Search Results (199)

The current automotive industry is undergoing structural changes. Sustainable vehicle components and environmentally friendly structures have become some of the most important parameters. To meet these demands, vehicles can be optimised in different ways. One of them is aerodynamic optimisation. Several weather conditions affect vehicles, including rain, wind, and air temperature. The effects of these parameters are less well studied, but based on previous investigations, they are essential to consider. The aim of the paper is to summarise the possibilities of CFD simulations for modelling weather-related factors. Three factors are examined: rain, wind, and air temperature. In case of precipitation, two different modelling methods are presented. One of them uses a multiphase flow simulation approach, while the other increases the average density of the air. Wind investigations were carried out using single- (side wind effect analysis) and multi-inlet settings (more complex wind effect study) with different angles of attack. The effect of temperature is examined over a wide range, from –20 to +40 °C, which covers the typical temperature conditions in Europe. The paper uses both theoretical knowledge and CFD results to identify and collect the most appropriate modelling methods. Based on the created simulation environment and calculated numerical results, limitations and necessary simplifications were defined. The paper summarises four main conclusions. Full article

This study aimed to optimize the spray-drying (SD) process for aquafaba and compare the physical and techno-functional properties of the resulting powder with those of its freeze-dried (FD) counterpart. A Box–Behnken design was employed to evaluate the effects of inlet air temperature (150–190 °C), air speed (3.5–4.3 m/s), and feed flow rate (0.3–0.5 L/h) on 14 quality responses. The optimized SD conditions were determined to be an inlet air temperature of 189 °C, an air speed of 4.2 m/s, and a feed flow rate of 0.3 L/h. Validation experiments demonstrated that the developed models had high predictive capacity, with only a small discrepancy (0.56–5.88%) between the predicted and experimental values. Comparative analysis showed that the optimized SD powder had significantly lower moisture content (2.47%) and water activity (0.18) than the FD powder (3.51% and 0.34, respectively), indicating superior storage stability. In addition, the SD powder exhibited greater whiteness (82.37), higher water solubility (88.44%), and substantially greater foaming capacity (266.67%) than the FD sample (243.33%). Although the FD powder demonstrated better wettability and water absorption capacity because of its porous structure, FTIR spectroscopy and protein secondary structure analysis confirmed that SD preserved the functional integrity of aquafaba. Specifically, SD induced a transition from disordered random-coil structures to more ordered β-sheet and β-turn configurations, thereby improving foaming performance. Overall, these findings indicate that optimized spray-drying is a highly efficient and industrially scalable alternative to freeze-drying for producing functional aquafaba powder for use as a plant-based egg substitute. Full article

To address uneven temperature and relative humidity distributions, localized heat accumulation, and insufficient air velocity in an enclosed stacked-cage laying hen house, a three-dimensional computational fluid dynamics (CFD) model of the laying hen house was developed using field-measured structural and environmental data, and a porous-media model was established for the cage zone. Model validation showed that the normalized mean square error (NMSE) values for temperature, relative humidity, and air velocity were all below 0.25, confirming the reliability of the CFD model. Through visualization analysis of the contour maps, the problems of uneven airflow distribution in the original ventilation system and significant heat accumulation at the fan end were identified. On this basis, numerical simulations were conducted for six air-inlet configurations by varying two key parameters: air-inlet spacing and air-inlet number. The simulation results showed that, compared with the original model, the configuration with an air-inlet spacing of 1.14 m and a total of 32 air inlets on the two gable walls improved the uniformity of temperature, air velocity, and relative humidity by 18.00%, 10.54%, and 18.38%, respectively, while reducing the mean effective temperature index (ETI) in the cage zone by 0.5 °C. This configuration effectively alleviated localized heat accumulation and improved air-velocity uniformity. These findings provide a theoretical basis and technical support for the structural optimization and environmental regulation of enclosed stacked-cage laying hen houses. Full article

Amidst global carbon neutrality goals, China’s building energy consumption gains prominence, with heating and cooling exceeding 50% of the total. Underground structures leverage inherent geological thermal inertia to significantly reduce ventilation energy demands. This study employs combined field measurements and numerical simulations to investigate heat exchange mechanisms and performance in underground hydropower station air intake tunnels. Four representative tunnels (Sichuan, Fujian, Hebei, Yunnan) served as case studies, monitoring air temperature, humidity, velocity, and wall temperature. Field-monitored parameters informed a computational fluid dynamics (CFD) model, enabling quantitative analysis of rock thermal conductivity, inlet air velocity, and wall temperature effect on heat exchange efficiency. Research shows that: (1) significant seasonal adaptive characteristics exist, achieving peak cooling efficiency (69.04%, summer) and heating efficiency (78.86%, winter); (2) rock thermal conductivity is the primary efficiency determinant—quartzite tunnels exhibited 11.8% higher average efficiency than tuff tunnels; and (3) inlet air velocity negatively correlates with efficiency, exceeding 90% at 0.1 m/s but declining to 69% at 1.5 m/s. This work provides a theoretical basis for optimizing energy-efficient ventilation in underground engineering and validates the pivotal role of rock thermal inertia in reducing operational building energy consumption. Full article

Understanding which structural parameters govern flow stability and particle separation is essential for turbo air classifier design. In this study, the Y160L-6 turbo air classifier was used to examine whether different categories of spatial structural parameters influence classification performance through the same flow mechanism or play distinct roles in regulating the internal flow field. Two representative parameters, namely the spacing between the secondary air inlet and the rotor cage and the spacing between the secondary air inlet and the feed inlet, were analyzed using computational fluid dynamics (CFD) coupled with the RNG k–ε turbulence model and the discrete phase model (DPM). The results show that the two parameters affect the classifier through different mechanisms. Increasing the secondary air inlet–rotor cage spacing causes a non-monotonic variation in wall pressure and tangential velocity, indicating a strong influence on the global swirling structure. At a spacing of 1490 mm, the pressure distribution in the classification zone becomes more uniform, the tangential velocity reaches a relatively high level, and the intensity of the precessing vortex core (PVC) is reduced. Under this condition, the cumulative proportion of 2–5 μm particles at the fine powder outlet increases by 34.1% compared with the initial configuration. In contrast, variations in the secondary air inlet–feed inlet spacing exert only a limited influence on the overall flow structure and classification characteristics under relatively low feed inlet velocity conditions, indicating that this parameter mainly affects local flow disturbance rather than global flow stability. These findings demonstrate that structural parameters associated with the coupling between secondary airflow and rotor rotation dominate classifier performance, whereas parameters related to feed–air interaction exert only a secondary effect under low feed momentum conditions. These findings provide design guidance for the investigated Y160L-6 turbo air classifier and may serve as a reference for similar classifier structures under comparable operating conditions. Full article

By itself or combining with other cooling technologies, the dew point indirect evaporative cooler (DIEC) will be the preferred solution for cooling buildings. However, there are still some gaps in the research on DIEC performance, one of which is that 3-D (3-dimensional) models and methods are not widely used to comprehensively indicate the cooling mechanism. Most of the available numerical methods adopted 1-D or 2-D models. Existing 3-D models and methods either ignore the water film and plate or are so complicated in the grid system and numerical calculation induced by huge size differences among calculation regions that their attractions are weak. A novel simplified numerical method for DIEC performance is first suggested in this paper, and then, its validity and more efficiency than an existing 3-D numerical method are verified with the help of experimental data and numerical results. Finally, the effects of structure and operating parameters on the performance of a plate DIEC are analyzed by this present method and COMSOL Multiphysics 6.3 software, especially η/η₀ (the reinforcement factor), which was innovatively introduced. Similar results to those of existing literature were obtained, which further indicated the practicability of this simplified method. In the conditions involved in this paper, a channel length of 1.5 m, a width of 4 mm, Re_in (the Reynolds number at the inlet) of 1483, and a (the air ratio) of 0.33 are recommended. In the condition suggested by this paper, η/η₀ is close to 1.2. In the same conditions, this proposed method reduces the number of mesh elements by approximately 58% and the wall-clock computational time by approximately 52% under the reported workstation conditions, and its value would be more obvious for more complicated problems. Full article

To protect human health and the environment, it is necessary to reduce the number of solid particles and harmful gases in the air or to minimize such pollution. Filtration and separation devices are intended for various industrial operations to capture pollutants from various technological processes. In the introduction, this article points out the use of cyclone filters in individual operations, names the most frequently occurring elements of pollution, and suggests the most suitable method of separation. In paint shops, grinding shops, welding workplaces, machining lines, and when handling powder materials, particles with very different properties are created. An important advantage of using cyclone filters is not only their simple construction but also their usability at high temperatures and pressures. Furthermore, this article highlights that cyclones are easy to maintain, typically contain no moving parts, are simple to manufacture, and are cost-effective, particularly as pre-filtration devices. Their efficiency generally ranges from 50% to 99% and is strongly influenced by design and operating parameters, especially cyclone geometry, which affects pressure drop, flow structure, cut diameter, and fractional collection efficiency. The article also summarizes that various modifications of the inlet, vortex finder, outlet pipe, and cyclone body have been proposed to enhance separation performance, particularly for smaller particles. Nevertheless, due to the centrifugal and inertial nature of cyclone separation, fine and submicrometric particulate matter remains difficult to remove using cyclones alone. Fabric filters are also analyzed as a possible solution, but high loading by coarse particles may cause clogging, increased pressure drop, and higher maintenance costs. In the end, the combination of a cyclone with an electrostatic precipitator is presented as a staged separation approach, enabling efficient removal of both coarse particles and fine particulate matter from the gas stream. Full article

With the ongoing trend of miniaturization and intelligent power transmission equipment, the compact design of environmentally friendly gas-insulated switchgear (GIS) has emerged as a critical technical challenge. This study presents a detailed case study of a 40.5 kV dry air-insulated switchgear under specific dimensional constraints. Specifically, the cabinet width was reduced from 1000 mm to 800 mm, significantly narrowing the phase-to-phase and phase-to-ground clearances. A high-fidelity three-dimensional electric field model was established using the finite element method to evaluate the dielectric stress distribution within the enclosure. Numerical results indicate pronounced electric field concentrations at critical regions—including copper busbar joints, disconnector contacts, and the inlet bushing shielding rings—where local intensities exceeded the insulation safety threshold. To mitigate these issues, integrated design refinement strategies were evaluated, encompassing the structural modification of shielding rings, the application of silicone rubber coatings, and insulation reinforcement via heat-shrinkable tubing. Comparative analysis and experimental results demonstrate that the refined configuration effectively suppressed the peak electric field intensity. Finally, the design was validated through comprehensive dielectric tests, including a 215 kV lightning impulse withstand voltage test. This work may offer useful engineering references and quantitative data for the ultra-compact design of eco-friendly switchgear under similar constraints. Full article

Deep stormwater drainage tunnels are increasingly being used to mitigate urban flooding, but in-tunnel sediment deposition reduces their discharge capacity and complicates their maintenance. With direct field observation constrained, numerical simulation is essential, and river-based total sediment load formulas require reassessment for use in deep tunnels. The three-phase (air–water–sediment) CFD solver SedInterFoam is first validated against a benchmark open-channel suspended sediment experiment, and is then applied to a horseshoe tunnel under a fixed design discharge for multiple inlet sediment concentrations spanning urban stormwater conditions. Four classical formulas (Yang, Shen–Hung, Ackers–White, Engelund–Hansen) are evaluated at the CFD-resolved hydraulic state; Toffaleti is omitted because its zone-based formulation is incompatible with the partially filled horseshoe geometry. The CFD consistently shows persistent retention of a substantial fraction of the inlet sediment load, whereas the transport capacity-limited interpretation of the classical formulas predicts near-complete sediment throughput—indicating structural inadequacy for the dilute, supply-limited regime typical of urban stormwater. A Universal Soil Loss Equation (USLE)-style dimensionless deposition formula is therefore proposed, with inlet sediment loading as the explicit independent variable and a tunnel correction factor $K_{tunnel}$ absorbing the geometric, hydraulic, and sediment variations. Its regression yields an almost linear scaling and a nearly constant deposition ratio, while analysis of the internal flow and concentration fields shows that the retained sediment is strongly concentrated near the bed and that near-bed turbulent mixing weakens moderately with a rising inlet concentration. While calibrated for a single non-cohesive settleable sand fraction, the framework provides a transferable basis for inlet-loading-dependent deposition prediction in deep stormwater drainage tunnels, and subsequent extension of $K_{tunnel}$ to broader sediment conditions with field-based validation is expected to enable maintenance planning, dredging volume estimation, and sediment retention risk assessment. Full article

Exhaust piping in diesel engines is subject to severe thermal stress arising from high-temperature, high-pressure gas flows, and spray cooling with atomizing nozzles has become a widely adopted method to safeguard structural reliability. However, at present, the understanding of the spray fragmentation mechanism of two-phase flow under low inlet pressure is still not comprehensive. This study establishes a three-dimensional model of a gas–liquid impinging-jet nozzle and applies a coupled Volume-of-Fluid to Discrete-Phase-Model (VOF–DPM) approach to resolve the liquid breakup process in detail. High-speed imaging experiments were carried out to validate the numerical results. Orthogonal tests were conducted at five pressure levels for both gas and water—0.28, 0.24, 0.20, 0.16, and 0.12 MPa—producing 25 data pairs of spray cone angle and Sauter Mean Diameter (SMD). Within the 0–0.3 MPa air inlet pressure range explored here, raising the pressure consistently reduced the SMD and widened the cone angle, although both trends weakened as the pressure increased. Water inlet pressure exhibited a nonlinear influence, with local extrema appearing in the higher-pressure region. The overall SMD reached a minimum of 34.12 μm and a maximum of 149.04 μm. Using these 25 data points, a genetic algorithm was employed to optimize the pressure ratio under the constraint of total hydraulic power, yielding optimization strategies for different power budgets. An additional outcome of the simulation was the identification of a structural weakness: by reshaping the original flat impingement surface into a full conical surface, atomization quality improved by 29.36% under identical boundary conditions. These findings clarify the atomization mechanism of gas–liquid impinging jets under low inlet pressure and offer practical guidance for nozzle optimization. Full article

To address heat accumulation, localized hot spots, and non-uniform temperature distribution in large-capacity lithium iron phosphate energy storage battery modules under high ambient temperature and high-rate charge/discharge conditions, this study proposes a fin-enhanced phase change material (PCM)-air hybrid thermal management structure for a 100 Ah prismatic lithium iron phosphate battery and a 2P18S energy storage battery module. First, the battery thermal model is validated using single-cell experimental data reported in the literature. Subsequently, a three-dimensional transient fluid–solid coupled heat transfer model is established by considering transient battery heat generation, PCM solid–liquid phase change, air-side flow and heat transfer, and temperature-dependent thermophysical properties. User-defined functions are employed to implement the transient heat source and temperature-dependent material properties. Under identical boundary conditions, the thermal management performances of three configurations, namely Fin-Air, PCM-Air, and Fin-PCM-Air, are compared. The effects of ambient temperature (20 °C, 25 °C, and 30 °C) and inlet air velocity (1 m/s, 2 m/s, and 3 m/s) on the maximum module temperature, temperature uniformity, PCM liquid fraction evolution, and flow field distribution are quantitatively analyzed. The results show that, compared with the Fin–Air system without PCM and the PCM-Air system without fins, the Fin-PCM-Air configuration reduces the maximum module temperature by 1.57% and 0.25%, respectively, at an ambient temperature of 30 °C and an inlet air velocity of 3 m/s. After four charge–discharge cycles, the peak maximum temperature of the module is approximately 38.56 °C, and the peak maximum temperature difference remains below 3.6 K, indicating good temperature uniformity and latent heat buffering capability. In addition, the air velocity trade-off analysis indicates that increasing the inlet air velocity can improve cooling performance but also increases the air-channel pressure drop and fan power consumption. Therefore, the Fin-PCM-Air structure is more suitable for high-thermal-load conditions, and its practical application should comprehensively consider cooling benefits, additional mass, manufacturing cost, and long-term reliability. This study provides a reference for the design and engineering application of hybrid thermal management structures for large-capacity energy storage battery modules. Full article

Traditional cryogenic air separation units are unsuitable for distributed, small-scale liquid oxygen production. Cryocooler-based liquefaction technology offers an alternative solution, featuring a large cooling capacity, high efficiency, a compact structure, and rapid start–stop capability. In this paper, an oxygen liquefaction system based on a high-capacity Stirling cryocooler was developed. Because the heat transfer performance of cryocoolers varies significantly across different temperature ranges, heat exchanger designs must be tailored to specific operating conditions. However, research on cold-end heat exchangers for large-capacity cryocoolers used in liquefaction systems remains limited. In the liquid oxygen temperature range, factors such as liquid film formation and incomplete condensation severely affect heat transfer performance and must be considered. In this paper, numerical simulations were performed to analyze the condensation behavior of oxygen, with particular attention paid to the matching between the heat exchange structure and the cooling capacity. Subsequently, a small-scale experimental system was constructed and tested. The successful operation of the experimental system validated the feasibility of the proposed heat exchanger design. Under the conditions of 300 K and an oxygen inlet gauge pressure of 0.45 MPa, the system achieved a liquefaction capacity of 7.4 L/h, corresponding to a cooling capacity of 787 W. The specific power consumption was 0.89 kW·h/kg, with a coefficient of performance (COP) of 0.116. This performance is competitive among small-scale cryocooler-based oxygen liquefaction systems. This study provides both theoretical and experimental support for further performance optimization and engineering application of such cryocoolers in liquid oxygen production. Full article

Ventilation air methane (VAM) discharged from coal mines is considerable in volume, causing serious environmental pollution and energy resource waste. The methane concentration of raw VAM is generally lower than 0.3%, which greatly limits its efficient utilization. Blending low-cost solid fuels with VAM for regenerative oxidation is a practical and promising strategy to overcome the technical bottlenecks of VAM resource recovery. Clarifying the gas–solid two-phase flow behaviors inside millimeter-scale regenerative microchannels is critical for optimizing the process parameters and structural design of regenerative oxidation devices. In this work, numerical simulations are conducted using ANSYS Fluent 2022 R2 software to systematically explore the flow evolution characteristics and corresponding influencing factors of gas–solid two-phase flow in millimeter-scale microchannels to investigate three key objectives: (1) reveal the flow evolution characteristics of gas–solid two-phase flow in millimeter-scale microchannels along the flow direction; (2) quantify the effects of particle size and inlet velocity on particle deposition rate and deposition velocity; and (3) propose optimal operational parameter ranges to avoid microchannel blockage and improve particle transport performance. Along the flow direction, the near-wall velocity gradient gradually declines with the flow distance, while the thickness of the boundary layer grows continuously. Both particle deposition rate and deposition velocity are positively correlated with particle size. At an inlet velocity of 2 m/s, once the particle size exceeds 60 μm, the deposition rate and velocity rise markedly, and the particle outflow probability decreases significantly. For a fixed particle size, increasing flow velocity reduces both deposition rate and deposition velocity, which enhances the transport ability of pulverized coal particles and weakens wall adhesion. When the flow velocity is lower than 2.5 m/s, the outlet deposition rate exceeds 60%, and the particle deposition velocity rises sharply. Accordingly, maintaining flow velocity above 2.5 m/s and controlling particle size below 60 μm can effectively inhibit rapid particle deposition, improve particle transport performance, and avoid microchannel blockage. This study provides a theoretical basis and parameter reference for the structural and operational optimization of horizontal microchannels in pulverized coal-blended VAM regenerative oxidation systems. Full article

Accurate and efficient modeling of laminar premixed flames is essential for chemical mechanism validation and parametric studies in combustion science. For this purpose, CombF was developed—a semi-analytical computational framework for one-dimensional (1D) laminar premixed flames—offering flexible control over nodal distributions and optional incorporation of experimental temperature data. Unlike conventional fully coupled solvers, CombF explicitly separates the initialization and solution stages, enabling structured control over intermediate structure and temperature constraints while preserving physical consistency. The methodology employs linear interpolation between pre- and post-reaction equilibrium states, adaptive grid refinement, and finite-difference solutions of species and energy conservation equations, with radiation heat transfer optionally included. CombF was validated for ethylene–air premixed flames by comparison with experimental data under varying equivalence ratios and inlet velocities using the YARC-AF kinetic mechanism, and for methane–air premixed flames by additional benchmark comparisons with Cantera, employing the DRM22 mechanism. CombF predictions were further validated against methane and propane–air flames under varying inlet compositions and velocities using the Diego mechanism and evaluated using the curve matching (CM) score, L₂ norms, and phase shift alignment via a nonparametric bootstrap approach. The results demonstrate strong agreement for major species (CO₂, H₂O), while intermediate species (CO, CH₂O) show higher sensitivity to temperature profile choice and nodal resolution, providing a more discriminating assessment of model fidelity. Incorporating experimental temperature fields substantially improves species distribution accuracy and structural alignment. Thus, CombF provides a reliable, flexible, and experimentally adaptive framework that is capable of accurately capturing flame structures, offering a practical tool for preliminary analyses, parametric exploration, and instructional applications in combustion research. Full article

The rapid increase in memory power density has made memory thermal management a critical challenge in high-density servers, where extremely limited DIMM spacing significantly reduces the effectiveness of air cooling. Compared with CPUs and GPUs, memory-level liquid cooling has received less systematic study, particularly regarding the influence of cold plate structural design on thermal and hydraulic performance under realistic server conditions. In this paper, three engineering-feasible memory liquid cooling solutions (water-flowing cold plate, clamp-type cold plate and heat-pipe-based cold plate) are experimentally compared on a high-density server system. Experiments are conducted at coolant inlet temperatures of 37–50 °C with a fixed flow rate of 0.8–1.5 L/min. Memory, CPU, and voltage regulator temperatures, as well as system pressure drop, are measured. Results show that memory temperature increases with coolant inlet temperature for all configurations, while their relative performance remains unchanged. Memory temperatures range from 62.04 to 71.13 °C, 57.65 to 66.98 °C, and 66.22 to 76.07 °C, with corresponding pressure drops of 24.19–26.69 kPa, 32.73–35.98 kPa, and 27.00–29.96 kPa. These results provide insight into the role of coolant distribution and flow-path topology in memory thermal performance. Full article