Search Results (503)

The push for higher energy density in electric vehicles has resulted in large-sized lithium-ion batteries, but their geometric upscaling exacts a heavy thermal price. Under high-rate discharge, these massive cells become heat traps, risking thermal runaway. To tame this instability, this paper engineered a hybrid management strategy fusing liquid cooling, Phase Change Materials (PCMs), and flow deflectors. With a primary focus on the structural optimization of the cooling channel, a three-dimensional numerical model, calibrated using experimentally determined thermophysical properties, was developed to overcome the thermal bottlenecks of conventional cooling architectures. Results indicated that the initial channel optimization effectively reduced the maximum temperature to 327.7 K, but it still remained near the safety threshold. Integrating PCM radically altered the thermal landscape, slashing the outlet temperature differential by 41.67% (from 2.76 K to 1.61 K) compared to pure liquid cooling and blunting peak thermal spikes. Furthermore, to overcome laminar stagnation, strategic deflector baffles were introduced to agitate the coolant, enhancing heat dissipation. Specifically, the optimal half-coverage (L = 1/2) baffle configuration successfully lowered the maximum temperature to 322.42 K while substantially reducing the system pressure drop from 948.16 Pa to 627.57 Pa, achieving a 33.33% reduction compared to the full-coverage scheme. Finally, a multi-variable sensitivity analysis confirmed the extraordinary engineering robustness of the optimized configuration, demonstrating a negligible maximum temperature fluctuation of less than 0.5% despite ±10% operational and material uncertainties. This synergistic system actively stabilizes the thermal envelope, offering a robust engineering blueprint for next-generation high-power battery packs. Full article

Droplet microfluidics enables precise manipulation of picoliter-to-nanoliter-scale droplets and supports key operations such as merging, splitting, sorting, and trapping, facilitating controlled handling of minute fluid volumes. These capabilities have significantly advanced high-throughput drug discovery, single-cell analysis, molecular diagnostics, and synthetic biology. Among these operations, droplet splitting is particularly important for multi-step biochemical assays and parallel processing. Splitting strategies can be broadly categorized as passive, relying on channel geometry or microstructures, or active, employing external stimuli such as thermal, magnetic, acoustic, or electric fields. Electric-field-based methods are especially attractive due to their rapid response and tunability; however, many reported systems require relatively high operating voltages. Here, we present a low-voltage microfluidic platform that integrates tilted interdigitated electrodes (IDEs) with an asymmetric Y-junction to enable electrically tunable droplet splitting and sorting within a single device architecture. Two independently addressable tilted IDE arrays generate localized electric-field gradients that induce dielectrophoretic droplet deflection at moderate voltages. By adjusting the applied voltage amplitude and selectively activating the electrode arrays, droplets can be dynamically routed into designated outlets or deterministically split in real time, providing adaptable electrohydrodynamic control with minimal structural complexity. Full article

Several studies have investigated counterflow and concurrent flow in channels separated by a membrane to simulate mass transfer through membranes; however, few of them have used computational fluid dynamics (CFD). The current study aimed to numerically simulate and physically describe the distribution of pressure and velocity in counter-current flow by solving Navier-Stokes (N-S) equations in the channel and membrane pores (vertical channels). This is in contrast to most previous studies, in which the channel flow was simulated using N-S equations while ultra-filtration membrane flow was simulated using Darcy’s law. Consequently, the current study was executed using a CFD simulation to achieve several significant features: avoiding the execution of experimental tests, reducing the effort of model design and the expense and time consumption of fabrication, and facilitating the easy observation of variations in the pressure and the horizontal and vertical velocity for each point in the model. Two-dimensional CFD methods directly simulated the flow in channels and membrane pores to solve the N-S equations for each point in the whole domain, for which the velocity (horizontal and vertical) and pressure were calculated. In the current study, it was found that the pressure decreased from the inlet to the outlet of the channel, the horizontal velocity decreased from the inlet to the middle of the channel length and then increased to the outlet of the channel, and the vertical velocity decreased from the inlet to the middle of the channel length (L/2) with an upward direction (positive) and from L/2 to the outlet of the channel with a downward direction (negative). The analytical solution (1D model) was used to validate a numerical simulation (CFD) for the current study, but there were slight differences in the results between them. The results were perfectly explored and displayed the flow distribution patterns inside the channels and the membrane pores (vertical channels). The current study model represents the hemodialysis process. Full article

As a critical hydraulic component of pumped storage power stations, the side inlet/outlet directly affects unit efficiency, flow stability, and system safety. This study investigates the side inlet/outlet of a pumped storage power station using three-dimensional numerical simulations, focusing on the influence of the diffuser length L on hydraulic performance, and further analyzes the underlying mechanisms of energy loss based on entropy production theory. The results indicate that, with increasing diffuser length L, the flow rates in individual channels gradually deviate from the design values, leading to an aggravated imbalance in flow distribution. In contrast, the velocity non-uniformity coefficient C_V at the trash rack decreases, accompanied by a pronounced attenuation of recirculation and local flow separation, resulting in a more uniform and stable flow field. Moreover, increasing L improves the streamwise velocity uniformity within each channel, while the extent and intensity of the top recirculation zone are reduced, suppressing local flow separation. Quantitative analysis shows that when L increases from 65 m to 85 m, the total turbulent dissipation entropy production rate in the diffuser section increases linearly from 2732.32 W/K to 2842.32 W/K, whereas the direct dissipation entropy production rate increases from 0.41 W/K to 0.59 W/K. This indicates that turbulent dissipation entropy production plays a dominant role in the overall energy loss. Shorter diffusers tend to induce high-intensity local dissipation, whereas longer diffusers reduce local peak dissipation but increase the overall entropy production within the diffuser, reflecting a trade-off between local optimization and global energy loss. This study reveals the sensitivity and governing effects of diffuser length on the hydraulic characteristics of side inlet/outlets, providing a reference for geometry optimization and engineering design of similar hydraulic components. Full article

Efficient ortho–para hydrogen conversion is essential to suppress spontaneous heat release and boil-off losses during cryogenic liquid hydrogen storage and pre-liquefaction processes. In this study, a novel catalyst-filled wavy plate-fin heat exchanger (CFHE) is proposed to simultaneously enhance heat transfer and ortho–para hydrogen conversion under cryogenic conditions. Compared with conventional straight-fin configurations, the wavy-fin structure introduces controlled flow perturbations and increased specific surface area, thereby intensifying transport processes. Three-dimensional computational fluid dynamics (CFD) simulations, using the SST k–ω turbulence model, coupled with an ortho–para hydrogen conversion kinetic model were performed to quantitatively investigate the effects of key geometric parameters and catalyst loading on hydrogen conversion, heat transfer, and pressure drop within a Reynolds number range of 941–1577 and a temperature range of 35–20 K. Within the same CFHE configuration, the para-hydrogen fraction remains nearly unchanged without catalyst but increases significantly with catalyst loading. However, the catalyst reduces the global average Colburn j-factor by about 25%. Despite higher friction losses, the outlet–inlet temperature difference decreases to about 0.866 times that of the non-catalyst case, indicating improved temperature uniformity. A comprehensive performance index e, integrating heat transfer enhancement, flow resistance, and conversion efficiency, was introduced and optimized using a genetic algorithm. The optimized CFHE achieves an outlet para-hydrogen fraction exceeding 95% of the thermodynamic equilibrium value while maintaining hydrogen entirely in the gaseous phase to avoid catalyst deactivation. Overall, the catalyst-packed wavy channel configuration demonstrates superior conversion efficiency, enhanced thermal uniformity, and improved overall performance compared with straight-fin structures, providing quantitative design guidance for high-performance heat exchangers in cryogenic hydrogen liquefaction systems. Full article

Journalists’ use of personal social media accounts and websites to disseminate content has necessitated investigating their significance for Kenyan media professionals. Based on a qualitative research design, this study draws on semi-structured in-depth interviews with Kenyan journalists (N = 22) to investigate their perceptions of migrating from traditional media outlets to digital platforms, in particular, personal social media channels and independent websites, the underlying reasons for this platform migration, and their perceptions of how legacy media are responding to such shifts. The findings highlight that economic incentives and challenging media environments are the primary drivers of platform migration and that participants perceive journalists’ independent websites (i.e., j-blogs) as valuable additions to the diversification of news sources. According to respondents, legacy media organizations have responded by restructuring their newsrooms, adopting convergence strategies, and establishing on-demand platforms to slow journalists’ migration to digital media. The implications for journalists, legacy and digital media, and media consumers are also discussed. Full article

This paper presents the design and industrial implementation of an adaptive discrete control system for a rotary dryer operating in potash fertilizer production. The drying process is characterized by high inertia, multivariable interactions, transport delay, and non-stationary behavior resulting from variations in raw material properties and external disturbances, which significantly reduce the effectiveness of conventional fixed-parameter controllers. A discrete-time mathematical model of the rotary drying process was developed using industrial experimental data collected from a full-scale production plant. The process was modeled as a coupled 2 × 2 multivariable system with pronounced time-delay effects in the main control channels. System identification was carried out using statistical and frequency-domain methods to capture the dominant dynamic characteristics required for controller synthesis. Based on the identified model, an adaptive discrete controller with online parameter adjustment was developed to regulate outlet moisture content and exhaust gas temperature. Simulation and industrial results confirmed stable operation under varying conditions, improved regulation accuracy, enhanced process stability, and an average production efficiency increase of approximately 1.8%, accompanied by reduced fuel consumption. Full article

This study numerically investigated the thermal performance of a rectangular channel incorporating scale-inspired biomimetic protrusion structures with micro-grooves on their surfaces. A three-dimensional numerical model was established and validated against experimental data under identical geometric parameters and boundary conditions, demonstrating good agreement in terms of outlet temperature and pressure drop over a wide range of Reynolds numbers. The effects of groove depth on friction factor, Colburn factor, and overall performance evaluation criterion (PEC) were systematically analyzed to elucidate the underlying flow and heat transfer mechanisms. The results indicated that the introduction of biomimetic grooves significantly modified the flow structure and thermal boundary layer development, thereby enhancing fluid mixing and heat transfer. However, excessive groove depth intensified flow separation and pressure loss, leading to performance deterioration. An optimal groove depth of 0.6 mm (approximately 40% of the fin height) was identified, which achieved the best balance between heat transfer enhancement and flow resistance. The findings provide theoretical guidance for the biomimetic surface design of high-efficiency heat exchangers. Full article

This study explores the passive separation of solid particles from liquid suspensions in spiral separators fabricated using fused filament fabrication (FFF) and stereolithography (SLA). Building on prior work, we investigate the effect of microchannel geometry, circular vs. square cross-sections of equal area, and printing method on separation performance. Devices were tested across a wider range of flow rates (150 mL min⁻¹–350 mL min⁻¹), extending into transitional regimes, to examine geometry-induced inertial effects. Separation performance was quantified using the normalized outlet mass difference (Δ) for talc, precipitated calcium carbonate, and quartz. Maximum separation was obtained for quartz sand in the SLA separator at 250 mL min⁻¹ (Δ = 0.2175 g per 100 mL), while talc showed the highest mass difference in the square FFF separator at 300 mL min⁻¹ (Δ = 0.1196 g per 100 mL). For calcium carbonate, the highest separation occurred in the SLA device at 250 mL min⁻¹ (Δ = 0.1721 g per 100 mL), though performance was limited by agglomeration and clogging in FFF devices. Overall, separation was predominantly mass-based rather than strictly size-selective, with channel geometry, flow regime, and fabrication method jointly governing performance. Full article

Particulate matter (PM) emissions are common in technological processes, and effective mitigation requires gas pre-treatment before high-efficiency filtration to reduce fine and ultrafine PM that are particularly dangerous to the human health. This study evaluates a multichannel electric field manipulator (agglomerator) as a flow pre-treatment stage and investigates the aerodynamic conditions that govern particle–gas flow distribution and variation in trajectories and dynamics at different flow rates. These factors provide meaningful assumptions about the possible behavior of particles in the flow, and they are critical for optimizing an agglomeration and its intensity. Such phenomena can have an impact on the probability of agglomeration in the manipulator channels, i.e., the adherence of small particles into larger ones, and this allows for improving the design and operating conditions of the apparatus. Gas flow velocities and pressure were analyzed experimentally at various cross-sectional points in the inlet and outlet ducts at inflow rates of 3.4 L/s and 50 L/s. The static inlet pressure of the manipulator ranged from 8 Pa to 178 Pa. This study provides new insights into flow pre-treatment using the electric field mechanism in a multichannel modular apparatus and provides a reasonable understanding of the necessary characteristics of gas flow distribution to support subsequent improvements targeting higher agglomeration. Full article

Thermal stratification in deep reservoirs can cause ecologically problematic cold-water releases, and many existing selective-withdrawal phenomena rely on a limited set of fixed intake levels, which constrains their ability to follow seasonal shifts in the thermocline. Stepless stratified intakes with continuously adjustable flap gates offer quasi-continuous control of withdrawal depth, but their multi-gate, multi-brace layouts generate complex internal hydraulics whose energy-loss mechanisms are not well captured by conventional head-loss and resistance-coefficient metrics. In this study, physical-model measurements are combined with a validated three-dimensional numerical model, and entropy-production theory is used as a diagnostic to resolve where and by which mechanisms mechanical energy is irreversibly degraded inside a single-unit stepless stratified intake. The analysis shows that turbulent entropy production accounts for more than 98% of total dissipation, concentrated mainly in the flow channel and gate shaft, while the reservoir and outlet pipe contribute only weakly. Local entropy-production-rate fields indicate that dominant irreversibilities are associated with flow turning at the active gate leaves and with separation and wake development around horizontal and vertical braces, which generate low-velocity bands across gate levels and a low-velocity corridor in the shaft. Five geometric modification schemes targeting gate-entrance shaping and brace layout are evaluated; a combined brace-alignment and edge-rounding configuration most effectively weakens dissipation hotspots, improves discharge sharing among gate levels and reduces total entropy production. These findings show that entropy-based diagnostics can complement traditional hydraulic indicators and provide effective guidance for the design and refinement of stepless stratified intake structures. Full article

This study investigated the temporal variation and removal efficiency of solid waste, together with the dynamics of water quality parameters and microbial community structure, in a recirculating aquaculture system (RAS) for mandarin fish (Siniperca chuatsi) fed a formulated diet. The average fish weight was 384.62 ± 12.13 g, and the stocking density was 25 kg/m³. The results showed that: (1) the contents of the stomach and intestine exhibited a bimodal pattern, characterized by an initial increase followed by a decrease, and a subsequent secondary increase and decline. In the culture tanks, the total suspended solid (TSS) concentration at the main discharge outlet of the dual-channel bottom drainage system was highest immediately after feeding (0 h), reached its lowest level at 5 h post-feeding, and displayed a double-peak pattern during the 6–24 h post-feeding period. The temporal variations of in-tank TSS and chemical oxygen demand (COD) generally followed the same trend as the TSS concentration at the main discharge outlet. (2) Total ammonia nitrogen (TAN) reached its maximum at 6 h, whereas nitrite nitrogen (NO₂⁻-N) peaked at 9 h. (3) The solid–liquid separation efficiencies of the dual-drain system, vertical flow clarifier, and Rotating drum microfilter were 30.40–58.33%, 51.30–76.61%, and 37.04–68.26%, respectively, with the highest removal efficiencies observed at 0 h post-feeding. (4) In the nitrifying biofilter, the TAN concentrations ranged from 0.22–0.99 mg/L at the inlet to 0.15–0.36 mg/L at the outlet. In contrast, NO₂⁻-N concentrations exhibited negligible differences between the inlet and outlet at the corresponding sampling times. At the phylum level, Pseudomonadota, Bacteroidota, and the superphylum Patescibacteria dominated the biofilter microbial communities. At the genus level, Sediminibacterium and Limnohabitans were predominant in BF_1, whereas taxa affiliated with norank_f__Hyphomicrobiales_ and unclassified_o__Saccharimonadales dominated BF_2. Overall, the results indicated that increasing water circulation and tank flow rate at 0 h and during the 7–14 h post-feeding period may facilitate the timely removal of solid waste, and that the installation of a foam fractionator could contribute to the removal of dissolved and fine organic matter. Full article

In the hydraulic hoist design for a water conservancy hub project in western China, the vertically positioned, high-speed, heavy-load hydraulic cylinder is required to achieve closing speeds of up to 16 m/min, which is 4–5 times faster than conventional hydraulic hoists. Traditional buffer structures in hydraulic cylinders are insufficient to meet these performance demands. To address this challenge, a labyrinth buffer sleeve with multi-stage labyrinth buffer channels was designed and manufactured using additive manufacturing technology. The feasibility and effectiveness of the labyrinth buffer sleeve were evaluated through numerical simulations and experimental testing. Results demonstrate that the sleeve offers superior flow capacity, speed control, and pressure reduction capabilities. The maximum flow velocity within the labyrinth flow field reaches 111.7–166.5 m/s at the narrowest section of the flow path. The pressure ranges from 9.95 MPa at the inlet to 0.5 MPa at the outlet. Upon entering the buffer stage, the cylinder’s velocity smoothly decreases from 8 to 9 m/min to 2 m/min. Compared to traditional spiral groove buffer sleeves, the 3D-printed labyrinth design enables staged buffering, reducing peak pressures by 80%, with peak values only 1/16 to 1/5 of those seen in conventional sleeves. This results in an 80% reduction in pressure impacts, eliminating the need for frequent on-site disassembly and reassembly for fit clearance adjustments. Full article

Conventional cooling schemes that rely on rigid heat-sink-to-die coupling in vertical stacks fail to track the dynamic, non-uniform heat map of high-performance artificial-intelligence (AI) chips employing chiplet-based heterogeneous integration, giving rise to local hot spots. To eliminate this mismatch, we present a leaf-vein-inspired fractal microchannel tailored for such AI processors. Its hierarchical bifurcation–confluence topology adaptively reshapes the flow field, delivering ultra-low thermal resistance, high heat-transfer coefficients, and uniform dissipation. Coupled with reconfigurable chiplet placement, the design is evaluated through FEM-based orthogonal experiments that rank the influence of coolant, channel diameter/depth, inlet/outlet position, substrate thickness, and flow rate via range analysis and Analysis of Variance (ANOVA). A machine-learned surrogate model of junction temperature is then fed to Particle Swarm Optimization (PSO) for multi-parameter optimization. When re-simulated with the optimal parameter set, the symmetric fractal network lowered the AI chip junction temperature from 127.80 °C to 30.97 °C, a 76% improvement, offering a theoretical basis for hotspot mitigation in advanced heterogeneous AI packages. Full article

Complex hydraulic transients induced during load adjustment of turbine units in long tailrace tunnels pose significant threats to the safety and stability of tailwater systems. In view of this, based on VOF multiphase flow and compressible water–air models, a three-dimensional full-flow-channel numerical model of long tailrace system incorporating surge shaft and downstream river channel was developed using computational fluid dynamics (CFD) software to explore the transient impact of load changes on flow rate, water level, and pressure pulsations under different flow regimes in the tailrace tunnel, including open channel flow, pressurized flow, and free-surface-pressurized flow. The results indicate that the discharge at the outlet of the tailrace tunnel exhibits attenuated oscillations in response to load variations, with the most severe fluctuations occurring due to the intense air–water interface mixing during free-surface-pressurized flow. Flow regime transitions are accompanied by air pocket phenomena, resulting in significant fluctuations in air volume fraction. Pressure pulsations show periodic variations, with energy gradually dissipating as they propagate downstream. Open channel flows predominantly feature high-frequency waves, while pressurized flows exhibit intense low-frequency pulsations. Additionally, load changes in one unit have an ultra-low-frequency impact on another unit sharing the same tailrace tunnel, with high-frequency waves being filtered out by the surge shaft. Full article