Search Results (3,288)

High-temperature heat pumps are a promising pathway for electrifying industrial process heat, but their application to large-temperature-glide duties remains technically challenging. Milk powder spray drying is one such application, requiring air heating to approximately 200 °C while offering only low-to-medium-temperature waste heat sources. Transcritical CO₂ heat pumps are attractive for this duty because the sensible cooling profile of supercritical CO₂ can be matched to the large temperature glide of air heating. However, the high operating pressures required in transcritical CO₂ cycles lead to substantial expansion losses, creating a potential opportunity for expansion work recovery. This study evaluates ejector- and expander-based expansion work recovery in high-temperature transcritical–transcritical CO₂ heat pump cycles for spray dryer air heating. Baseline and modified cycle configurations were modelled using steady-state thermodynamic analysis and compared using heating coefficient of performance, maximum achievable sink temperature, component-level exergy destruction, and discharge-pressure sensitivity. Under the investigated conditions and assumed component efficiencies, expanders improved the COP of all evaluated cycles. TTX-2 achieved a COP of 2.35, 5.4% above its corresponding TT-2 baseline. TT-2 and the external benchmark TT-4 each achieved a COP of 2.23 at 150 bar for the investigated duty. The comparison with TT-4 is a benchmark comparison, not an evaluation of a TT-4 recovery variant. The improvement was modest, and an upper-bound break-even expander cost of approximately 150 EUR/kW of delivered heat was estimated for the most favourable expander case. Ejector cycles reduced expansion losses in some cases but did not provide a clear cycle-level COP improvement because they altered compressor pressure ratios, gas-cooler outlet conditions, and cascade heat transfer performance. These findings apply to the investigated spray dryer duty and demonstrate that reducing expansion exergy destruction alone is insufficient to guarantee improved whole-cycle performance under the stated operating and component-efficiency assumptions. Full article

To clarify the effects of biomass char injection position on combustion characteristics and NO formation, a three-dimensional CFD model of a 300 MW tangentially fired pulverized coal boiler was developed using ANSYS Fluent. The Realizable k-ε model, discrete phase model, species transport model, and P-1 radiation model were employed to describe the flow, combustion, heat transfer, and NO formation processes. The model was validated against field measurements under pure pulverized coal combustion conditions. Based on the validated model, five co-firing cases were designed by injecting biomass char through primary air nozzles located at five different elevations in the burner zone. The results show that biomass char injection position significantly affects furnace flow organization, heat release distribution, carbon conversion, and NO formation, while maintaining the overall tangential swirling structure. Case C achieved the highest outlet velocity of 10.42 m/s, which was 9.1% higher than that of Case E, and exhibited the lowest CO concentration, indicating improved carbon conversion performance. However, the intensified oxidation environment in Case C promoted fuel-N conversion and resulted in the highest NO concentration of 313 ppm. Case B achieved the highest outlet temperature of 1429 K, which was 6.8% higher than that of Case E. In comparison, Case D maintained a similar CO₂ mole fraction of 0.1546 to Case C, which was 0.1545, while reducing the NO concentration from 313 ppm in Case C to 145 ppm, corresponding to a reduction of 53.7%. Therefore, Case D achieved the most favorable balance between carbon conversion and NO emission control under the investigated conditions. This study demonstrates that biomass char injection position is an important operational parameter for optimizing biomass utilization and reducing NO emissions in tangentially fired pulverized coal boilers. Full article

Directed energy deposition (DED) of low-alloy steels involves strongly coupled effects among alloy composition, solidification behavior, and post-deposition heat treatment, making mechanical property prediction difficult when target-domain data are limited. This study develops a transfer-learning and continuous optimization framework for predicting heat treatment-dependent yield strength (YS), ultimate tensile strength (UTS), hardness (HV), and as-solidified phase fractions of martensite, ferrite, and austenite in DED-processed low-alloy steels. A CALPHAD-based dataset was generated for 125 low-alloy steel compositions. A multilayer perceptron (MLP) surrogate was first trained as a baseline model, then fine-tuned through transfer learning and progressively updated as staged continuous optimization; the composition pool increased from 72 to 125 compositions using Random, Greedy, and Bayesian upper-confidence-bound acquisition strategies. The heat treatment prediction accuracy improved from an average R² of 0.757 for the baseline model to 0.929 after transfer learning and to approximately 0.997 after continuous optimization, with a nearly 78% reduction in RMSE relative to transfer learning. For the solidification outputs, the average R² increased from 0.770 after transfer learning to approximately 0.859 after optimization. Bayesian-UCB provided the most stable and data-efficient improvement by balancing predicted performance with model uncertainty. The optimized prediction system showed low case-study errors for both solidification and heat treatment properties, demonstrating its potential as a rapid screening tool for alloy composition and tempering-condition selection in DED low-alloy steel development. Full article

This study evaluates the effects of novel metal-based fuel additives on the combustion, thermal behavior, and emissions of a common-rail diesel engine. Two transition metal complexes, Bis-[N-(1,1′-biphenyl)-2-chlorobenzoylthioureato]nickel(II) (NiL₂) and cobalt(II) (CoL₂), were synthesized and utilized as diesel additives for the first time. Experiments were conducted on a 1.5-L, four-cylinder engine at 1750 rpm under three load conditions: 50, 75, and 100 Nm. The results demonstrated that 25 ppm of NiL₂ and CoL₂ altered the combustion kinetics. At medium loads, the additives increased maximum cylinder pressure by 3% and shortened ignition delay at low loads. Peak heat release and heat transfer rates improved by 4% and 7%, respectively. CoL₂ exhibited the most pronounced thermal effect, raising average in-cylinder gas temperatures by up to 4% at high loads. However, despite these thermodynamic changes, the additives did not yield any reductions in NO, HC, or CO emissions; in fact, emission levels were generally similar to or slightly higher than those of neat diesel. These findings suggest that while these specific complexes act as combustion modifiers that enhance in-cylinder thermal parameters, they do not offer significant advantages regarding emissions under the tested configurations. Full article

Abiotic stresses—drought, salinity, extreme temperature, flooding, and heavy-metal toxicity—constrain rice (Oryza sativa L.) yield worldwide, and the cellular programmes underlying them are unevenly distributed across cell types that bulk-tissue assays average together. This review examines, from a methodological standpoint, what single-cell and spatial omics technologies can and cannot establish about rice abiotic stress biology. We first define the modality space: single-cell omics measures RNA, chromatin accessibility, DNA methylation, protein, or metabolite features at the resolution of individual cells or nuclei, whereas spatial omics measures such features while retaining tissue coordinates; the two are complementary rather than interchangeable. We then treat each platform class—droplet-based scRNA-seq, combinatorial-indexing approaches including SPLiT-seq, nuclei-based snRNA-seq and multiome, sequencing-based and imaging-based spatial transcriptomics—under a common template covering measurement principle, the questions each can answer, applicability to rice tissues, dominant biases, and the inferences each cannot support. To make evidence strength comparable across a heterogeneous literature, we apply a four-tier scheme throughout: Tier A, direct rice cell-resolved or spatial evidence with functional or field validation; Tier B, robust rice functional and localization evidence without single-cell data; Tier C, cell-resolved evidence without causal validation; and Tier D, cross-species analogy or reasoned proposal. Applying this scheme shows that the genes with genuine breeding traction in rice—SUB1A, OsHKT1;5, OsHMA3, OsNRAMP5, DRO1—rest on Tier B evidence from classical genetics and field testing, whereas the most cell-resolved rice evidence concentrates in root outer layers and barrier formation at Tier C, and heat and cold stress, despite dominating yield loss, lack rice cell-resolved data almost entirely. We extend the discussion beyond transcriptomics to single-cell DNA methylome profiling, spatial proteomics and metabolomics, and three-dimensional analysis of thick plant tissues, in each case distinguishing demonstrated plant capability from mammalian-only capability, and we assess the expanding role of artificial intelligence in annotation, segmentation, batch correction, integration, and perturbation prediction alongside its documented failure modes. Rice, maize, and wheat are compared to identify transferable methodology. Cell-resolved omics has to date improved biological interpretation and candidate prioritization; demonstrating an incremental breeding advantage from it remains an unmet requirement. Full article

The valorization of waste cooking oil (WCO) offers a sustainable pathway for improving building’s energy efficiency while supporting circular economy principles. This study developed a novel shape-stabilized bio-based phase change material (Bb-PCM) derived from WCO fatty acids for passive thermal regulation of building envelopes. Purified fatty acids were obtained through filtration, saponification, acidification, and solvent purification. The resulting Bb-PCM was then incorporated into a natural clay–cellulose supporting matrix containing four activated-carbon loading levels using a direct impregnation method. The composites were characterized using spectroscopic, thermal, and microstructural techniques. Differential scanning calorimetry under nitrogen at 2 °C min⁻¹ showed melting temperatures of 34–35 °C and melting latent heats of 35.2–45.9 J g⁻¹. Thermogravimetric analysis confirmed thermal stability below 100 °C, while microstructural characterization demonstrated differences in matrix densification and structural ordering among the composite formulations investigated. The composite containing 25 wt.% activated carbon exhibited the highest melting latent heat (45.9 J g⁻¹) and favorable thermal conductivity (0.29 W m⁻¹ K⁻¹), representing the optimum composite formulation that balances thermal storage capacity, heat transfer, and structural stability. Outdoor evaluation demonstrated stable thermal performance, reducing indoor temperatures by approximately 2 °C, indicating strong potential for sustainable passive cooling applications in buildings. Full article

The semi-underground granary is a new type of energy-saving grain storage facility that can use shallow geothermal energy to reduce energy consumption during grain storage. However, unclear temperature fields and the lack of grain pile temperature control methods are not conducive to the design and application of semi-underground granaries. In this study, the temperature fields and temperature control methods for grain piles in a semi-underground granary were numerically investigated by using an experimentally verified COMSOL model and a collaborative simulation method combining steady-state heat transfer and dynamic heat transfer. Multiple grain storage temperature control methods for the semi-underground granary were presented to improve grain storage safety, including an intermediate floor slab, an embedded-pipe wall, floor burial depth, and envelope insulation. The results showed that there was significant spatial heterogeneity in the temperature field distribution of the grain pile in the semi-underground granary. The large thermal inertia of the soil and the stable low-temperature soil environment reduced the influence of outdoor air temperature variations on the grain pile temperature field. Installing an intermediate floor slab could achieve natural low-temperature grain storage in the underground section of the semi-underground granary. An embedded-pipe wall could effectively solve the problem of local temperature increases in grain piles caused by heat transfer through the granary walls. The floor burial depth of the semi-underground granary was a key influencing factor of heat transfer through the granary wall. Granary wall thickness had a significant impact on the thermal performance of the walls and the grain pile temperature field due to changes in wall insulation. These results can provide beneficial suggestions for guiding the design of grain storage temperature control methods in semi-underground granaries. Full article

This study employs numerical simulations to systematically investigate the combustion characteristics of methane/ethanol blended fuel–air mixtures under non-premixed turbulent conditions. The effects of the methane blending ratio on the flow-field structure, flame morphology, NO emissions, and combustion efficiency are analyzed. The results show that, with increasing methane blending ratio, the recirculation mechanism gradually shifts from near-field local entrainment to far-field transport, accompanied by a reduction in local shear intensity. Methane addition enhances flame intensity, accelerates combustion, shortens flame length, mitigates heat transfer limitations, and reduces combustion delay. At the initial 10% and the final 20% of the methane blending range, the combustion process exhibits pronounced instability. Methane addition significantly suppresses NO formation, with temperature being the dominant controlling factor, while fuel composition also plays an important role. The overall combustion efficiency is improved. However, a slight decrease is observed at low blending ratios (0–0.1), and the enhancement becomes marginal when the methane blending ratio exceeds 0.6. Full article

Wind gusts are known to significantly influence wildfire behavior, yet their direct role in ignition dynamics remains underexplored in laboratory settings. This study investigates how controlled wind gusts affect ignition behavior, combustion transitions, and heat re-lease characteristics of wildland fuels using a bench-scale wind tunnel. Three fuel types, Excelsior, wild oat (Avena), and Wheatgrass were exposed to heated stainless-steel par-ticles under varying wind speeds (1.0 and 2.0 m/s) and gust frequencies (0.03, 0.05, and 0.07 Hz). Key ignition parameters, including ignition temperature, ignition delay, smol-dering-to-flaming (StF) transition, burnout time, and heat release rate (HRR), were measured and analyzed. The results show that increasing gust frequency consistently impacted ignition behavior which reduces ignition and transition times across all fuels while raising ignition temperatures and HRR. For instance, StF transition times in Avena dropped from 58 to 42 s and flaming ignition temperatures rose from ~415 °C to ~498 °C as gust frequency increased from 0.03 Hz to 0.07 Hz at 2.0 m/s wind speed. Also, for the same set of experiments, HRR rose from 1674 J/s to 2372 J/s with increasing gusts. These findings indicate that gusty winds enhance convective heat transfer and oxygen availability, accelerating fire initiation and intensifying combustion. The results offer valuable insights for improving predictive fire spread models, ignition risk assessments, and wildfire mitigation strategies under transient wind conditions. Full article

Thermochemical energy storage (TCES) has emerged as one of the pivotal technologies for enhancing the stability and efficiency of energy systems, owing to its advantages including high energy storage density, low heat loss and long-term energy storage capability. Among various TCES technologies, solid–gas reaction-based TCES exhibits tremendous potential in medium- and high-temperature applications. This paper first overviews the research progress of solid–gas reaction-based TCES technologies. Focusing on four major TCES material systems, namely hydroxides, carbonates, metal oxides and metal hydrides, it discusses their energy storage mechanisms, material modification strategies, and reaction kinetics, as well as approaches to improve thermal conductivity and cycling stability. Subsequently, reactor types (including fixed bed, moving bed and fluidized bed reactors) applicable to different materials and the latest research progress of diverse reaction systems are elaborated in detail, and the optimal designs of heat transfer performance for the four reaction materials in corresponding reactors are clarified. Based on the comparative analysis, the Ca(OH)₂/CaO system is identified as the most promising material system for engineering deployment, owing to its moderate operating temperature, low material cost, and validated pilot-scale performance. The intrinsic complementarity between material modification strategies and reactor heat transfer enhancement is also elucidated, providing a theoretical foundation for scalable implementation. Full article

The convective drying of agricultural materials is an energy-intensive process, and optimizing dryer design is critical for improving efficiency and product quality. This study presents a comprehensive heat and mass transfer model for the convective drying of alfalfa leaves in a rotary drum dryer. Freshly harvested leaves with an initial moisture content of approximately 70% (w.b.) were used as the test material. The proposed system features a simplified drum design aimed at enhancing process efficiency while reducing equipment complexity. The primary objective was to reduce the moisture content of alfalfa leaves to below 50% to ensure their quality during subsequent storage and transportation. To determine the optimal operating conditions, the kinematics of leaf motion inside the rotating drum and the associated heat and mass transfer phenomena were investigated through analytical modeling, numerical simulation, and experimental studies on a laboratory-scale physical model. An analytical model was developed to establish relationships between transverse kinematic characteristics (detachment condition, Froude number, drum inclination angle), average longitudinal velocity, and residence time. Numerical simulations based on the Navier–Stokes equations (continuity, momentum, and energy) provided detailed moisture content distributions within individual leaves under varying airflow orientations and drying durations. The novelty of this work lies in the integrated determination of optimized operating parameters through combined analytical, numerical, and experimental approaches. A regression model relating final moisture content to key process variables (air velocity, temperature of 60 °C, drum rotation frequency and mass of loaded material) was developed from experimental data, yielding practical recommendations for the design and operation of rotary drum dryers for alfalfa and similar agricultural materials. Full article

Rice cooking is a time-consuming process, and conventional heating methods often suffer from low heating efficiency and non-uniform heat transfer, which may compromise cooking quality. Although pulsed ohmic heating (OH) has shown potential for accelerating food heating, its effects on the quality formation and structural evolution of cooked rice remain insufficiently understood. Therefore, this study applied OH technology to improve the cooking efficiency and quality of indica rice. Through single-factor and response surface methods, the optimal OH parameters were determined: 18 min treatment time, 9.4 μs pulse width, 0.52 kV/cm electric field strength, and 265 Hz frequency. Under these conditions, the cooking time was significantly reduced by 28% compared to traditional rice cookers, achieving a comprehensive quality score of 88.42 points. Optimized OH treatment improved water absorption and volume expansion ratio, reduced hardness, and enhanced the overall flavor characteristics, accompanied by changes in the microstructure and starch organization. Multi-scale structural analyses indicated that OH treatment was associated with accelerated starch gelatinization, reduced starch crystallinity, enhanced moisture migration, and possible alterations in starch–protein interactions, which were consistent with the observed improvements in rice texture. Importantly, at the 18 min maturation point, the estimated glycemic index of OH-treated rice showed no significant difference compared with traditionally cooked rice (83.69 vs. 82.88, p > 0.05), ensuring nutritional quality. These findings suggest that OH is a promising technology for improving rice cooking efficiency and quality while maintaining nutritional properties. Full article

A three-dimensional structural model of a cylindrical lithium-ion battery pack incorporating composite phase change material (PCM) is developed in this study, and numerical simulations are conducted using CFD software to investigate the heat dissipation characteristics of the battery pack. The results show that the composite PCM effectively suppresses the temperature rise within the battery pack, maintaining both the temperature and the temperature difference in the battery pack within acceptable ranges. Parameter analysis reveals that increasing the radial thermal conductivity of the battery reduces the heating rate and improves the temperature uniformity of the overall system. Within the investigated parameter range, increasing the thermal conductivity of the composite PCM beyond approximately 1 W/(m·K) results in a region of diminishing improvement in thermal performance. Beyond this range, further increases in thermal conductivity result in only marginal reductions in the maximum temperature, indicating that excessive enhancement of thermal conductivity provides limited thermal benefits and should be balanced with latent heat capacity. An increase in the latent heat of the composite PCM lowers both the maximum temperature and the maximum temperature difference at the end of discharge, thereby enhancing system temperature uniformity. Conversely, enlarging the external air convection heat transfer coefficient yields a limited cooling effect while deteriorating the temperature uniformity within the system. Therefore, on the principle of fully utilizing latent heat and minimizing energy consumption, the external convection heat transfer coefficient should be set as low as possible. This study provides theoretical guidance for the parametric design of PCM-based thermal management systems. Full article

Starch-based bioplastics are renewable and biodegradable, but their wider use is constrained by moisture sorption, humidity-dependent aging, insufficient tensile performance, and weak water- and oxygen barrier stability. This review critically synthesizes the peer-reviewed literature from 2020 to 2026 on enzymatically engineered starch for film, packaging, and thermoplastic applications using an architecture–property framework that links enzyme specificity, chain-length distribution, crystallinity, processing route, and material response. Controlled α-1,4 hydrolysis mainly improves processability by lowering molecular weight, viscosity, and gelatinization resistance. However, excessive hydrolysis can increase water uptake, solubility, and loss of cohesive strength. Debranching by pullulanase or isoamylase increases amylose-like linear chains and can promote B-type crystallinity or V-type starch–lipid complexes, with reported gains in tensile strength, contact angle, and water vapor barrier when the chain lengths and recrystallization conditions are controlled. Branching enzymes and transglycosylases increase branch density or redistribute glucan chains, suppressing retrogradation and improving flexibility, water retention, and aging resistance, but often with trade-offs in strength, crystallinity, and barrier performance. Lipase- and laccase-catalyzed functionalization expands starch functionality by increasing hydrophobicity, compatibility with hydrophobic phases, antioxidant activity, and active-packaging potential. The evidence indicates that enzymatic modification should not be generalized as uniformly improving starch bioplastics; performance gains are conditional on the starch source, amylose content, enzyme dosage, reaction severity, plasticizer composition, processing method, film conditioning, and storage humidity. Industrial implementation remains limited by enzyme cost and reuse, high-solids mass transfer, reaction time, enzyme stability under heat and shear, and reproducibility across botanical sources. Overall, enzymatic molecular editing is most promising when mechanistic architecture control is coupled with standardized structure–property reporting and scalable processing, such as immobilized-enzyme reactors, high-solids systems, and reactive extrusion. Full article

Temperature uniformity in thermostatic chambers is critical for material testing, biological incubation, and precision measurements, as even minor thermal gradients can compromise reliability. However, in chambers designed to avoid airflow disturbances, such as those used in semiconductor fabrication and optical experiments, forced convection and mechanical stirring are often impractical. Consequently, natural convection becomes the dominant heat transfer mechanism, introducing significant nonlinearity, large thermal inertia, and multivariable coupling among multiple heat sources. To address these issues, this study develops a multi-input–multi-output (MIMO) temperature control strategy for a rectangular chamber equipped with eight heating elements (grouped into four channels) and adjustable-angle baffles. The proposed method combines a multi-PID controller array with genetic algorithm (GA)-based parameter tuning using a transfer-function matrix model. Experiments demonstrate that baffle angles below 90° improve spatial uniformity, and the relative grouping of heaters outperforms adjacent grouping in both thermal inertia and correlation. Using GA-optimized PID parameters, the controller maintains steady-state error within ±0.5 °C and reduces settling time by approximately 140 s compared to conventional Ziegler–Nichols tuning. Validated through simulations and experiments, the proposed approach provides a reliable and cost-effective alternative to forced convection for airflow-sensitive applications, achieving superior uniformity and steady-state accuracy. Full article