Metal Flow Research Articles

Advancing Flow Batteries: High Energy Density and Ultra‐Fast Charging via Room‐Temperature Liquid Metal

AbstractGlobal climate change necessitates urgent carbon neutrality. Energy storage is crucial in this effort, but adoption is hindered by current battery technologies due to low energy density, slow charging, and safety issues. A novel liquid metal flow battery using a gallium, indium, and zinc alloy (Ga80In10Zn10, wt.%) is introduced in an alkaline electrolyte with an air electrode. This system offers ultrafast charging comparable to gasoline refueling (<5 min) as demonstrated in the repeated long‐term discharging (123 h) process of 317 mAh capacity at the current density of 10 mA cm−2 with an average voltage of 1.1 V. A high practical capacity density of 635.1 mAh g−1 is achieved in this brand‐new battery with a potential theoretical value of 1004.4 mAh g−1. Microscopic and numerical simulations reveal significant hydrogen evolution reaction and dendrite suppression compared to Zn and pure Ga electrodes. The potassium iodide (KI)‐modified Ga80In10Zn10‐air battery exhibits a reduced charging voltage of 1.77 V and high energy efficiency of 57% at 10 mA cm−2 over 800 cycles, outperforming conventional Pt/C and Ir/C‐based systems with 22% improvement. This innovative battery addresses the limitations of traditional lithium‐ion batteries, flow batteries, and Zn‐air batteries, contributing advanced energy storage technologies to global carbon neutrality.

Impact of MHD mixed convection on heat and mass transfer in a typical DCLL breeder blanket

Abstract A typical dual-coolant lead lithium (DCLL) liquid blanket employs eutectic liquid lithium lead alloy (PbLi) as coolant and tritium breeder for Tokamak nuclear fusion reactor, and is responsible for transporting heat and tritium. The blanket is subjected to both strong magnetic field and strong radially non-uniform neutron volume heating. The flow of liquid metal is influenced by the combined effects of magnetohydrodynamics (MHD), buoyancy, and inertial effects, resulting in a complex MHD mixed convection phenomenon. This study employs direct numerical simulation (DNS) based on finite volume method to analyze the flow, heat transfer, and mass transfer within blanket unit. The results demonstrate that mixed convection has a significant impact on the MHD pressure drop and flow characteristics. The complex MHD mixed convection gives rise to a considerable number of vortices, particularly in regions of the turn and the downward poloidal duct. The formation of low-speed zones and jets within the blanket has the potential to significantly impact heat and mass transfer, leading to the accumulation of heat and tritium. On the other hand, the markedly elevated tritium production rate is a significant contributing factor to the obviously elevated tritium concentration in the vicinity of the first wall.

Surface-Grinding-Induced Recrystallization and Metal Flow Causes Corrosion-Assisted Penetrating Attack of High-Mn–Low-CR Casting Steel in Humid Environments

This study examined the surface-grinding-induced microstructural modifications and corrosion attacks in a penetrating form of a high-Mn–low-Cr casting steel slab under humid environments. Various experimental and analytical findings from field-emission scanning electron microscopy, electron backscatter diffraction, transmission electron microscopy, and electrochemical analyses revealed that the abrasive grinding process led to the formation of a surface deformed region, comprising a recrystallized fine grain layer and multiple streamlines. Corrosion initially occurs preferentially along the boundary areas where Cr(Mn)23C6 particles are precipitated. Moreover, the corrosion products (Fe-based oxy/hydroxides) with a high volumetric expansion ratio detach readily from the surface deformed regions, facilitating the easy penetration of corrosive media. In contrast to conventional low-alloyed steels, which exhibit uniform corrosion behavior, corrosion-assisted penetrating attacks on ground high-Mn–low-Cr casting steel slabs occur more severely and frequently during the summer/dry season (i.e., relative humidity levels around 60% to 80%, rather than 100%) when a thin water film can form on the steel surface. Based on the result, effective technical strategies in terms of metallurgical and environmental aspects to mitigate the risk of corrosion-assisted penetrating attack of high-Mn–low-Cr casting steel were discussed.

Experimental research on heat transfer enhancement by a wall-proximity circular cylinder under an axial magnetic field

This work experimentally investigates the flow and heat transfer of liquid metal around a cylinder in a rectangular channel with a heated bottom wall under an axial magnetic field. Wall electrical potential probes measure the streamwise and vertical velocity components, while an immersed array probe measures the temperature distribution in the vertical profile. The coupling effects of the gap ratio (ratio of the distance between the center of the cylinder and the wall to the diameter of the cylinder) and the magnetic field on heat transfer enhancement are studied. The experimental results suggest that the Lorentz force suppresses the wall recirculation zone from shedding secondary vortices and alters the trajectory of the vortex street, affecting the thermal boundary layer. The probability density function of temperature indicates that the magnetohydrodynamics effect causes a bimodal distribution due to a quasi-two-dimensional vortex street and a trimodal distribution due to additional secondary vortices. The vortex street notably reduces the thermal boundary layer thickness and the local temperature of the heated wall. The analysis of the correlation coefficients between velocity and temperature fluctuations and the frequency spectrum reveals the physical mechanism enhancing heat transfer. The wall-proximity effect and buoyancy strengthen flow fluctuations and enhance heat transfer. For Ha (Hartmann number) ranging from 161.6 to 646.4, optimal heat transfer occurs at G/d = 1.0, whereas for 808 ≤ Ha ≤ 1131.2, optimal heat transfer is achieved at G/d = 0.5, which is attributed to the coupling effect of the magnetic field and gap flow on vortex dynamics.

Scaling down recombinant carbonic anhydrase isolation with immobilized metal ion chromatography (IMAC): Harnessing enzymatic carbon dioxide capture and mineralization

BackgroundHuman activities have led to increased atmospheric CO2 levels, raising concerns about climate change. Carbonic anhydrase (CA) enzymes show promise for transforming CO2 into valuable products like calcium carbonate (CaCO3) through mineralization. Purifying and immobilizing CA enzymes on nanofiber membranes enhances their catalytic activity, enabling efficient CO2 conversion and mineralization. MethodsRecombinant CA was purified using immobilized metal affinity chromatography (IMAC), optimizing pH, biomass concentration, flow rate, and loading volume for maximum efficiency. The CA enzyme was then immobilized onto a weak ion exchange nanofiber membrane functionalized with AEA-COOH to create the CA-modified membrane (AEA-COOH-CA), enhancing CO2 conversion and CaCO3 mineralization. Significant findingsOptimal purification conditions (pH 7, 1 % biomass, 0.1 mL/min flow rate, 1.0 mL loading volume) were determined using IMAC. The CA-modified membrane effectively converted CO2 and mineralized CaCO3, demonstrating the potential for environmental CO2 sequestration. The immobilized CA activities of the AEA-COOH-CA nanofiber membranes exhibited 473.42 WAU/g-membrane, corresponding to 7.10 WAU per membrane piece. The CaCO3 precipitation reached 83.90 mg, with a precipitation efficiency of 11.82 mg CaCO3/WAU. These findings underscore the promise of enzymatic carbon capture using CA-modified membranes, offering a sustainable solution for greenhouse gas mitigation.

Reconstruction of liquid metal flow velocity field based on electromagnetic flow tomography

Reconstruction of liquid metal flow velocity field based on electromagnetic flow tomography

Influencing of Molten Pool Dynamic Behavior on the Weld Formation during the Laser‐Arc Hybrid Welding of 12 mm Thick Steel

A numerical simulation model is put forward to study the molten pool dynamic behavior and clarify its influencing mechanism on the undercut defects in laser‐arc hybrid welding (LAHW). The undercut defect is a common and challenging problem to address. However, a controversy exists on whether the dynamic process of molten pool can affect undercut defects, and the potential mechanism has been still unclear. The results suggest that profile variation of molten pool surface is driven by surface tension gradient, and the existence of eddy can alter the morphology and surface tension distribution of molten pool, which is the main factor to homogenize the flow field. Compared with the short‐circuit transfer mode, the molten metal flows toward the welds edge at a constant velocity (2.5–3.75 m min−1) in the spray transfer mode, which improves the stability of molten pool flow. It can be observed that the irregular fluctuation of molten metal during the solidification process can directly cause the undercut defects.

A computational fluid dynamics-based girth welding model for large-diameter pipeline to reveal vertical weld formation mechanism

Welding quality significantly impacts the safety of large-diameter, long-distance pipelines. The molten pool flow, influenced by gravity, results in variations in the girth weld seam at different circumferential orientations. A three-dimensional transient computational fluid dynamics model was developed to study the multi-layer, multi-pass welding process of X80M pipeline, incorporating arc heat, droplet heat, gravity, and fluid flow in the molten pool. The model also simulates dual-torch automatic welding to examine heat transfer and flow characteristics. Notably, it reveals the morphological evolution of the girth weld seam from the 2 to 3 o'clock positions during continuous welding, an area lacking prior research. The results, validated by experiments, show good agreement between the simulation and thermal cycle curves. The weld pool solidifies from the sides toward the center, creating a concave shape due to downward metal flow, with dual-torch welding intensifying this effect. The second torch increases the concavity of filler layers, with depths rising by 21.81% and 32.20%. These findings offer new insights into pipeline girth welding.

Study on the effects of extreme climate and human activities on the growth mechanisms of Zostera japonica in the Yellow River estuary

Zostera japonica, as one of the major seagrasses in the Yellow River Estuary, plays a critical ecological role, particularly in providing habitat for marine organisms, stabilizing sediment, and contributing significantly to carbon sequestration. In recent years, Zostera japonica seagrass beds have receded extensively due to multiple impacts of natural factors and human activities. This study investigates the complex effects of extreme climate events and human activities on the growth mechanisms of Zostera japonica in the Yellow River Estuary using a combination of field sampling, laboratory analysis, and quantitative calculations. The result shows that there are significant differences in sediment characteristics between the north and south shores, with the south shore having finer sediments and higher nutrient content, which support more robust seagrass growth. The Water and Sediment Regulation Scheme (WSRS) dramatically alters water quality by reducing salinity and increasing turbidity, thus inhibiting photosynthesis and disrupting the physiological functions of Zostera japonica. Additionally, WSRS introduces an increase in heavy metals, which could potentially impact plant health and stress levels. Extreme weather events, particularly Super Typhoon Lekima, further compound these impacts by causing soil erosion, uprooting seagrass beds, and reducing biomass and seed production. The interplay of WSRS, climate change, and anthropogenic activities necessitates integrated management strategies to mitigate adverse effects and enhance habitat resilience. This study underscores the need for specific management strategies, such as controlling heavy metal inflows, implementing sediment stabilization techniques, and regulating freshwater discharge during key growth periods, to mitigate adverse effects and enhance habitat resilience for Zostera japonica in the Yellow River Estuary.

Microstructure Evolution and Mechanical Behavior of TiB-Reinforced Ti-6.5Al-2Zr-1Mo-1V Matrix Composites Obtained by Vacuum Arc Melting and Spark Plasma Sintering

Ti-6.5Al-2Zr-1Mo-1V/TiB metal matrix composites with 3 wt.% of TiB2 were obtained using vacuum arc melting and spark plasma sintering methods and compared with an unreinforced Ti-6.5Al-2Zr-1Mo-1V alloy. The microstructures of the unreinforced Ti6.5Al-2Zr-1Mo-1V alloy in the as-cast and as-sintered conditions were quite typical and consisted of colonies of α-lamellae embedded in the β matrix. The microstructure of the as-cast Ti-6.5Al-2Zr-1Mo-1V/TiB composite composed of TiB fibers randomly distributed within the two-phase α/β matrix, while the as-sintered composite had a network-like microstructure, in which areas of the two-phase α/β matrix were delineated by walls of TiB fibers. At room temperature, the yield strength of the as-cast and as-sintered Ti-6.5Al-2Zr-1Mo-1V alloy were 800 and 915 MPa, respectively, with a plasticity of 18% in both conditions. The addition of TiB fibers contributed to a ~40 and 50% strength increment, with values of 1100 and 1370 MPa for the as-cast and as-sintered composites, respectively. In the as-sintered composite, the strengthening effect reduced at 400 °C and almost disappeared at elevated temperatures of 800–950 °C. The as-cast composite showed much higher strength during warm and hot deformation—at 800–950 °C, the yield strength of the as-cast composite was 50% higher compared to the Ti-6.5Al-2Zr-1Mo-1V unreinforced alloy. A higher rate and degree of globularization were established for the as-cast composite compared to the unreinforced alloy. For the as-sintered composite, a noticeably lower rate and degree of globularization was shown. During hot compression of the as-cast composite, TiB fibers reoriented towards the metal flow direction, while the network microstructure formed in the as-sintered composite transformed into clusters of borides unevenly distributed within the matrix. Based on the obtained results, the apparent activation energy of plastic deformation was calculated, and the operating deformation mechanisms were discussed both for the as-cast and as-sintered composites. The Arrhenius flow stress model and the dynamic material model were used to evaluate the deformation behavior of composites beyond the experimentally studied temperatures and strain rates.

Experimental study on the effect of wall proximity on the flow around a cylinder under an axial magnetic field

Investigations are conducted on the effect of wall proximity on the flow around a cylinder under an axial magnetic field, using the electrical potential probe technology to measure the velocity of liquid metal flow. The study focused on the impact of the inlet velocity of the fluid, the magnetic field and wall proximity on the characteristics of velocity fields, particularly on the vortex-shedding mode. Based on different magnitudes of the magnetic field and the distance from the cylinder to the duct wall, three types of vortex-shedding modes are identified, (I) shear layer oscillation state, (II) quasi-two-dimensional vortex-shedding states and (III) transition of the magnetohydrodynamic to hydrodynamic Kármán street. The transitions between these modes are analysed in detail. The experimental results show that the weak wall-proximity effect leads to the formation of the Kármán vortex street, while a reverse Kármán vortex street and secondary vortices emerge under a strong wall-proximity effect. It is noticed that the Kelvin–Helmholtz instability drives vortex shedding under regime I, leading to an increase in the Strouhal number (St) with stronger magnetic fields. Additionally, under a strong axial magnetic field, the wall-proximity effect (‘Shercliff layer effect’) promotes the instability of shear layers on both sides of the cylinder. These unique coupling effects are validated by variations in modal coefficients and energy proportions under different vortex-shedding regimes using the proper orthogonal decomposition method.

Numerical simulation of cathode-spot crater and droplet formation with linear and circular motion process

Abstract In this paper, a three-dimensional cathode spot erosion model is proposed to study the development of cathode spot motion 
process on the surface of copper cathode. The formation and development process of cathode spots motion without external 
magnetic field is studied. In this model, energy flux density, pressure, and current value are considered as external parameters. 
The simulation results compared the cathode spot ablation trajectories and temperature distribution under different motion 
forms and motion velocities. The results indicated that during the spots expansion process, the flow of liquid metal will form a 
convex structure on the surface of the cathode and a hollow structure inside the cathode. Comparing different motion types, the 
annular motion significantly increased the roughness of the cathode surface. With the increase of the speed of spots movement, 
the interaction between the craters is significantly weakened, which will reduce the temperature and the roughness of the 
cathode surface. The simulation results are consistent with the experimental results.

Actual problems of modeling thermal-hydraulic processes in fast neutron reactors

The results of studies on hydrodynamics and heat transfer processes in fast neutron reactors are presented. Data on turbulent momentum transfer in rod bundles are analyzed. It is shown that the intensification of turbulent momentum transfer in the rod bundle channels is due to large-scale turbulent momentum transfer (secondary currents). The intensification of interchannel turbulent exchange in close-packed lattices of rods is explained. A dependence is obtained for the dissimilarity coefficients of interchannel convective exchange forced by wire wrapping in bundles of rods. The methods and results of numerical modeling of thermal hydraulics using the Monte Carlo method, thermomechanical analysis of the temperature field in fuel rod assemblies in the lifetime process are presented. The results of modeling based on a water model of temperature fields and the structure of coolant movement in the primary circuit of the reactor in various regimes are presented. A stable temperature stratification of the coolant was revealed in the peripheral zone of the upper chamber of the reactor above the side screens. It is shown that the process of boiling liquid metals in fuel assemblies has a complex structure, characterized by stable and pulsating regimes and a heat transfer crisis. The agreement between the results of experimental and numerical modeling is shown. A cartogram of the flow regimes of a two-phase flow of liquid metals in fuel rod assemblies has been plotted. The influence of the surface roughness of fuel elements on the boiling process and heat transfer during boiling of liquid metals is analyzed. Long-term cooling of a fuel assembly with a “sodium cavity” above the reactor core in accident regimes with boiling of liquid metals is shown. The objectives of further research are formulated.

Adsorption of hexavalent chromium from wastewater using magnetic biochar derived from peanut hulls

In this study, the utilization of peanut hulls as a precursor for the preparation of magnetic biochar through pyrolysis was investigated. To enhance the magnetic and adsorption properties of the biochar, the peanut hulls biomass was modified using ferric chloride hexahydrate and magnesium chloride hexahydrate. Response surface methodology was employed to evaluate the influence of biomass metal concentration, pyrolysis temperature, pyrolysis period and flow of nitrogen on the yield and Cr (VI) adsorption efficiency of the synthesized biochar. A 17-run experimental matrix was generated using Optimal Design to investigate the interactions among four input parameters. The results led to the development of a quadratic model, which demonstrated a high degree of predictability in accordance with the experimental data. Analysis of variance (ANOVA) confirmed that the models for yield and Cr (VI) adsorption efficiency were highly significant (p < 0.05), with coefficients of determination (R2) values of 0.891 and 0.988, respectively. The optimal synthesis conditions for producing biochar with superior physicochemical properties were identified as a pyrolysis temperature of 300 °C, a pyrolysis duration of 2 h, a metal-to-biomass ratio of 0.5, and a constant flow of nitrogen. A desirability of 85% was achieved through numerical optimization, corresponding to a yield of 63% and complete Cr (VI) removal. Further optimization of Cr (VI) adsorption efficiency, considering the effects of pH (3–12), adsorbent loading (1–15 g/L), and initial Cr (VI) concentration (5–20 mg/L), was performed using a 19-run experimental matrix. ANOVA for Cr (VI) adsorption efficiency model revealed high significance (p < 0.05) with an R2 value of 0.916.The magnetic biochar demonstrated a remarkable adsorption efficiency of 98% under the experimental conditions of solution pH 3, adsorbent dosage of 5 g/L, and an initial Cr (VI) concentration of 20 mg/L. The desirability of 100% was obtained by a numerical optimization method representing Cr (VI) removal of 98%. The adsorption behaviour was adequately described by the Freundlich isotherm model, suggesting multilayer adsorption, with a maximum adsorption capacity of 12 mg/g. Biochar also proved to have strong magnetic properties which enhanced solid-liquid separation post adsorption experiments.

Numerical analysis of the influence of cooling design on temperature uniformity in the large proton exchange membrane fuel cell stack

The temperature distribution has a significant influence on the performance and lifespan of proton exchange membrane fuel cell (PEMFC) stacks. However, analyzing the temperature distribution of large PEMFC stacks is challenging and has been rarely conducted. In this study, a simplified model of a large PEMFC stack is developed using computational fluid dynamics (CFD) methods, which includes 300 cells and 60 cooling plates. The influence of cooling parameters, including configurations, dimension and flow rate, is discussed. The study indicates that U-type stack exhibits better temperature uniformity than Z-type stack. Increasing the coolant flow rate can effectively reduce the stack temperature. The study proposes a modified cooling design, which effectively reduces the heat accumulation at the end of the stack. Lastly, a comparison between traditional serpentine channels and porous foam metal flow fields reveals that the porous foam metal flow field exhibits superior thermal management characteristics. The results can offer insights for thermal management of large-scale PEMFC stacks.

An analytical gradient method to model interfacial heat and mass transfer in multi-field CFD codes

Phase change at the interface between a liquid and a gas, commonly referred to as bulk condensation/boiling or interface condensation/boiling, is often overshadowed by wall condensation/boiling. However, interfacial phase change plays a critical role in various industrial applications, including boiling flows in microchannels and boiling liquid metal flows. In this article, we introduce a novel analytical model based on the gradient method. This model accounts for interfacial phase change within multi-field codes. It is validated against both analytical and experimental cases involving bulk boiling, demonstrating excellent agreement. Notably, the mesh convergence aligns with the methods employed in single-fluid codes. Additionally, we propose a hybrid approach that combines the high accuracy of this model with the computational efficiency of dispersed methods.

Optimizing waste heat recovery for hydrogen production: Modeling and simulation of ternary size metallic granule flow in a cooling cylinder

In order to recover the waste heat of high temperature metallic granules to produce steam for hydrogen production, a waste heat recovery cooling cylinder with cooling water channel is innovatively developed. The simulation is carried out based on DEM and soft sphere model to study the flow characteristics of ternary size metallic granules. The model of cooling cylinder is established and verified by comparing to the experiment data. The change rule of bed shape in the waste heat recovery cooling cylinder is examined, and the inclination angle, rotational speed and filling rate are assessed to find their influence on the flow characteristics of ternary size metallic granules. The results indicated that, with the increase of inclination angle, the axial velocity increases by 482.76%, which means the reduce of residence time of granules. With the increase of rotational speed, the axial velocity has an increase of 161.54%, the sum velocity increases by 158.49%, leading to a decrease of residence time. As the filling rate increases from 1.5% to 15.5%, the contact number has an increase of 91.53%, which lead to the increase of heat transfer area. The residence time and heat transfer area will directly affect the waste heat recovery efficiency, so a proper arrangement of granule flow is significant for enhancing the heat transfer efficiency.

Metal flow behavior and energy consumption model during the extrusion process of a 6063 aluminum alloy profile with complex cross-section

Metal flow behavior and energy consumption model during the extrusion process of a 6063 aluminum alloy profile with complex cross-section

Microstructure and mechanical properties of aluminum alloy laser welded joint assisted by alternating magnetic field

Magnetic field-assisted laser welding is an effective method to improve the quality of laser-welded joints. In this study, laser welding was conducted on a 2 mm thick sheet of 6061-T6 aluminum alloy, with the assistance of an alternating magnetic field oriented perpendicular to the surface of the sheet. The effects of the alternating magnetic field on the macrostructure, molten pool flow, porosity, grain morphology, and microhardness of the weld seam were analyzed. The results indicate that applying the alternating magnetic field results in more uniform and finer fish scale patterns on the upper surface of the weld. The porosity of the weld is significantly reduced. The Lorentz force generated by the alternating magnetic field suppresses liquid metal flow from the center to the edges of the molten pool, thereby hindering the heat flow and transfer within the pool. This concentration of heat in the lower part of the molten pool increases the size of equiaxed grains at the weld center and promotes the formation of more branches in the columnar grains near the fusion line. Some columnar grains in the columnar grain zone transform into equiaxed grains. Moreover, the microhardness distribution of the weld becomes more uniform, and the hardness in the heat-affected zone increases. Tensile tests revealed that all samples fractured within the weld seam, with the tensile strength of the welded joints increasing by 12.7%. The fracture mode transitions from a mixed ductile-brittle fracture to a purely ductile fracture.

Effect of nozzle clogging on vortexing during continuous casting processes: results of an experimental simulation

ABSTRACT Exogenous oxide inclusions in continuously cast steel primarily arise from the entrapment of slag during various stages of steelmaking, including in furnaces, ladles, and molds. To maintain steel cleanliness, operators often pause ladle and tundish processes before ‘slag vortexing’ begins, since this phenomenon (slag vortexing) can adversely affect product quality. Previous studies indicate that sub-entry nozzle clogging can lead to productivity issues and quality defects in cast products. Clogging can cause non-uniform reductions in nozzle diameter along the molten metal flow direction. This study examines the impact of drain port taper (a representation of nozzle clogging) on air core vortex formation during water drainage (simulating molten metal) using a parameter, ‘Characteristic Volume of Air Core.’ Results show that clogged drain ports are prone to vigorous vortexing, significantly affecting efflux velocity and static pressure at drain outlets. The current study also analyzes the dynamic behavior of air core vortexing due to nozzle clogging, revealing that clogging can induce fluctuations in liquid discharge, adversely affecting the casting process. These findings have practical implications for continuous casting processes in steel and other metals.