In this paper,self-designed multi-hollow needle electrodes are used as a high-voltage electrode in a packed bed dielectric barrier discharge reactor to facilitate fast gas flow through the active discharge area and ac...In this paper,self-designed multi-hollow needle electrodes are used as a high-voltage electrode in a packed bed dielectric barrier discharge reactor to facilitate fast gas flow through the active discharge area and achieve large-volume stable discharge.The dynamic characteristics of the plasma,the generated active species,and the energy transfer mechanisms in both positive discharge(PD)and negative discharge(ND)are investigated by using fast-exposure intensified charge coupled device(ICCD)images and time-resolved optical emission spectra.The experimental results show that the discharge intensity,number of discharge channels,and discharge volume are obviously enhanced when the multi-needle electrode is replaced by a multihollow needle electrode.During a single voltage pulse period,PD mainly develops in a streamer mode,which results in a stronger discharge current,luminous intensity,and E/N compared with the diffuse mode observed in ND.In PD,as the gap between dielectric beads changes from 0 to250μm,the discharge between the dielectric bead gap changes from a partial discharge to a standing filamentary micro-discharge,which allows the plasma to leave the local area and is conducive to the propagation of surface streamers.In ND,the discharge only appears as a diffusionlike mode between the gap of dielectric beads,regardless of whether there is a discharge gap.Moreover,the generation of excited states N_(2)^(+)(B^(2)∑_(u)^(+))and N2(C^(3)Π_(u))is mainly observed in PD,which is attributed to the higher E/N in PD than that in ND.However,the generation of the OH(A^(2)∑^(+))radical in ND is higher than in PD.It is not directly dominated by E/N,but mainly by the resonant energy transfer process between metastable N_(2)(A^(3)∑_(u)^(+))and OH(X^(2)Π).Furthermore,both PD and ND demonstrate obvious energy relaxation processes of electron-to-vibration and vibration-to-vibration,and no vibration-to-rotation energy relaxation process is observed.展开更多
This study is focused on the simulation and optimization of packed-bed solar thermal energy storage by using sand as a storage material and hot-water is used as a heat transfer fluid and storage as well.The analysis h...This study is focused on the simulation and optimization of packed-bed solar thermal energy storage by using sand as a storage material and hot-water is used as a heat transfer fluid and storage as well.The analysis has been done by using the COMSOL multi-physics software and used to compute an optimization charging time of the storage.Parameters that control this optimization are storage height,storage diameter,heat transfer fluid flow rate,and sand bed particle size.The result of COMSOL multi-physics optimized thermal storage has been validated with Taguchi method.Accordingly,the optimized parameters of storage are:storage height of 1.4m,storage diameter of 0.4 m,flow rate of 0.02 kg/s,and sand particle size 12 mm.Among these parameters,the storage diameter result is the highest influenced optimized parameter of the thermal storage fromthe ANOVA analysis.For nominal packed bed thermal storage,the charging time needed to attain about 520 K temperature is more than 3500 s,while it needs only about 2000 s for the optimized storage which is very significant difference.Average charging energy efficiency of the optimized is greater than the nominal and previous concrete-based storage by 13.7%,and 13.1%,respectively in the charging time of 2700 s.展开更多
Rotating packed bed(RPB) is one of the most effective gas–liquid mass transfer enhancement reactors, its effective specific mass transfer area(ae) is critical to understand the mass transfer process. By using the NaO...Rotating packed bed(RPB) is one of the most effective gas–liquid mass transfer enhancement reactors, its effective specific mass transfer area(ae) is critical to understand the mass transfer process. By using the NaOH–CO_(2) chemical absorption method, the aevalues of three RPB reactors with different rotor sizes were measured under different operation conditions. The results showed that the high gravity factor and liquid flow rate were major affecting factors, while the gas flow rate exhibited minor influence.The radius of packing is the dominant equipment factor to affect aevalue. The results indicated that the contact area depends on the dispersion of the liquid phase, thus the centrifugal force of rotating packed bed greatly influenced the aevalue. Moreover, the measured ae/ap(effective specific mass transfer area/specific surface area of packing) values were fitted with dimensionless correlation formulas. The unified correlation formula with dimensionless bed size parameter can well predict the experimental data and the prediction errors were within 15%.展开更多
Thermal Energy Storage is becoming a necessary component of sustainable energy production systems as it helps alleviate intrinsic limitations of Renewable Energy Sources, such as intermittent use and mismatch between ...Thermal Energy Storage is becoming a necessary component of sustainable energy production systems as it helps alleviate intrinsic limitations of Renewable Energy Sources, such as intermittent use and mismatch between power demand and supply. This paper discusses a packed bed thermocline tank as a thermal energy storage solution. Firstly, this paper presents the development of a numerical model calculating heat transfers within the tank, based on a discretization over several nodes and the nodal formulation of the heat balance equation. The model considers a filler material and a heat transferring fluid and uses the finite difference method to calculate the temperature evolution of the two media across the tank. The model was validated with two different packed bed systems from the literature during a discharging process, presenting a good fit with the experimental results. Secondly, the experimental packed bed is presented and characterized for a charging cycle from ambient temperature to approximately 180?C. The charging experiment was accurately reproduced with the numerical model requiring minimal computational time. Two additional charging modes were simulated with different inlet HTF conditions: constant temperature and varying temperature following the profile produced by a thermal solar collector field. The temperature profiles obtained from the three charging modes were analysed and compared to each other. The proposed numerical and experimental tools will be used in future studies for a better understanding of the design and operating conditions of packed bed thermal energy storage systems.展开更多
Methods and procedures of three-dimensional （3D） characterization of the pore structure features in the packed ore particle bed are focused. X-ray computed tomography was applied to deriving the cross-sectional imag...Methods and procedures of three-dimensional （3D） characterization of the pore structure features in the packed ore particle bed are focused. X-ray computed tomography was applied to deriving the cross-sectional images of specimens with single particle size of 1-2, 2-3, 3-4, 4-5, 5-6, 6-7, 7-8, 8-9, 9-10 ram. Based on the in-house developed 3D image analysis programs using Matlab, the volume porosity, pore size distribution and degree of connectivity were calculated and analyzed in detail. The results indicate that the volume porosity, the mean diameter of pores and the effective pore size （d50） increase with the increasing of particle size. Lognormal distribution or Gauss distribution is mostly suitable to model the pore size distribution. The degree of connectivity investigated on the basis of cluster-labeling algorithm also increases with increasing the particle size approximately.展开更多
The hot forging of large-scale P/M TiAl alloy billet deformation was investigated based on a joint application of Deform-3D-based numerical simulation and physical simulation techniques.The temperature dependence on t...The hot forging of large-scale P/M TiAl alloy billet deformation was investigated based on a joint application of Deform-3D-based numerical simulation and physical simulation techniques.The temperature dependence on the thermal and mechanical properties of the billet was considered and the optimum hot working temperature of packed TiAl alloy was 1150-1200 °C.Based on the simulation,the material flow and thermo mechanical field variables,such as stress,strain,and temperature distribution were obtained and the relationships of load—displacement and load—time were figured out.To verify the validity of the simulation results,the experiments were also carried out in a forging plant,and a pancake with diameter of 150 mm was obtained exhibiting a regular shape.展开更多
计算机网络发展初期阶段,许多研究机构、计算机厂商和公司都推出了自己的网络系统,然而它们之间没有兼容性可言,也无法相互通信。为了解决网络之间兼容性的问题,国际标准组织ISO(International Standard Organized)于1984提出了开放系...计算机网络发展初期阶段,许多研究机构、计算机厂商和公司都推出了自己的网络系统,然而它们之间没有兼容性可言,也无法相互通信。为了解决网络之间兼容性的问题,国际标准组织ISO(International Standard Organized)于1984提出了开放系统互边参考模型OSI/RM(Open System Interconnection/Reference Model),该模型很快成为了计算机网络体系结构中理论模型。展开更多
The performance of a rotating packed bed （RPter solutioB） with three kinds of packings was investigated using alcohol/wan under continuous distillation conditions at atmospheric pressure. The effects of average high...The performance of a rotating packed bed （RPter solutioB） with three kinds of packings was investigated using alcohol/wan under continuous distillation conditions at atmospheric pressure. The effects of average high gravity factor （β）, reflux ratio （R）, and feedstock flux （F） on mass-transfer in distillation were examined separately. Experimental results indicated that the total number of theoretical units （NTU） of RPB increased with β, R, and F.Of the three kinds of packings, the wave thread packing of stainless steel （Packing-Ⅲ）-had the best mass transfer efficiency with the height equivalent of a theoretical plate （HETP） of approximately 7.35 mm- 23.58 ram, whereas the corrugated disk pacing of stainless steel,（Packing Ⅰ） had the worst one with the HETP of about 13.4 mm-48.07 mm.Correlations were cleveloped to describe the mass transfer efficiency for packings Comparing.experimental data with the data calculated by correlation, the average deviate obtained for each packing was 0.72%, 1.98%, and 2.7%, respectively, implying that the accuracy of correlations developed was reasonable.展开更多
For an alcohol/water system and with fin baffle packing,continuous distillation experiments were carried out in a rotating packed bed(RPB)system at atmospheric pressure.The effects of the average high gravity factor(...For an alcohol/water system and with fin baffle packing,continuous distillation experiments were carried out in a rotating packed bed(RPB)system at atmospheric pressure.The effects of the average high gravity factor(β),liquid reflux ratio(R)and feedstock flux(F)on the momentum transfer and mass transfer were investigated. The gas phase pressure drop of RPB increased with the average high gravity factor,liquid reflux ratio and feedstock flux,which was 13.55-64.37 Pa atβof 2.01-51.49,R of 1.0-2.5,and F of 8-24 L·h1for a theoretical tray in the RPB with fin baffle packing.The investigation on the mass transfer in the RPB with different packings showed that the number of transfer units of RPB with a packing also increased with the average high gravity factor,reflux ratio and feedstock flux.It is found that the fin baffle packing(packing III)presents the best mass transfer performance and lowest pressure drop for the height equivalent to a theoretical plate(HETP),which is 6.59-9.84 mm.展开更多
Absorption of NOx into nitric acid solutions was studied in the presence of ozone by using a rotating packed bed(RPB) contactor.The influences of operating parameters,such as high gravity number,amount of ozone,gas ve...Absorption of NOx into nitric acid solutions was studied in the presence of ozone by using a rotating packed bed(RPB) contactor.The influences of operating parameters,such as high gravity number,amount of ozone,gas velocity,liquid spray density and inlet concentration of NOx,on the removal efficiency of NOx were investigated,among which the high gravity number and ozone amount are more important.Ozone was introduced to oxidize HNO2 to HNO3 to prevent the decomposition of HNO2 in the liquid phase.The high gravity number presents the effective external force for enhancing the mass transfer of ozone from gas phase to liquid phase.Under the experimental condition,the removal efficiency of NOx is higher than 90%and the concentration of nitric acid product exceeds 45%.展开更多
Absorption of SO2 from a SO2/air mixture with sodium citrate buffer solution was investigated using a rotating packed bed(RPB) in laboratory scale.The effects of operating parameters,such as the rotation speed of RPB,...Absorption of SO2 from a SO2/air mixture with sodium citrate buffer solution was investigated using a rotating packed bed(RPB) in laboratory scale.The effects of operating parameters,such as the rotation speed of RPB,liquid-gas ratio,inlet gas flow rate,inlet concentration of SO2 in flue gas,sodium citrate buffer concentration and initial pH of absorption solution,on the SO2 concentration in the absorption solution or removal efficiency of SO2 were examined.Incremental rate of sulfate radical ions in the absorption solution was also examined.Experimental results indicate that the efficiency of this regenerative process will be improved by using RPB under appropriate operating conditions,and the generation of SO2-4 will be restrained in the process in RPB.展开更多
A mass transfer model for devolatilization process of highly viscous media in rotating packed bed(RPB) was developed based on penetration theory and mass conservation.Before establishing the model,some mass transfer e...A mass transfer model for devolatilization process of highly viscous media in rotating packed bed(RPB) was developed based on penetration theory and mass conservation.Before establishing the model,some mass transfer experiments of thin film were conducted in a designed diffusion cell including vacuum and feeding system. In this study,acetone was used as the volatile organic compound(VOC) and syrup as the highly viscous media.The thickness of thin film was changed by using different liquid distributor.It was found that bubbling played an important role in the devolatilization.The correlation of diffusion coefficient of acetone in highly viscous dilute solution was proposed.The relative error between predicted and experimental data was within the range of ± 30% for diffusion coefficient of acetone in syrup.A comparison of experimental data of RPB with model indicated that the relative error was within ± 30% for efficiency of acetone removal.展开更多
The traditional fixed-bed reactor design is usually not suitable for the low tube-to-particle diameter ratios(N = D/d b 8) where the local phenomena of channeling near the wall and backflow in the bed are dominant. Th...The traditional fixed-bed reactor design is usually not suitable for the low tube-to-particle diameter ratios(N = D/d b 8) where the local phenomena of channeling near the wall and backflow in the bed are dominant. The recent"solid particle" meshing method is too complicated for mesh generation, especially for non-spherical particles in large random packed beds, which seriously hinders its development. In this work, a novel high-fidelity mesh model is proposed for simulation of fixed bed reactors by combining the immersed boundary and adaptive meshing methods. This method is suitable for different shapes of particles, which ingeniously avoids handling the complex "contact point" problem. Several packed beds with two different shapes of particles are investigated with this model, and the local flow in the bed is simulated without geometrical simplification. The predicted pressure drop across the fixed bed and heat transfer of the single particle are in good agreement with the corresponding empirical relations. Compared with spherical particles, the packed bed packing with pentaphyllous particles has lower pressure drop and better heat/mass transfer performance, and it shows that this method can be used for the screening of particle shapes in a fixed bed.展开更多
The removal of a volatile organic compound (VOC) from high viscous liquid was carried out in a rotat-ing packed bed (RPB) in this study. The mixed liquid of syrup and acetone was used as simulated high viscous polymer...The removal of a volatile organic compound (VOC) from high viscous liquid was carried out in a rotat-ing packed bed (RPB) in this study. The mixed liquid of syrup and acetone was used as simulated high viscous polymer solution with acetone as the volatile compound. The influence of the rotating speed of RPB, liquid viscos-ity, liquid flow rate, vacuum degree, and initial acetone content in the liquid on acetone removal efficiency was in-vestigated. The experimental results indicated that the removal efficiency increased with increasing rotating speed and initial acetone content in the viscous liquid and decreased with increasing liquid viscosity and flow rate. It was also observed that acetone removal efficiency increased with an increasing vacuum degree and reached 58% at a vacuum degree of 0.1 MPa. By the comparison with a flash tank devolatilizer, it was found that acetone removal ef-ficiency in RPB increased by about 67%.展开更多
A new type of reactor,featured with impinging stream-rotating packed bed（IS-RPB）and coil pipes,was designed and used to prepare p-hydroxybenzaldehyde（PHB）by hydrolysis from diazonium salts.The influence of operati...A new type of reactor,featured with impinging stream-rotating packed bed（IS-RPB）and coil pipes,was designed and used to prepare p-hydroxybenzaldehyde（PHB）by hydrolysis from diazonium salts.The influence of operating parameters,such as reaction temperature,reaction time and high gravity factor,on the yield of PHB was investigated.Compared with the traditional kettle-type reactor,the yield of PHB with the new reactor is increased significantly and the reaction time is much shorter.Under the optimum conditions,the yield of PHB is increased from 51%to 84.1%.The reactor offers an opportunity for replacing the traditional batch mode operation with a continuous process.展开更多
Rotating packing bed(RPB) has a better mixing performance than traditional mixers and shows potential application in the petroleum industry. However, acquisition of information about the mixing process directly throug...Rotating packing bed(RPB) has a better mixing performance than traditional mixers and shows potential application in the petroleum industry. However, acquisition of information about the mixing process directly through experiments is difficult because of the compact structure and complex multiphase flow pattern in RPB. To study the mixing characteristic, Fluent, the computational fluid dynamics(CFD) software, was used to explore the effect of airflow field on droplet diameter. For conducting calculations, the gas-liquid two-phase flow inside the packing was simulated with the RNG k-ε turbulence model and the Lagrange Discrete Phase Model(DPM), respectively. The numerical calculation results showed that coalescence and breakup of droplets can take place in the gas phase flow inside the packing and can be strengthened with increased rotating speed, thereby leading to the enlargement of the average diameter.展开更多
Owing to its high heat storage capacity and fast heat transfer rate,packed bed latent heat storage(LHS)is considered as a promising method to store thermal energy.In a packed bed,the wall effect can impact the packing...Owing to its high heat storage capacity and fast heat transfer rate,packed bed latent heat storage(LHS)is considered as a promising method to store thermal energy.In a packed bed,the wall effect can impact the packing arrangement of phase change material(PCM)capsules,inducing radial porosity oscillation.In this study,an actual-arrangement-based three-dimensional packed bed LHS model was built to consider the radial porosity oscillation.Its fluid flow and heat transfer were analyzed.With different cylindrical sub-surfaces intercepted along the radial direction in the packed bed,the corresponding relationships between the arrangement of capsules and porosity oscillation were identified.The oscillating distribution of radial porosity led to a non-uniform distribution of heat transfer fluid(HTF)velocity.As a result,radial temperature distributions and liquid fraction distributions of PCMs were further affected.The effects of different dimensionless parameters(e.g.,tube-to-capsule diameter ratio,Reynolds number,and Stefan number)on the radial characteristics of HTF and PCMs were discussed.The results showed that different diameter ratios correspond to different radial porosity distributions.Further,with an increase in diameter ratio,HTF velocity varies significantly in the near wall region while the non-uniformity of HTF velocity in the center region will decrease.The Reynolds and Stefan numbers slightly impact the relative velocity distribution of the HTF-while higher Reynolds numbers can lead to a proportional improvement of velocity,an increase in Stefan number can promote heat storage of the packed bed LHS system.展开更多
This study investigated catalytic decomposition and mass transfer of aqueous ozone promoted by Fe-MnCu/γ-Al_(2)O_(3)(Cat)in a rotating packed bed(RPB)for the first time.The results showed that the value of the overal...This study investigated catalytic decomposition and mass transfer of aqueous ozone promoted by Fe-MnCu/γ-Al_(2)O_(3)(Cat)in a rotating packed bed(RPB)for the first time.The results showed that the value of the overall decomposition rate constant of ozone(K_(c))and overall volumetric mass transfer coefficient(K_(L)a)are 4.28×10^(-3) s^(-1) and 11.60×10^(-3) s^(-1) respectively at an initial pH of 6,βof 40,Co3(g)of 60 mg·L^(-1)and Q_(L) of 85 L·h^(-1) in deionized water,respectively.Meanwhile,the K_(c) and K_(L)a values of Fenhe water are0.88×10^(-3) s^(-1) and 2.51×10^(-3) s^(-1) lower than deionized water,respectively.In addition,the K_(c) and K_(L)a values in deionized water for the Cat/O_(3)-RPB system are 44.86%and 47.41%higher than that for the Cat/O_(3)-BR(bubbling reactor)system,respectively,indicating that the high gravity technology can facilitate the decomposition and mass transfer of ozone in heterogeneous catalytic ozonation and provide some insights into the industrial wastewater.展开更多
基金supported by National Natural Science Foundations of China(Nos.51977023 and 52077026)the Fundamental Research Funds for the Central Universities(No.DUT23YG227)。
文摘In this paper,self-designed multi-hollow needle electrodes are used as a high-voltage electrode in a packed bed dielectric barrier discharge reactor to facilitate fast gas flow through the active discharge area and achieve large-volume stable discharge.The dynamic characteristics of the plasma,the generated active species,and the energy transfer mechanisms in both positive discharge(PD)and negative discharge(ND)are investigated by using fast-exposure intensified charge coupled device(ICCD)images and time-resolved optical emission spectra.The experimental results show that the discharge intensity,number of discharge channels,and discharge volume are obviously enhanced when the multi-needle electrode is replaced by a multihollow needle electrode.During a single voltage pulse period,PD mainly develops in a streamer mode,which results in a stronger discharge current,luminous intensity,and E/N compared with the diffuse mode observed in ND.In PD,as the gap between dielectric beads changes from 0 to250μm,the discharge between the dielectric bead gap changes from a partial discharge to a standing filamentary micro-discharge,which allows the plasma to leave the local area and is conducive to the propagation of surface streamers.In ND,the discharge only appears as a diffusionlike mode between the gap of dielectric beads,regardless of whether there is a discharge gap.Moreover,the generation of excited states N_(2)^(+)(B^(2)∑_(u)^(+))and N2(C^(3)Π_(u))is mainly observed in PD,which is attributed to the higher E/N in PD than that in ND.However,the generation of the OH(A^(2)∑^(+))radical in ND is higher than in PD.It is not directly dominated by E/N,but mainly by the resonant energy transfer process between metastable N_(2)(A^(3)∑_(u)^(+))and OH(X^(2)Π).Furthermore,both PD and ND demonstrate obvious energy relaxation processes of electron-to-vibration and vibration-to-vibration,and no vibration-to-rotation energy relaxation process is observed.
文摘This study is focused on the simulation and optimization of packed-bed solar thermal energy storage by using sand as a storage material and hot-water is used as a heat transfer fluid and storage as well.The analysis has been done by using the COMSOL multi-physics software and used to compute an optimization charging time of the storage.Parameters that control this optimization are storage height,storage diameter,heat transfer fluid flow rate,and sand bed particle size.The result of COMSOL multi-physics optimized thermal storage has been validated with Taguchi method.Accordingly,the optimized parameters of storage are:storage height of 1.4m,storage diameter of 0.4 m,flow rate of 0.02 kg/s,and sand particle size 12 mm.Among these parameters,the storage diameter result is the highest influenced optimized parameter of the thermal storage fromthe ANOVA analysis.For nominal packed bed thermal storage,the charging time needed to attain about 520 K temperature is more than 3500 s,while it needs only about 2000 s for the optimized storage which is very significant difference.Average charging energy efficiency of the optimized is greater than the nominal and previous concrete-based storage by 13.7%,and 13.1%,respectively in the charging time of 2700 s.
基金the support from the National Natural Science Foundation of China (22008157,21978178)。
文摘Rotating packed bed(RPB) is one of the most effective gas–liquid mass transfer enhancement reactors, its effective specific mass transfer area(ae) is critical to understand the mass transfer process. By using the NaOH–CO_(2) chemical absorption method, the aevalues of three RPB reactors with different rotor sizes were measured under different operation conditions. The results showed that the high gravity factor and liquid flow rate were major affecting factors, while the gas flow rate exhibited minor influence.The radius of packing is the dominant equipment factor to affect aevalue. The results indicated that the contact area depends on the dispersion of the liquid phase, thus the centrifugal force of rotating packed bed greatly influenced the aevalue. Moreover, the measured ae/ap(effective specific mass transfer area/specific surface area of packing) values were fitted with dimensionless correlation formulas. The unified correlation formula with dimensionless bed size parameter can well predict the experimental data and the prediction errors were within 15%.
文摘Thermal Energy Storage is becoming a necessary component of sustainable energy production systems as it helps alleviate intrinsic limitations of Renewable Energy Sources, such as intermittent use and mismatch between power demand and supply. This paper discusses a packed bed thermocline tank as a thermal energy storage solution. Firstly, this paper presents the development of a numerical model calculating heat transfers within the tank, based on a discretization over several nodes and the nodal formulation of the heat balance equation. The model considers a filler material and a heat transferring fluid and uses the finite difference method to calculate the temperature evolution of the two media across the tank. The model was validated with two different packed bed systems from the literature during a discharging process, presenting a good fit with the experimental results. Secondly, the experimental packed bed is presented and characterized for a charging cycle from ambient temperature to approximately 180?C. The charging experiment was accurately reproduced with the numerical model requiring minimal computational time. Two additional charging modes were simulated with different inlet HTF conditions: constant temperature and varying temperature following the profile produced by a thermal solar collector field. The temperature profiles obtained from the three charging modes were analysed and compared to each other. The proposed numerical and experimental tools will be used in future studies for a better understanding of the design and operating conditions of packed bed thermal energy storage systems.
基金Projects(50934002,51074013,51304076,51104100)supported by the National Natural Science Foundation of ChinaProject(IRT0950)supported by the Program for Changjiang Scholars Innovative Research Team in Universities,ChinaProject(2012M510007)supported by China Postdoctoral Science Foundation
文摘Methods and procedures of three-dimensional （3D） characterization of the pore structure features in the packed ore particle bed are focused. X-ray computed tomography was applied to deriving the cross-sectional images of specimens with single particle size of 1-2, 2-3, 3-4, 4-5, 5-6, 6-7, 7-8, 8-9, 9-10 ram. Based on the in-house developed 3D image analysis programs using Matlab, the volume porosity, pore size distribution and degree of connectivity were calculated and analyzed in detail. The results indicate that the volume porosity, the mean diameter of pores and the effective pore size （d50） increase with the increasing of particle size. Lognormal distribution or Gauss distribution is mostly suitable to model the pore size distribution. The degree of connectivity investigated on the basis of cluster-labeling algorithm also increases with increasing the particle size approximately.
基金Project (2011CB605505) supported by the National Basic Research Program of ChinaProject (2011QNZT041) supported by the freedom explore Program of Central South University,ChinaProject (84088) supported by the and Postdoctoral Foundation Supported Project of Central South University,China
文摘The hot forging of large-scale P/M TiAl alloy billet deformation was investigated based on a joint application of Deform-3D-based numerical simulation and physical simulation techniques.The temperature dependence on the thermal and mechanical properties of the billet was considered and the optimum hot working temperature of packed TiAl alloy was 1150-1200 °C.Based on the simulation,the material flow and thermo mechanical field variables,such as stress,strain,and temperature distribution were obtained and the relationships of load—displacement and load—time were figured out.To verify the validity of the simulation results,the experiments were also carried out in a forging plant,and a pancake with diameter of 150 mm was obtained exhibiting a regular shape.
文摘计算机网络发展初期阶段,许多研究机构、计算机厂商和公司都推出了自己的网络系统,然而它们之间没有兼容性可言,也无法相互通信。为了解决网络之间兼容性的问题,国际标准组织ISO(International Standard Organized)于1984提出了开放系统互边参考模型OSI/RM(Open System Interconnection/Reference Model),该模型很快成为了计算机网络体系结构中理论模型。
基金the Specialized Research Fund for the Doctoral Program of Higher Education of China(20060110003)
文摘The performance of a rotating packed bed （RPter solutioB） with three kinds of packings was investigated using alcohol/wan under continuous distillation conditions at atmospheric pressure. The effects of average high gravity factor （β）, reflux ratio （R）, and feedstock flux （F） on mass-transfer in distillation were examined separately. Experimental results indicated that the total number of theoretical units （NTU） of RPB increased with β, R, and F.Of the three kinds of packings, the wave thread packing of stainless steel （Packing-Ⅲ）-had the best mass transfer efficiency with the height equivalent of a theoretical plate （HETP） of approximately 7.35 mm- 23.58 ram, whereas the corrugated disk pacing of stainless steel,（Packing Ⅰ） had the worst one with the HETP of about 13.4 mm-48.07 mm.Correlations were cleveloped to describe the mass transfer efficiency for packings Comparing.experimental data with the data calculated by correlation, the average deviate obtained for each packing was 0.72%, 1.98%, and 2.7%, respectively, implying that the accuracy of correlations developed was reasonable.
基金Supported by the Specialized Research Fund for the Doctoral Program of Higher Education of China(20060110003)the Youth Science and Technology Research Fund of Shanxi Province(2008021009-1)the Development Project Fund for Colleges and Universities of Shanxi Province(20091127)
文摘For an alcohol/water system and with fin baffle packing,continuous distillation experiments were carried out in a rotating packed bed(RPB)system at atmospheric pressure.The effects of the average high gravity factor(β),liquid reflux ratio(R)and feedstock flux(F)on the momentum transfer and mass transfer were investigated. The gas phase pressure drop of RPB increased with the average high gravity factor,liquid reflux ratio and feedstock flux,which was 13.55-64.37 Pa atβof 2.01-51.49,R of 1.0-2.5,and F of 8-24 L·h1for a theoretical tray in the RPB with fin baffle packing.The investigation on the mass transfer in the RPB with different packings showed that the number of transfer units of RPB with a packing also increased with the average high gravity factor,reflux ratio and feedstock flux.It is found that the fin baffle packing(packing III)presents the best mass transfer performance and lowest pressure drop for the height equivalent to a theoretical plate(HETP),which is 6.59-9.84 mm.
基金Supported by the Fund of Science and Technology of Shanxi for Young Scholars(2007021012)Research Project of Shanxi Provincial Science and Technology Department(20090321113)
文摘Absorption of NOx into nitric acid solutions was studied in the presence of ozone by using a rotating packed bed(RPB) contactor.The influences of operating parameters,such as high gravity number,amount of ozone,gas velocity,liquid spray density and inlet concentration of NOx,on the removal efficiency of NOx were investigated,among which the high gravity number and ozone amount are more important.Ozone was introduced to oxidize HNO2 to HNO3 to prevent the decomposition of HNO2 in the liquid phase.The high gravity number presents the effective external force for enhancing the mass transfer of ozone from gas phase to liquid phase.Under the experimental condition,the removal efficiency of NOx is higher than 90%and the concentration of nitric acid product exceeds 45%.
基金Supported by the National Natural Science Foundation of China （20572128）
文摘Absorption of SO2 from a SO2/air mixture with sodium citrate buffer solution was investigated using a rotating packed bed(RPB) in laboratory scale.The effects of operating parameters,such as the rotation speed of RPB,liquid-gas ratio,inlet gas flow rate,inlet concentration of SO2 in flue gas,sodium citrate buffer concentration and initial pH of absorption solution,on the SO2 concentration in the absorption solution or removal efficiency of SO2 were examined.Incremental rate of sulfate radical ions in the absorption solution was also examined.Experimental results indicate that the efficiency of this regenerative process will be improved by using RPB under appropriate operating conditions,and the generation of SO2-4 will be restrained in the process in RPB.
基金Supported by the National Natural Science Foundation of China（20821004 20990221） the National High Technology Research and Development Program of China（2006AA030202）+1 种基金 the Program for New Century Excellent Talents in University of China（NCET-07-0053） the National Basic Research Program of China（2009CB219903）
文摘A mass transfer model for devolatilization process of highly viscous media in rotating packed bed(RPB) was developed based on penetration theory and mass conservation.Before establishing the model,some mass transfer experiments of thin film were conducted in a designed diffusion cell including vacuum and feeding system. In this study,acetone was used as the volatile organic compound(VOC) and syrup as the highly viscous media.The thickness of thin film was changed by using different liquid distributor.It was found that bubbling played an important role in the devolatilization.The correlation of diffusion coefficient of acetone in highly viscous dilute solution was proposed.The relative error between predicted and experimental data was within the range of ± 30% for diffusion coefficient of acetone in syrup.A comparison of experimental data of RPB with model indicated that the relative error was within ± 30% for efficiency of acetone removal.
基金Supported by the National Key Research and Development Program(2016YFB0301702)National Natural Science Foundation of China(21490584,21878298,91534105)+2 种基金Major National Scientific Instrument and Equipment Development Project(21427814)Key Research Program of Frontier Sciences of CAS(QYZDJ-SSW-JSC030)Jiangsu National Synergetic Innovation Center for Advanced Materials.
文摘The traditional fixed-bed reactor design is usually not suitable for the low tube-to-particle diameter ratios(N = D/d b 8) where the local phenomena of channeling near the wall and backflow in the bed are dominant. The recent"solid particle" meshing method is too complicated for mesh generation, especially for non-spherical particles in large random packed beds, which seriously hinders its development. In this work, a novel high-fidelity mesh model is proposed for simulation of fixed bed reactors by combining the immersed boundary and adaptive meshing methods. This method is suitable for different shapes of particles, which ingeniously avoids handling the complex "contact point" problem. Several packed beds with two different shapes of particles are investigated with this model, and the local flow in the bed is simulated without geometrical simplification. The predicted pressure drop across the fixed bed and heat transfer of the single particle are in good agreement with the corresponding empirical relations. Compared with spherical particles, the packed bed packing with pentaphyllous particles has lower pressure drop and better heat/mass transfer performance, and it shows that this method can be used for the screening of particle shapes in a fixed bed.
基金Supported by the National Natural Science Foundation of China (20821004)the National High Technology Research and Development Program of China (2006AA030202)the Program for New Century Excellent Talents in University of China(NCET-07-0053)
文摘The removal of a volatile organic compound (VOC) from high viscous liquid was carried out in a rotat-ing packed bed (RPB) in this study. The mixed liquid of syrup and acetone was used as simulated high viscous polymer solution with acetone as the volatile compound. The influence of the rotating speed of RPB, liquid viscos-ity, liquid flow rate, vacuum degree, and initial acetone content in the liquid on acetone removal efficiency was in-vestigated. The experimental results indicated that the removal efficiency increased with increasing rotating speed and initial acetone content in the viscous liquid and decreased with increasing liquid viscosity and flow rate. It was also observed that acetone removal efficiency increased with an increasing vacuum degree and reached 58% at a vacuum degree of 0.1 MPa. By the comparison with a flash tank devolatilizer, it was found that acetone removal ef-ficiency in RPB increased by about 67%.
基金Supported by the Science and Technology Key Projects of Shanxi Province(20090321113)
文摘A new type of reactor,featured with impinging stream-rotating packed bed（IS-RPB）and coil pipes,was designed and used to prepare p-hydroxybenzaldehyde（PHB）by hydrolysis from diazonium salts.The influence of operating parameters,such as reaction temperature,reaction time and high gravity factor,on the yield of PHB was investigated.Compared with the traditional kettle-type reactor,the yield of PHB with the new reactor is increased significantly and the reaction time is much shorter.Under the optimum conditions,the yield of PHB is increased from 51%to 84.1%.The reactor offers an opportunity for replacing the traditional batch mode operation with a continuous process.
基金financially supported by the Natural Science Foundations of China(No.21206153,21376229)the Excellent Youth Science and Technology Foundation of Province Shanxi of China(No.2014021007)+1 种基金the Natural Science Foundation of Shanxi Province(Grant No.2011021012,2012011008-2)the Program for the Outstanding Innovative Teams of Higher Learning Institutions of Shanxi(201316)
文摘Rotating packing bed(RPB) has a better mixing performance than traditional mixers and shows potential application in the petroleum industry. However, acquisition of information about the mixing process directly through experiments is difficult because of the compact structure and complex multiphase flow pattern in RPB. To study the mixing characteristic, Fluent, the computational fluid dynamics(CFD) software, was used to explore the effect of airflow field on droplet diameter. For conducting calculations, the gas-liquid two-phase flow inside the packing was simulated with the RNG k-ε turbulence model and the Lagrange Discrete Phase Model(DPM), respectively. The numerical calculation results showed that coalescence and breakup of droplets can take place in the gas phase flow inside the packing and can be strengthened with increased rotating speed, thereby leading to the enlargement of the average diameter.
基金This work is supported by the Foundation for Innovative Research Groups of the National Natural Science Foundation of China(51521004)the National Natural Science Foundation of China(51906150).
文摘Owing to its high heat storage capacity and fast heat transfer rate,packed bed latent heat storage(LHS)is considered as a promising method to store thermal energy.In a packed bed,the wall effect can impact the packing arrangement of phase change material(PCM)capsules,inducing radial porosity oscillation.In this study,an actual-arrangement-based three-dimensional packed bed LHS model was built to consider the radial porosity oscillation.Its fluid flow and heat transfer were analyzed.With different cylindrical sub-surfaces intercepted along the radial direction in the packed bed,the corresponding relationships between the arrangement of capsules and porosity oscillation were identified.The oscillating distribution of radial porosity led to a non-uniform distribution of heat transfer fluid(HTF)velocity.As a result,radial temperature distributions and liquid fraction distributions of PCMs were further affected.The effects of different dimensionless parameters(e.g.,tube-to-capsule diameter ratio,Reynolds number,and Stefan number)on the radial characteristics of HTF and PCMs were discussed.The results showed that different diameter ratios correspond to different radial porosity distributions.Further,with an increase in diameter ratio,HTF velocity varies significantly in the near wall region while the non-uniformity of HTF velocity in the center region will decrease.The Reynolds and Stefan numbers slightly impact the relative velocity distribution of the HTF-while higher Reynolds numbers can lead to a proportional improvement of velocity,an increase in Stefan number can promote heat storage of the packed bed LHS system.
基金supported by the Specialized Research Fund for Sanjin Scholars Program of Shanxi Province(201707)Key Research&Development Plan of Shanxi Province(201903D321059)+2 种基金Scientific Activities of Selected Returned Overseas Professionals in Shanxi Province(20200004)Transformation and Cultivation Projects of Scientific and Technological Achievements in Universities of Shanxi Province Institutions(2020CG040)the China National Key Project of Science and Technology “Major Science and Technology Program for Water Pollution Control and Treatment”(2018ZX07601001)。
文摘This study investigated catalytic decomposition and mass transfer of aqueous ozone promoted by Fe-MnCu/γ-Al_(2)O_(3)(Cat)in a rotating packed bed(RPB)for the first time.The results showed that the value of the overall decomposition rate constant of ozone(K_(c))and overall volumetric mass transfer coefficient(K_(L)a)are 4.28×10^(-3) s^(-1) and 11.60×10^(-3) s^(-1) respectively at an initial pH of 6,βof 40,Co3(g)of 60 mg·L^(-1)and Q_(L) of 85 L·h^(-1) in deionized water,respectively.Meanwhile,the K_(c) and K_(L)a values of Fenhe water are0.88×10^(-3) s^(-1) and 2.51×10^(-3) s^(-1) lower than deionized water,respectively.In addition,the K_(c) and K_(L)a values in deionized water for the Cat/O_(3)-RPB system are 44.86%and 47.41%higher than that for the Cat/O_(3)-BR(bubbling reactor)system,respectively,indicating that the high gravity technology can facilitate the decomposition and mass transfer of ozone in heterogeneous catalytic ozonation and provide some insights into the industrial wastewater.
