The agitated thin-film evaporator(ATFE)plays a crucial role in evaporation and concentration processes.The design of the scraper for processing high-viscosity non-Newtonian fluids in the ATFE is complex.The intricate ...The agitated thin-film evaporator(ATFE)plays a crucial role in evaporation and concentration processes.The design of the scraper for processing high-viscosity non-Newtonian fluids in the ATFE is complex.The intricate scraping action of the scraper introduces gas into the liquid film,leading to the formation of a gas ring along the wall.This process subsequently reduces wall heat flow,thereby affecting heat transfer.Computational fluid dynamics(CFD)is used to simulate the flow field of the non-Newtonian fluid in the ATFE.The investigation focuses on understanding the mechanism behind the formation of gas rings in the liquid film and proposes methods to prevent their formation.The results demonstrate a transition of the gas from a gas ring suspended in the liquid to a gas ring attached to the wall after entering the liquid film.The scraping action around the circumference of the scraper helps to expel gas rings,indicating the necessity of adjusting the scraper arrangement and increasing the frequency of scraping to enhance gas ring expulsion.The spiral motion of the bow wave serves as the source of gas entry into the liquid film.Therefore,the rotation speed can appropriately increase to reduce the size of the bow wave,thereby inhibiting the formation of the gas ring from the source.This research investigates the mechanism of gas ring generation and expulsion,offering theoretical guidance for processing high-viscosity non-Newtonian materials in the flow field of the ATFE.展开更多
This paper presents the heat transfer characteristics of A1203-water nanofluid in a coiled agitated vessel with propeller agitator. The experimental study was conducted using 0.10%, 0.20% and 0.30% volume concentra ti...This paper presents the heat transfer characteristics of A1203-water nanofluid in a coiled agitated vessel with propeller agitator. The experimental study was conducted using 0.10%, 0.20% and 0.30% volume concentra tion of A1203-water nanofluids. The results showed considerable enhancement of convective heat transfer using the nanofluids. The empirical correlations developed for Nusselt number in terms of Reynolds number, Prandtl number, viscosity ratio and volume concentration fit with the experimental data within ±10%. The heat transfer characteris tics were also simulated using computational fluid dynamics using FLUENT software with the standard ke model and multiple reference frame were adopted. The computational fluid dynamics （CFD） predicted Nusselt number agrees well with the experimental value and the discrepancy is found to be less than ＋8%.展开更多
The flow field of liquid phase (water) of agitated extraction columns is simulated with the help of computational fluid dynamics (CFD). Four kinds of Reynolds-averaged turbulence models, i.e. the standard k-ε model, ...The flow field of liquid phase (water) of agitated extraction columns is simulated with the help of computational fluid dynamics (CFD). Four kinds of Reynolds-averaged turbulence models, i.e. the standard k-ε model, the RNG (renormalization group) k-s model, the realizable k-ε model and the Reynolds stress model, are compared in detail in order to judge which is the best model in terms of the accuracy, less CPU time and memory required. The performance of the realizable k-s model is obviously improved by reducing the model constant from C2 = 1.90 to C2 = 1.61. It is concluded that the improved realizable k-e model is the optimal model.展开更多
The Issue of mixing efficiency in agitated tanks has drawn serious concern in many industrial processes. The turbulence model is very critical to predicting mixing process in agitated tanks. On the basis of computatio...The Issue of mixing efficiency in agitated tanks has drawn serious concern in many industrial processes. The turbulence model is very critical to predicting mixing process in agitated tanks. On the basis of computational fluid dynamics（CFD） software package Fluent 6.2, the mixing characteristics in a tank agitated by dual six-blade-Rushton-turbines（6-DT） are predicted using the detached eddy simulation（DES） method. A sliding mesh（SM） approach is adopted to solve the rotation of the impeller. The simulated flow patterns and liquid velocities in the agitated tank are verified by experimental data in the literature. The simulation results indicate that the DES method can obtain more flow details than Reynolds-averaged Navier-Stokes（RANS） model. Local and global mixing time in the agitated tank is predicted by solving a tracer concentration scalar transport equation. The simulated results show that feeding points have great influence on mixing process and mixing time. Mixing efficiency is the highest for the feeding point at location of midway of the two impellers. Two methods are used to determine global mixing time and get close result. Dimensionless global mixing time remains unchanged with increasing of impeller speed. Parallel, merging and diverging flow pattern form in the agitated tank, respectively, by changing the impeller spacing and clearance of lower impeller from the bottom of the tank. The global mixing time is the shortest for the merging flow, followed by diverging flow, and the longest for parallel flow. The research presents helpful references for design, optimization and scale-up of agitated tanks with multi-impeller.展开更多
Solid-liquid suspension in an agitated tank with a draft tube was investigated witha newly developed infrared turbidimeter for measuring solid concentration.The diameter of theflared inlet transition tube and the dist...Solid-liquid suspension in an agitated tank with a draft tube was investigated witha newly developed infrared turbidimeter for measuring solid concentration.The diameter of theflared inlet transition tube and the distance from the inlet to the tank bottom are two importantparameters for draft tube design The NAX-4 impeller,developed in this study,is characterized byits high flow efficiency and low power consumption.Some modifications are made to the Bald′smodel by considering the effects of solid concentration and fluid viscosity on the critical speed forcomplete off-bottom suspension.The modified equation fits the experimental data satisfactority andcan be used in scale-up展开更多
Gas–liquid flow and bubble coalescence and breakup behavior were studied in a top blown-rotary agitated reactor for steelmaking.Several important models of bubble coalescence and breakup mechanisms were considered an...Gas–liquid flow and bubble coalescence and breakup behavior were studied in a top blown-rotary agitated reactor for steelmaking.Several important models of bubble coalescence and breakup mechanisms were considered and compared,and water model experiment was carried out to verify and optimize the mathematical models.The influence of different operating parameters including paddle arrangement,stirring speed and top blowing flow rate on the bubble size and distribution was revealed.The results show that the predicted bubble size and distribution present a good agreement with the experimental results using the improved Luo–Laakkonen combination model.As the position of the stirring paddle moves from the center to the side wall,the bubble distribution in the reactor becomes more uniform,and the bubble size gradually decreases.With the increase in the paddle rotation speed,the bubble size decreases.However,this effect begins to weaken when the paddle rotation speed exceeds 150 r/min.Increasing the top blowing flow rate will increase the bubble size in the reactor,but it has a weak effect on bubble dispersion.When the top blowing rate exceeds 2.0 m^(3)/h,the bubble size in the bath is basically not less than 5 mm.展开更多
Characteristics of the liquid flow were studied in the impeller region for an unbaffied vessel agitated with an angularly oscillating impeller whose rotation proceeds while periodically reversing its direction at the ...Characteristics of the liquid flow were studied in the impeller region for an unbaffied vessel agitated with an angularly oscillating impeller whose rotation proceeds while periodically reversing its direction at the set angle, namely, rotating unsteadily with sinusoidal variation of the set amplitude. Measurement of the velocity of the liquid flow was performed, abreast of that of the torque of the shaft attached with the impeller. A disk turbine impeller with six flat blades was used in angular oscillation mode at the different amplitudes. The power characteristics were analyzed with the power number during one cycle of the angular oscillation consisting of a process for the impeller to stop and to reverse and that to rotate with a certain acceleration-deceleration in a uniform orientation. The power number in the process for the impeller to rotate exhibited slightly lower values compared with that of the identical design of impeller used in unidirectional rotation mode in a fully baffled vessel, being higher values in its process to stop and to reverse. Under such an operating condition in the amplitude, a time series of images was analyzed by particle tracking velocimetry （PTV） to characterize the fluctuation components of the velocities of the circumferential and radial flows inside the impeller rotational region. The impeller in its rotation process produced flows having a relatively large turbulence, independent of the amplitude condition. For the radial flow relating to the discharge flow, which contributes to transport of the turbulence throughout the vessel, operation at higher amplitude was clarified to be successful.展开更多
The aim of this paper is to study the effect of agitator’s types on the turbulent flows in stirred tanks without and with baffles.The hydrodynamics behavior induced by four different agitator’s types:a Rushton turbi...The aim of this paper is to study the effect of agitator’s types on the turbulent flows in stirred tanks without and with baffles.The hydrodynamics behavior induced by four different agitator’s types:a Rushton turbine(RT),a circular blade turbine(CBT),a diverging triangular blade turbine(DTBT)and converging triangular blade turbine(CTBT)are numerically predicted by solving the Navier-Stokes equations and RNGκ–εturbulent model.The simulations are carried out using the Multi Reference Frame(MRF)approach.The numerical results showed good agreement with experiment.We find that the agitator CTBT gives an important profit on the power consumption per report/ratio the others and DTBT give a good reduction of the vortex size of the impeller angles.展开更多
Pneumatically agitated slurry reactors,including bubble column reactors and airlift loop reactors(ALRs),are important gas-liquid-solid multiphase reactors.These reactors have been widely applied in many processes,espe...Pneumatically agitated slurry reactors,including bubble column reactors and airlift loop reactors(ALRs),are important gas-liquid-solid multiphase reactors.These reactors have been widely applied in many processes,especially in the biological fermentation and energy chemical industry,due to their low shear stress,good mixing,perfect mass-/heat-transfer properties,and relatively low costs.To further improve the performance of slurry reactors(i.e.,mixing and mass/heat transfer)and to satisfy industrial require-ments(e.g.,temperature control,reduction of back-mixing,and product separation),the process intensi-fication of slurry reactors is essential.This article starts by reviewing the latest advancements in the intensification of mixing and mass/heat transfer in these two types of reactors.It then summarizes process-intensification methods for mixing and separation that allow continuous production in these slurry reactors.Process-intensification technology that integrates directional flow in an ALR with simple solid-liquid separation in a hydrocyclone is recommended for its high efficiency and low costs.This arti-cle also systematically addresses vital considerations and challenges,including flow regime discrimina-tion,gas spargers,solid particle effects,and other concerns in slurry reactors.It introduces the progress of numerical simulation using computational fluid dynamics(CFD)for the rational design of slurry reactors and discusses difficulties in modeling.Finally,it presents conclusions and perspectives on the design of industrial slurry reactors.展开更多
1 INTRODUCTIONMany chemical engineering operations involve the mass and heat transfer between two liquidphases in reactions.Mechanically agitated liquid-liquid extractor can be one of the examples forsuch operations.I...1 INTRODUCTIONMany chemical engineering operations involve the mass and heat transfer between two liquidphases in reactions.Mechanically agitated liquid-liquid extractor can be one of the examples forsuch operations.It has been well developed and used in the nuclear energy,petrochemical andother chemical industries.However,not much attention has been paid to the gas agitated liquid-展开更多
1.Introduction The recent increase in life expectancy in China is also leading to an increased incidence of dementia.Dementia is a common,chronic,organic disease,which manifests extensive degenerative changes in the b...1.Introduction The recent increase in life expectancy in China is also leading to an increased incidence of dementia.Dementia is a common,chronic,organic disease,which manifests extensive degenerative changes in the brain.In addition to cognitive dysfunction,people with dementia often have additional mental and/or behavioral symptoms.展开更多
Objective: Intramuscular (IM) Benzodiazepines and/or Haloperidol alone or with benzodiazepines are frequently used to treat agitation. Based on emerging literature regarding Quetiapine used for the control of anxiety ...Objective: Intramuscular (IM) Benzodiazepines and/or Haloperidol alone or with benzodiazepines are frequently used to treat agitation. Based on emerging literature regarding Quetiapine used for the control of anxiety we examined Quetiapine as a possible alternative in selected cases. Methods: This study was a single-blind randomized study comparing Quetiapine PO (300 mg) with a combination of Haloperidol (5 mg), Benztropine mesylate (2 mg) and lorazepam (2 mg) administered IM to treat agitated patients seeking care in a busy psychiatric emergency setting. Male or female patients (18 - 60), deemed by the attending (admitting) psychiatrist to be indicative of agitated and/or aggressive behavior and had a Positive and Negative Syndrome Score-Excited Component (PANSS-EC), as evaluated by the Research Psychiatrist, and total score equal to or greater than 15. Patients deemed competent were randomized into one of the following treatment groups: Quetiapine 300 or Haloperidol 5 mg, benztropine mesylate, or lorazepam given by the IM route. Two scales, PANSS-EC and CGI-C were used to assess patients in the trial. The primary outcome measure PANSS-EC at 2 hours after administration of the medication. Results: Sixty-eight patients were included in the study. There were no significant treatment group differences in baseline condition. There was no significant difference between the two conditions. There was, however, a significant within-group decrease from baseline condition. Conclusion: Finding no significant differences suggests that in general the two treatments were equivalent. To sum up, Quetiapine 300 mg as a single dose appeared safe and effective in agitated patients treated in an ER. The results were similar to a comparison group receiving an intra-muscular combination of Haloperidol, Lorazepam and Benztropine. This study has significant limitations. The study was single blind and the use of a placebo would have strengthened the design but would be considered unethical. The sample size was relatively small and the group of patients who come to the ER may not be representative of the population of patients who visit across the country. And finally it was a select subgroup who made up the study population and who were probably less severely ill than other subjects who came to our ER.展开更多
Large quantities of <em>Rhizobium leguminosarum</em> by conventional technique are a time-consuming and labor-intensive method of production. The selection of different types of nutrient media for the prod...Large quantities of <em>Rhizobium leguminosarum</em> by conventional technique are a time-consuming and labor-intensive method of production. The selection of different types of nutrient media for the production of large amounts of rhizobium at low cost, determination of environmental regulators of culture medium and the effect of different levels of air flow into nutrition media have been investigated. <em>Rhizobium</em> cultured in modified air lift bioreactor as improved conventional system using Yeast Extract Mannitol Broth by assessing aeration and agitation in their submerged growth. For selection of suitable nutrient media for <em>Rhizobium </em>before mass production, YMA (Yeast Mannitol Agar), YSA (Yeast Sucrose Agar), YMA + bromthymol blue (BTB), YMA + Congo red (CR) medium was tested. To optimize the growing conditions of different temperatures, pH levels and salt strengths were investigated. Three air flow speeds at the rate of 0.01, 0.05 and 0.1 VVM for oxygen supply were ensured. A thick off-white bacterial colony was observed on the YMA plate among different culture media. Room temperature (25<span style="white-space:nowrap;"><span style="white-space:nowrap;">˚</span></span>C - 30<span style="white-space:nowrap;"><span style="white-space:nowrap;">˚</span></span>C), neutral pH (7.0), low salinity (1%) was observed to be suitable among the environmental conditions for <em>Rhizobium</em> mass production. The maximum density of <em>Rhizobium</em> was observed using air supply of 0.1 VVM level in bioreactor system. The result seemed that the air supply and agitation was an important growth factor in submerged cultivation. This study provides useful information on large scale production of <em>Rhizobium</em> of interest employing low cost effective modified air lift bioreactor within less time.展开更多
Employing the arc discharge method we prepared carbon nanotubes, CNTs, in open air deionized water. Their morphology was studied varying the annealing temperature and characterizing by Raman Spectroscopy, Transmission...Employing the arc discharge method we prepared carbon nanotubes, CNTs, in open air deionized water. Their morphology was studied varying the annealing temperature and characterizing by Raman Spectroscopy, Transmission Electron Microscopy (TEM), X-Ray Diffractogram (XRD) and Energy Dispersion X-Ray (EDX). According to the study, the CNTs are found self-assembled where the graphene sheets and/or defects are observed sort out themselves with enhancement of temperature.展开更多
Since the low seed filling speed of mechanical seed metering devices reduces the low qualified rate of seed spacing during high-speed practices,it is significant to design agitated seed metering devices with horizonta...Since the low seed filling speed of mechanical seed metering devices reduces the low qualified rate of seed spacing during high-speed practices,it is significant to design agitated seed metering devices with horizontal seed filling that are suitable for high-speed practices.The combination of horizontal seed filling and agitated seed filling can accelerate the seed filling of mechanical seed metering devices,and improve the qualified rate of seed spacing during high-speed practices.In this study,theoretical analysis,discrete element method-based simulation and indoor bench test verification were conducted to investigate how key parameters of the agitated seed metering device with horizontal seed filling(angles,installation position and number of agitating plates,diameters of convex spoons)would affect the characteristics of soybean seed movement,seed number and seeding performance(qualified index,multiple index,missing seeding index)under different working speeds.Computer-based simulation,test design and regression analysis were combined to analyze the population moving rules and optimize the design parameters of seed metering devices.Based on the test scheme as designed,simulations were conducted on Fluent EDEM,and the optimal angle of the agitating plates was determined by analyzing the population migrating rules.Regression equations were established through the regression of test results,and used to find out the optimal design parameters(diameter of convex spoon,positions and number of agitating plates)of seed metering devices.Then the optimal parameter combination among different working conditions was determined that the angle,position and number of agitating plates were 30°,24.4 mm,and 13,respectively,and the diameter of convex spoon was 11.0 mm.With the optimal parameter combination and at the seeding speed of 12 km/h,the qualified index,multiple index and missing seeding index were 93.1%,2.1%and 4.8%,respectively.Under high-speed practices,the new seed metering device was not significantly different from the pneumatic seed metering device,but significantly outperformed the mechanical seed metering device.展开更多
In this paper we report results from on-going theoretical and experimental studies carried out jointly at Imperial College London and University College London. Laser-induced fluorescence （LIF） is used to investigat...In this paper we report results from on-going theoretical and experimental studies carried out jointly at Imperial College London and University College London. Laser-induced fluorescence （LIF） is used to investigate liquid-liquid phase inversion experimentally and to observe in detail phenomena that accompany the inversion process, such as secondary dispersions and drop coalescence and breakup. Theoretically, a two-region model together with a criterion based on a dynamic balance between drop coalescence and breakup is employed to predict phase inversion. The concept of a radial distribution function for hard spheres was also utilized in order to better model the interaction of drops at high dispersed phase holdup, The modeling work is capable of predicting the existence of ambivalent ranges which are in good agreement with experimental observations.展开更多
To develop a suitable production process for fiber reinforced investment casting shell mold,three methods were studied:the traditional method(M_(1)),the method of adding fiber into silica sol with mechanical stirring ...To develop a suitable production process for fiber reinforced investment casting shell mold,three methods were studied:the traditional method(M_(1)),the method of adding fiber into silica sol with mechanical stirring and ultrasonic agitation(M_(2)),and the method of adding fiber into slurry with mechanical stirring and ultrasonic agitation for durations of 3,15,30,and 45 min(M_(3)).The bending strength,high-temperature self-load deformation,and thermal conductivity of the shell molds were investigated.The results reveal that the enhancement of fiber dispersion through ultrasonic agitation improves the comprehensive performance of the shell molds.The maximum green bending strength of the shell mold by M_(2) reaches 3.29 MPa,which is 29% higher than that of the shell mold prepared by M_(1).Moreover,the high-temperature self-load deformation of the shell mold is reduced from 0.62% to 0.44%.In addition,simultaneous ultrasonic agitation and mechanical stirring effectively shorten the slurry preparation time while maintaining comparable levels of fiber dispersion.With the process M_(3)-45 min,the fillers are uniformly dispersed in the slurry,and the fired bending strength and the high-temperature self-load deformation reach 6.25 MPa and 0.41%,respectively.Therefore,the proposed ultrasonic agitation route is promising for the fabrication of fiber-reinforced shell molds with excellent fibers dispersion.展开更多
Agitation is a neuropsychiatric syndrome characterized by excessive motor and/or verbal behaviors,with or without aggressive behaviors.The prevalence of agitation in Alzheimer’s disease varies from 5%to over 50%.Mult...Agitation is a neuropsychiatric syndrome characterized by excessive motor and/or verbal behaviors,with or without aggressive behaviors.The prevalence of agitation in Alzheimer’s disease varies from 5%to over 50%.Multiple factors have been implicated in its pathophysiology,including disease stage,comorbidity with other symptoms(e.g.,psychosis,anxiety/depression),and psychosocial factors.Ruling out delirium and identifying environmental triggers are fundamental steps in the management of agitation in Alzheimer’s disease.For establishing an effective therapeutic plan,it is important to define duration,severity,and potential for harm.While non-pharmacological approaches are considered the first line of intervention,pharmacological agents are frequently used in the treatment of agitation.Antipsychotics are commonly used in acute agitation.For chronic agitation,serotonin-selective reuptake inhibitors,especially citalopram and escitalopram,are often preferred due to safety concerns associated with the longterm use of antipsychotics.Promising novel strategies,such as new compounds and neuromodulation,are likely to be incorporated into agitation therapeutics in the next few years.展开更多
Unintended dural tear(DT)is not an infrequent complication of biportal percutaneous endoscopic spinal surgery(BESS).DT manifests in neurological deficits,including seizure,headache,and intracranial hemorrhage.Meanwhil...Unintended dural tear(DT)is not an infrequent complication of biportal percutaneous endoscopic spinal surgery(BESS).DT manifests in neurological deficits,including seizure,headache,and intracranial hemorrhage.Meanwhile,DT may be a risk of emergence agitation(EA)after BESS,which has not yet been reported.We presented a case of a 55-year-old man with L5-S1 intervertebral disc herniation receiving BESS under general anesthesia.A DT about 3-4 mm occurred during the operation,and was repaired immediately.The patient presented EA shouting for a headache after the surgery in post anesthesia care unit(PACU).Sedative agents(midazolam,propofol and dexmedetomidine)were used,only continuously infusion of dexmedetomidine for about 4 h successfully improved EA in PACU.He had no neurologic deficits in following 3 months.This case report highlights the risk of EA when a DT occurs during BESS.Adequate sedation in early phase is critical to resolve the mass effect caused by EA.展开更多
基金National Natural Science Foundation of China(No.51905089)Fundamental Research Funds for the Central Universities,China(No.2232020D-31)。
文摘The agitated thin-film evaporator(ATFE)plays a crucial role in evaporation and concentration processes.The design of the scraper for processing high-viscosity non-Newtonian fluids in the ATFE is complex.The intricate scraping action of the scraper introduces gas into the liquid film,leading to the formation of a gas ring along the wall.This process subsequently reduces wall heat flow,thereby affecting heat transfer.Computational fluid dynamics(CFD)is used to simulate the flow field of the non-Newtonian fluid in the ATFE.The investigation focuses on understanding the mechanism behind the formation of gas rings in the liquid film and proposes methods to prevent their formation.The results demonstrate a transition of the gas from a gas ring suspended in the liquid to a gas ring attached to the wall after entering the liquid film.The scraping action around the circumference of the scraper helps to expel gas rings,indicating the necessity of adjusting the scraper arrangement and increasing the frequency of scraping to enhance gas ring expulsion.The spiral motion of the bow wave serves as the source of gas entry into the liquid film.Therefore,the rotation speed can appropriately increase to reduce the size of the bow wave,thereby inhibiting the formation of the gas ring from the source.This research investigates the mechanism of gas ring generation and expulsion,offering theoretical guidance for processing high-viscosity non-Newtonian materials in the flow field of the ATFE.
文摘This paper presents the heat transfer characteristics of A1203-water nanofluid in a coiled agitated vessel with propeller agitator. The experimental study was conducted using 0.10%, 0.20% and 0.30% volume concentra tion of A1203-water nanofluids. The results showed considerable enhancement of convective heat transfer using the nanofluids. The empirical correlations developed for Nusselt number in terms of Reynolds number, Prandtl number, viscosity ratio and volume concentration fit with the experimental data within ±10%. The heat transfer characteris tics were also simulated using computational fluid dynamics using FLUENT software with the standard ke model and multiple reference frame were adopted. The computational fluid dynamics （CFD） predicted Nusselt number agrees well with the experimental value and the discrepancy is found to be less than ＋8%.
文摘The flow field of liquid phase (water) of agitated extraction columns is simulated with the help of computational fluid dynamics (CFD). Four kinds of Reynolds-averaged turbulence models, i.e. the standard k-ε model, the RNG (renormalization group) k-s model, the realizable k-ε model and the Reynolds stress model, are compared in detail in order to judge which is the best model in terms of the accuracy, less CPU time and memory required. The performance of the realizable k-s model is obviously improved by reducing the model constant from C2 = 1.90 to C2 = 1.61. It is concluded that the improved realizable k-e model is the optimal model.
基金Supported by Key Scientific Research Project of Sichuan Provincial Education Department(Grant No.15ZA0107)Doctor Foundation of Southwest University of Science and Technology(Grant No.11zx7162)
文摘The Issue of mixing efficiency in agitated tanks has drawn serious concern in many industrial processes. The turbulence model is very critical to predicting mixing process in agitated tanks. On the basis of computational fluid dynamics（CFD） software package Fluent 6.2, the mixing characteristics in a tank agitated by dual six-blade-Rushton-turbines（6-DT） are predicted using the detached eddy simulation（DES） method. A sliding mesh（SM） approach is adopted to solve the rotation of the impeller. The simulated flow patterns and liquid velocities in the agitated tank are verified by experimental data in the literature. The simulation results indicate that the DES method can obtain more flow details than Reynolds-averaged Navier-Stokes（RANS） model. Local and global mixing time in the agitated tank is predicted by solving a tracer concentration scalar transport equation. The simulated results show that feeding points have great influence on mixing process and mixing time. Mixing efficiency is the highest for the feeding point at location of midway of the two impellers. Two methods are used to determine global mixing time and get close result. Dimensionless global mixing time remains unchanged with increasing of impeller speed. Parallel, merging and diverging flow pattern form in the agitated tank, respectively, by changing the impeller spacing and clearance of lower impeller from the bottom of the tank. The global mixing time is the shortest for the merging flow, followed by diverging flow, and the longest for parallel flow. The research presents helpful references for design, optimization and scale-up of agitated tanks with multi-impeller.
文摘Solid-liquid suspension in an agitated tank with a draft tube was investigated witha newly developed infrared turbidimeter for measuring solid concentration.The diameter of theflared inlet transition tube and the distance from the inlet to the tank bottom are two importantparameters for draft tube design The NAX-4 impeller,developed in this study,is characterized byits high flow efficiency and low power consumption.Some modifications are made to the Bald′smodel by considering the effects of solid concentration and fluid viscosity on the critical speed forcomplete off-bottom suspension.The modified equation fits the experimental data satisfactority andcan be used in scale-up
基金The authors wish to express thanks to the National Natural Science Foundation of China(51604147 and 51774178)for supporting this work.
文摘Gas–liquid flow and bubble coalescence and breakup behavior were studied in a top blown-rotary agitated reactor for steelmaking.Several important models of bubble coalescence and breakup mechanisms were considered and compared,and water model experiment was carried out to verify and optimize the mathematical models.The influence of different operating parameters including paddle arrangement,stirring speed and top blowing flow rate on the bubble size and distribution was revealed.The results show that the predicted bubble size and distribution present a good agreement with the experimental results using the improved Luo–Laakkonen combination model.As the position of the stirring paddle moves from the center to the side wall,the bubble distribution in the reactor becomes more uniform,and the bubble size gradually decreases.With the increase in the paddle rotation speed,the bubble size decreases.However,this effect begins to weaken when the paddle rotation speed exceeds 150 r/min.Increasing the top blowing flow rate will increase the bubble size in the reactor,but it has a weak effect on bubble dispersion.When the top blowing rate exceeds 2.0 m^(3)/h,the bubble size in the bath is basically not less than 5 mm.
文摘Characteristics of the liquid flow were studied in the impeller region for an unbaffied vessel agitated with an angularly oscillating impeller whose rotation proceeds while periodically reversing its direction at the set angle, namely, rotating unsteadily with sinusoidal variation of the set amplitude. Measurement of the velocity of the liquid flow was performed, abreast of that of the torque of the shaft attached with the impeller. A disk turbine impeller with six flat blades was used in angular oscillation mode at the different amplitudes. The power characteristics were analyzed with the power number during one cycle of the angular oscillation consisting of a process for the impeller to stop and to reverse and that to rotate with a certain acceleration-deceleration in a uniform orientation. The power number in the process for the impeller to rotate exhibited slightly lower values compared with that of the identical design of impeller used in unidirectional rotation mode in a fully baffled vessel, being higher values in its process to stop and to reverse. Under such an operating condition in the amplitude, a time series of images was analyzed by particle tracking velocimetry （PTV） to characterize the fluctuation components of the velocities of the circumferential and radial flows inside the impeller rotational region. The impeller in its rotation process produced flows having a relatively large turbulence, independent of the amplitude condition. For the radial flow relating to the discharge flow, which contributes to transport of the turbulence throughout the vessel, operation at higher amplitude was clarified to be successful.
文摘The aim of this paper is to study the effect of agitator’s types on the turbulent flows in stirred tanks without and with baffles.The hydrodynamics behavior induced by four different agitator’s types:a Rushton turbine(RT),a circular blade turbine(CBT),a diverging triangular blade turbine(DTBT)and converging triangular blade turbine(CTBT)are numerically predicted by solving the Navier-Stokes equations and RNGκ–εturbulent model.The simulations are carried out using the Multi Reference Frame(MRF)approach.The numerical results showed good agreement with experiment.We find that the agitator CTBT gives an important profit on the power consumption per report/ratio the others and DTBT give a good reduction of the vortex size of the impeller angles.
基金supported by the National Key Research and Development Program of China(2016YFB0301701)the National Natural Science Foundation of China(21808234,21878318,and 21938009)+3 种基金the DNL Cooperation Fund,Chinese Academy of Sciences(CAS)(DNL201902)the Strategic Priority Research Program of the CAS(XDA21060400)the QIBEBT and Dalian National Laboratory for Clean Energy of the CAS(QIBEBT ZZBS201803 and QIBEBT I201907)the CAS Key Technology Talent Program.
文摘Pneumatically agitated slurry reactors,including bubble column reactors and airlift loop reactors(ALRs),are important gas-liquid-solid multiphase reactors.These reactors have been widely applied in many processes,especially in the biological fermentation and energy chemical industry,due to their low shear stress,good mixing,perfect mass-/heat-transfer properties,and relatively low costs.To further improve the performance of slurry reactors(i.e.,mixing and mass/heat transfer)and to satisfy industrial require-ments(e.g.,temperature control,reduction of back-mixing,and product separation),the process intensi-fication of slurry reactors is essential.This article starts by reviewing the latest advancements in the intensification of mixing and mass/heat transfer in these two types of reactors.It then summarizes process-intensification methods for mixing and separation that allow continuous production in these slurry reactors.Process-intensification technology that integrates directional flow in an ALR with simple solid-liquid separation in a hydrocyclone is recommended for its high efficiency and low costs.This arti-cle also systematically addresses vital considerations and challenges,including flow regime discrimina-tion,gas spargers,solid particle effects,and other concerns in slurry reactors.It introduces the progress of numerical simulation using computational fluid dynamics(CFD)for the rational design of slurry reactors and discusses difficulties in modeling.Finally,it presents conclusions and perspectives on the design of industrial slurry reactors.
文摘1 INTRODUCTIONMany chemical engineering operations involve the mass and heat transfer between two liquidphases in reactions.Mechanically agitated liquid-liquid extractor can be one of the examples forsuch operations.It has been well developed and used in the nuclear energy,petrochemical andother chemical industries.However,not much attention has been paid to the gas agitated liquid-
文摘1.Introduction The recent increase in life expectancy in China is also leading to an increased incidence of dementia.Dementia is a common,chronic,organic disease,which manifests extensive degenerative changes in the brain.In addition to cognitive dysfunction,people with dementia often have additional mental and/or behavioral symptoms.
文摘Objective: Intramuscular (IM) Benzodiazepines and/or Haloperidol alone or with benzodiazepines are frequently used to treat agitation. Based on emerging literature regarding Quetiapine used for the control of anxiety we examined Quetiapine as a possible alternative in selected cases. Methods: This study was a single-blind randomized study comparing Quetiapine PO (300 mg) with a combination of Haloperidol (5 mg), Benztropine mesylate (2 mg) and lorazepam (2 mg) administered IM to treat agitated patients seeking care in a busy psychiatric emergency setting. Male or female patients (18 - 60), deemed by the attending (admitting) psychiatrist to be indicative of agitated and/or aggressive behavior and had a Positive and Negative Syndrome Score-Excited Component (PANSS-EC), as evaluated by the Research Psychiatrist, and total score equal to or greater than 15. Patients deemed competent were randomized into one of the following treatment groups: Quetiapine 300 or Haloperidol 5 mg, benztropine mesylate, or lorazepam given by the IM route. Two scales, PANSS-EC and CGI-C were used to assess patients in the trial. The primary outcome measure PANSS-EC at 2 hours after administration of the medication. Results: Sixty-eight patients were included in the study. There were no significant treatment group differences in baseline condition. There was no significant difference between the two conditions. There was, however, a significant within-group decrease from baseline condition. Conclusion: Finding no significant differences suggests that in general the two treatments were equivalent. To sum up, Quetiapine 300 mg as a single dose appeared safe and effective in agitated patients treated in an ER. The results were similar to a comparison group receiving an intra-muscular combination of Haloperidol, Lorazepam and Benztropine. This study has significant limitations. The study was single blind and the use of a placebo would have strengthened the design but would be considered unethical. The sample size was relatively small and the group of patients who come to the ER may not be representative of the population of patients who visit across the country. And finally it was a select subgroup who made up the study population and who were probably less severely ill than other subjects who came to our ER.
文摘Large quantities of <em>Rhizobium leguminosarum</em> by conventional technique are a time-consuming and labor-intensive method of production. The selection of different types of nutrient media for the production of large amounts of rhizobium at low cost, determination of environmental regulators of culture medium and the effect of different levels of air flow into nutrition media have been investigated. <em>Rhizobium</em> cultured in modified air lift bioreactor as improved conventional system using Yeast Extract Mannitol Broth by assessing aeration and agitation in their submerged growth. For selection of suitable nutrient media for <em>Rhizobium </em>before mass production, YMA (Yeast Mannitol Agar), YSA (Yeast Sucrose Agar), YMA + bromthymol blue (BTB), YMA + Congo red (CR) medium was tested. To optimize the growing conditions of different temperatures, pH levels and salt strengths were investigated. Three air flow speeds at the rate of 0.01, 0.05 and 0.1 VVM for oxygen supply were ensured. A thick off-white bacterial colony was observed on the YMA plate among different culture media. Room temperature (25<span style="white-space:nowrap;"><span style="white-space:nowrap;">˚</span></span>C - 30<span style="white-space:nowrap;"><span style="white-space:nowrap;">˚</span></span>C), neutral pH (7.0), low salinity (1%) was observed to be suitable among the environmental conditions for <em>Rhizobium</em> mass production. The maximum density of <em>Rhizobium</em> was observed using air supply of 0.1 VVM level in bioreactor system. The result seemed that the air supply and agitation was an important growth factor in submerged cultivation. This study provides useful information on large scale production of <em>Rhizobium</em> of interest employing low cost effective modified air lift bioreactor within less time.
文摘Employing the arc discharge method we prepared carbon nanotubes, CNTs, in open air deionized water. Their morphology was studied varying the annealing temperature and characterizing by Raman Spectroscopy, Transmission Electron Microscopy (TEM), X-Ray Diffractogram (XRD) and Energy Dispersion X-Ray (EDX). According to the study, the CNTs are found self-assembled where the graphene sheets and/or defects are observed sort out themselves with enhancement of temperature.
基金supported by the 13th Five-Year Plan for National Science and Technology(Grant No.2016YFD0700302)National Natural Science Foundation of China(51705194)(JJKH20170811KJ).
文摘Since the low seed filling speed of mechanical seed metering devices reduces the low qualified rate of seed spacing during high-speed practices,it is significant to design agitated seed metering devices with horizontal seed filling that are suitable for high-speed practices.The combination of horizontal seed filling and agitated seed filling can accelerate the seed filling of mechanical seed metering devices,and improve the qualified rate of seed spacing during high-speed practices.In this study,theoretical analysis,discrete element method-based simulation and indoor bench test verification were conducted to investigate how key parameters of the agitated seed metering device with horizontal seed filling(angles,installation position and number of agitating plates,diameters of convex spoons)would affect the characteristics of soybean seed movement,seed number and seeding performance(qualified index,multiple index,missing seeding index)under different working speeds.Computer-based simulation,test design and regression analysis were combined to analyze the population moving rules and optimize the design parameters of seed metering devices.Based on the test scheme as designed,simulations were conducted on Fluent EDEM,and the optimal angle of the agitating plates was determined by analyzing the population migrating rules.Regression equations were established through the regression of test results,and used to find out the optimal design parameters(diameter of convex spoon,positions and number of agitating plates)of seed metering devices.Then the optimal parameter combination among different working conditions was determined that the angle,position and number of agitating plates were 30°,24.4 mm,and 13,respectively,and the diameter of convex spoon was 11.0 mm.With the optimal parameter combination and at the seeding speed of 12 km/h,the qualified index,multiple index and missing seeding index were 93.1%,2.1%and 4.8%,respectively.Under high-speed practices,the new seed metering device was not significantly different from the pneumatic seed metering device,but significantly outperformed the mechanical seed metering device.
基金Supported by the EPSRC (Nos. GR/R54699/01 and GR/R56044/01).
文摘In this paper we report results from on-going theoretical and experimental studies carried out jointly at Imperial College London and University College London. Laser-induced fluorescence （LIF） is used to investigate liquid-liquid phase inversion experimentally and to observe in detail phenomena that accompany the inversion process, such as secondary dispersions and drop coalescence and breakup. Theoretically, a two-region model together with a criterion based on a dynamic balance between drop coalescence and breakup is employed to predict phase inversion. The concept of a radial distribution function for hard spheres was also utilized in order to better model the interaction of drops at high dispersed phase holdup, The modeling work is capable of predicting the existence of ambivalent ranges which are in good agreement with experimental observations.
基金supported by the National Natural Science Foundation of China (Grant No. 5186504)the University Science Foundation for Young Science and Technology Talents in Inner Mongolia Autonomous Region of China (Grant No. NJYT22078)+2 种基金the Basic Scientific Research Expenses Program of Universities directly under Inner Mongolia Autonomous Region (Grant No. JY20220059)the Inner Mongolia Autonomous Region ‘Grassland Talent’ project Young Innovative Talent Training Program Level ⅠBasic Research Expenses of Universities directly under the Inner Mongolia Autonomous Region (Grant No. ZTY2023040)。
文摘To develop a suitable production process for fiber reinforced investment casting shell mold,three methods were studied:the traditional method(M_(1)),the method of adding fiber into silica sol with mechanical stirring and ultrasonic agitation(M_(2)),and the method of adding fiber into slurry with mechanical stirring and ultrasonic agitation for durations of 3,15,30,and 45 min(M_(3)).The bending strength,high-temperature self-load deformation,and thermal conductivity of the shell molds were investigated.The results reveal that the enhancement of fiber dispersion through ultrasonic agitation improves the comprehensive performance of the shell molds.The maximum green bending strength of the shell mold by M_(2) reaches 3.29 MPa,which is 29% higher than that of the shell mold prepared by M_(1).Moreover,the high-temperature self-load deformation of the shell mold is reduced from 0.62% to 0.44%.In addition,simultaneous ultrasonic agitation and mechanical stirring effectively shorten the slurry preparation time while maintaining comparable levels of fiber dispersion.With the process M_(3)-45 min,the fillers are uniformly dispersed in the slurry,and the fired bending strength and the high-temperature self-load deformation reach 6.25 MPa and 0.41%,respectively.Therefore,the proposed ultrasonic agitation route is promising for the fabrication of fiber-reinforced shell molds with excellent fibers dispersion.
基金Supported by the National Institutes of Health/National Institute on Aging,No.1R21AG091282.
文摘Agitation is a neuropsychiatric syndrome characterized by excessive motor and/or verbal behaviors,with or without aggressive behaviors.The prevalence of agitation in Alzheimer’s disease varies from 5%to over 50%.Multiple factors have been implicated in its pathophysiology,including disease stage,comorbidity with other symptoms(e.g.,psychosis,anxiety/depression),and psychosocial factors.Ruling out delirium and identifying environmental triggers are fundamental steps in the management of agitation in Alzheimer’s disease.For establishing an effective therapeutic plan,it is important to define duration,severity,and potential for harm.While non-pharmacological approaches are considered the first line of intervention,pharmacological agents are frequently used in the treatment of agitation.Antipsychotics are commonly used in acute agitation.For chronic agitation,serotonin-selective reuptake inhibitors,especially citalopram and escitalopram,are often preferred due to safety concerns associated with the longterm use of antipsychotics.Promising novel strategies,such as new compounds and neuromodulation,are likely to be incorporated into agitation therapeutics in the next few years.
文摘Unintended dural tear(DT)is not an infrequent complication of biportal percutaneous endoscopic spinal surgery(BESS).DT manifests in neurological deficits,including seizure,headache,and intracranial hemorrhage.Meanwhile,DT may be a risk of emergence agitation(EA)after BESS,which has not yet been reported.We presented a case of a 55-year-old man with L5-S1 intervertebral disc herniation receiving BESS under general anesthesia.A DT about 3-4 mm occurred during the operation,and was repaired immediately.The patient presented EA shouting for a headache after the surgery in post anesthesia care unit(PACU).Sedative agents(midazolam,propofol and dexmedetomidine)were used,only continuously infusion of dexmedetomidine for about 4 h successfully improved EA in PACU.He had no neurologic deficits in following 3 months.This case report highlights the risk of EA when a DT occurs during BESS.Adequate sedation in early phase is critical to resolve the mass effect caused by EA.
