amendment within circular economy frameworks. Full article

Maintaining the required relative humidity values in the vehicle cabin is an important HVAC task, along with considerations related to the temperature, velocity, air pressure and noise. Deviation from the optimal values worsens the psycho-physiological state of the driver and affects the energy efficiency of the train. In this study, a model of liquid film formation on and removal from various cabin surfaces was constructed using the fundamental Navier–Stokes hydrodynamic equations. A special transport model based on the liquid vapor diffusion equation was used to simulate the air environment inside the cabin. The evaporation and condensation of surface films were simulated using the Euler film model, which directly considers liquid–gas and gas–liquid transitions. Numerical results were obtained using the RANS equations and a turbulence model by means of the finite volume method in Ansys CFD. Conjugate fields of temperature, velocity and moisture concentration were constructed for various time intervals, and the dependence values for the film thicknesses on various surfaces relative to time were determined. The verification was conducted in comparison with the experimental data, based on the protocol for measuring the microclimate indicators in workplaces, as applied to the train cabin: the average ranges encompassed temperature changes from 11% to 18%, and relative humidity ranges from 16% to 26%. Comparison with the results of other studies, without considering the phase transition and condensation, shows that, for the warm mode, the average air temperature in the cabin with condensation is 12.5% lower than without condensation, which is related to the process of liquid evaporation from the heated walls. The difference in temperature values for the model with and without condensation ranged from −12.5% to +4.9%. We demonstrate that, with an effective mode of removing condensate film from the window surface, including recirculation modes, the energy consumption of the climate control system improves significantly, but this requires a more accurate consideration of thermodynamic parameters and relative humidity. Thus, considering the moisture condensation model reveals that this variable can significantly affect other parameters of the microclimate in cabins: in particular, the temperature. This means that it should be considered in the numerical modeling, along with the basic heat transfer equations. Full article

In this work, the thermodynamics of molecular transport between two compartments connected by a nanochannel is investigated through an analysis of internal energy and entropy changes, with a focus on how these changes depend on intermolecular interaction strength. When interactions are weak, resembling gas-like behavior, entropy dominates and favors configurations in which molecules are evenly distributed between the two compartments, despite an increase in internal energy. In contrast, strong interactions, characteristic of liquid-like behavior, lead to dominant energetic contributions that favor configurations with molecules localized in a single compartment, despite entropy loss. Intermediate interaction strengths yield comparable entropic and energetic contributions that cancel each other out, resulting in oscillatory behavior between evenly distributed and localized configurations, as observed in previous work. This thermodynamic analysis reveals energy–entropy compensation, in which entropic and energetic contributions offset each other across different interaction strengths; notably, this compensatory relationship exhibits a linear trend. These findings provide insight into the thermodynamic origins of molecular transport behavior and highlight fundamental parallels between molecular transport and molecular binding, the latter being particularly relevant to molecular recognition and drug design. Full article

Gas–liquid two-phase flow is very common in fluid machinery and has complex multiphase flow characteristics. Under the gas-containing conditions, common issues in fluid machinery include the transport of liquid, bubble variations, and pressure drop characteristics; these can be analyzed using a simplified venturi tube. In order to investigate the influence of incoming gas on the gas–liquid flow, a venturi tube with the range of inlet gas volume fraction (IGVF) from 0 to 16% was used in this experiment. The development of a two-phase flow was recorded by using high-speed photography. Under different initial liquid flow rates and gas content conditions, the evolution of the two-phase flow was similar, with the main difference being the rate of evolution. The incoming gas mainly underwent a process from column shape to expansion and then to fragmentation passing through the venturi tube. In the experimental images, the projected area of the main bubble increased linearly with the increase in IGVF. Meanwhile, the transporting ability of the venturi tube was weakened due to the blockage caused by high gas content, especially when the IGVF exceeded 10%. The pressure drop characteristics indicated an increase in losses with the increase in gas content. Full article

This study focuses on addressing the issues of water flooding and mass transfer limitations in proton exchange membrane fuel cells (PEMFCs) under high current density conditions. A multi-scale gradient pore gas diffusion layer (GDL) is designed to enhance fuel cell performance. The pore structure is precisely controlled using a self-assembled mold, resulting in the fabrication of a GDL with a gradient distribution of pore diameters ranging from 80 to 170 μm. Experimental results indicate that, with the optimized gradient pore GDL, the peak power density of the fuel cell reaches 1.18 W·cm−², representing a 20% improvement compared to the traditional structure. A mechanism analysis reveals that this structure establishes a concentrated water transport pathway through channels while enabling gas diffusion and transport driven by concentration gradients, thereby achieving the collaborative optimization of gas–liquid transport. This approach offers a novel solution for managing water in PEMFCs operating under high current density conditions, and holds significant implications for advancing the commercialization of PEMFC technology. Full article

The growing interest in alternative fuels stems from the need to reduce greenhouse gas emissions and promote sustainable development. Despite the dominance of fossil fuels in aviation, pulsejet engines offer a promising platform for testing new fuels due to their simple design and fuel versatility. This study presents a multi-criteria analysis of alternative fuels for use in pulsejet engines, emphasizing environmental impacts. Both gaseous (biogas, ethyne, LPG, and natural gas) and liquid fuels (methanol, ethanol, biodiesel, Jet A-1, and SAF) were examined. Exhaust emissions (CO₂, H₂O, CO) were simulated in Ansys 2025 based on literature data and chemical calculations. Additional factors analyzed included calorific value, production cost, thermal expansion, density, life cycle emissions (LCA), CO₂ emissions per fuel mass, and renewable energy content. Using the zero-unitization method, results were normalized into a single aggregate variable for each fuel. The highest values were recorded for biogas and methanol, respectively, indicating their potential as alternative fuels. The findings support further development of sustainable fuels for pulsejet engines. Future research should address combustion optimization and noise reduction, enhancing viability in aviation and other transport sectors. Integration with the current fuel infrastructure is also recommended to facilitate broader implementation. Full article

Carbon Capture and Storage (CCS) is a key technology for reducing anthropogenic greenhouse gas emissions, in which pipelines play a vital role in transporting CO₂ captured from industrial emitters to geological storage sites. To aid the efficient and safe operation of the CO₂ transport infrastructure, robust, accurate, and reliable solutions for monitoring pipelines transporting industrial CO₂ streams are urgently needed. This literature review study summarizes the monitoring objectives and identifies the problems and relevant mathematical algorithms developed for optimization of monitoring systems for pipeline transportation of water, oil, and natural gas, which can be relevant to the future CO₂ pipelines and pipeline networks for CCS. The impacts of the physical properties of CO₂ and complex designs and operation scenarios of CO₂ transport on the pipeline monitoring systems design are discussed. It is shown that the most relevant to liquid- and dense-phase CO₂ transport are the sensor placement optimization methods developed in the context of detecting leaks and flow anomalies for water distribution systems and pipelines transporting oil and petroleum liquids. The monitoring solutions relevant to flow assurance and monitoring impurities in CO₂ pipelines are also identified. Optimizing the CO₂ pipeline monitoring systems against several objectives, including the accuracy of measurements, the number and type of sensors, and the safety and environmental risks, is discussed. Full article

Fatty acids (FAs) play a crucial role in human physiology, including energy production and serving as signaling molecules. However, a dysregulation in their balance can lead to multiple disorders, such as obesity and metabolic syndrome. These pathological conditions alter the balance between the heart’s energetic substrates, promoting an increased reliance on FAs and decreased cardiac efficiency. A therapeutic application of a non-psychotropic phytocannabinoid, cannabigerol (CBG), seems to be a promising target since it interacts with different receptors and ion channels, including cannabinoid receptors—CB₁ and CB₂, α2 adrenoceptor, or 5-hydroxytryptamine receptor. Therefore, in the current study, we evaluated a concentration-dependent effect of CBG (2.5 µM, 5 µM, and 10 µM) on H9c2 cardiomyocytes in lipid overload conditions. Gas–liquid chromatography and Western blotting techniques were used to determine the cellular lipid content and the level of selected proteins involved in FA metabolism, glucose transport, and the insulin signaling pathway. The glucose uptake assay was performed using a colorimetric method. Eighteen-hour CBG treatment in the highest concentration (10 µM) significantly diminished the accumulation of diacylglycerols (DAGs) and the saturation status of this lipid fraction. Moreover, the same concentration of CBG markedly decreased the level of FA transporters, namely fatty acid translocase (CD36) and plasma membrane fatty acid-binding protein (FABPpm), in the presence of palmitate (PA) in the culture medium. The results of our experiment suggest that CBG can significantly modulate lipid storage and composition in cardiomyocytes, thereby protecting against lipid-induced cellular dysfunction. Full article

The eutectic PbLi (15.7 at.% Li) alloy appears promising for producing tritium from fertile materials. Currently, in nuclear fusion design, the technologies being explored for tritium extraction in molten phases primarily focus on (i) established processes based on Gas–Liquid Contactor (GLC), such as bubble, packed, or spray columns, or on (ii) exploiting hydrogen permeation phenomena using dense metallic membranes, i.e., Permeation Against Vacuum (PAV). This work introduces a new concept, a Membrane Gas–Liquid Contactor, to address several open issues related to mass transport phenomena within the previously mentioned technologies. The MGLC concept merges the advantages of Permeation Against Vacuum (PAV) and Gas–Liquid Contactor (GLC), which have been extensively applied to extract hydrogen and its isotopes from liquid metals. A comprehensive description of the MGLC’s operation is then provided, suggesting a mass transfer model suitable for the practical application of this new concept. Finally, the results of the experimental campaign conducted on a lab-scale test facility are presented and critically analyzed. Full article

Low-carbon liquid fuels are needed for decarbonization of hard-to-decarbonize segments of the transportation sector. This decarbonization can be limited by the amount of renewable carbon. Thermochemical conversion of biomass/municipal solid waste (MSW) through gasification is a promising route for producing low-carbon fuels. There are two major opportunities for increasing the amount of low-carbon liquid fuel that can be produced from gasification in any region. One is to increase the amount of liquid fuel from a given amount of biomass/MSW, particularly by hydrogen-enhancement of gasification synthesis gas. Second is the potential for large expansion of use of biomass feedstocks from its present level. Such biomass feedstocks include agricultural waste, forestry waste, MSW, and specially grown biomass that does not interfere with food production. The use of MSW may provide advantages of an established network for pickup and transportation of feedstock to disposal sites and the avoidance of methane produced from landfilling of MSW. As a case study, we looked at potential expansion of US low-carbon fuel production, considering the recent projections of the 2024 USDOE report, which estimated potential production of a billion tons/yr of biomass/MSW feedstocks in the US. This report included an estimated potential for liquid biofuel production of 60 billion gallons/yr of diesel energy equivalent fuel without the use of hydrogen enhancement. By hydrogen-enhanced biomass/MSW gasification, this projection could be doubled to 120 billion gallons/yr of diesel energy equivalent fuel. Furthermore, the co-location potential of biomass/MSW resources with potential renewable energy generation sites is explored. This overlap of hydrogen production and biomass production in the US are located in regions such as the US Midwest, Texas, and California. This co-location strategy enhances logistical feasibility, reducing transport costs and optimizing energy system integration; and can be applied to other geographical locations. Hydrogen-enhanced biomass/MSW gasification offers a promising route to substantially increase low-carbon liquid fuel production (e.g., methanol) and support increased liquid fuel production and greenhouse gas reduction goals. Full article

This review offers an in-depth analysis of soil contamination, discussing the origins, impacts, and remediation strategies, as well as the complex connections with interfacial chemistry. Interfacial chemistry plays a critical role in addressing soil contamination by governing the interactions between pollutants, soil particles, water, and remediation agents at phase boundaries (solid–liquid, solid–gas). Some key aspects include adsorption/desorption that controls pollutants binding to soil surfaces; chemical transformation which facilitates redox, hydrolysis, or catalytic reactions at interfaces to degrade contaminants; colloidal transport that affects the movement of nanoparticle-bound contaminants through soil pores; and techniques like soil washing, phytoremediation and permeable reactive barriers that can neutralize soil pollutants. The combination of interfacial chemistry and soil remediation techniques offers rich opportunities for improving predictive models of contaminant fate. Such approaches represent a paradigm shift from equilibrium-based remediation to dynamic process management. The review demonstrates how heterogeneous interfaces and molecular-scale dynamics dictate contaminant behavior. Furthermore, in addition to consolidating existing knowledge, the review also pioneers new directions by revealing how interfacial processes can optimize soil decontamination, offering actionable insights for researchers and policy makers. By understanding and manipulating interfacial chemical processes, scientists can develop more precise and sustainable cleanup methods. Full article