The dissolved hydrogen, rather than gaseous hydrogen, plays a crucial role in the hydrogenation process. A thorough understanding of hydrogen dissolution is essential for optimizing the hydrogenation process. In this ...The dissolved hydrogen, rather than gaseous hydrogen, plays a crucial role in the hydrogenation process. A thorough understanding of hydrogen dissolution is essential for optimizing the hydrogenation process. In this paper, the dynamic pressure step method was modified to reduce the temperature difference between the hydrogen and solution, from which the hydrogen solubility and volumetric liquid-side mass transfer coefficient (k_(L)a) of the vacuum residue were obtained. It was discovered that temperature was the most critical factor in hydrogen dissolution, simultaneously enhancing both the hydrogen solubility and k_(L)a. Pressure played a significant role in promoting hydrogen solubility, but had a relatively small impact on kLa. Stirring speed, although it enhanced k_(L)a, did not affect hydrogen solubility. By normalizing the dissolution parameter, the results showed that the gas-liquid mass transfer rate decreased continuously during hydrogen dissolution and that the SD-tD curves after normalization were almost the same in all experimental conditions.展开更多
Combining the advantages of high efficiency,low-pressure drop,and large throughput,the pore arrayenhanced tube-in-tube microchannel(PA-TMC) is a promising microreactor for industrial applications.However,most of the m...Combining the advantages of high efficiency,low-pressure drop,and large throughput,the pore arrayenhanced tube-in-tube microchannel(PA-TMC) is a promising microreactor for industrial applications.However,most of the mass transfer takes place in the upstream pore region,while the contribution of the downstream annulus is limited.In this work,helical wires were introduced into the annulus by adhering to the outer surface of the inner tube.Mixing behavior and mass transfer of liquid-liquid twophase flow in PA-TMC with different helical wires have been systematically studied by a combination of experiments and volume of fluid(VOF) method.The introduction of helical wires improves the overall volumetric mass transfer coefficient KLa by up to 133% and the mass transfer efficiency E by up to 117%.The simulation results show that the helical wire brings extra phase mixing regions and increases the specific interface area,while accelerating the fluid flow and expanding the area of enhanced turbulent dissipation rate.Influences of helical wires in various configurations are compared by the comprehensive index I concerning the pressure drop and mass transfer performance simultaneously and a new correlation between KLa and specific energy consumption φ is proposed.This research deepens the understanding of the mixing behavior and mass transfer in the PA-TMCs and provides practical experience for the process intensification of microchannel reactors.展开更多
The engineering diseases caused by seasonal sulfate saline soil in Hexi region of Gansu Province seriously affect the local infrastructure construction and operation maintenance.To address this issue,this study explor...The engineering diseases caused by seasonal sulfate saline soil in Hexi region of Gansu Province seriously affect the local infrastructure construction and operation maintenance.To address this issue,this study explored the thermal mass transfer law,pore fluid phase transition,soil deformation and microstructure of unsaturated sulfate saline soil under the open system.Firstly,based on the theories of porous media mechanics and continuum mechanics,combined with the conservation equations of mass,energy and momentum and considering the phase transition of pore fluid,a multi-field coupled mathematical model of hydro-thermal-salt-gasmechanical for unsaturated sulfate saline soil was established.Secondly,basic unknown variables such as pore water pressure,concentration,temperature,porosity,and displacement were selected to perform numerical simulation analysis on the equation system by“Comsol Multiphysics”finite element method.Finally,a comparative analysis was conducted between the on-site measured data and the numerical simulation results.The results show that the water and salt phase transitions caused by temperature change could lead to soil salt heave and frost heave,alter the pore structure of the soil,and reduce the compactness of the soil,ultimately being reflected in the changes in soil porosity.The influence of external temperature on soil temperature gradually decreases with increasing depth,and the sensitivity of frozen areas to external temperature is much higher than that of unfrozen areas.This study not only enriches the theoretical results of thermal mass transfer law and deformation of unsaturated sulfate saline soil,but also provides practical guidance for the prevention and control of engineering diseases in local sulfate saline soil.展开更多
The structural and operational optimization of gas-liquid stirred bioreactors presents both complexity and critical importance for enhancing mass transfer performance. This study proposes a machine learning (ML)-drive...The structural and operational optimization of gas-liquid stirred bioreactors presents both complexity and critical importance for enhancing mass transfer performance. This study proposes a machine learning (ML)-driven approach to identify key features and predict the volumetric mass transfer coefficient (kLa). Four ML models were adopted and compared for kLa prediction in Newtonian and non-Newtonian fluids by evaluative indices, with CatBoost and XGBoost emerging as the optimal models, respectively. Specifically, it is demonstrated that Catboost has higher prediction accuracy (AARD = 18.84%) than empirical equations by effectively incorporating multidimensional features (structural, impeller, and operational), while simultaneously extending applicability to diverse Newtonian fluids. For non-Newtonian fluids, XGBoost outperforms empirical equations by effectively incorporating fluid rheological parameters (consistency coefficient, power-law index), thereby better capturing shear-thinning behavior. Feature importance analysis further identified rotational speed (for Newtonian fluids) and liquid height (for non-Newtonian fluids) as the key features, while 2D partial dependence analysis establishes quantitative optimization ranges. This ML approach provides an efficient predictive tool for gas-liquid stirred bioreactor design and optimization.展开更多
The limited activity of atomically-dispersed M-N-C electrocatalysts severely restricts their applicability in the oxygen reduction reaction(ORR)for proton exchange membrane fuel cells(PEMFC).Herein,we design and synth...The limited activity of atomically-dispersed M-N-C electrocatalysts severely restricts their applicability in the oxygen reduction reaction(ORR)for proton exchange membrane fuel cells(PEMFC).Herein,we design and synthesize Se-doped Fe-N-C hierarchical porous electrocatalyst(FeN_(4)/SeC_(2))by optimizing carbon structure and FeN_(4)coordination environment.The FeN_(4)/SeC_(2)electrocatalyst exhibits outstanding ORR activity in 0.1 mol L^(-1)HClO_(4),and the resulting PEMFC presents a peak power density of 1.20 W cm^(-2)in H_(2)-O_(2)condition at a back pressure of 200 kPa,ranking in the top levels among most reported non-precious metal catalyst-based fuel cells.The lower O_(2)transfer resistance of FeN_(4)/SeC_(2)-based membrane electrode assembly than FeN_(4)-based one means faster O_(2)transport in triple-phase boundary(TPB),and Density functional theory calculation further reveals that the synergistic catalysis between porous SeC_(2)and FeN_(4)-OH species can efficiently lower the energy barriers for the rate-determining step of the ORR.In short,the outstanding performance of FeN_(4)/SeC_(2)in PEMFC is ascribed to the Se-doping,which introduces more defects and larger mesoporosity and therefore facilitates ionomer infiltration and O_(2)transfer and charge transfer in TPB.The effective strategy of enhancing mass and charge transfers in TPB is anticipated to be applicable in the construction of highly efficient ORR electrocatalysts.展开更多
Production of green hydrogen through water electrolysis powered by renewable energy sources has garnered increasing attention as an attractive strategy for the storage of clean and sustainable energy.Among various ele...Production of green hydrogen through water electrolysis powered by renewable energy sources has garnered increasing attention as an attractive strategy for the storage of clean and sustainable energy.Among various electrolysis technologies,the emerging anion exchange membrane water electrolyser(AEMWE)exhibits the most potential for green hydrogen production,offering a potentially costeffective and sustainable approach that combines the advantages of high current density and fast start from proton exchange membrane water electrolyser(PEMWE)and low-cost catalyst from traditional alkaline water electrolyser(AWE)systems.Due to its relatively recent emergence over the past decade,a series of efforts are dedicated to improving the electrochemical reaction performance to accelerate the development and commercialization of AEMWE technology.A catalytic electrode comprising a gas diffusion layer(GDL)and a catalyst layer(CL)is usually called a gas diffusion electrode(GDE)that serves as a fundamental component within AEMWE,and also plays a core role in enhancing mass transfer during the electrolysis process.Inside the GDEs,bubbles nucleate and grow within the CL and then are transported through the GDL before eventually detaching to enter the electrolyte in the flow field.The transfer processes of water,gas bubbles,charges,and ions are intricately influenced by bubbles.This phenomenon is referred to as bubble-associated mass transfer.Like water management in fuel cells,effective bubble management is crucial in electrolysers,as its failure can result in various overpotential losses,such as activation losses,ohmic losses,and mass transfer losses,ultimately degrading the AEMWE performance.Despite significant advancements in the development of new materials and techniques in AEMWE,there is an urgent need for a comprehensive discussion focused on GDEs,with a particular emphasis on bubbleassociated mass transfer phenomena.This review aims to highlight recent findings regarding mass transfer in GDEs,particularly the impacts of bubble accumulation;and presents the latest advancements in designing CLs and GDLs to mitigate bubble-related issues.It is worth noting that a series of innovative bubble-free-GDE designs for water electrolysis are also emphasized in this review.This review is expected to be a valuable reference for gaining a deeper understanding of bubble-related mass transfer,especially the complex bubble behavior associated with GDEs,and for developing innovative practical strategies to advance AEMWE for green hydrogen production.展开更多
Improving the seepage of leaching solution in the ore body and strengthening the mass transfer process of rare earth ions during in-situ leaching are two critical methods to improve the leaching efficiency of rare ear...Improving the seepage of leaching solution in the ore body and strengthening the mass transfer process of rare earth ions during in-situ leaching are two critical methods to improve the leaching efficiency of rare earth.In this study,2 wt%MgSO_(4)solution was used for the indoor simulated column leaching experiment on rare earth samples and an electric field was applied at both ends of the samples.Then the effects of different intensities,initial application time and duration of the electric field on the rare earth leaching system and its mechanism were investigated.The results show that compared with the single MgSO_(4)solution leaching,applying an electric field with a strength of 6 V/cm can save the leaching time of 30 min and increase the flow velocity of the rare earth leachate by 26.98%.Under the optimal conditions of applying an electric field with a strength of 6 V/cm for 20 min to the leaching system after10 min of the rare earth leachate flowing out,the leaching efficiency of sample increases from 81.20% to 86.05% with the increase of 4.85%.The mechanism analysis shows that when a direct current electric field is applied to the rare earth leaching system,rare earth ions rapidly change from disorderly movement with the seepage into faster and directional movement.In addition,the seepage of the leaching solution is also improved due to the increase of the cross-sectional area of the seepage channel,the polarized water molecules migrate directionally by force from the negative pole,and the movement of the hydrogen is generated by the electrolytic water.More impo rtantly,based on the principle of in-situ leaching process,the layout of injection holes and deflector holes in this process provides a natural site for the electrode layout of the electric field.With the simple equipme nt and the ope ration,the rare earth leaching process with the applied electric field has high feasibility in industrial application.展开更多
Temperature-induced cracking during the construction of mass concrete is a significant concern.Numerical simulations of concrete temperature have primarily assumed that the concrete is placed in an open environment.Th...Temperature-induced cracking during the construction of mass concrete is a significant concern.Numerical simulations of concrete temperature have primarily assumed that the concrete is placed in an open environment.The problem of heat transfer between the air and concrete has been simplified to the concrete’s heat dissipation boundary.However,in the case of tubular concrete structures,where air inlet and outlet are relatively limited,the internal air temperature does not dissipate promptly to the external environment as it rises.To accurately simulate the temperature and creep stress in tubular concrete structures with enclosed air spaces during construction,we establish an air–concrete coupled heat transfer model according to the principles of conjugate heat transfer,and the accuracy of the model is verified through experiments.Furthermore,we conduct a case study to analyze the impact of airflow within the ship lock corridor on concrete temperature and creep stress.The results demonstrate that enhancing airflow within the corridor can significantly reduce the maximum concrete temperature.Compared with cases in which airflow within the corridor is neglected,the maximum concrete temperature and maximum tensile stress can be reduced by 12.5℃ and 0.7 MPa,respectively,under a wind speed of 4 m/s.The results of the traditional calculation method are relatively close to those obtained at a wind speed of 1 m/s.However,the temperature reduction process in the traditional method is faster,and the method yields greater tensile stress values for the corridor location.展开更多
The morphology characteristics of CH_(4),CO_(2),and CO_(2)+N_(2)hydrate film forming on the suspending gas bubbles are studied using microscopic visual method at supercooling conditions from 1.0 to 3.0 K.The hydrate f...The morphology characteristics of CH_(4),CO_(2),and CO_(2)+N_(2)hydrate film forming on the suspending gas bubbles are studied using microscopic visual method at supercooling conditions from 1.0 to 3.0 K.The hydrate film vertical growth rate and thickness along the planar gas-water interface are measured to study the hydrate formation kinetics and mass transfer process.Adding N_(2)in the gas mixture plays the same role as lowering the supercooling conditions,both retarding the crystal nucleation and growth rates,which results in larger single crystal size and rough hydrate morphology.N_(2)in the gas mixture helps to delay the secondary nucleation on the hydrate film,which is beneficial to maintain the porethroat structure and enhance the mass transfer.The vertical growth rate of hydrate film mainly depends on the supercooling conditions and gas compositions but has weak dependence on the experimental temperature and pressure.Under the same gas composition condition,the final film thickness shows a linear relationship with the supercooling conditions.The mass transfer coefficient of CH_(4)molecules in hydrates ranges from 4.54×10^(-8)to 7.54×10^(-8)mol·cm^(-2)·s^(-1)·MPa^(-1).The maximum mass transfer coefficient for CO_(2)t N_(2)hydrate occurs at the composition of 60%CO_(2)t 40%N_(2),which is 3.98×10^(-8)mol·cm^(-2)·s^(-1)·MPa^(-1).展开更多
Catalytic ozonation is an effective wastewater purification process.However,the low ozone mass transfer in packed bubble columns leads to low ozone utilization efficiency(OUE),poor organic degradation performance,and ...Catalytic ozonation is an effective wastewater purification process.However,the low ozone mass transfer in packed bubble columns leads to low ozone utilization efficiency(OUE),poor organic degradation performance,and high energy consumption.Therefore,there is an urgent need to develop efficient supported catalysts that can enhancemass transfer and performance.However,the reaction mechanism of the support on ozone mass transfer remains unclear,which hinders the development of catalytic ozonation applications.In this study,lava rocks(LR)-supported catalysts,specifically CuMn_(2)O_(4)@LR and MnO_(2)–Co_(3)O_(4)@LR,were proposed for catalytic ozonation of IBP degradation due to their superior catalytic activity,stability,and high OUE.Addition of CuMn_(2)O_(4)@LR or MnO_(2)–Co_(3)O_(4)@LR increased IBP removal efficiency from 85%to 91%or 88%,and reduced energy consumption from 2.86 to 2.14 kWh/m^(3)or 2.60 kWh/m^(3),respectively.This improvement was attributed to LRsupported catalysts enhancing mass transfer and promoting O3 decomposition to generate•OH and•O_(2)^(−),leading to IBP degradation.Furthermore,this study investigated the effects of ozone dose,supporter sizes,and catalyst components on ozone-liquid mass transfer.The results revealed that the size of the supporter influenced stacked porosity and consequently affected ozone mass transfer.Larger-sized LR(kLa=0.172 min^(−1))exhibited better mass transfer compared to smaller-sized supports.Based on these findings,it was concluded that both CuMn_(2)O_(4)@LR and MnO_(2)–Co_(3)O_(4)@LR are potential catalysts for catalytic ozonation in residual IBP degradation of pharmaceutical wastewater,and LR showed good credibility as a catalyst supporter.Understanding the effects of supporters and active components on ozone mass transfer provides a fundamental principle for designing supported catalysts in catalytic ozonation applications.展开更多
Attaining a decarbonized and sustainable energy system,which is the core solution to global energy issues,is accessible through the development of hydrogen energy.Proton-exchange membrane water electrolyzers(PEMWEs)ar...Attaining a decarbonized and sustainable energy system,which is the core solution to global energy issues,is accessible through the development of hydrogen energy.Proton-exchange membrane water electrolyzers(PEMWEs)are promising devices for hydrogen production,given their high efficiency,rapid responsiveness,and compactness.Bipolar plates account for a relatively high percentage of the total cost and weight compared with other components of PEMWEs.Thus,optimization of their design may accelerate the promotion of PEMWEs.This paper reviews the advances in materials and flow-field design for bipolar plates.First,the working conditions of proton-exchange membrane fuel cells(PEMFCs)and PEMWEs are compared,including reaction direction,operating temperature,pressure,input/output,and potential.Then,the current research status of bipolar-plate substrates and surface coatings is summarized,and some typical channel-rib flow fields and porous flow fields are presented.Furthermore,the effects of materials on mass and heat transfer and the possibility of reducing corrosion by improving the flow field structure are explored.Finally,this review discusses the potential directions of the development of bipolar-plate design,including material fabrication,flow-field geometry optimization using threedimensional printing,and surface-coating composition optimization based on computational materials science.展开更多
Thin-film composite(TFC)reverse osmosis(RO)membranes have attracted considerable attention in water treatment and desalination processes due to their specific separation advantages.Nevertheless,the trade-off effect be...Thin-film composite(TFC)reverse osmosis(RO)membranes have attracted considerable attention in water treatment and desalination processes due to their specific separation advantages.Nevertheless,the trade-off effect between water flux and salt rejection poses huge challenges to further improvement in TFC RO membrane performance.Numerous research works have been dedicated to optimizing membrane fabrication and modification for addressing this issue.In the meantime,several reviews summarized these approaches.However,the existing reviews seldom analyzed these methods from a theoretical perspective and thus failed to offer effective optimization directions for the RO process from the root cause.In this review,we first propose a mass transfer model to facilitate a better understanding of the entire process of how water and solute permeate through RO membranes in detail,namely the migration process outside the membrane,the dissolution process on the membrane surface,and the diffusion process within the membrane.Thereafter,the water and salt mass transfer behaviors obtained from model deduction are comprehensively analyzed to provide potential guidelines for alleviating the trade-off effect between water flux and salt rejection in the RO process.Finally,inspired by the theoretical analysis and the accurate identification of existing bottlenecks,several promising strategies for both regulating RO membranes and optimizing operational conditions are proposed to further exploit the potential of RO membrane performance.This review is expected to guide the development of high-performance RO membranes from a mass transfer theory standpoint.展开更多
In order to increase efficiency and avoid NH^(4+)-N pollution in the leaching process of weathered crust elution-deposited rare earth ores,the mass transfer in heap leaching with Al_(2)(SO_(4))_(3) solution was simula...In order to increase efficiency and avoid NH^(4+)-N pollution in the leaching process of weathered crust elution-deposited rare earth ores,the mass transfer in heap leaching with Al_(2)(SO_(4))_(3) solution was simulated with column elution and experimentally optimized.The results indicate that the leaching yield is also up to 99%for leaching with aluminum sulfate instead of ammonium sulfate.The optimal flow rate is 60 mL/h,the height equivalent to a theoretical plate(HETP)is 1.29 mm correspondingly.The peak value position of RE^(3+)is 60 mL/h,Fe^(3+)is 100 mL/h,however,Al^(3+)is 150 mL/h,and the heap leaching process has kinetic separation effect.展开更多
In-site soil flushing and aeration are the typical synergetic remediation technology for contaminated sites.The surfactant present in flushing solutions is bound to affect the aeration efficiency.The purpose of this s...In-site soil flushing and aeration are the typical synergetic remediation technology for contaminated sites.The surfactant present in flushing solutions is bound to affect the aeration efficiency.The purpose of this study is to evaluate the effect of surfactant frequently used in soil flushing on the oxygen mass transfer in micro-nano-bubble(MNB)aeration system.Firstly,bio-surfactants and chemical surfactants were used to investigate their effects on Sauter mean diameter of bubble(dBS),gas holdup(ε),volumetric mass-transfer coefficient(kLa)and liquid-side mass-transfer coefficient(kL)in the MNB aeration system.Then,based upon the experimental results,the Sardeing's and Frossling's models were modified to describe the effect of surfactant on kL in the MNB aeration.The results showed that,for the twenty aqueous surfactant solutions,with the increase in surfactant concentration,the value of dBS,kLa and kL decreased,while the value ofεand gas-liquid interfacial area(a)increased.These phenomena were mainly attributed to the synergistic effects of immobile bubble surface and the suppression of coalescence in the surfactant solutions.In addition,with the presence of electric charge,MNBs in anionic surfactant solutions were smaller and higher in number than in non-ionic surfactant solutions.Furthermore,the accumulation of surfactant on the gas-liquid interface was more conspicuous for small MNB,so the reduction of kL in anionic surfactant solutions was larger than that in non-ionic surfactant solutions.Besides,the modified Frossling's model predicted the effect of surfactant on kL in MNB aeration system with reasonable accuracy.展开更多
A comprehensive three-dimensional transient computational fluid dynamics(CFD)model was developed to ana-lyze the thermophysical phenomena in the arc wire additive manufacturing(WAAM)process.The model includes droplet ...A comprehensive three-dimensional transient computational fluid dynamics(CFD)model was developed to ana-lyze the thermophysical phenomena in the arc wire additive manufacturing(WAAM)process.The model includes droplet impact,gravity,heat and mass transfer,molten metal flow,and solid-liquid phase changes.By integrating the mass,energy,momentum,and volume of fluid(VOF)equations,a layer-by-layer additive process was suc-cessfully simulated.The accuracy of the model was validated by comparing the simulation results of single-pass single-layer weld beads at three welding positions with experimental data.The established model was utilized to quantitatively investigate the effects of three crucial welding process parameters-welding direction,droplet transfer frequency,and initial temperature-on the multi-layer cladding process.These findings suggest that the use of opposite welding directions in two adjacent layers can result in a well-distributed overall morphology of the weld bead.Moreover,the high initial droplet temperature enhanced the inclination of the weld bead mor-phology while decreasing the height of each layer.However,the high droplet transfer frequency caused both the height and width of the weld to increase.This research contributes to explaining the formation mechanism of the multi-layer cladding process and offers insights for improving weld bead morphology.This provides valuable theoretical guidance for the process optimization and control of arc additive manufacturing technology.展开更多
Though Zn-air batteries(ZABs)are one of the most promising system for energy storage and conversion,challenge still persists in its commercial application due to the sluggish kinetics of oxygen reduction/evolution rea...Though Zn-air batteries(ZABs)are one of the most promising system for energy storage and conversion,challenge still persists in its commercial application due to the sluggish kinetics of oxygen reduction/evolution reaction(ORR/OER).Hereby,a polyvinylidene fluoride(PVDF)-assisted pyrolysis strategy is proposed to develop a novel corrugated plate-like bifunctional electrocatalyst using two-dimensional zeolitic imidazolate frameworks(2D ZIF-67)as the precursor.The employed PVDF plays an important role in inheriting the original 2D structure of ZIF-67 and modulating the composition of the final products.As a result,a corrugated plate-like electrocatalyst,high-density Co nanoparticles decorated 2D Co,N,and F tri-doped carbon nanosheets,can be obtained.The acquired electrocatalyst enables efficient active sites and rapid mass transfer simultaneously,thus showing appreciable electrocatalytic performance for rechargeable Zn-air batteries.Undoubtedly,our proposed strategy offers a new perspective to the design of advanced oxygen electrocatalysts.展开更多
Turbulent fluidized bed possesses a distinct advantage over bubbling fluidized bed in high solids contact efficiency and thus exerts great potential in applications to many industrial processes.Simulation for fluidiza...Turbulent fluidized bed possesses a distinct advantage over bubbling fluidized bed in high solids contact efficiency and thus exerts great potential in applications to many industrial processes.Simulation for fluidization of fluid catalytic cracking(FCC)particles and the catalytic reaction of ozone decomposition in turbulent fluidized bed is conducted using the EulerianeEulerian approach,where the recently developed two-equation turbulent(TET)model is introduced to describe the turbulent mass diffusion.The energy minimization multi-scale(EMMS)drag model and the kinetic theory of granular flow(KTGF)are adopted to describe gaseparticles interaction and particleeparticle interaction respectively.The TET model features the rigorous closure for the turbulent mass transfer equations and thus enables more reliable simulation.With this model,distributions of ozone concentration and gaseparticles two-phase velocity as well as volume fraction are obtained and compared against experimental data.The average absolute relative deviation for the simulated ozone concentration is 9.67%which confirms the validity of the proposed model.Moreover,it is found that the transition velocity from bubbling fluidization to turbulent fluidization for FCC particles is about 0.5 m$se1 which is consistent with experimental observation.展开更多
The spiral-wound heat exchanger(SWHE) is the primary low-temperature heat exchanger for large-scale LNG plants due to its high-pressure resistance, compact structure, and high heat exchange efficiency. This paper stud...The spiral-wound heat exchanger(SWHE) is the primary low-temperature heat exchanger for large-scale LNG plants due to its high-pressure resistance, compact structure, and high heat exchange efficiency. This paper studied the shell-side heat and mass transfer characteristics of vapor-liquid two-phase mixed refrigerants in an SWHE by combining a multi-component model in FLUENT software with a customized multicomponent mass transfer model. Besides, the mathematical model under the sloshing condition was obtained through mathematical derivation, and the corresponding UDF code was loaded into FLUENT as the momentum source term. The results under the sloshing conditions were compared with the relevant parameters under the steady-state condition. The shell-side heat and mass transfer characteristics of the SWHE were investigated by adjusting the component ratio and other working conditions. It was found that the sloshing conditions enhance the heat transfer performance and sometimes have insignificant effects. The sloshing condition is beneficial to reduce the flow resistance. The comprehensive performance of multi-component refrigerants has been improved and the improvement is more significant under sloshing conditions, considering both the heat transfer and pressure drop.These results will provide theoretical support for the research and design of multi-component heat and mass transfer enhancement of LNG SWHE under ocean sloshing conditions.展开更多
In this work,a gas-solid two-phase gliding arc discharge(GS-GAD)reactor was built.Gliding arc was formed in the gap between the blade electrodes,and solid powder was deposited on the sieve plate positioned beneath the...In this work,a gas-solid two-phase gliding arc discharge(GS-GAD)reactor was built.Gliding arc was formed in the gap between the blade electrodes,and solid powder was deposited on the sieve plate positioned beneath the blade electrodes.A range of experimental parameters,including the inter-electrode spacing,gas flow rate,applied voltage,and the type of the powder,were systematically varied to elucidate the influence of solid powder matter on the dynamics of gliding arc discharge(GAD).The discharge images were captured by ICCD and digital camera to investigate the mass transfer characteristics of GS-GAD,and the electrical parameters,such as the effective values of voltage,current,and discharge power were record to reveal the discharge characteristics of GS-GAD.The results demonstrate that powder undergoes spontaneous movement towards the upper region of the gliding arc due to the influence of electric field force.Increasing the discharge voltage,decreasing relative dielectric constant of the powder and reducing the electrode-to-sieve-plate distance all contribute to a greater involvement of powder in the GAD process,subsequently resulting in an enhanced powder concentration within the GAD region.Additionally,powder located beneath the gliding arc experiences downward resistance caused by the opposing gas flow and arc.Excessive gas flow rate notably hampers the powder concentration within the discharge region,and the velocity of powder motion in the upper part of the GAD region is reduced.Under the condition of electrode-to-sieve-plate distance of 30 mm,gas flow rate of 1.5 L/min,and peak-to-peak voltage of 31 kV,the best combination of arc gliding and powder spark discharge phenomena can be achieved with the addition of Al_(2)O_(3) powder.展开更多
Fe-N-C catalysts are widely considered as promising non-precious-metal candidates for electrocatalytic oxygen reduction reaction(ORR),Yet despite their high catalytic activity through rational modulation,challenges re...Fe-N-C catalysts are widely considered as promising non-precious-metal candidates for electrocatalytic oxygen reduction reaction(ORR),Yet despite their high catalytic activity through rational modulation,challenges remain in their low site density and unsatisfactory mass transfer structure.Herein,we present a structural engineering approach employing a soft-template coating strategy to fabricate a hollow and hierarchically porous N-doped carbon framework anchored with atomically dispersed Fe sites(FeNCh) as an efficient ORR catalyst.The combination of hierarchical porosity and high exterior surface area is proven crucial for exposing more active sites,which gives rise to a remarkable ORR performance with a half-wave potential of 0.902 V in 0.1 m KOH and 0.814 V in 0.1 m HClO_(4),significantly outperforming its counterpart with solid structure and dominance of micropores(FeNC-s).The mass transfer property is revealed by in-situ electrochemical impedance spectroscopy(EIS) measurement.The distribution of relaxation time(DRT) analysis is further introduced to deconvolve the kinetic and mass transport processes,which demonstrates an alleviated mass transport resistance for FeNC-h,validating the effectiveness of structural engineering.This work not only provides an effective structural engineering approach but also contributes to the comprehensive mass transfer evaluation on advanced electrocatalyst for energy conversion applications.展开更多
基金supported by the National Key R&D Program of China(No.2022YFB4101300)National Natural Science Foundation of China(NSFC)(No.22278430 and 21878329)Project of R&D Department of CNPC(2020B-2011 and 21-CB-05-05).
文摘The dissolved hydrogen, rather than gaseous hydrogen, plays a crucial role in the hydrogenation process. A thorough understanding of hydrogen dissolution is essential for optimizing the hydrogenation process. In this paper, the dynamic pressure step method was modified to reduce the temperature difference between the hydrogen and solution, from which the hydrogen solubility and volumetric liquid-side mass transfer coefficient (k_(L)a) of the vacuum residue were obtained. It was discovered that temperature was the most critical factor in hydrogen dissolution, simultaneously enhancing both the hydrogen solubility and k_(L)a. Pressure played a significant role in promoting hydrogen solubility, but had a relatively small impact on kLa. Stirring speed, although it enhanced k_(L)a, did not affect hydrogen solubility. By normalizing the dissolution parameter, the results showed that the gas-liquid mass transfer rate decreased continuously during hydrogen dissolution and that the SD-tD curves after normalization were almost the same in all experimental conditions.
基金the National Natural Science Foundation of China(22208320)the Science and Technology Program of Henan Province(212102210044)The Henan Association for Science and Technology Youth Talent Support Program(2022HYTP026).
文摘Combining the advantages of high efficiency,low-pressure drop,and large throughput,the pore arrayenhanced tube-in-tube microchannel(PA-TMC) is a promising microreactor for industrial applications.However,most of the mass transfer takes place in the upstream pore region,while the contribution of the downstream annulus is limited.In this work,helical wires were introduced into the annulus by adhering to the outer surface of the inner tube.Mixing behavior and mass transfer of liquid-liquid twophase flow in PA-TMC with different helical wires have been systematically studied by a combination of experiments and volume of fluid(VOF) method.The introduction of helical wires improves the overall volumetric mass transfer coefficient KLa by up to 133% and the mass transfer efficiency E by up to 117%.The simulation results show that the helical wire brings extra phase mixing regions and increases the specific interface area,while accelerating the fluid flow and expanding the area of enhanced turbulent dissipation rate.Influences of helical wires in various configurations are compared by the comprehensive index I concerning the pressure drop and mass transfer performance simultaneously and a new correlation between KLa and specific energy consumption φ is proposed.This research deepens the understanding of the mixing behavior and mass transfer in the PA-TMCs and provides practical experience for the process intensification of microchannel reactors.
基金supported by the National Natural Science Foundation of China(12362032)the Key Research and Development Program of Gansu Province-Social Development(25YFGA072)+2 种基金Natural Science Foundation of Gansu Province(22JR5RA805)Key Research and Development and Transformation Program of Qinghai Province(2025-QY-217)Gansu Province University Industry Support Plan(2025CYZC-033).
文摘The engineering diseases caused by seasonal sulfate saline soil in Hexi region of Gansu Province seriously affect the local infrastructure construction and operation maintenance.To address this issue,this study explored the thermal mass transfer law,pore fluid phase transition,soil deformation and microstructure of unsaturated sulfate saline soil under the open system.Firstly,based on the theories of porous media mechanics and continuum mechanics,combined with the conservation equations of mass,energy and momentum and considering the phase transition of pore fluid,a multi-field coupled mathematical model of hydro-thermal-salt-gasmechanical for unsaturated sulfate saline soil was established.Secondly,basic unknown variables such as pore water pressure,concentration,temperature,porosity,and displacement were selected to perform numerical simulation analysis on the equation system by“Comsol Multiphysics”finite element method.Finally,a comparative analysis was conducted between the on-site measured data and the numerical simulation results.The results show that the water and salt phase transitions caused by temperature change could lead to soil salt heave and frost heave,alter the pore structure of the soil,and reduce the compactness of the soil,ultimately being reflected in the changes in soil porosity.The influence of external temperature on soil temperature gradually decreases with increasing depth,and the sensitivity of frozen areas to external temperature is much higher than that of unfrozen areas.This study not only enriches the theoretical results of thermal mass transfer law and deformation of unsaturated sulfate saline soil,but also provides practical guidance for the prevention and control of engineering diseases in local sulfate saline soil.
基金supported by the National Natural Science Foundation of China(22494713,22178160,22327809 and 22208141)Natural Science Foundation of Jiangsu Province,China(BK20220349).
文摘The structural and operational optimization of gas-liquid stirred bioreactors presents both complexity and critical importance for enhancing mass transfer performance. This study proposes a machine learning (ML)-driven approach to identify key features and predict the volumetric mass transfer coefficient (kLa). Four ML models were adopted and compared for kLa prediction in Newtonian and non-Newtonian fluids by evaluative indices, with CatBoost and XGBoost emerging as the optimal models, respectively. Specifically, it is demonstrated that Catboost has higher prediction accuracy (AARD = 18.84%) than empirical equations by effectively incorporating multidimensional features (structural, impeller, and operational), while simultaneously extending applicability to diverse Newtonian fluids. For non-Newtonian fluids, XGBoost outperforms empirical equations by effectively incorporating fluid rheological parameters (consistency coefficient, power-law index), thereby better capturing shear-thinning behavior. Feature importance analysis further identified rotational speed (for Newtonian fluids) and liquid height (for non-Newtonian fluids) as the key features, while 2D partial dependence analysis establishes quantitative optimization ranges. This ML approach provides an efficient predictive tool for gas-liquid stirred bioreactor design and optimization.
文摘The limited activity of atomically-dispersed M-N-C electrocatalysts severely restricts their applicability in the oxygen reduction reaction(ORR)for proton exchange membrane fuel cells(PEMFC).Herein,we design and synthesize Se-doped Fe-N-C hierarchical porous electrocatalyst(FeN_(4)/SeC_(2))by optimizing carbon structure and FeN_(4)coordination environment.The FeN_(4)/SeC_(2)electrocatalyst exhibits outstanding ORR activity in 0.1 mol L^(-1)HClO_(4),and the resulting PEMFC presents a peak power density of 1.20 W cm^(-2)in H_(2)-O_(2)condition at a back pressure of 200 kPa,ranking in the top levels among most reported non-precious metal catalyst-based fuel cells.The lower O_(2)transfer resistance of FeN_(4)/SeC_(2)-based membrane electrode assembly than FeN_(4)-based one means faster O_(2)transport in triple-phase boundary(TPB),and Density functional theory calculation further reveals that the synergistic catalysis between porous SeC_(2)and FeN_(4)-OH species can efficiently lower the energy barriers for the rate-determining step of the ORR.In short,the outstanding performance of FeN_(4)/SeC_(2)in PEMFC is ascribed to the Se-doping,which introduces more defects and larger mesoporosity and therefore facilitates ionomer infiltration and O_(2)transfer and charge transfer in TPB.The effective strategy of enhancing mass and charge transfers in TPB is anticipated to be applicable in the construction of highly efficient ORR electrocatalysts.
基金support from the National Natural Science Foundation of China(Grant No.52006029)the Promotion Foundation for Young Science and Technology Talents in Jilin Province(Grant No.QT202113)+2 种基金the Special Foundation of Industrial Innovation in Jilin Province(Grant No.2019C056-2)the Special Foundation for Outstanding Young Talents Training in Jilin(Grant No.20200104107)the UK EPSRC(EP/W03784X/1)。
文摘Production of green hydrogen through water electrolysis powered by renewable energy sources has garnered increasing attention as an attractive strategy for the storage of clean and sustainable energy.Among various electrolysis technologies,the emerging anion exchange membrane water electrolyser(AEMWE)exhibits the most potential for green hydrogen production,offering a potentially costeffective and sustainable approach that combines the advantages of high current density and fast start from proton exchange membrane water electrolyser(PEMWE)and low-cost catalyst from traditional alkaline water electrolyser(AWE)systems.Due to its relatively recent emergence over the past decade,a series of efforts are dedicated to improving the electrochemical reaction performance to accelerate the development and commercialization of AEMWE technology.A catalytic electrode comprising a gas diffusion layer(GDL)and a catalyst layer(CL)is usually called a gas diffusion electrode(GDE)that serves as a fundamental component within AEMWE,and also plays a core role in enhancing mass transfer during the electrolysis process.Inside the GDEs,bubbles nucleate and grow within the CL and then are transported through the GDL before eventually detaching to enter the electrolyte in the flow field.The transfer processes of water,gas bubbles,charges,and ions are intricately influenced by bubbles.This phenomenon is referred to as bubble-associated mass transfer.Like water management in fuel cells,effective bubble management is crucial in electrolysers,as its failure can result in various overpotential losses,such as activation losses,ohmic losses,and mass transfer losses,ultimately degrading the AEMWE performance.Despite significant advancements in the development of new materials and techniques in AEMWE,there is an urgent need for a comprehensive discussion focused on GDEs,with a particular emphasis on bubbleassociated mass transfer phenomena.This review aims to highlight recent findings regarding mass transfer in GDEs,particularly the impacts of bubble accumulation;and presents the latest advancements in designing CLs and GDLs to mitigate bubble-related issues.It is worth noting that a series of innovative bubble-free-GDE designs for water electrolysis are also emphasized in this review.This review is expected to be a valuable reference for gaining a deeper understanding of bubble-related mass transfer,especially the complex bubble behavior associated with GDEs,and for developing innovative practical strategies to advance AEMWE for green hydrogen production.
基金Projects supported by the National Key R&D Program of China(2020YFC1909000)Self-deployed Projects of Ganjiang Innovation Academy,Chinese Academy of Sciences(E055A001,E055A002)+1 种基金Key Research Programs of the Chinese Academy of Sciences(ZDRW-CN-2021-3)National Natural Science Foundation of China(52174113,51874148)。
文摘Improving the seepage of leaching solution in the ore body and strengthening the mass transfer process of rare earth ions during in-situ leaching are two critical methods to improve the leaching efficiency of rare earth.In this study,2 wt%MgSO_(4)solution was used for the indoor simulated column leaching experiment on rare earth samples and an electric field was applied at both ends of the samples.Then the effects of different intensities,initial application time and duration of the electric field on the rare earth leaching system and its mechanism were investigated.The results show that compared with the single MgSO_(4)solution leaching,applying an electric field with a strength of 6 V/cm can save the leaching time of 30 min and increase the flow velocity of the rare earth leachate by 26.98%.Under the optimal conditions of applying an electric field with a strength of 6 V/cm for 20 min to the leaching system after10 min of the rare earth leachate flowing out,the leaching efficiency of sample increases from 81.20% to 86.05% with the increase of 4.85%.The mechanism analysis shows that when a direct current electric field is applied to the rare earth leaching system,rare earth ions rapidly change from disorderly movement with the seepage into faster and directional movement.In addition,the seepage of the leaching solution is also improved due to the increase of the cross-sectional area of the seepage channel,the polarized water molecules migrate directionally by force from the negative pole,and the movement of the hydrogen is generated by the electrolytic water.More impo rtantly,based on the principle of in-situ leaching process,the layout of injection holes and deflector holes in this process provides a natural site for the electrode layout of the electric field.With the simple equipme nt and the ope ration,the rare earth leaching process with the applied electric field has high feasibility in industrial application.
基金This work was supported by Construction Simulation and Support Optimization of Hydraulic Tunnel Based on Bonded Block-Synthetic Rock Mass Method and Hubei Province Postdoctoral Innovative Practice Position.
文摘Temperature-induced cracking during the construction of mass concrete is a significant concern.Numerical simulations of concrete temperature have primarily assumed that the concrete is placed in an open environment.The problem of heat transfer between the air and concrete has been simplified to the concrete’s heat dissipation boundary.However,in the case of tubular concrete structures,where air inlet and outlet are relatively limited,the internal air temperature does not dissipate promptly to the external environment as it rises.To accurately simulate the temperature and creep stress in tubular concrete structures with enclosed air spaces during construction,we establish an air–concrete coupled heat transfer model according to the principles of conjugate heat transfer,and the accuracy of the model is verified through experiments.Furthermore,we conduct a case study to analyze the impact of airflow within the ship lock corridor on concrete temperature and creep stress.The results demonstrate that enhancing airflow within the corridor can significantly reduce the maximum concrete temperature.Compared with cases in which airflow within the corridor is neglected,the maximum concrete temperature and maximum tensile stress can be reduced by 12.5℃ and 0.7 MPa,respectively,under a wind speed of 4 m/s.The results of the traditional calculation method are relatively close to those obtained at a wind speed of 1 m/s.However,the temperature reduction process in the traditional method is faster,and the method yields greater tensile stress values for the corridor location.
基金financially supported by the National Natural Science Foundation of China(52106002,22378424)Natural Science Foundation of Hunan Province(2023JJ40026)+2 种基金Hunan Provincial Department of Education Scientific Research Project(22B0310)Natural Science Foundation of Guangdong Province(2021A1515010578,2020A1515110693)Shanghai Key Laboratory of Multiphase Materials Chemical Engineering(MMCE2023001).
文摘The morphology characteristics of CH_(4),CO_(2),and CO_(2)+N_(2)hydrate film forming on the suspending gas bubbles are studied using microscopic visual method at supercooling conditions from 1.0 to 3.0 K.The hydrate film vertical growth rate and thickness along the planar gas-water interface are measured to study the hydrate formation kinetics and mass transfer process.Adding N_(2)in the gas mixture plays the same role as lowering the supercooling conditions,both retarding the crystal nucleation and growth rates,which results in larger single crystal size and rough hydrate morphology.N_(2)in the gas mixture helps to delay the secondary nucleation on the hydrate film,which is beneficial to maintain the porethroat structure and enhance the mass transfer.The vertical growth rate of hydrate film mainly depends on the supercooling conditions and gas compositions but has weak dependence on the experimental temperature and pressure.Under the same gas composition condition,the final film thickness shows a linear relationship with the supercooling conditions.The mass transfer coefficient of CH_(4)molecules in hydrates ranges from 4.54×10^(-8)to 7.54×10^(-8)mol·cm^(-2)·s^(-1)·MPa^(-1).The maximum mass transfer coefficient for CO_(2)t N_(2)hydrate occurs at the composition of 60%CO_(2)t 40%N_(2),which is 3.98×10^(-8)mol·cm^(-2)·s^(-1)·MPa^(-1).
基金supported by the National Key Research and Development Program of China(No.2021YFE0100800)the National Natural Science Foundation of China(Nos.22076012,52100002,52200035,and 51878047)+4 种基金the Beijing Forestry University Outstanding Young Talent Cultivation Project(No.2019JQ03008)the Yangtze River Joint Research Phase II Program(Nos.2022-LHYJ-02-0510-02,and 2022-LHYJ-02-0502-02-06)the Open Project of State Key Laboratory of Urban Water Resources and Environment(No.HC202328)the Fundamental Research Funds for the Central Universities(No.BLX202153)the China Postdoctoral Science Foundation(No.2021M700448).
文摘Catalytic ozonation is an effective wastewater purification process.However,the low ozone mass transfer in packed bubble columns leads to low ozone utilization efficiency(OUE),poor organic degradation performance,and high energy consumption.Therefore,there is an urgent need to develop efficient supported catalysts that can enhancemass transfer and performance.However,the reaction mechanism of the support on ozone mass transfer remains unclear,which hinders the development of catalytic ozonation applications.In this study,lava rocks(LR)-supported catalysts,specifically CuMn_(2)O_(4)@LR and MnO_(2)–Co_(3)O_(4)@LR,were proposed for catalytic ozonation of IBP degradation due to their superior catalytic activity,stability,and high OUE.Addition of CuMn_(2)O_(4)@LR or MnO_(2)–Co_(3)O_(4)@LR increased IBP removal efficiency from 85%to 91%or 88%,and reduced energy consumption from 2.86 to 2.14 kWh/m^(3)or 2.60 kWh/m^(3),respectively.This improvement was attributed to LRsupported catalysts enhancing mass transfer and promoting O3 decomposition to generate•OH and•O_(2)^(−),leading to IBP degradation.Furthermore,this study investigated the effects of ozone dose,supporter sizes,and catalyst components on ozone-liquid mass transfer.The results revealed that the size of the supporter influenced stacked porosity and consequently affected ozone mass transfer.Larger-sized LR(kLa=0.172 min^(−1))exhibited better mass transfer compared to smaller-sized supports.Based on these findings,it was concluded that both CuMn_(2)O_(4)@LR and MnO_(2)–Co_(3)O_(4)@LR are potential catalysts for catalytic ozonation in residual IBP degradation of pharmaceutical wastewater,and LR showed good credibility as a catalyst supporter.Understanding the effects of supporters and active components on ozone mass transfer provides a fundamental principle for designing supported catalysts in catalytic ozonation applications.
基金the National Natural Science Foundation of China(No.52125102)the National Key Research and Development Program of China(No.2021YFB4000101)Fundamental Research Funds for t he Central Universities(No.FRF-TP-2021-02C2)。
文摘Attaining a decarbonized and sustainable energy system,which is the core solution to global energy issues,is accessible through the development of hydrogen energy.Proton-exchange membrane water electrolyzers(PEMWEs)are promising devices for hydrogen production,given their high efficiency,rapid responsiveness,and compactness.Bipolar plates account for a relatively high percentage of the total cost and weight compared with other components of PEMWEs.Thus,optimization of their design may accelerate the promotion of PEMWEs.This paper reviews the advances in materials and flow-field design for bipolar plates.First,the working conditions of proton-exchange membrane fuel cells(PEMFCs)and PEMWEs are compared,including reaction direction,operating temperature,pressure,input/output,and potential.Then,the current research status of bipolar-plate substrates and surface coatings is summarized,and some typical channel-rib flow fields and porous flow fields are presented.Furthermore,the effects of materials on mass and heat transfer and the possibility of reducing corrosion by improving the flow field structure are explored.Finally,this review discusses the potential directions of the development of bipolar-plate design,including material fabrication,flow-field geometry optimization using threedimensional printing,and surface-coating composition optimization based on computational materials science.
基金supported by the Natural Science Foundation of Sichuan Province(No.2022NSFSC1042)National Natural Science Foundation of China(No.52200051)+1 种基金Outstanding Youth Fund of Heilongjiang Natural Science Foundation(No.YQ2023E021)Open Project of State Key Laboratory of Urban Water Resource and Environment,Harbin Institute of Technology(No.HC202236).
文摘Thin-film composite(TFC)reverse osmosis(RO)membranes have attracted considerable attention in water treatment and desalination processes due to their specific separation advantages.Nevertheless,the trade-off effect between water flux and salt rejection poses huge challenges to further improvement in TFC RO membrane performance.Numerous research works have been dedicated to optimizing membrane fabrication and modification for addressing this issue.In the meantime,several reviews summarized these approaches.However,the existing reviews seldom analyzed these methods from a theoretical perspective and thus failed to offer effective optimization directions for the RO process from the root cause.In this review,we first propose a mass transfer model to facilitate a better understanding of the entire process of how water and solute permeate through RO membranes in detail,namely the migration process outside the membrane,the dissolution process on the membrane surface,and the diffusion process within the membrane.Thereafter,the water and salt mass transfer behaviors obtained from model deduction are comprehensively analyzed to provide potential guidelines for alleviating the trade-off effect between water flux and salt rejection in the RO process.Finally,inspired by the theoretical analysis and the accurate identification of existing bottlenecks,several promising strategies for both regulating RO membranes and optimizing operational conditions are proposed to further exploit the potential of RO membrane performance.This review is expected to guide the development of high-performance RO membranes from a mass transfer theory standpoint.
基金Project supported by the National Natural Science Foundation of China(51964021,51774156)China’s NationalKey R&D Plan Project(2019YFC060025000)。
文摘In order to increase efficiency and avoid NH^(4+)-N pollution in the leaching process of weathered crust elution-deposited rare earth ores,the mass transfer in heap leaching with Al_(2)(SO_(4))_(3) solution was simulated with column elution and experimentally optimized.The results indicate that the leaching yield is also up to 99%for leaching with aluminum sulfate instead of ammonium sulfate.The optimal flow rate is 60 mL/h,the height equivalent to a theoretical plate(HETP)is 1.29 mm correspondingly.The peak value position of RE^(3+)is 60 mL/h,Fe^(3+)is 100 mL/h,however,Al^(3+)is 150 mL/h,and the heap leaching process has kinetic separation effect.
基金financially supported by the National Natural Science Foundation of China(41877240)National Key Research and Development Program of China(2018YFC1802300)Scientific Research Foundation of Graduate School of Southeast University(YBPY2154).
文摘In-site soil flushing and aeration are the typical synergetic remediation technology for contaminated sites.The surfactant present in flushing solutions is bound to affect the aeration efficiency.The purpose of this study is to evaluate the effect of surfactant frequently used in soil flushing on the oxygen mass transfer in micro-nano-bubble(MNB)aeration system.Firstly,bio-surfactants and chemical surfactants were used to investigate their effects on Sauter mean diameter of bubble(dBS),gas holdup(ε),volumetric mass-transfer coefficient(kLa)and liquid-side mass-transfer coefficient(kL)in the MNB aeration system.Then,based upon the experimental results,the Sardeing's and Frossling's models were modified to describe the effect of surfactant on kL in the MNB aeration.The results showed that,for the twenty aqueous surfactant solutions,with the increase in surfactant concentration,the value of dBS,kLa and kL decreased,while the value ofεand gas-liquid interfacial area(a)increased.These phenomena were mainly attributed to the synergistic effects of immobile bubble surface and the suppression of coalescence in the surfactant solutions.In addition,with the presence of electric charge,MNBs in anionic surfactant solutions were smaller and higher in number than in non-ionic surfactant solutions.Furthermore,the accumulation of surfactant on the gas-liquid interface was more conspicuous for small MNB,so the reduction of kL in anionic surfactant solutions was larger than that in non-ionic surfactant solutions.Besides,the modified Frossling's model predicted the effect of surfactant on kL in MNB aeration system with reasonable accuracy.
基金supported by National Natural Science Foundation of China(Grant Nos.52076216,51706246).
文摘A comprehensive three-dimensional transient computational fluid dynamics(CFD)model was developed to ana-lyze the thermophysical phenomena in the arc wire additive manufacturing(WAAM)process.The model includes droplet impact,gravity,heat and mass transfer,molten metal flow,and solid-liquid phase changes.By integrating the mass,energy,momentum,and volume of fluid(VOF)equations,a layer-by-layer additive process was suc-cessfully simulated.The accuracy of the model was validated by comparing the simulation results of single-pass single-layer weld beads at three welding positions with experimental data.The established model was utilized to quantitatively investigate the effects of three crucial welding process parameters-welding direction,droplet transfer frequency,and initial temperature-on the multi-layer cladding process.These findings suggest that the use of opposite welding directions in two adjacent layers can result in a well-distributed overall morphology of the weld bead.Moreover,the high initial droplet temperature enhanced the inclination of the weld bead mor-phology while decreasing the height of each layer.However,the high droplet transfer frequency caused both the height and width of the weld to increase.This research contributes to explaining the formation mechanism of the multi-layer cladding process and offers insights for improving weld bead morphology.This provides valuable theoretical guidance for the process optimization and control of arc additive manufacturing technology.
基金supported by the National Natural Science Foundation of China (No.21908049,52274298,and 51974114)Hunan Provincial Natural Science Foundation of China (No.2022JJ40035,2020JJ4175,2024JJ4022,2023JJ30277)+2 种基金Science and Technology Talents Lifting Project of Hunan Province (No.2022TJ-N16)Open Fund of State Key Laboratory of Advanced Metallurgy,University of Science and Technology Beijing (K1:24-09)Postdoctoral Fellowship Program (No.GZC20233205)。
文摘Though Zn-air batteries(ZABs)are one of the most promising system for energy storage and conversion,challenge still persists in its commercial application due to the sluggish kinetics of oxygen reduction/evolution reaction(ORR/OER).Hereby,a polyvinylidene fluoride(PVDF)-assisted pyrolysis strategy is proposed to develop a novel corrugated plate-like bifunctional electrocatalyst using two-dimensional zeolitic imidazolate frameworks(2D ZIF-67)as the precursor.The employed PVDF plays an important role in inheriting the original 2D structure of ZIF-67 and modulating the composition of the final products.As a result,a corrugated plate-like electrocatalyst,high-density Co nanoparticles decorated 2D Co,N,and F tri-doped carbon nanosheets,can be obtained.The acquired electrocatalyst enables efficient active sites and rapid mass transfer simultaneously,thus showing appreciable electrocatalytic performance for rechargeable Zn-air batteries.Undoubtedly,our proposed strategy offers a new perspective to the design of advanced oxygen electrocatalysts.
基金financial support from the National Natural Science Foundation of China(22078230)the National Key Research and Development Program of China(2023YFB4103600)the State Key Laboratory of Heavy Oil Processing(SKLHOP202202008).
文摘Turbulent fluidized bed possesses a distinct advantage over bubbling fluidized bed in high solids contact efficiency and thus exerts great potential in applications to many industrial processes.Simulation for fluidization of fluid catalytic cracking(FCC)particles and the catalytic reaction of ozone decomposition in turbulent fluidized bed is conducted using the EulerianeEulerian approach,where the recently developed two-equation turbulent(TET)model is introduced to describe the turbulent mass diffusion.The energy minimization multi-scale(EMMS)drag model and the kinetic theory of granular flow(KTGF)are adopted to describe gaseparticles interaction and particleeparticle interaction respectively.The TET model features the rigorous closure for the turbulent mass transfer equations and thus enables more reliable simulation.With this model,distributions of ozone concentration and gaseparticles two-phase velocity as well as volume fraction are obtained and compared against experimental data.The average absolute relative deviation for the simulated ozone concentration is 9.67%which confirms the validity of the proposed model.Moreover,it is found that the transition velocity from bubbling fluidization to turbulent fluidization for FCC particles is about 0.5 m$se1 which is consistent with experimental observation.
基金funded by the National Natural Science Foundation of China(No.51806236,No.51806239)the Fundamental Research Funds for the Central Universities(No.2015XKMS059)+1 种基金Shaanxi Postdoctoral Fund Project(No.2018BSHEDZZ56)Foundation of Key Laboratory of Thermo-Fluid Science and Engineering(Xi'an Jiaotong University),Ministry of Education(No.KLTFSE2017KF01)。
文摘The spiral-wound heat exchanger(SWHE) is the primary low-temperature heat exchanger for large-scale LNG plants due to its high-pressure resistance, compact structure, and high heat exchange efficiency. This paper studied the shell-side heat and mass transfer characteristics of vapor-liquid two-phase mixed refrigerants in an SWHE by combining a multi-component model in FLUENT software with a customized multicomponent mass transfer model. Besides, the mathematical model under the sloshing condition was obtained through mathematical derivation, and the corresponding UDF code was loaded into FLUENT as the momentum source term. The results under the sloshing conditions were compared with the relevant parameters under the steady-state condition. The shell-side heat and mass transfer characteristics of the SWHE were investigated by adjusting the component ratio and other working conditions. It was found that the sloshing conditions enhance the heat transfer performance and sometimes have insignificant effects. The sloshing condition is beneficial to reduce the flow resistance. The comprehensive performance of multi-component refrigerants has been improved and the improvement is more significant under sloshing conditions, considering both the heat transfer and pressure drop.These results will provide theoretical support for the research and design of multi-component heat and mass transfer enhancement of LNG SWHE under ocean sloshing conditions.
基金supported by 173 Program of China,and National Natural Science Foundation of China(No.92271116).
文摘In this work,a gas-solid two-phase gliding arc discharge(GS-GAD)reactor was built.Gliding arc was formed in the gap between the blade electrodes,and solid powder was deposited on the sieve plate positioned beneath the blade electrodes.A range of experimental parameters,including the inter-electrode spacing,gas flow rate,applied voltage,and the type of the powder,were systematically varied to elucidate the influence of solid powder matter on the dynamics of gliding arc discharge(GAD).The discharge images were captured by ICCD and digital camera to investigate the mass transfer characteristics of GS-GAD,and the electrical parameters,such as the effective values of voltage,current,and discharge power were record to reveal the discharge characteristics of GS-GAD.The results demonstrate that powder undergoes spontaneous movement towards the upper region of the gliding arc due to the influence of electric field force.Increasing the discharge voltage,decreasing relative dielectric constant of the powder and reducing the electrode-to-sieve-plate distance all contribute to a greater involvement of powder in the GAD process,subsequently resulting in an enhanced powder concentration within the GAD region.Additionally,powder located beneath the gliding arc experiences downward resistance caused by the opposing gas flow and arc.Excessive gas flow rate notably hampers the powder concentration within the discharge region,and the velocity of powder motion in the upper part of the GAD region is reduced.Under the condition of electrode-to-sieve-plate distance of 30 mm,gas flow rate of 1.5 L/min,and peak-to-peak voltage of 31 kV,the best combination of arc gliding and powder spark discharge phenomena can be achieved with the addition of Al_(2)O_(3) powder.
基金National Natural Science Foundation of China (Nos. 22078242 and U20A20153)Applied Basic Research Program of Yunnan Province (Nos. 202101BE070001-032 and 202101BH070002)。
文摘Fe-N-C catalysts are widely considered as promising non-precious-metal candidates for electrocatalytic oxygen reduction reaction(ORR),Yet despite their high catalytic activity through rational modulation,challenges remain in their low site density and unsatisfactory mass transfer structure.Herein,we present a structural engineering approach employing a soft-template coating strategy to fabricate a hollow and hierarchically porous N-doped carbon framework anchored with atomically dispersed Fe sites(FeNCh) as an efficient ORR catalyst.The combination of hierarchical porosity and high exterior surface area is proven crucial for exposing more active sites,which gives rise to a remarkable ORR performance with a half-wave potential of 0.902 V in 0.1 m KOH and 0.814 V in 0.1 m HClO_(4),significantly outperforming its counterpart with solid structure and dominance of micropores(FeNC-s).The mass transfer property is revealed by in-situ electrochemical impedance spectroscopy(EIS) measurement.The distribution of relaxation time(DRT) analysis is further introduced to deconvolve the kinetic and mass transport processes,which demonstrates an alleviated mass transport resistance for FeNC-h,validating the effectiveness of structural engineering.This work not only provides an effective structural engineering approach but also contributes to the comprehensive mass transfer evaluation on advanced electrocatalyst for energy conversion applications.
