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23 pages, 2268 KiB  
Article
Potential for Drought Stress Alleviation in Lettuce (Lactuca sativa L.) with Humic Substance-Based Biostimulant Applications
by Santiago Atero-Calvo, Francesco Magro, Giacomo Masetti, Eloy Navarro-León, Begoña Blasco and Juan Manuel Ruiz
Plants 2025, 14(15), 2386; https://doi.org/10.3390/plants14152386 - 2 Aug 2025
Viewed by 187
Abstract
In the present study, we evaluated the potential use of a humic substance (HS)-based biostimulant in mitigating drought stress in lettuce (Lactuca sativa L.) by comparing both root and foliar modes of application. To achieve this, lettuce plants were grown in a [...] Read more.
In the present study, we evaluated the potential use of a humic substance (HS)-based biostimulant in mitigating drought stress in lettuce (Lactuca sativa L.) by comparing both root and foliar modes of application. To achieve this, lettuce plants were grown in a growth chamber on a solid substrate composed of vermiculite and perlite (3:1). Plants were exposed to drought conditions (50% of Field Capacity, FC) and 50% FC + HS applied as radicular (‘R’) and foliar (‘F’) at concentrations: R-HS 0.40 and 0.60 mL/L, respectively, and 7.50 and 10.00 mL/L, respectively, along with a control (100% FC). HSs were applied three times at 10-day intervals. Plant growth, nutrient concentration, lipid peroxidation, reactive oxygen species (ROS), and enzymatic and non-enzymatic antioxidants were estimated. Various photosynthetic and chlorophyll fluorescence parameters were also analyzed. The results showed that HS applications alleviated drought stress, increased plant growth, and reduced lipid peroxidation and ROS accumulation. HSs also improved the net photosynthetic rate, carboxylation efficiency, electron transport flux, and water use efficiency. Although foliar HSs showed a greater tendency to enhance shoot growth and photosynthetic capacity, the differences between the application methods were not significant. Hence, in this preliminary work, the HS-based product evaluated in this study demonstrated potential for alleviating drought stress in lettuce plants at the applied doses, regardless of the mode of application. This study highlights HS-based biostimulants as an effective and sustainable tool to improve crop resilience and support sustainable agriculture under climate change. However, further studies under controlled growth chamber conditions are needed to confirm these results before field trials. Full article
(This article belongs to the Special Issue Biostimulation for Abiotic Stress Tolerance in Plants)
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27 pages, 10397 KiB  
Article
Methods for Measuring and Computing the Reference Temperature in Newton’s Law of Cooling for External Flows
by James Peck, Tom I-P. Shih, K. Mark Bryden and John M. Crane
Energies 2025, 18(15), 4074; https://doi.org/10.3390/en18154074 (registering DOI) - 31 Jul 2025
Viewed by 214
Abstract
Newton’s law of cooling requires a reference temperature (Tref) to define the heat-transfer coefficient (h). For external flows with multiple temperatures in the freestream, obtaining Tref is a challenge. One widely used method, [...] Read more.
Newton’s law of cooling requires a reference temperature (Tref) to define the heat-transfer coefficient (h). For external flows with multiple temperatures in the freestream, obtaining Tref is a challenge. One widely used method, referred to as the adiabatic-wall (AW) method, obtains Tref by requiring the surface of the solid exposed to convective heat transfer to be adiabatic. Another widely used method, referred to as the linear-extrapolation (LE) method, obtains Tref by measuring/computing the heat flux (qs) on the solid surface at two different surface temperatures (Ts) and then linearly extrapolating to qs=0. A third recently developed method, referred to as the state-space (SS) method, obtains Tref by probing the temperature space between the highest and lowest in the flow to account for the effects of Ts or qs on Tref. This study examines the foundation and accuracy of these methods via a test problem involving film cooling of a flat plate where qs switches signs on the plate’s surface. Results obtained show that only the SS method could guarantee a unique and physically meaningful Tref where Ts=Tref on a nonadiabatic surface qs=0. The AW and LE methods both assume Tref to be independent of Ts, which the SS method shows to be incorrect. Though this study also showed the adiabatic-wall temperature, TAW, to be a good approximation of Tref (<10% relative error), huge errors can occur in h about the solid surface where |TsTAW| is near zero because where Ts=TAW, qs0. Full article
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21 pages, 3327 KiB  
Article
Numerical Analysis of Heat Transfer and Flow Characteristics in Porous Media During Phase-Change Process of Transpiration Cooling for Aerospace Thermal Management
by Junhyeon Bae, Jukyoung Shin and Tae Young Kim
Energies 2025, 18(15), 4070; https://doi.org/10.3390/en18154070 (registering DOI) - 31 Jul 2025
Viewed by 179
Abstract
Transpiration cooling that utilizes the phase change of a liquid coolant is recognized as an effective thermal protection technique for extreme environments. However, the introduction of phase change within the porous structure brings about challenges, such as vapor blockage, pressure fluctuations, and temperature [...] Read more.
Transpiration cooling that utilizes the phase change of a liquid coolant is recognized as an effective thermal protection technique for extreme environments. However, the introduction of phase change within the porous structure brings about challenges, such as vapor blockage, pressure fluctuations, and temperature inversion, which critically influence system reliability. This study conducts numerical analyses of coupled processes of heat transfer, flow, and phase change in transpiration cooling using a Two-Phase Mixture Model. The simulation incorporates a Local Thermal Non-Equilibrium approach to capture the distinct temperature fields of the solid and fluid phases, enabling accurate prediction of the thermal response within two-phase and single-phase regions. The results reveal that under low heat flux, dominant capillary action suppresses dry-out and expands the two-phase region. Conversely, high heat flux causes vaporization to overwhelm the capillary supply, forming a superheated vapor layer and constricting the two-phase zone. The analysis also explains a paradoxical pressure drop, where an initial increase in flow rate reduces pressure loss by suppressing the high-viscosity vapor phase. Furthermore, a local temperature inversion, where the fluid becomes hotter than the solid matrix, is identified and attributed to vapor counterflow and its subsequent condensation. Full article
(This article belongs to the Section J1: Heat and Mass Transfer)
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17 pages, 3944 KiB  
Article
Functionalized Magnetic Nanoparticles as Recyclable Draw Solutes for Forward Osmosis: A Sustainable Approach to Produced Water Reclamation
by Sunith B. Madduri and Raghava R. Kommalapati
Separations 2025, 12(8), 199; https://doi.org/10.3390/separations12080199 - 29 Jul 2025
Viewed by 236
Abstract
Magnetic nanoparticles (MNPs), especially iron oxide (Fe3O4), display distinctive superparamagnetic characteristics and elevated surface-area-to-volume ratios, facilitating improved physicochemical interactions with solutes and pollutants. These characteristics make MNPs strong contenders for use in water treatment applications. This research investigates the [...] Read more.
Magnetic nanoparticles (MNPs), especially iron oxide (Fe3O4), display distinctive superparamagnetic characteristics and elevated surface-area-to-volume ratios, facilitating improved physicochemical interactions with solutes and pollutants. These characteristics make MNPs strong contenders for use in water treatment applications. This research investigates the application of iron oxide MNPs synthesized via co-precipitation as innovative draw solutes in forward osmosis (FO) for treating synthetic produced water (SPW). The FO membrane underwent surface modification with sulfobetaine methacrylate (SBMA), a zwitterionic polymer, to increase hydrophilicity, minimize fouling, and elevate water flux. The SBMA functional groups aid in electrostatic repulsion of organic and inorganic contaminants, simultaneously encouraging robust hydration layers that improve water permeability. This adjustment is vital for sustaining consistent flux performance while functioning with MNP-based draw solutions. Material analysis through thermogravimetric analysis (TGA), scanning electron microscopy (SEM), and Fourier-transform infrared spectroscopy (FTIR) verified the MNPs’ thermal stability, consistent morphology, and modified surface chemistry. The FO experiments showed a distinct relationship between MNP concentration and osmotic efficiency. At an MNP dosage of 10 g/L, the peak real-time flux was observed at around 3.5–4.0 L/m2·h. After magnetic regeneration, 7.8 g of retrieved MNPs generated a steady flow of ~2.8 L/m2·h, whereas a subsequent regeneration (4.06 g) resulted in ~1.5 L/m2·h, demonstrating partial preservation of osmotic driving capability. Post-FO draw solutions, after filtration, exhibited total dissolved solids (TDS) measurements that varied from 2.5 mg/L (0 g/L MNP) to 227.1 mg/L (10 g/L MNP), further validating the effective dispersion and solute contribution of MNPs. The TDS of regenerated MNP solutions stayed similar to that of their fresh versions, indicating minimal loss of solute activity during the recycling process. The combined synergistic application of SBMA-modified FO membranes and regenerable MNP draw solutes showcases an effective and sustainable method for treating produced water, providing excellent water recovery, consistent operational stability, and opportunities for cyclic reuse. Full article
(This article belongs to the Section Purification Technology)
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17 pages, 6623 KiB  
Article
Numerical Study on Flow Field Optimization and Wear Mitigation Strategies for 600 MW Pulverized Coal Boilers
by Lijun Sun, Miao Wang, Peian Chong, Yunhao Shao and Lei Deng
Energies 2025, 18(15), 3947; https://doi.org/10.3390/en18153947 - 24 Jul 2025
Viewed by 162
Abstract
To compensate for the instability of renewable energy sources during China’s energy transition, large thermal power plants must provide critical operational flexibility, primarily through deep peaking. To investigate the combustion performance and wear and tear of a 600 MW pulverized coal boiler under [...] Read more.
To compensate for the instability of renewable energy sources during China’s energy transition, large thermal power plants must provide critical operational flexibility, primarily through deep peaking. To investigate the combustion performance and wear and tear of a 600 MW pulverized coal boiler under deep peaking, the gas–solid flow characteristics and distributions of flue gas temperature, wall heat flux, and wall wear rate in a 600 MW tangentially fired pulverized coal boiler under variable loads (353 MW, 431 MW, 519 MW, and 600 MW) are investigated in this study employing computational fluid dynamics numerical simulation method. Results demonstrate that increasing the boiler load significantly amplifies gas velocity, wall heat flux, and wall wear rate. The maximum gas velocity in the furnace rises from 20.9 m·s−1 (353 MW) to 37.6 m·s−1 (600 MW), with tangential airflow forming a low-velocity central zone and high-velocity peripheral regions. Meanwhile, the tangential circle diameter expands by ~15% as the load increases. The flue gas temperature distribution exhibits a “low-high-low” profile along the furnace height. As the load increases from 353 MW to 600 MW, the primary combustion zone’s peak temperature rises from 1750 K to 1980 K, accompanied by a ~30% expansion in the coverage area of the high-temperature zone. Wall heat flux correlates strongly with temperature distribution, peaking at 2.29 × 105 W·m−2 (353 MW) and 2.75 × 105 W·m−2 (600 MW) in the primary combustion zone. Wear analysis highlights severe erosion in the economizer due to elevated flue gas velocities, with wall wear rates escalating from 3.29 × 10−7 kg·m−2·s−1 (353 MW) to 1.23 × 10−5 kg·m−2·s−1 (600 MW), representing a 40-fold increase under full-load conditions. Mitigation strategies, including ash removal optimization, anti-wear covers, and thermal spray coatings, are proposed to enhance operational safety. This work provides critical insights into flow field optimization and wear management for large-scale coal-fired boilers under flexible load operation. Full article
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26 pages, 2652 KiB  
Article
Predictive Framework for Membrane Fouling in Full-Scale Membrane Bioreactors (MBRs): Integrating AI-Driven Feature Engineering and Explainable AI (XAI)
by Jie Liang, Sangyoup Lee, Xianghao Ren, Yingjie Guo, Jeonghyun Park, Sung-Gwan Park, Ji-Yeon Kim and Moon-Hyun Hwang
Processes 2025, 13(8), 2352; https://doi.org/10.3390/pr13082352 - 24 Jul 2025
Viewed by 328
Abstract
Membrane fouling remains a major challenge in full-scale membrane bioreactor (MBR) systems, reducing operational efficiency and increasing maintenance needs. This study introduces a predictive and analytic framework for membrane fouling by integrating artificial intelligence (AI)-driven feature engineering and explainable AI (XAI) using real-world [...] Read more.
Membrane fouling remains a major challenge in full-scale membrane bioreactor (MBR) systems, reducing operational efficiency and increasing maintenance needs. This study introduces a predictive and analytic framework for membrane fouling by integrating artificial intelligence (AI)-driven feature engineering and explainable AI (XAI) using real-world data from an MBR treating food processing wastewater. The framework refines the target parameter to specific flux (flux/transmembrane pressure (TMP)), incorporates chemical oxygen demand (COD) removal efficiency to reflect biological performance, and applies a moving average function to capture temporal fouling dynamics. Among tested models, CatBoost achieved the highest predictive accuracy (R2 = 0.8374), outperforming traditional statistical and other machine learning models. XAI analysis identified the food-to-microorganism (F/M) ratio and mixed liquor suspended solids (MLSSs) as the most influential variables affecting fouling. This robust and interpretable approach enables proactive fouling prediction and supports informed decision making in practical MBR operations, even with limited data. The methodology establishes a foundation for future integration with real-time monitoring and adaptive control, contributing to more sustainable and efficient membrane-based wastewater treatment operations. However, this study is based on data from a single full-scale MBR treating food processing wastewater and lacks severe fouling or cleaning events, so further validation with diverse datasets is needed to confirm broader applicability. Full article
(This article belongs to the Special Issue Membrane Technologies for Desalination and Wastewater Treatment)
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20 pages, 8459 KiB  
Article
Membrane Processes for Remediating Water from Sugar Production By-Product Stream
by Amal El Gohary Ahmed, Christian Jordan, Eva Walcher, Selma Kuloglija, Reinhard Turetschek, Antonie Lozar, Daniela Tomasetig and Michael Harasek
Membranes 2025, 15(7), 207; https://doi.org/10.3390/membranes15070207 - 12 Jul 2025
Viewed by 538
Abstract
Sugar production generates wastewater rich in dissolved solids and organic matter, and improper disposal poses severe environmental risks, exacerbates water scarcity, and creates regulatory challenges. Conventional treatment methods, such as evaporation and chemical precipitation, are energy-intensive and often ineffective at removing fine particulates [...] Read more.
Sugar production generates wastewater rich in dissolved solids and organic matter, and improper disposal poses severe environmental risks, exacerbates water scarcity, and creates regulatory challenges. Conventional treatment methods, such as evaporation and chemical precipitation, are energy-intensive and often ineffective at removing fine particulates and dissolved impurities. This study evaluates membrane-based separation as a sustainable alternative for water reclamation and sugar recovery from sugar industry effluents, focusing on replacing evaporation with membrane processes, ensuring high permeate quality, and mitigating membrane fouling. Cross-flow filtration experiments were conducted on a lab-scale membrane system at 70 °C to suppress microbial growth, comparing direct reverse osmosis (RO) of the raw effluent to an integrated ultrafiltration (UF)–RO process. Direct RO resulted in rapid membrane fouling. A tight UF (5 kDa) pre-treatment before RO significantly mitigated fouling and improved performance, enabling 28% water recovery and 79% sugar recovery, maintaining permeate conductivity below 0.5 mS/cm, sustaining stable flux, and reducing membrane blocking. Additionally, the UF and RO membranes were tested via SEM, EDS, and FTIR to elucidate the fouling mechanisms. Full article
(This article belongs to the Special Issue Emerging Superwetting Membranes: New Advances in Water Treatment)
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15 pages, 2181 KiB  
Article
The Impact of Shifts in Both Precipitation Pattern and Temperature Changes on River Discharge in Central Japan
by Bing Zhang, Jingyan Han, Jianbo Liu and Yong Zhao
Hydrology 2025, 12(7), 187; https://doi.org/10.3390/hydrology12070187 - 9 Jul 2025
Viewed by 453
Abstract
Rivers play a crucial role in the hydrological cycle and serve as essential freshwater resources for both human populations and ecosystems. Climate change significantly alters precipitation patterns and river discharge variability. However, the impact of precipitation patterns (rainfall and snowfall) and air temperature [...] Read more.
Rivers play a crucial role in the hydrological cycle and serve as essential freshwater resources for both human populations and ecosystems. Climate change significantly alters precipitation patterns and river discharge variability. However, the impact of precipitation patterns (rainfall and snowfall) and air temperature on river discharge in coastal zones remains inadequately understood. This study focused on Toyama Prefecture, located along the Sea of Japan, as a representative coastal area. We analyzed over 30 years of datasets, including air temperature, precipitation, snowfall, and river discharge, to assess the effects of climate change on river discharge. Trends in hydroclimatic datasets were assessed using the rescaled adjusted partial sums (RAPS) method and the Mann–Kendall (MK) non-parametric test. Furthermore, a correlation analysis and the Structural Equation Model (SEM) were applied to construct a relationship between precipitation, temperature, and river discharge. Our findings indicated a significant increase in air temperature at a rate of 0.2 °C per decade, with notable warming observed in late winter (January and February) and early spring (March). The average river fluxes for the Jinzu, Oyabe, Kurobe, Shou, and Joganji rivers were 182.52 m3/s, 60.37 m3/s, 41.40 m3/s, 38.33 m3/s, and 18.72 m3/s, respectively. The tipping point for snowfall decline occurred in 1992, marked by an obvious decrease in snowfall depth. The SEM showed that, although rainfall dominated the changes in river discharge (loading = 0.94), the transition from solid (snow) to liquid (rain) precipitation may alter the river discharge regime. The percentage of flood occurrence increased from 19% (1940–1992) to 41% (1993–2020). These changes highlight the urgent need to raise awareness about the impacts of climate change on river floods and freshwater resources in global coastal regions. Full article
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15 pages, 4738 KiB  
Article
Mechanical Performance of Ceria-Coated 3D-Printed Black Zirconia Cellular Structures After Solar Thermochemical CO/H2 Fuel Production Cycles
by Fernando A. Costa Oliveira, Manuel Sardinha, Joaquim M. Justino Netto, Miguel Farinha, Marco Leite, M. Alexandra Barreiros, Stéphane Abanades and Jorge Cruz Fernandes
Crystals 2025, 15(7), 629; https://doi.org/10.3390/cryst15070629 - 8 Jul 2025
Viewed by 350
Abstract
Solar fuels production requires developing redox active materials with porous structures able to withstand thermochemical cycles with enhanced thermal stability under concentrated solar irradiation conditions. The mechanical performance of 3D-printed, macroporous black zirconia gyroid structures, coated with redox-active ceria, was assessed for their [...] Read more.
Solar fuels production requires developing redox active materials with porous structures able to withstand thermochemical cycles with enhanced thermal stability under concentrated solar irradiation conditions. The mechanical performance of 3D-printed, macroporous black zirconia gyroid structures, coated with redox-active ceria, was assessed for their suitability in solar thermochemical cycles for CO2 and H2O splitting. Experiments were conducted using a 1.5 kW solar furnace to supply the high-temperature concentrated heat to a windowed reaction chamber to carry out thermal redox cycling under realistic on-sun conditions. The ceria coating on ceramic structures improved the thermal stability and redox efficiency while minimizing the quantity of the redox material involved. Crushing strength measurements showed that samples not directly exposed to the concentrated solar flux retained their mechanical performance after thermal cycling (~10 MPa), while those near the concentrated solar beam focus exhibited significant degradation due to thermal stresses and the formation of CexZr1−xO2 solid solutions (~1.5 MPa). A Weibull modulus of 8.5 was estimated, marking the first report of such a parameter for fused filament fabrication (FFF)-manufactured black zirconia with gyroid architecture. Failure occurred via a damage accumulation mechanism at both micro- and macro-scales. These findings support the viability of ceria-coated cellular ceramics for scalable solar fuel production and highlight the need for optimized reactor designs. Full article
(This article belongs to the Section Materials for Energy Applications)
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28 pages, 3292 KiB  
Article
Optimization of the Quality of Reclaimed Water from Urban Wastewater Treatment in Arid Region: A Zero Liquid Discharge Pilot Study Using Membrane and Thermal Technologies
by Maria Avramidi, Constantinos Loizou, Maria Kyriazi, Dimitris Malamis, Katerina Kalli, Angelos Hadjicharalambous and Constantina Kollia
Membranes 2025, 15(7), 199; https://doi.org/10.3390/membranes15070199 - 1 Jul 2025
Viewed by 760
Abstract
With water availability being one of the world’s major challenges, this study aims to propose a Zero Liquid Discharge (ZLD) system for treating saline effluents from an urban wastewater treatment plant (UWWTP), thereby supplementing into the existing water cycle. The system, which employs [...] Read more.
With water availability being one of the world’s major challenges, this study aims to propose a Zero Liquid Discharge (ZLD) system for treating saline effluents from an urban wastewater treatment plant (UWWTP), thereby supplementing into the existing water cycle. The system, which employs membrane (nanofiltration and reverse osmosis) and thermal technologies (multi-effect distillation evaporator and vacuum crystallizer), has been installed and operated in Cyprus at Larnaca’s WWTP, for the desalination of the tertiary treated water, producing high-quality reclaimed water. The nanofiltration (NF) unit at the plant operated with an inflow concentration ranging from 2500 to 3000 ppm. The performance of the installed NF90-4040 membranes was evaluated based on permeability and flux. Among two NF operation series, the second—operating at 75–85% recovery and 2500 mg/L TDS—showed improved membrane performance, with stable permeability (7.32 × 10−10 to 7.77 × 10−10 m·s−1·Pa−1) and flux (6.34 × 10−4 to 6.67 × 10−4 m/s). The optimal NF operating rate was 75% recovery, which achieved high divalent ion rejection (more than 99.5%). The reverse osmosis (RO) unit operated in a two-pass configuration, achieving water recoveries of 90–94% in the first pass and 76–84% in the second. This setup resulted in high rejection rates of approximately 99.99% for all major ions (Cl, Na+, Ca2+, and Mg2+), reducing the permeate total dissolved solids (TDS) to below 35 mg/L. The installed multi-effect distillation (MED) unit operated under vacuum and under various inflow and steady-state conditions, achieving over 60% water recovery and producing high-quality distillate water (TDS < 12 mg/L). The vacuum crystallizer (VC) further concentrated the MED concentrate stream (MEDC) and the NF concentrate stream (NFC) flows, resulting in distilled water and recovered salts. The MEDC process produced salts with a purity of up to 81% NaCl., while the NFC stream produced mixed salts containing approximately 46% calcium salts (mainly as sulfates and chlorides), 13% magnesium salts (mainly as sulfates and chlorides), and 38% sodium salts. Overall, the ZLD system consumed 12 kWh/m3, with thermal units accounting for around 86% of this usage. The RO unit proved to be the most energy-efficient component, contributing 71% of the total water recovery. Full article
(This article belongs to the Special Issue Applications of Membrane Distillation in Water Treatment and Reuse)
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17 pages, 4438 KiB  
Article
Y5F3[AsO3]4 and Y5Cl3[AsO3]4: Two Non-Isostructural Yttrium Halide Oxoarsenates(III) and Their Potential as Hosts for Luminescent Eu3+- and Tb3+-Doping
by Ralf J. C. Locke, Martina Mikuta, Florian Ledderboge, Frank C. Zimmer, Henning A. Höppe and Thomas Schleid
Crystals 2025, 15(7), 611; https://doi.org/10.3390/cryst15070611 - 30 Jun 2025
Viewed by 272
Abstract
Y5F3[AsO3]4 crystallizes needle-shaped in the tetragonal space group P4/ncc with the lattice parameters a = 1143.80(8) pm, c = 1078.41(7) pm and c/a = 0.9428 for Z = 4. The yttrium-fluoride substructure [...] Read more.
Y5F3[AsO3]4 crystallizes needle-shaped in the tetragonal space group P4/ncc with the lattice parameters a = 1143.80(8) pm, c = 1078.41(7) pm and c/a = 0.9428 for Z = 4. The yttrium-fluoride substructure linked via secondary contacts forms a three-dimensional network 3{[Y5F3]12+} and the remaining part consists of ψ1-tetrahedral [AsO3]3− units, which leave lone-pair channels along [001]. In contrast, platelet-shaped Y5Cl3[AsO3]4 crystals adopt the monoclinic space group C2/c with the lattice parameters a = 1860.56(9) pm, b = 536.27(3) pm, c = 1639.04(8) pm and β = 105.739(3)° for Z = 4. Condensation of [(Y1,2)O8]13− polyhedra via four common edges each leads to fluorite-like 2 {[(Y1,2)O e8/2 ]5−} layers spreading out parallel to the (100) plane. Their three-dimensional linkage occurs via the (Y3)3+ cations with their Cl ligands on the one hand and the As3+ cations with their lone-pairs of electrons on the other, which also form within [AsO3]3− anions lone-pair channels along [010]. Both colorless compounds can be obtained by solid-state reactions from corresponding mixtures of the binaries (Y2O3, As2O3 and YX3 with X = F and Cl) at elevated temperatures of 825 °C, most advantageously under halide-flux assistance (CsBr for Y5F3[AsO3]4 and ZnCl2 for Y5Cl3[AsO3]4). By replacing a few percent of YX3 with EuX3 or TbX3, Eu3+- or Tb3+-doped samples are accessible, which show red or green luminescence upon excitation with ultraviolet radiation. Full article
(This article belongs to the Special Issue Synthesis and Crystal Structure of Rare-Earth Metal Compounds)
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22 pages, 6648 KiB  
Article
Conjugate Heat Transfer Modelling in a Centrifugal Compressor for Automotive Applications
by Carlo Cravero, Pierre-Alain Hoffer, Davide Marsano, Daniele Mattiello and Luigi Mosciaro
Energies 2025, 18(13), 3348; https://doi.org/10.3390/en18133348 - 26 Jun 2025
Viewed by 222
Abstract
In the automotive industry, the increasing stringent standards to reduce fuel consumption and pollutant emissions has driven significant advancements in turbocharging systems. The centrifugal compressor, as the most widely used power-absorbing machinery, plays a crucial role but remains one of the most complex [...] Read more.
In the automotive industry, the increasing stringent standards to reduce fuel consumption and pollutant emissions has driven significant advancements in turbocharging systems. The centrifugal compressor, as the most widely used power-absorbing machinery, plays a crucial role but remains one of the most complex components to study and design. While most numerical studies rely on adiabatic models, this work analyses several Computational Fluid Dynamics (CFD) models with conjugate heat transfer (CHT) of varying complexity, incorporating real solid components. This approach allowed a sensitivity analysis of the performance obtained from the different models compared to the adiabatic case, highlighting the effects of internal heat exchange losses. Moreover, an analysis of the temperature distribution of the wheel was conducted, along with a thermal assessment of the various heat flux contributions across the different components, to gain a deeper understanding of the performance differences. The impact of including the seal plate has been evaluated and different boundary conditions on the seal plate have been tested to assess the uncertainty in the results. Finally, the influence of heat exchange between the shroud and the external environment is also examined to further refine the model’s accuracy. One of the objectives of this work is to obtain a correct temperature profile of the rotor for a subsequent thermo-mechanical analysis. Full article
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17 pages, 5093 KiB  
Article
Enhancing Solar Thermal Energy Storage via Torsionally Modified TPMS Structures Embedded in Sodium Acetate Trihydrate
by Martin Beer and Radim Rybár
Energies 2025, 18(13), 3234; https://doi.org/10.3390/en18133234 - 20 Jun 2025
Viewed by 353
Abstract
This study focuses on the numerical analysis of the impact of geometric modifications of sheet-gyroid structures on heat transfer in thermal energy storage systems utilizing sodium acetate trihydrate as a phase change material. The aim was to enhance the thermal conductivity of SAT, [...] Read more.
This study focuses on the numerical analysis of the impact of geometric modifications of sheet-gyroid structures on heat transfer in thermal energy storage systems utilizing sodium acetate trihydrate as a phase change material. The aim was to enhance the thermal conductivity of SAT, which is inherently low in the solid phase, by embedding a thermally conductive metallic structure made of aluminum alloy 6061. The simulations compared four gyroid configurations with different degrees of torsional deformation (0°, 90°, 180°, and 360°) alongside a reference model without any structure. Using numerical analysis, the study evaluated the time required to heat the entire volume of SAT above its phase transition temperature (58 °C) as well as the spatial distribution of the temperature field. The results demonstrate that all gyroid configurations significantly reduced the charging time compared with the reference case, with the highest efficiency achieved by the 360° twisted structure. Temperature maps revealed a more uniform thermal distribution within the phase change material and a higher heat flux into the volume. These findings highlight the strong potential of TPMS-based structures for improving the performance of latent heat thermal energy storage systems. Full article
(This article belongs to the Special Issue Solar Energy and Resource Utilization—2nd Edition)
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16 pages, 3301 KiB  
Article
Crystal Chemistry and Thermodynamic Properties of Mineralogically Probable Phosphate Ca2.62Cu1.94Co1.44(PO4)4—Structurally Related to Natural Arsenate Zubkovaite
by Olga Yakubovich, Galina Kiriukhina, Larisa Shvanskaya and Alexander Vasiliev
Minerals 2025, 15(6), 645; https://doi.org/10.3390/min15060645 - 13 Jun 2025
Viewed by 331
Abstract
In this paper, we report the details of the synthesis, single crystal X-ray diffraction study, comparative crystal chemical analysis, and magnetic behavior of a new phosphate variation of the arsenate mineral zubkovaite. The title compound was obtained as a high-temperature flux product in [...] Read more.
In this paper, we report the details of the synthesis, single crystal X-ray diffraction study, comparative crystal chemical analysis, and magnetic behavior of a new phosphate variation of the arsenate mineral zubkovaite. The title compound was obtained as a high-temperature flux product in the form of a partly ordered solid solution and was studied using scanning electron microscopy and microprobe analysis. It possesses a monoclinic symmetry with a P21/n space group; the unit cell parameters are a = 8.8040 (2), b = 4.8970 (1), c = 14.5772 (3), and β = 93.993(2)°. The Ca2.62Cu1.94Co1.44(PO4)4 crystal structure exhibits some statistical disorder. Our refinement showed that two positions are mixed, being occupied by Cu/Co (M1) and Ca/Co (M2) atoms. Two types of layers that are nearly parallel to the (101) plane can be distinguished in the structure. One of them is built by sharing corners of CuO4 squares, M1O5 square pyramids, and PO4 tetrahedra. The second type of layer formed from Ca2+- and M2+-centered polyhedra alternates in the [1¯01] direction to construct a tri-periodic framework. Ca2.62Cu1.94Co1.44(PO4)4 experiences long-range antiferromagnetic ordering at low temperatures, as evidenced by both dc— and ac—magnetic susceptibilities, as well as by the specific heat measurements. Full article
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23 pages, 1533 KiB  
Article
Oil and Water Recovery from Palm Oil Mill Effluent: A Comparative Study of PVDF and α-Al2O3 Ultrafiltration Membranes
by Saqr A. A. Al-Muraisy, Jiamin Wu, Mingliang Chen, Begüm Tanis, Sebastiaan G. J. Heijman, Shahrul bin Ismail, Jules B. van Lier and Ralph E. F. Lindeboom
Membranes 2025, 15(6), 176; https://doi.org/10.3390/membranes15060176 - 10 Jun 2025
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Abstract
Recovering oil and water from palm oil mill effluent reduces environmental pollution and promotes sustainable practices. An effective method to achieve this is ultrafiltration (UF), which uses semi-permeable membranes to separate oil, solids, and other contaminants from wastewater under pressure. To assess the [...] Read more.
Recovering oil and water from palm oil mill effluent reduces environmental pollution and promotes sustainable practices. An effective method to achieve this is ultrafiltration (UF), which uses semi-permeable membranes to separate oil, solids, and other contaminants from wastewater under pressure. To assess the most effective recovery method, an experimental comparison was conducted between PVDF and α-Al2O3 UF membranes at constant permeate of 20–50 LMH for PVDF and 20–70 LMH for α-Al2O3 membranes. Both membranes achieved 99.8% chemical oxygen demand (COD) rejection, with oil concentration factor (Fo) of 186.8% and 253.0%, and water recovery (Rw) of 46.6% and 60.5%, respectively. The permeate water quality was superior to the Malaysian discharge standards, and the fat, oil, and grease (FOG) content was suitable for phase separation processes. The optimal permeate fluxes, with stable transmembrane pressures (TMP), were observed at 40 LMH (PVDF) and 60 LMH (α-Al2O3). Total resistance (Rt) values were 1.30 × 1012 m−1 (PVDF) and 1.59 × 1012 m−1 (α-Al2O3). The ratio of irreversible to total resistances (Rir/Rt) was 0.02 (PVDF) and 0.06 (α-Al2O3), indicating minimal irreversible fouling. Overall, the α-Al2O3 membrane demonstrated superior performance in oil and water recovery with more stable operation compared to the PVDF membrane. UF membrane technology emerges as an efficient technique for recovering oil and water compared to conventional methods. Full article
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