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A strategy for strengthening chaotic mixing of dual shaft eccentric mixers by changing non-Newtonian fluids kinetic energy distribution

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Chinese Journal of Chemical Engineering 2024年第5期69卷 122-134页

作者： Songsong wang Tong Meng Qian Zhang Changyuan Tao yundong wang Zequan Li Zuohua Liu School of Chemistry and Chemical Engineering Chongqing UniversityChongqing 400044China State Key Laboratory of Coal Mine Disaster Dynamics and Control Chongqing 400044China Department of Chemical Engineering Tsinghua UniversityBeijing 100084China

Efficiently modulating the velocity distribution and flow pattern of non-Newtonian fluids is a critical challenge in the context of dual shaft eccentric mixers for process intensification,posing a significant barrier for the existing ***,this work reports a convenient strategy that changes the kinetic energy to controllably regulate the flow patterns from radial flow to axial *** showed that the desired velocity distribution and flow patterns could be effectively obtained by varying the number and structure of baffles to change kinetic energy,and a more uniform velocity distribution,which could not be reached normally in standard baffle dual shaft mixers,was easily ***,a comparative analysis of velocity and shear rate distributions is employed to elucidate the mechanism behind the generation of flow patterns in various dual-shaft eccentric ***,there is little difference in the power number of the laminar flow at the same Reynolds number,meaning that the baffle type has no effect on the power consumption,while the power number of both unbaffle and U-shaped baffle mixing systems decreases compared with the standard baffle mixing system in the transition ***,at the same rotational condition,the dimensionless mixing time of the U-shaped baffle mixing system is 15.3%and 7.9%shorter than that of the standard baffle and the unbaffle mixing system,respectively,which shows the advantage of the U-shaped baffle in stirring rate.

关键词： Dual shaft “U-shaped”baffle Flow pattern Mixing time Power demand

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Effect of aspect ratio of elliptical stirred vessel on mixing time and flow field characteristics in the absence of baffles

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Chinese Journal of Chemical Engineering 2024年第1期65卷 63-74页

作者： Yuan Yao Peiqiao Liu Qian Zhang Zequan Li Benjun Xi Changyuan Tao yundong wang Zuohua Liu School of Chemistry and Chemical Engineering Chongqing UniversityChongqing 400044China Hubei Three Gorges Laboratory Yichang 443007China Department of Chemical Engineering Tsinghua UniversityBeijing 100084China

Elliptical tanks were used as an alternative to circular tanks in order to improve mixing efficiency and reduce mixing time in unbaffled stirred tanks(USTs). Five different aspect ratios of elliptical vessels were designed to compare their mixing time and flow field. Computational fluid dynamics(CFD) simulations were performed using the k–ε model to calculate the mixing time and simulate turbulent flow field features, such as streamline shape, velocity distribution, vortex core region distribution, and turbulent kinetic energy(TKE) transfer. Visualization was also carried out to track the tinctorial evolution of the liquid phase. Results reveal that elliptical stirred tanks can significantly improve mixing performance in USTs. Specifically, the mixing time at an aspect ratio of 2.00 is only 45.3% of the one of a circular stirred tank. Furthermore, the secondary flow is strengthened and the vortex core region increases with the increase of aspect ratio. The axial velocity is more sensitive to the aspect ratio than the circumferential and radial velocity. Additionally, the TKE transfer in elliptical vessels is altered. These findings suggest that elliptical vessels offer a promising alternative to circular vessels for enhancing mixing performance in USTs.

关键词： Mixing time CFD Stirred tank Secondary flow Mixing performance

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翻转课堂与小规模限制性在线课程混合设计在“内科学”教学中的探索

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科技风 2024年第15期 56-58页

作者：王运东皖南医学院第一附属医院消化内科安徽芜湖241001

目的:观察线下翻转课堂与线上小规模限制性在线课程(SPOC)混合设计在“内科学”课程教学中的探索和应用效果。方法:选择“内科学”课程的“消化性溃疡疾病”为教学内容,以皖南医学院2018级的临床医学专业五年制2个大班的310名学生为研... 详细信息

目的:观察线下翻转课堂与线上小规模限制性在线课程(SPOC)混合设计在“内科学”课程教学中的探索和应用效果。方法:选择“内科学”课程的“消化性溃疡疾病”为教学内容,以皖南医学院2018级的临床医学专业五年制2个大班的310名学生为研究对象,其中一个班采用翻转课堂+SPOC混合设计的教学方法,本班级为实验组;另一个班采用以讲授为基础的教学方法(LBL),本班级为对照班。观察两组学生的课前测试和课后测试成绩,并开展教学效果问卷调查评价。结果:实验组学生的课前测试成绩与课后测试成绩均比对照组有显著提升(P<0.01)。说明翻转课堂+SPOC教学方法可以提高预习的有效性和学生对知识的掌握能力。结论:翻转课堂+SPOC混合设计的教学模式是一种可行的、有效的教学模式,可在“内科学”课程的教学中广泛应用。

关键词：翻转课堂小规模限制性在线课程内科学消化性溃疡疾病

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Solvent extraction kinetics of Sm(Ⅲ),Eu(Ⅲ) and Gd(Ⅲ) with 2-ethylhexyl phosphoric acid-2-ethylhexyl ester

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Chinese Journal of Chemical Engineering 2018年第2期26卷 317-321页

作者： Zhuo Chen yundong wang State Key Laboratory of Chemical Engineering Department of Chemical EngineeringTsinghua University

Solvent extraction kinetics of Sm（Ⅲ）, Eu（Ⅲ） and Gd（Ⅲ） from hydrochloric acid have been focused on using 2-ethylhexyl phosphoric acid-2-ethylhexyl ester （P507） with Anordning for Kontinuerlig Undersokning av Fordelningsfaktore rid Vatske Extraction （AKUFVE）. Compared with the conventional set-up, some advantages emerge obviously, for example, fast phase separation, easy operation and convenience of kinetic data acquisition. First of all, the extraction mechanism was discussed based on the dimeric model of P507. Secondly, the effects of stirring speed were investigated and 420 r-min-1 was determined of the following experiments. The effects of pH, concentration of rare earth elements （REEs） and P507 on the extraction rate were analyzed. The results indicated that the extraction mechanism changed with the increasing concentration of P507. Then, the experiments with different temperature were carried out. It turned out that the values of apparent activation energy （Ea） for Sm（Ⅲ）, Eu（Ⅲ） and Gd（Ⅲ） extracted by P507 were 26.80 kJ-mol-1, 13.40 ***-1 and 1.10 kJ- mol- 1 respectively, the resistance of the entire process was limited by diffusion or both of diffusion and reaction. Finally, the correlation equations were obtained, and the theoretical results fit with the experimental data well, most relative error was within ± 30%.

关键词： Rare earth elements (REEs)Extraction Kinetics Model

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Continuous synthesis of ultrasmall core-shell upconversion nanoparticles via a flow chemistry method

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Nano Research 2022年第2期15卷 1199-1204页

作者： Di Liu Junyu Yan Kai wang yundong wang Guangsheng Luo The State Key Lab of Chemical Engineering Department of Chemical EngineeringTsinghua UniversityBeijing 100084China

A continuous synthesis method for the less than 10 nm core-shell upconversion nanoparticles was developed via coiled tube embedded flask reactors and a flow solvothermal co-participation reaction up to 300℃.Fast nucleation of hexagonal nanocrystals in less than 9 min residence time was achieved owing to the excellent heating ability of the reactors,and a two-step reaction strategy was created for the synthesis of β-NaYF4:Gd,Yb,Er/Ho/Tm@NaYF_(4) particles without intermediate purification.

关键词： sodium rare earth tetrafluoride upconversion nanoparticle core-shell structure flow chemistry synthesis

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Structural optimization of a settler via CFD simulation in a mixer-settler

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Chinese Journal of Chemical Engineering 2020年第4期28卷 995-1015页

作者： Sishi Ye Qiao Tang yundong wang Weiyang Fei The State Key Laboratory of Chemical Engineering.Department of Chemical Engineering Tsinghua UniversityBeijing 100084China SINOPEC Research Institute of Petroleum Processing Beijing 100083China

This work is aimed at optimizing a settler structure in a *** different aspects have been ***,the flowcharacteristics of a settler have been examined by computational fluid dynamics(CFD)simulation with various agitation speeds of the mixer,as well as organic phase volume fractions ranging from 0.075 to *** aqueous and organic phase turbulent flow fields were measured by particle image velocimetry(PIV)technique to verify the CFD *** organic phases with different physical properties were assessed in the CFD simulation to simulate the liquid-liquid systems related to rare earth element extraction,i.e.,0.072 mol·L^-1 P507/kerosene and 1.8 mol·L^-1 P507/***,the CFD simulation was carried out in a settler equipped with *** effects of number and location of the baffle in the settler on flow features and entrainments of the aqueous and organic outlet were ***,different settler/mixer volume ratios were also *** analyses and comparisons,an optimal design for settler was *** can provide a significant guidance to better mixer-settler design.

关键词： Settler Liquid-liquid CFD RANS equations Optimization

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Efficient extraction and stripping of Nd(Ⅲ),Eu(Ⅲ) and Er(Ⅲ) by membrane dispersion micro-extractors

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Journal of Rare Earths 2018年第8期36卷 851-856页

作者： Zhuo Chen Jianhong Xu Funing Sang yundong wang The State Key Laboratory of Chemical Engineering Department of Chemical Engineering Tsinghua University

The extraction of low concentration rare earth elements at high phase ratio was investigated. The traditional extraction set-up, such as mixer-settler, have drawbacks of easy emulsification, difficult separation and low efficiency if operated at the above condition. Membrane dispersion micro-extractor,owing to its well-dispersed, high surface-to-volume ratio and fast mass transfer rate, was employed in our work. Nd（Ⅲ）,Eu（Ⅲ）,Er（Ⅲ） were chosen to represent light, medium,heavy rare earth elements（REEs）. The extraction process of REEs with 2-ethylhexyl phosphoric acid-2-ethylhexyl ester（P507） was investigated by membrane dispersion micro-extractors. Firstly, the extraction equilibrium of these three elements was explored in the stirred conical flasks, and it is indicated that the extraction efficiencies can be 0.95, 0.97 and 0.98, respectively within 40 min at phase ratio of 100：1. Then the effects of operational conditions such as the residence time, organic and aqueous flow rates on extraction efficiency were also explored in micro-extractors. The results indicate that the efficiency decreases and then increases if increasing aqueous phase flow rate, residence time and droplets＇ diameter are the key factors of this process. Increasing the phase ratio reduces the extraction efficiency significantly. When the REEs solution has an initial pH of 4.00, the flow rates of continuous and dispersed phase are 40 and 1.6 mL/min,respectively, and 90 mg/L Nd（Ⅲ）, Eu（Ⅲ） and Er（Ⅲ） is extracted by 1 mol/L P507 at the out-let length of8 m. The extraction efficiencies are 0.978,0.983 and 0.991, respectively. Finally the stripping process was also studied with the micro-extractor. The stripping efficiencies of Nd（Ⅲ）, Eu（Ⅲ） and Er（Ⅲ） can reach0.99, 0.96 and 0.91, respectively when the out-let length is 8 m and the concentration of hydrochloric acid is 1 mol/L. The developed approach offers a novel and simple strategy on the fast extraction and enrichment of low concentration rare earth el

关键词： Rare earth elements Membrane dispersion micro-extractor Extraction Stripping

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Continuous synthesis of few-layer MoS_(2) with highly electrocatalytic hydrogen evolution

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Green Energy & Environment 2021年第6期6卷 858-865页

作者： Meng Shao Peican wang Yimeng wang Baoguo wang yundong wang Jianhong Xu The State Key Laboratory of Chemical Engineering Department of Chemical EngineeringTsinghua UniversityBeijing100084China

As one of the most promising alternative fuels,hydrogen is expected with high *** electrolysis of water is regarded as the cleanest and most efficient method of hydrogen *** disulfide(MoS_(2))is deemed as one of the most promising alternatives HER catalysts owing to its high catalytic activity and low *** continuous production and efficient preparation become the key problems in future industrial *** this work,we first developed a continuous micro-reaction approach with high heat and mass transfer rates to synthesize few-layer MoS_(2)nanoplates with abundant active *** defective MoS_(2)ultrathin nanoplates exhibit excellent HER performance with an overpotential of 260 m V at a current density of 10 m A cm^(-2),small Tafel slope(53.6 m V dec^(-1))and prominent durability,which are comparable to most reported MoS_(2)based *** the existence of continuous devices,it's suitable for the synthesis of MoS_(2)as highperformance electrocatalysts for the industrial water *** novel preparation method may open up a new way to synthesize all two-dimension materials toward HER.

关键词： MoS_(2) Micro-reactor Ultrathin Nanoplates Hydrogen evolution reaction

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A state-of-the-art review on single drop study in liquid–liquid extraction:Experiments and simulations

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Chinese Journal of Chemical Engineering 2019年第12期27卷 2857-2875页

作者： Jiyizhe Zhang yundong wang Geoffrey WStevens Weiyang Fei The State Key Laboratory of Chemical Engineering Department of Chemical EngineeringTsinghua UniversityBeijing 100084China Department of Chemical Engineering The University of MelbourneParkvilleVictoria 3010Australia

The experimental and numerical investigations of single drop in liquid/liquid extraction system have been reviewed with particular focus on experimental techniques and computational fluid dynamic simulation *** surveys of available experimental techniques and numerical approaches for single drop rising and falling were ***,single drop mass transfer was also reviewed both experimentally and ***,single drop breakage and coalescence process and the influencing factors were summarized and compared,so as to establish sub-models for population balance *** directions on single drop mass transfer,drop breakage and coalescence were *** is believed that the single drop is a powerful tool to assist extraction process design from lab-scale to pilot-scale.

关键词： Solvent extraction Mass transfer Single drop Drop breakage and coalescence CFD simulation Population balance model

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Experimental investigation of dynamic mass transfer during droplet formation using micro-LIF in a coaxial microchannel

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Chinese Journal of Chemical Engineering 2021年第11期34卷 51-58页

作者： Zhuo Chen Qiqiang Xiong Shaowei Li yundong wang Jianhong Xu The State Key Laboratory of Chemical Engineering Department of Chemical EngineeringTsinghua UniversityBeijing 100084China Collaborative Innovation Center of Advanced Nuclear Energy Technology Institute of Nuclear and New Energy TechnologyTsinghua UniversityBeijing 100084China

The mass transfer of Rhodamine 6G from the droplet to the continuous phase in a coaxial micro-channel is studied using micro-LIF(Laser-Induced Fluorescence).The mass distribution inside droplet is measured and *** experimental results affirm that there exists the internal circulation inside the droplet and it could enhance the convective mass *** stagnant center of vortices is also *** extraction fraction could reach 40%80%.In order to establish the mass transfer model,different flow rates of the dispersed and continuous phase are *** high continuous phase flow rate and low dispersed phase flow rate are both beneficial to enhance mass transfer by expediting the internal circulation.A modified mass transfer model is found to calculate the extraction fraction.A good agreement between the model and experiment in various conditions demonstrates that the mass transfer model in this work is reliable and feasible.

关键词： Droplet formation Micro-LIF measurement Internal circulation Mass transfer model

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