Search Results (1,511)

Inverse fuzzy model control (IFMC) is an attractive strategy for regulating nonlinear thermal processes, where complex heat-transfer dynamics, disturbances, and actuator constraints challenge conventional control approaches. However, traditional direct and indirect inverse schemes often exhibit limited generalization and sensitivity to noise. This paper presents a data-driven inverse fuzzy control framework for temperature regulation in thermal systems, combining Takagi–Sugeno modeling, functional cancelation feedback, and auxiliary-input optimization. Gaussian antecedents and affine consequents are jointly identified via nonlinear least squares from input–output data generated by the theoretical PHE model. The same theoretical model is used as the numerical plant in all closed-loop simulations, whereas the forward and inverse fuzzy models are constructed only from the generated data and do not use the analytical PHE equations during identification or online inference. The learned inverse model estimates control actions that achieve the desired temperature trajectory while respecting actuator constraints. The method is evaluated in simulation on a plate heat exchanger (PHE) benchmark under tracking and disturbance-rejection scenarios. Results show accurate temperature regulation, smooth actuator behavior, and disturbance rejection in the tested scenarios. Compared with a numerically tuned PI baseline, the proposed approach reduces tracking RMSE by 27.5% and the standard deviation of the primary control current by 9.6% in the reported simulation scenario, indicating improved tracking and smoother primary actuation. In general, the proposed framework provides an interpretable and efficient solution for nonlinear thermal processes, with potential applications in energy systems, heat exchangers, and related thermal engineering technologies. Full article

Solar stills are considered an effective solution to produce fresh drinking water from saline water. Solar stills utilize solar energy, which is available in abundant quantity for long periods across Middle Eastern countries like Oman. In this study, two single-slope passive solar stills are fabricated with two configurations: a Conventional Solar Still (CSS) and a Modified Solar Still (MSS). The CSS is the basic model, whereas the MSS is a model obtained by incorporating copper tubes that are filled with phase change material (PCM) combined with nano copper oxide particles, which are attached inside the basin. The objective of this study is to compare the performance of the two systems from energy, exergy, and economical aspects. The solar stills were fabricated according to the geometrical conditions of the city Nizwa, Oman, and the standards for the fabrication of each solar still component. The highlights of this research are comparing the performance of the CSS and MSS under the prevailing atmospheric conditions of the city Nizwa, Oman, and investigating the effects of the nano materials and phase change materials used in the MSS on its performance. The results of the study reveal certain important facts; for example, higher thermal conductivity of the copper tubes increases the heat transfer and evaporation of saline water inside the basin. The freshwater production in the MSS was higher than in the CSS, with an average difference of about 79.75%. This difference in freshwater production is due to the accumulated heat storage and release of heat from the PCM material combined with nanoparticles during reduced solar radiation. The nanoparticles contributed to an increase in the heat transfer rate of the PCM. The presence of copper tubes filled with nano-PCM in the MSS influences and increases both energy and exergy efficiencies to around 30 to 35% and 1 to 1.5% compared to those in the CSS. The increased efficiencies in the MSS are due to its improved evaporation and condensation rates, which enhance the energy utilization in the process of converting saline water to freshwater. Full article

Standalone use of EAHEs for room cooling is a passive and nature-based alternative to air conditioning technology that can be used to mitigate the increase in electricity and GWP-refrigerant consumption associated with cooling in buildings. EAHEs replacing air conditioning is documented in the technical and research literature. However, for office-room cooling, EAHEs are mostly employed as a support to air conditioning systems for precooling outdoor air. The larger cooling loads and the stricter design conditions commonly used in the sizing of office rooms prevent the most commonly investigated EAHE typologies from operating effectively in standalone cooling mode. To assess the feasibility of alternative typologies, such as large-diameter EAHEs, tools that are capable of modeling the complexity of the coupled heat and moisture transfer between air and soil are particularly valuable. For detailed assessments, researchers typically turn to advanced commercial tools; however, developments in free and open-source scientific programming languages that combine symbolic computation packages with efficient numerical solvers of partial differential equations allow analyses at reduced cost that are comparable to those from commercial tools. This paper shows how one such programming language can be used to study the coupled heat and moisture transfer problem in EAHEs. Starting from the symbolic form of the mathematical problem, the numerical implementation is described and validated with monitoring data from an existing large-diameter EAHE. Using the validated computational model, the paper proceeds to study the sensitivity of load removal in EAHEs operating in standalone and precooling cooling modes, highlighting fundamental differences between both operating modes, identifying the most relevant design parameters and providing guidance on the conditions under which an EAHE enables self-sufficient cooling of office buildings. The results show how, for a hot and dry climate, standalone EAHEs with large diameters (∼1 m), buried at depths larger than 3 m, allow the removal of up to 20 kWh/m² of room sensible cooling loads, a level that is consistent with the cooling demand of low-energy office buildings. Full article

Accelerating the renovation of existing residential buildings is essential for achieving European climate targets, but aggregate renovation rates do not show whether interventions are sufficiently deep, well targeted, or cost-effective. This paper develops a transparent scenario framework for prioritising renovation strategies at local building stock scale. The workflow combines a literature-based screening of renovation indicators and implementation conditions, semi-structured expert interviews used for qualitative triangulation, and a typology-based bottom-up model of the South Tyrolean residential stock. The stock model uses census and provincial floor-area data, representative space heating and domestic hot water demand values from SINFONIA and previous South Tyrolean studies, and static end-state renovation assumptions. Three scenarios are compared: deep renovation of priority high-demand clusters, medium renovation of the same clusters, and light renovation of the whole stock. The baseline model estimates residential heating and domestic hot water demand at approximately 1990 GWh/year. The selected priority clusters account for about 56% of floor area and nearly 59% of baseline demand. Under the central assumptions, targeted deep renovation would reduce demand by approximately 704 GWh/year (35%), targeted medium renovation by 352 GWh/year (18%), and whole-stock light renovation by 299 GWh/year (15%). Indicative CO₂ reductions are reported separately and are proportional to the same final energy reduction assumptions because carrier switching is not modelled. A static cost-effectiveness screening using Italy-level energy-related renovation cost data is reported as an order-of-magnitude range rather than a local investment forecast. The results show that renovation depth and target selection should be considered jointly, and that the framework is transferable where typological stock data and representative energy demand values are available. Full article

Electricity spot markets with time-of-use pricing create hour-by-hour variations in the economic value of thermal adjustments, requiring coal-fired units to adapt cold-end operation to real-time price signals. However, the nonlinear coupling between circulating water flow and condenser backpressure remains insufficiently characterized across the full operating envelope, and existing optimization strategies target steady-state heat consumption without accounting for the time-varying economic value of identical thermal adjustments under spot pricing. This study develops a quasi-steady-state thermodynamic–economic model that links real-time electricity prices with the nonlinear heat-transfer response of the circulating water system. The model enables the adaptive selection of pump combinations and blade-opening angles by balancing marginal pump power savings against marginal turbine output losses under time-of-use price signals. Using actual electricity spot market data from Zhejiang Province, simulations under different seasonal conditions show clear economic gains. The maximum hourly saving reaches 2190.79 CNY during summer negative-price periods, which is about 5.3 times higher than that in winter, while backpressure deviations remain within 12.5% of the design value. The seasonal disparity is governed by the initial heat exchange driving force, a fundamental thermodynamic property amplified by the negative-price superposition effect. The framework establishes a physical basis for market-responsive cold-end regulation across seasonal and load conditions, supporting the economic dispatch of coal-fired units in spot market environments. Full article

NASA’s Fire Information for Resource Management System (FIRMS) provides near-real-time thermal anomaly detections from VIIRS, but not all detections correspond to wildfire incidents: industrial heat, agricultural burning, and sensor artifacts produce false alarms that contribute to alert fatigue for emergency-management analysts. We study whether contextual machine learning (ML) features improve wildfire-incident classification from FIRMS detections, and—more importantly—whether reported gains survive leakage-controlled evaluation. We construct a labeled dataset by matching 521,395 VIIRS SNPP detections across CONUS in 2024 to 3766 NIFC 2024 wildfire perimeters, yielding 131,771 (25.3%) wildfire-matched and 389,624 candidate non-wildfire detections spanning 1067 distinct wildfire incidents. We benchmark five operational baselines and six classifiers under four validation regimes (random, event-aware, 5° spatial-block, and temporal holdout) with and without raw geographic coordinates. A naive random split inflates LightGBM to F1 = 0.985, but a leakage-controlled event-aware split reduces it to F1 = 0.767, and a spatial-block holdout to F1 = 0.627. Feature attribution shows geographic coordinates account for 88.9% of model gain—the summed share of LightGBM’s total split-gain attributed to the three coordinate features within the full-feature model; removing coordinates improves spatial-block generalization from F1 = 0.627 to 0.818, demonstrating that raw coordinates drive memorization of where 2024 fires occurred rather than transferable discrimination. We further show that spatiotemporal clustering must be causal: a model using full-partition clustering appears strong (F1 = 0.908) but leaks future detections, whereas a properly causal trailing-window version ties plain LightGBM in-distribution (F1 = 0.762). Combining causal clustering with no raw coordinates is the most robust configuration under spatial transfer (spatial-block F1 = 0.868 vs. 0.627 for the coordinate model). Bootstrap 95% confidence intervals show these gaps far exceed statistical uncertainty, and sensitivity analyses show the conclusions are robust to the spatial-block size and to the clustering-window choice. Under natural class prevalence (14%), precision falls to 0.69, and results are sensitive to the labeling buffer. All ML models nonetheless far exceed FIRMS high-confidence thresholding (F1 = 0.128). We argue that spatial leakage—not raw accuracy—is the central methodological issue for FIRMS wildfire-incident classification, and recommend coordinate-free, causal spatiotemporal-clustering features evaluated under spatial holdout. The system is intended as an analyst-prioritization decision-support layer, not autonomous incident confirmation. Full article

Photovoltaic–thermal (PVT) collectors co-generate electricity and heat—natural front ends for thermochemical energy storage (TCES)—provided the heat transfer fluid stays above the reactor’s desorption temperature. Using an eight-node model of a 0.6834 m² collector at 8.64° N whose thermal core is partially validated against measured data from the same tropical–coastal site (rooftop PV module temperature, RMSE 3.8 °C; prototype absorber-to-water heat transfer, RMSE 1.3 °C), flow-regulated to the ≈95 °C SrCl₂/NH₃ desorption threshold, we quantify the energy and exergy delivered for charging under tropical–monsoon intermittency. The 95 °C setpoint operation, the ≈5.3 h charging window, and all reported exergy yields are simulated: the built prototype delivered hot water peaking at 79 °C and did not reach the 95 °C setpoint. On a measured clear-sky day (clearness index K_t = 0.52), the collector yields 1.38 kWh of energy but only 0.43 kWh of exergy (first-law efficiency ≈ 38%; gross exergy efficiency ≈ 13%); across a 30-seed synthetic-intermittency ensemble, the exergy yield is 0.678 kWh at ≈14% gross exergy efficiency (≈52% combined first-law efficiency). In both cases, the thermal stream dominates the energy output while the electrical stream dominates the exergy output—on the sunlit day, the exergy is about 80% electrical—because 95 °C heat carries a Carnot factor (exergetic quality factor, 1 − T_a/T₇, at the instantaneous ambient dead state) of only ≈0.18 and an integrated Bejan/Kotas thermal-exergy quality of only ≈0.09. The controller holds the outlet within 1.4 K of the setpoint for ≈5.3 h, whereas no fixed flow in the 0.5–5.0 L min⁻¹ range ever reaches it: feedback control is a structural enabler, not an optimisation. On overcast days, the threshold is never reached and charging heat collapses to zero, leaving a PV-only generator. Exergy delivery is nonetheless nearly controller-independent: the accumulated exergy delivery deficit after a 50% irradiance drop is 937 kJ, a controller-independent value changing only 1.3% across a systematic 4 × 4 gain sweep (K_p 0.33–2.7×, K_d 0.25–5× of nominal), and predictive control improves it by ≤1%. For PVT–TCES at this scale, the decisive lever is deployability, not control sophistication. Full article

In the current work, pulsating airflow and an external heat source are proposed to improve the evaporation performance of falling films. A volume of fluid (VOF) multiphase flow model is established based on the commercial software ANSYS Fluent 2023 R1 (ANSYS, Inc., Canonsburg, PA, USA) to simulate the falling film evaporation process. Numerical simulations are conducted under combined working conditions with variable average inlet velocity (u₀), relative pulsating amplitude (A), and wall heat flux (q_w). The spatial and temporal distributions of physical fields are visualized via numerical contours and characteristic curves, and the heat and mass transfer enhancement mechanism is revealed from three aspects, namely, the promotion of driving potential difference by wall heat flux, the increase in heat and mass transfer gradients induced by pulsating airflow, and the synergistic effect of the above two factors. The results indicate that the evaporation ratio (Ψ) increases monotonically with the rise of u₀, with a maximum growth rate of 83.8%. By contrast, under the condition of fixed A₀ = 1 m/s while varying u₀, the evaporation ratio exhibits a convex variation with the relative amplitude A = A₀/u₀, and the global optimal value is achieved at A = 1/6, corresponding to u₀ = 6 m/s and A₀ = 1 m/s. Comparative analysis demonstrates that wall heat flux exerts a more significant influence on evaporation performance than pulsating airflow. Specifically, the evaporation ratio at q_w = 10,000 W/m² is 3~4 times higher than that under the adiabatic wall condition. The reliability of the numerical model is first confirmed by comparing the predictions with published experimental data for vertical falling film evaporation. Based on this validated model, the quantified parametric effects and optimal operating conditions provide practical design references for falling film evaporators in seawater desalination and related thermal separation applications. Full article

Magnesium-based materials remain among the most intensively studied solid-state hydrogen storage systems because they combine high theoretical hydrogen capacity, elemental abundance, and comparatively low cost. Yet their practical performance is still constrained by sluggish sorption kinetics, difficult hydrogen release, surface passivation, and transport instability under repeated cycling. This perspective argues that these long-standing limitations are most coherently understood not as isolated thermodynamic or kinetic problems, but as a multiscale hydrogen transport-network problem. In this view, hydrogen storage performance depends on whether hydrogen can be admitted, transferred, redistributed, and released through a sufficiently continuous and durable sequence of interfaces, phases, defects, and microstructural pathways. The discussion therefore moves from activated interfaces, which govern hydrogen entry, to phase-network engineering, in which alloying reorganizes internal transport connectivity, and then to hierarchical architectures, where porous hosts, scaffolded secondary phases, and multicomponent microstructures amplify transport efficiency across scales. The perspective further emphasizes that these material-internal transport advantages become meaningful only when they remain compatible with heat and mass transfer at the level of a working storage body and device. Possible descriptors, including active-interface density, connected phase fraction, effective diffusion length, pathway tortuosity, apparent network efficiency, and rate retention during cycling, are further discussed to make this framework more operational. On this basis, the article proposes that future progress in Mg-based hydrogen storage will depend less on isolated optimization of additives or descriptors and more on the deliberate design of connected hydrogen transport networks from the atomic and interfacial scales to the system scale. Full article

Natural river sand constraints motivate the use of sustainable alternative fine aggregates in concrete production. This study investigates partially replacing natural sand with quarry dust (QD), ceramic waste (CW), and their combination at 0% to 50% levels. Fresh and hardened properties were evaluated through slump, 7-day and 28-day compressive strength, water absorption, and steady-state thermal conductivity across all modification streams. Ceramic-only mixes achieved the highest compressive strengths, reaching 55.13 MPa at 50% replacement due to intensive angular particle interlocking visible at 7 days, though water absorption increased significantly. QD mixes provided the best durability performance, reducing water absorption to 2.01–2.39% while maintaining near-control strength at 40% replacement. Hybrid mixes showed no consistent synergistic benefits. Comprehensive thermal conductivity profiling revealed significant heat transfer reductions; the QD series achieved optimum insulation at 20% replacement (27.3% lower than control), while ceramic-only mixes displayed a progressive decline down to 0.5256 W/m·K at 40% substitution. Overall, QD at 40% offered the best structural–durability balance, while ceramic waste configurations proved highly effective for specialized applications requiring high mechanical strength combined with enhanced thermal isolation. Full article

This study aims to develop polypropylene (PP) as an insulation material by engineering it into a multi-hollow structured board using 3D printing technology. A previous experimental study determined the effective thermal conductivity of the porous PP board using a hot box test, yielding a value of 0.0033 W/mK, which represents a significant improvement over conventional building insulators like rock wool and cellulose. To validate the experimental results, a numerical simulation using COMSOL Multiphysics 6.2 software was conducted to model the heat transfer process within the porous PP board. The simulation employed an appropriate methodology, including parameter definition, geometry creation, material definition, steady-state porous heat transfer module, initial and boundary conditions, meshing, and analysis. The numerical analysis focused on determining the indoor surface temperature, evaluating the total heat flux, and calculating the effective thermal conductivity of the porous PP board. The simulation results revealed an effective thermal conductivity of 0.0036 W/mK, closely matching the experimentally obtained value from the hot box test. The agreement between the experimental and numerical results validates the numerical study and demonstrates the potential of combining 3D printing technology with materials like polypropylene to develop highly efficient insulation solutions for building applications. Full article

Drying is a key operation for extending the shelf life of agricultural products and maintaining food quality, and its efficiency and product outcomes are governed by coupled heat and mass transfer. This review critically summarizes the mechanisms, technological characteristics, research methods and application prospects of agricultural-product drying from a heat- and mass-transfer perspective. The moisture-migration pathways, including surface evaporation, internal diffusion, capillary flow, vapor diffusion and bound-water desorption, are first discussed within a porous-medium framework. Governing equations based on Fourier’s law, Fick’s law, energy conservation and convective transfer are then introduced to clarify the theoretical basis of drying models. Typical convective, radiative, conductive and combined drying technologies are compared in terms of transfer mechanisms, drying efficiency, energy consumption, product-quality retention, carbon-footprint potential and industrial feasibility. Particular attention is given to the effects of drying-induced heat and mass transfer on color, texture, rehydration, bioactive compounds, antioxidant activity and microstructure. Current theoretical, experimental, numerical and data-driven research methods are further reviewed, and the limitations of existing studies are identified, including simplified homogeneous assumptions, insufficient model validation, limited quantitative comparison and weak scale-up applicability. Finally, future directions are proposed, including refined multi-scale and multi-field coupled models, advanced in situ characterization, multi-energy-field synergistic drying, digital twins, predictive modeling and multi-objective intelligent optimization. This review aims to provide a more mechanism-based and application-oriented reference for developing efficient, low-carbon and quality-preserving drying systems for agricultural products. Full article

MagnetoRheological Brakes (MRBs) can provide wear-free, electrically controllable braking torque, but repeated high-load braking can cause rapid heat accumulation in the narrow rotor–stator gap and degrade MRF performance. This study evaluates rotor-only, stator-only and combined rotor–stator liquid-cooling configurations using transient 3-D conjugate heat-transfer CFD in ANSYS Fluent 2024 R1 for a UN Regulation No. 13-H-based 10-cycle duty profile (8.5 s acceleration, 20 s constant speed and 2.5 s braking per cycle). The activated MRF is modeled as an incompressible laminar Herschel–Bulkley fluid during braking, while the field-OFF phases use a Newtonian viscosity of 0.114 Pa·s; viscous dissipation and coil volumetric heating are included as internal heat sources. Cooling simulations apply water with a 130 kPa (absolute) inlet pressure and a conservative +20% heat-load margin with adiabatic external boundaries. Baseline uncooled dynamometer data (no integrated cooling) verify the thermal implementation, with a 7.06% underprediction of the measured temperature rise. In the uncooled case, the MRF reaches a temperature of 501 K after ten cycles; rotor-only and stator-only cooling reduce temperatures but do not fully suppress cumulative heating, whereas the combined configuration maintains the MRF below 400 K after ten cycles. These results indicate that cooling both dominant heat paths is required for stable MRB thermal operation under severe repeated braking. Full article

Rankine cycle CO₂ pumped thermal energy storage (R-CPTES) offers high-density, emission-free grid storage, but existing designs are limited by modest turbine inlet temperatures and produce electricity only, leaving their thermal potential unused. This paper introduces a Rankine CO₂ storage cycle driven by a high-concentration parabolic dish collector (PDC) and configured solely for combined heat and power, representing a combination of point focus solar energy with CO₂ pumped thermal storage that has received limited attention in the literature. During discharge, the dish superheats the working fluid and raises the high temperature turbine inlet from 456 °C to 500 °C, boosting net power. A heating recovery exchanger placed ahead of the second regenerator then extracts useful heat from the turbine exhaust for district or process supply, without the absorption refrigeration subsystem used in comparable cooling inclusive designs. The aim is to characterise this system through energy, exergy, and parametric analysis. A closed, pinch-consistent model is developed under steady-state assumptions using the Span–Wagner equation of state, with the discharge low pressure, discharge mass flow rate, and PDC outlet temperature varied independently and jointly at a fixed 10 MPa high-pressure boundary. The analysis reveals a power-versus-heat trade-off governed by the discharge pressure and bounded by physical limits rather than interior optima, shows that the solar superheat is a prerequisite for cogeneration, and identifies the system as heat-transfer destruction dominated, with the latent cold storage the largest single source of irreversibility. At the design point the system delivers 16.1 MW of power and 2.5 MW of heat, attaining a storage round-trip efficiency of 73.2% (electricity-only), a solar-inclusive electrical efficiency of 58%, an energy utilization factor of 67%, and an overall exergy efficiency of 61.3%. A preliminary economic assessment gives a levelised cost of storage of 0.10–0.18 $/kWh, competitive with comparable CO₂ storage systems. The proposed system thus provides a simple, fossil-free cogeneration solution for high-DNI regions based on a modular, point focus solar configuration. Full article

Traditional windcatchers are often discussed as passive cooling devices for hot–arid climates, yet their sustainability performance under contemporary comfort-controlled operation remains insufficiently understood. This study evaluates the energy and load-based carbon implications of integrating a windcatcher into a high-thermal-mass courtyard house in Şanlıurfa, Türkiye. A combined DesignBuilder v6.1/EnergyPlus v8.2 and CFD-based assessment was used: annual heating and cooling loads were calculated through EnergyPlus-based building energy simulation, while CFD analyses were used to interpret representative airflow behavior and localized thermal effects within the semi-open iwan. Scenarios varied operational schedule, geometry, material configuration, ventilation openings, and water pool integration. The results show strongly context-dependent performance rather than uniform energy or carbon benefit. Continuous operation weakened annual performance, whereas seasonal operation produced more balanced outcomes. The P.1 configuration produced the lowest total annual energy demand among the tested scenarios, decreasing total demand from 70,929.99 to 70,806.65 kWh/a, corresponding to a reduction of 123.34 kWh/a or 0.17% relative to the baseline. However, this limited reduction was accompanied by a 6.02% increase in cooling demand and a 2.52% decrease in heating demand. Consequently, the total load-based carbon indicator increased from 18.32 to 18.60 tCO₂/year, corresponding to an increase of 0.28 tCO₂/year or 1.53%. CFD results indicate that the semi-open iwan geometry and its orientation relative to prevailing winds constrained airflow effectiveness and limited the transfer of local cooling effects to conditioned zones. This study demonstrates that vernacular passive systems should be evaluated through integrated annual energy, airflow, and load-based carbon analyses before being adopted in sustainable renovation or climate-responsive design. Full article