Search Results (558)

This study investigates the performance of a diesel engine exhaust gas-driven Rankine Cycle-supported vapor compression refrigeration system using quantum chemical approaches beyond conventional thermodynamic analyses. The study focuses on R448A and its components, namely R32, R125, R134a, R1234yf, and R1234ze(E), evaluated at both the system level and the molecular level. At the system level, the Rankine–VCR system was analyzed using a Fortran-based macroscopic thermodynamic model, in which the thermophysical properties of the working fluids were obtained from the NIST Chemistry WebBook. At the molecular level, Density Functional Theory (DFT) calculations were performed to determine molecular structure parameters, including entropy, heat capacity, chemical hardness, and thermal enthalpy correction. The main objective is to investigate the possible relationships between these molecular descriptors and system-level performance indicators, while considering that mass flow rate is primarily governed by cycle thermodynamic properties. The results show that molecular stability and structural order are strongly associated with system performance. Among the R448A components, R32, with the highest chemical hardness (8.19 eV) and lowest molecular entropy (58.9 cal/mol K), exhibits the most favorable exergetic behavior and achieves the highest plant exergy efficiency of 44.92%. In contrast, R1234ze(E), chemically softer (η = 4.42 Ev) and higher in entropy, exhibits the lowest performance. Additionally, R32’s lower thermal enthalpy correction is associated with higher latent heat of vaporization under the selected operating conditions, reducing the required mass flow by approximately 60–70% compared to the other components. This study demonstrates that, in refrigerant selection, not only the global warming potential (GWP) but also quantum parameters such as chemical hardness, molecular entropy, heat capacity, and thermal enthalpy correction can serve as important complementary performance indicators when interpreted together with macroscopic thermodynamic and exergetic results. Full article

This study investigated a high-temperature heat pump for industrial steam production at 200 °C. Considering refrigerant thermal degradation at elevated temperatures, R1336mzz(Z) was selected because of its thermal stability. Two systems were analyzed: a flash tank (FT) cycle producing steam using a water valve and flash tank, and a steam generator (SG) cycle directly generating steam in the gas cooler. Unlike previous studies focusing primarily on cycle-level thermodynamic performance, this study systematically compares two steam production configurations for a 3 MW-class HTHP by considering heat pump–steam loop interactions and further evaluates their economic and environmental feasibility through LCC and LCCP analyses. Applying an internal heat exchanger reduced the operating pressure and increased the heat pump coefficient of performance (COP) by up to 13%, depending on the pressurized water temperature. In the FT cycle, lowering the valve outlet temperature from 180 °C to 150 °C increased the heat pump COP to a maximum of 3.06. However, the additional mechanical vapor recompression (MVR) power limited the overall system COP to 2.29–2.44. In the SG cycle, the system COP ranged from 1.94 to 2.54 according to the saturated water temperature at the gas cooler inlet, although operation at lower water temperatures approached the critical region, resulting in a narrower operating margin. LCC and LCCP analyses showed that replacing conventional boilers with heat pumps reduced operating costs by 26–59%, depending on regional energy prices, with payback periods of 2.27–8.76 years. Heat pump adoption also reduced life cycle climate impacts by 13–72%. These results demonstrate that high-temperature heat pumps can provide an economically and environmentally viable alternative for industrial steam production at 200 °C. Full article

The edge-defined film-fed growth (EFG) method is the dominant industrial technique for producing large-area β-Ga₂O₃ single-crystal substrates, but thermal stress-induced dislocation generation remains a critical barrier. This work presents a coupled thermo-mechanical finite-element framework for thermal-stress management in EFG-grown β-Ga₂O₃. The central methodological contribution is a 500-sample gradient-boosting surrogate sensitivity analysis ($R^2=0.955$, mean absolute error (MAE) $=11.3$ MPa) that quantitatively decomposes thermal-stress variance into controllable process factors and irreducible material-property uncertainties. The physical foundation comprises two enabling elements: (i) the full 21-component monoclinic Voigt stiffness matrix with explicit crystal–model coordinate mapping, for which the orthotropic model is rigorously shown to be exact in 2D plane strain through an exact kinematic theorem showing that the 2D plane-strain results of prior orthotropic EFG analyses are unaffected by the coupling terms, while the monoclinic formulation provides the essential foundation for future 3D studies; and (ii) a dimensionless and numerical justification for omitting melt convection, which enables 100% solver convergence (500/500 Latin hypercube samples) with stress errors < 1.5 MPa. Afterheater temperature $T_{\mathrm{AH}}$ is the leading controllable parameter (35.9%), nearly tied with the elastic constant $C_{33}$ (35.5%), followed by the thermal-expansion component ${\alpha }_c$ (15.9%). Elevating $T_{\mathrm{AH}}$ from 1900 K to 1950 K reduces the peak von Mises stress by ∼29% (COMSOL Multiphysics 6.2-verified); the 2D plane-strain baseline anchors the surrogate analysis at ${\sigma }_{max}=223$ MPa, while the afterheater-free 3D configuration gives ${\sigma }_{max}=187$ MPa at the crystal periphery near the solid–liquid interface. The isotropic approximation underestimates peak stress by 39.6%, confirming that directional anisotropy is essential for quantitatively reliable thermal stress prediction in monoclinic oxide crystals. Full article

This study presents a numerical investigation of alternative-fuel combustion in the riser duct of a cement clinker production installation, with particular emphasis on the locations of the tertiary-air inlets. Computational fluid dynamics (CFD) was used to identify favorable tertiary-air inlet positions and establish an appropriate configuration for subsequent analyses of combustion and calcination processes. The numerical model was developed using an Eulerian–Lagrangian approach, in which the gas phase was described within an Eulerian framework and the motion of solid particles was tracked using a Lagrangian approach. The model incorporates the standard k–ε turbulence model, heat-transfer mechanisms, and the P1 radiation model. At this stage of the study, simplified fuel properties were assumed, whereas limestone-meal particles and their calcination were included in the numerical model to provide a more realistic representation of the thermal and physicochemical conditions within the industrial riser duct. The CFD simulations enabled the determination of velocity fields, temperature distributions, and gas-flow structures inside the riser duct. Particular attention was devoted to the recirculation zones and mixing conditions resulting from the different tertiary-air injection configurations. The results demonstrate that the locations of the tertiary-air inlets significantly influence the combustion environment and may affect the subsequent calcination process and the overall thermal efficiency of the installation. The proposed numerical approach provides a basis for the further development of advanced multiphase models incorporating more detailed representations of alternative-fuel conversion, calcination kinetics, and pollutant formation in modern cement kiln systems. Full article

Studies on the use of LPG in maritime applications mostly evaluate emissions, engine performance, or system safety separately; approaches that integrate experimental findings with ship-level risks remain limited. This study aims to evaluate the trade-offs between the environmental advantages of LPG and energy performance and safety requirements within a common decision support framework. In the experimental phase, a single-cylinder gasoline–LPG spark-ignition engine was tested at five LPG mixture ratios and six load levels between 500–3000 W; specific fuel consumption, thermal efficiency, CO, CO₂, and HC were measured. Using legislation, the literature, and engineering evaluation, 38 failure types were identified from the experimental findings and prioritized using FMEA and entropy-weighted multi-criteria decision-making methods. The final ranking was obtained using the Borda method, and inter-method agreement and ranking stability were validated with sensitivity analyses. The results showed that increasing the LPG ratio reduced CO, CO₂, and HC emissions, but higher ratios increased fuel consumption and decreased thermal efficiency. Specific fuel consumption, gas detection error, and thermal efficiency were identified as the three most prioritized risks. The findings reveal that the emission benefits of LPG in maritime applications should be evaluated in conjunction with sensing, insulation, emergency stop reliability, and energy performance. This integrated approach provides a scientific basis for balanced and transparent fuel decisions. Full article

The Dafosi well field is a typical Huang-Long Jurassic low-rank coalbed methane (CBM) field. Clarifying its CBM geochemical characteristics and the mechanisms of its formation is of significant importance for deepening the understanding of the formation mechanisms of low-rank CBM in China and for the scientific assessment of its resource potential. A total of eight gas emission samples from six coalbed methane wells in the Dafosi coalfield were collected, along with 22 coal samples from the 4^# coal seam. Detailed analyses of microscopic coal petrographic components, gas chemical compositions, and carbon isotopes were performed. By integrating data from the 20 relevant literature sources on coalbed gas composition and isotopic characteristics within the study area, a comprehensive dataset comprising 28 sets was utilized to examine the carbon isotope characteristics and genesis types of both CH₄ and CO₂ in the coalbeds, as well as elucidate the mechanism behind CH₄ carbon isotope depletion. The findings indicate that in the primary 4^# coal seam’s microscopic petrographic composition, the organic matter content is considerably higher, averaging 93.2%. Among these, the inertinite group is dominant, averaging 68.2%; the vitrinite group is the next most abundant, averaging 22.8%. The CBM composition is predominantly CH₄, with concentrations varying from 68.753% to 98.006%, averaging 80.276%. N₂ concentrations range from 1.259% to 29.926%, averaging 17.476%. CO₂ concentrations vary from 0.04% to 2.380%, averaging 1.032%. The average concentration of heavier hydrocarbons C₂ and above is less than 0.078%, indicative of typical dry gas characteristics, C₁/C_1~n > 0.999. The concentration of CH₄ and N₂ was negatively correlated. δ¹³C₁ ranges from −87.200‰ to −62.400‰, averaging −75.802‰. CH₄ is composed of secondary biogenic gas with dominant content and a small amount of thermogenic gas. δ¹³C_CO2 ranges from −41.693‰ to −7.065‰, averaging −20.016‰. CO₂ is an organic gas, mainly derived from thermal degradation and microbial degradation of organic matter. The mechanism responsible for the light carbon isotopic composition of δ¹³C₁ lies in the fact that most of CH₄ is produced by CO₂ reduction, and a small amount is produced by acetic acid fermentation. In the gas generation process of these two pathways, biogenic methane will eventually enrich light carbon isotopes, resulting in light δ¹³C₁. Full article

The large-scale integration of photovoltaic generation into distribution grids has introduced significant operational challenges, including voltage excursions, reverse power flows, and increased variability. Battery energy storage systems (BESSs) offer a versatile solution by providing coordinated active- and reactive-power support. However, their scheduling in active distribution networks is challenging because of the non-convex alternating-current (AC) power-flow equations, the nondifferentiability of battery-degradation modeling, and uncertainty in renewable generation and demand. This paper proposes a two-stage methodology for the day-ahead operation of BESSs in ADNs. In the first stage, parallel particle swarm optimization (PPSO) determines the hourly active- and reactive-power schedules of the BESS units. In the second stage, a matrix-based multi-period AC power flow based on successive approximations evaluates the schedules and verifies voltage, thermal, converter-capability, and state-of-charge (SoC) constraints. A rainflow-counting degradation model is incorporated into the objective function to account for cycling and calendar aging costs. The methodology is assessed through ablation analyses comparing active-power-only and coordinated P–Q dispatches, degradation-unaware and degradation-aware scheduling, and serial and parallel PSO implementations. It is validated on modified 33-, 69-, and 136-node systems under deterministic and uncertainty-based operating conditions, including 100 demand and PV-generation scenarios. PPSO is compared with parallel versions of the adaptive Jaya algorithm (AJAYA), genetic algorithm (GA), multi-verse optimizer (MVO), salp swarm algorithm (SSA), grey wolf optimizer (GWO), and vortex search algorithm (VSA), using operating-cost reduction, computational time, solution variability, feasibility indicators, BESS lifetime, and weekly cost analysis. Additionally, exact one-sided Wilcoxon signed-rank tests with Holm adjustment are used to assess the statistical significance of the economic differences between PPSO and the benchmark methods. Results show that PPSO provides the lowest or most competitive operating costs and the shortest computational time in the evaluated cases, while all network and storage constraints remain satisfied. Full article

The performance of a Proton Exchange Membrane Fuel Cell (PEMFC) stack is largely determined during assembly, where component materials, sealant selection, and clamping force jointly influence both sealing effectiveness and interfacial losses. These factors interact through coupled mechanical, thermal, and electrical phenomena. Although detailed multiphysics models can accurately capture these effects, their high computational cost limits their application in parametric analyses and optimisation studies. The Equivalent Stiffness Model (ESM) provides an efficient alternative, representing each stack component as a simplified stiffness formulation. Starting from an earlier ESM that reproduces the nonlinear compression of the Membrane Electrode Assembly (MEA) and sealants, this work adds the calculation of the electrical contact resistance at the Gas Diffusion Layer (GDL)–Bipolar Plate (BPP) interface and the resulting GDL porosity. Given the large number of input parameters, a Design of Experiments (DoE) approach systematically explores a wide range of stack configurations and operating conditions. The analysis shows that GDL type, sealant properties, and clamping force are the main drivers of assembly-related performance, whereas BPP material and thermo-hygrometric conditions become more influential during operation. These results provide quantitative guidance on which design and operating choices most strongly affect stack behaviour and under which conditions. Full article

Background: Incomplete microwave ablation (iMWA) of lung cancer often leads to rapid recurrence and metastasis, yet the underlying mechanisms remain unclear. This study explored whether iMWA promotes tumor progression by activating the cyclic GMP–AMP synthase–stimulator of interferon genes (cGAS–STING) signaling pathway and its downstream effector ZEB1 in tumor cells. Materials and Methods: An in vivo iMWA model was established in nude mice bearing H1650 lung tumors, and an in vitro sublethal heat treatment model was used to mimic incomplete ablation. Transcriptomic profiling, molecular assays and functional analyses assessed cellular behavior and signaling activity changes post-iMWA; genetic and pharmacologic interventions modulated STING signaling and autophagy. Results: Post-iMWA residual cells exhibited enhanced proliferation and invasion. Thermal injury induced necrosis and inhibited mitophagy, causing cytosolic mtDNA accumulation that activated the intrinsic cGAS–STING pathway. This upregulation of ZEB1 drove epithelial–mesenchymal transition and dissemination. Notably, silencing STING or ZEB1, or pharmacologically restoring autophagy, significantly suppressed tumor growth and metastasis. Conclusions: iMWA drives malignant progression of lung cancer through an mtDNA–cGAS–STING–ZEB1 signaling axis. Targeting this pathway—by inhibiting STING or enhancing autophagy—may represent a promising therapeutic strategy to mitigate recurrence and metastasis following microwave ablation. Full article

Agricultural hazelnut shell waste was converted into biochar by slow pyrolysis at 500, 700, and 900 °C and evaluated as a sustainable adsorbent for waste frying oil purification. The biochars were characterized by proximate, thermal, spectroscopic, morphological, and elemental analyses, including Brunauer–Emmett–Teller (BET) surface-area measurement, and benchmarked against activated carbon and Magnesol. Pyrolysis markedly developed the pore structure, increasing the BET surface area from 1.68 m²/g in the raw shell to 666.05 m²/g at 900 °C, and an exploratory principal component analysis summarized 90.85% of the total variance. Acid-extractable element concentrations were screened against feed-grade biochar and oenological bentonite reference values, without establishing regulatory compliance or food-contact suitability. All three biochars significantly reduced free fatty acidity (27.6–37.8%) and p-anisidine value (23.3–27.5%), with no significant difference relative to activated carbon (Tukey’s test, p > 0.05); however, total polar material was not significantly reduced under these mild, short-contact conditions. Gas chromatography showed no significant changes in the major unsaturated fatty acids of the glyceride-bound fraction, and total color differences remained small (ΔE* = 0.71–1.82). Hazelnut-shell biochar therefore shows potential as a waste-derived, circular adsorbent for selected oil-degradation products. Full article

High-purity quartz is a critical raw material for high-tech industries such as semiconductors and photovoltaics, yet its purity is severely constrained by gas–liquid inclusions within quartz crystals that are difficult to eliminate. The calcination–water quenching process is a key pretreatment step for removing inclusions and achieving deep purification, but its underlying mechanisms and the influence of process parameters on removal efficiency remain insufficiently understood. In this study, systematic calcination–water quenching experiments at different temperature gradients (500 °C, 700 °C, 900 °C, and 1100 °C) were conducted on high-purity quartz samples from Inner Mongolia and Angola. Comprehensive analytical techniques, including X-ray diffraction (XRD), major and trace element analyses, and polarizing microscopy, were employed to investigate the microstructural evolution, inclusion morphology, impurity element concentration changes, and phase transformation behavior before and after treatment. With increasing temperature, the quartz samples exhibited pronounced whitening and pulverization, accompanied by a significant reduction in the number of internal linear inclusions. Elemental analysis revealed that calcination–water quenching effectively removed certain alkali metals, alkaline-earth metals, and iron impurities, with 900 °C identified as the optimal calcination temperature; moreover, the sand-sized samples consistently showed better impurity removal efficiency than the lump-sized counterparts. XRD analysis was used to verify the phase transformation of quartz during calcination. Excessive temperatures (e.g., 1100 °C) led to a rebound in the content of some impurity elements. The calcination–water quenching process promotes inclusion decrepitation, exposure, and subsequent removal through the combined effects of volumetric strain induced by quartz phase transitions, thermal pressurization of inclusions, and thermal-shock stress from water quenching. This study establishes the optimal process window (hold at 900 °C for 2 h, sand-sized morphology) for the specific ore samples, elucidates the multi-factor synergistic mechanism of inclusion rupture, and provides both experimental and theoretical bases for the industrial purification of high-purity quartz. Full article

Annular trapped pressure is an important factor affecting wellbore integrity during the production of high-temperature and high-pressure oil and gas wells. In wells with multilayer casing structures, one or more enclosed annuli may form because of cement top, packer setting, wellbore structural constraints and wellhead sealing. When the temperature and pressure fields in the wellbore change during production, the annular fluid undergoes thermal expansion, compressive deformation and possible phase-state changes, causing trapped pressure to evolve continuously with time. Conventional annular pressure prediction methods are usually based on a single annulus, quasi-static assumptions or simplified fluid properties, and therefore cannot fully describe deformation transfer among annuli, thermal expansion of tubular strings and nonlinear gas–liquid compression. To address this problem, this study analyses the formation mechanism of annular trapped pressure from the perspective of thermal–fluid–solid coupling and develops a dynamic pressure evolution model that accounts for transient temperature variation, annular fluid thermal expansion and compression, elastic deformation of tubular strings and multi-annulus coupling. The analysis indicates that annular trapped pressure is essentially a pressure response produced by fluid thermal expansion under structural confinement. A multi-annulus system is not a set of independent annuli, but a pressure–deformation–volume feedback system coupled through shared casing walls. The proposed solution framework and pressure evolution analysis provide a theoretical basis for annular pressure prediction, casing safety assessment and wellbore-integrity management in high-temperature and high-pressure gas wells. Full article

This study explores the utilization of local biomass through slow pyrolysis in a multifunctional domestic reactor, with a view to producing renewable energy and improving soil quality in arid regions. Four underutilized biomass sources were studied: millet stalks, cashew shells, cashew shell meal, and rumen contents. Thermal monitoring using thermocouples showed pyrolysis temperatures ranging from 270 to 350 °C, while the combustion chamber reached up to 800 °C depending on the biomass. Four thermal phases were identified (heating, devolatilization, stabilization, and cooling), confirming stable reactor operation. Gas analyses revealed a predominance of CO (approximately 1000 ppm) as well as variations in O₂, H₂S, and hydrocarbons, indicating a conversion process dependent on the type of biomass and interactions between chambers. Mass and energy balances show that performance depends heavily on the physicochemical properties of the feedstocks, particularly the content of volatiles, lignin, and ash. Cashew shells exhibited the highest energy efficiency (approximately 42.9%), followed by rumen contents (approximately 34.4%), while cashew shell meal showed lower performance due to prior extraction of volatiles. Biochar yields and energy distribution vary significantly depending on the biomass, highlighting the importance of feedstock selection in decentralized pyrolysis systems. Overall, household pyrolysis enables simultaneous energy recovery and biochar production under realistic, non-optimized conditions. These results provide new insights into biomass–reactor interactions and support the development of decentralized bioenergy solutions tailored to sub-Saharan regions. Full article

Hierarchical zeolites have emerged as an effective strategy to mitigate diffusional limitations and catalyst deactivation during the catalytic cracking of heavy feedstocks. However, conventional alkaline desilication often lacks selectivity, leading to partial loss of crystallinity and unfavorable alterations in acidic properties. In this work, microwave-assisted desilication is explored as an alternative route to engineer hierarchical Y zeolites with improved structural control and catalytic performance. A systematic comparison between conventional and microwave-assisted treatments was carried out using a 0.20 mol L⁻¹ NaOH solution, followed by hydrothermal stabilization. The resulting materials were comprehensively characterized by X-ray diffraction, nitrogen physisorption, scanning electron microscopy, ICP–OES, and pyridine-adsorbed FTIR. Catalytic performance was evaluated in the cracking of nitrogen-containing vacuum gas oil under microactivity test conditions representative of FCC operation. Microwave-assisted desilication promotes a more homogeneous development of mesoporosity, yielding higher mesopore volumes and larger pore diameters while preserving a greater fraction of the FAU crystalline structure and Brønsted acidity compared to conventional treatment. These features translate into enhanced catalytic behavior, including higher and more stable conversions, increased gasoline selectivity (up to 63 wt%), and significantly reduced coke yields. In addition, spectroscopic and thermal analyses reveal that coke formed on the microwave-treated zeolite is less condensed and more readily oxidizable, indicating a reduced propensity for irreversible deactivation. Finally, the results demonstrate that the mode of energy input during desilication plays a critical role in dictating the balance between pore architecture and acidity, ultimately governing catalytic performance. Microwave-assisted desilication emerges as an efficient strategy for designing hierarchical Y zeolites with improved accessibility, selectivity, and resistance to deactivation under severe FCC conditions. Full article

The Hailijin uranium (U) deposit is one of the super-large U-deposits recently discovered in the Qianjiadian ore field, southwestern Songliao Basin. The ore bodies are mainly hosted in the lower member sandstones of the Upper Cretaceous Yaojia Formation and occur as multilayered tabular bodies. The nature and source of the ore-forming fluids remain unclear, limiting the understanding of the genetic type of the deposit. This study integrated drill-core observation, mineralogy, whole-rock geochemistry, in situ pyrite trace elements and sulfur isotopes, fluid-inclusion, and Raman spectroscopy to constrain ore-forming fluids. The host sandstones experienced hematitization, limonitization, carbonate cementation, clay alteration, sulfidation and bleaching. Pitchblende and coffinite occur as submicron grains in dissolution pores of quartz and feldspar, on clay-mineral surfaces and within mobile organic matter (OM), commonly associated with pyrite and sphalerite. The ores and gray mineralized sandstones are enriched in U, Mo, Re, Co, Ni, Zn and Pb, and syn-ore pyrite shows positive correlations between U and As, Mo, Cu, Zn, Se and Sb. Mineralization-related fluid-inclusion assemblages occur mainly in syn-ore dolomite/ankerite cements and in secondary trails along microfractures in detrital quartz; they yield homogenization temperatures of 130–190 °C and salinities of 3–8 wt.% NaCl eq., higher than the normal burial temperature of the basin (80–90 °C), especially meteoric fluid. Raman and gas-chromatographic analyses indicate carbonaceous matter, CH₄, CO₂, H₂ and minor O₂. Pyrite δ³⁴S values of −49.24‰ to −23.1‰ indicate isotopically light reduced sulfur ultimately related to microbial sulfate reduction and/or thermal decomposition of sulfur-bearing OM, whereas thermochemical sulfate reduction was unlikely to be dominant. Therefore, the ore-forming fluid is interpreted as a low-temperature, low-salinity organic-rich fluid, most likely derived from U-enriched source rocks at depth, and the uranium mineralization is closely associated with the exudation of such deep-derived organic fluids. Full article