Simulation of drop breakage in liquid–liquid system by coupling of CFD and PBM: Comparison of breakage kernels and effects of agitator configurations

This work focuses on drop breakage for liquid-liquid system with an adoption of numerical simulation by using computational fluid dynamics and population balance model (PBM) coupled with two-fluid model (TFM). Two different breakage kernels based on identical breakage mechanism but different descriptions of breaking time are take n into account in this work. Eight cases corresp on ding to distinct configurations of agitator are carried out to validate numerical predictions, namely agitators with different porosity and hole diameters, respectively implemented in Cases 1 to 5 and Cases 6 to 8. The results are compared with experimental data for testing the applicability of both kernels. Simulations are implemented, in this work, with an approach of class method for the solution of population balance model by the special-purpose computational fluid dynamics solver Fluent 16.1 based on finite volume method, and the grids used for meshing the solution domain are accomplished in a commercial software Gambit 2.4.6. The effects of configurations of agitator corresponding to different parameters mentioned above on final Sauter mean diameter are equally concentrated in this work. Analysis of both kernels and comparisons with experimental results reveal that, the second kernel has more decent agreement with experiments, and the results of investigations on effects of agitator configurations show that the in fluences of these parameters on Sauter mean diameter are marginal, but appropriate porosity and hole diameter are actually able to decrease Sauter mean diameter. These outcomes allow us to draw general conclusions and help investigate performances of liquid-liquid system.

Effect of Agitator’s Types on the Hydrodynamic Flow in an Agitated Tank

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.

Variation law of gas holdup in an autoclave during the pressure leaching process by using a mixed-flow agitator

The multiphase reaction process of pressure leaching is mainly carried out in the liquid phase. Therefore, gas holdup is essential for the gas–liquid–solid phase reaction and the extraction rate of valuable metals. In this paper, a transparent quartz autoclave, a six blades disc turbine-type agitator, and a high-speed camera were used to investigate the gas holdup of the pressure leaching process. Furthermore, experiments determining the effects of agitation rate, temperature, and oxygen partial pressure on gas holdup were carried out. The results showed that when the agitation rate increased from 350 to 600 r/min, the gas holdup increased from 0.10% to 0.64%. When the temperature increased from 363 to 423 K, the gas holdup increased from 0.14% to 0.20%. When the oxygen partial pressure increased from 0.1 to 0.8 MPa, the gas holdup increased from 0.13% to 0.19%. A similar criteria relationship was established by Homogeneous Principle and Buckingham's theorem. Comprehensively, empirical equation of gas holdup was deduced on the basis of experimental data and the similarity theory, where the criterion equation was determined as ε=4.54×10^(-11)n^(3.65)T^(2.08)P_g^(0.18). It can be seen from the formula that agitation rate made the most important impact on gas holdup in the pressure leaching process using the mixed-flow agitator.

AN INNOVATED REACTOR WITH VARYING DIAMETER AGITATOR AND ITS APPLICATIONS

The reactor is equipped with two different types of agitators: the diameter-variable agitator and the two-pitched-paddle agitator. The diameter of the former can be varied according to the requirement of the chemical reactions, thus making the concentration and temperature of the whole reaction system uniform throughout the reactor without any stagnant zone. It is shown that the apparatus has the preponderance over conventional agitator, especially when extremely rapid reactions are accompanied by large amount of reaction heat and when the viscosity of the reaction system varies in a wide range. The reactor is very effective when applied to the polycondensation reaction between paraphenylene diamine （PPDA） and terephthyl chloride （TPC）. The inherent viscosity (ηinh) of the polymer comes up to more than 5. This innovative agitator has the advantage of simplicity in structure and flexibility in operation, etc.

Agitator tank device and drag reduction agent evaluation

The device that consists of tank and disk agitator for evaluation drag reduction agents(DRA) was established.The effect of DRA was defined by testing the changes of agitator torque that drives the disk rotation.The HG-DRA for oil pipeline from Linyi to Puyang was studied by agitator tank device.The relationships between the drag reduction rate and Reynolds number,concentration,balance time were studied.The best concentration and the highest Renords number for the best drag reduction rate were confirmed.The results show that the drag reduction rate tested in agitator tank is close to that in pipeline.The maximum error of drag reduction rate between pipeline and agitator tank is 18.3%,which indicates that the agitator tank device is available to evaluate the effect of DRA for pipeline and it also has the advantages of simple,easy to be operated and using small volume of oil.Those are very helpful for operaters to know the properties of DRA and operate pipeline well.

Emergency department management of acute agitation in the reproductive age female and pregnancy

BACKGROUND:Agitation is a common presentation within emergent departments(EDs).Agitation during pregnancy should be treated as an obstetric emergency,as the distress may jeopardize both the patient and fetus.The safety of psychotropic medications in the reproductive age female has not been well established.This review aimed to explore a summary of general agitation recommendations with an emphasis on ED management of agitation during pregnancy.METHODS:A literature review was conducted to explore the pathophysiology of acute agitation and devise a preferred treatment plan for ED management of acute agitation in the reproductive age or pregnant female.RESULTS:While nonpharmacological management is preferred,ED visits for agitation often require medical management.Medication should be selected based on the etiology of agitation and the clinical setting to avoid major adverse effects.Adverse effects are common in pregnant females.For mild to moderate agitation in pregnancy,diphenhydramine is an effective sedating agent with minimal adverse effects.In moderate to severe agitation,high-potency typical psychotropics are preferred due to their neutral effects on hemodynamics.Haloperidol has become the most frequently utilized psychotropic for agitation during pregnancy.Second generation psychotropics are often utilized as second-line therapy,including risperidone.Benzodiazepines and ketamine have demonstrated adverse fetal outcomes.CONCLUSION:While randomized control studies cannot be ethically conducted on pregnant patients requiring sedation,animal models and epidemiologic studies have demonstrated the effects of psychotropic medication exposure in utero.As the fetal risk associated with multiple doses of psychotropic medications remains unknown,weighing the risks and benefits of each agent,while utilizing the lowest effective dose remains critical in the treatment of acute agitation within the EDs.

Correlation between pre-anesthesia anxiety and emergence agitation in non-small cell lung cancer surgery patients

BACKGROUND Preoperative anxiety is a common emotional problem during the perioperative period and may adversely affect postoperative recovery.Emergence agitation(EA)is a common complication of general anesthesia that may increase patient discomfort and hospital stay and may be associated with the development of postoperative complications.Pre-anesthetic anxiety may be associated with the development of EA,but studies in this area are lacking.AIM To determine the relationship between pre-anesthetic anxiety and EA after radical surgery in patients with non-small cell lung cancer(NSCLC).METHODS Eighty patients with NSCLC undergoing surgical treatment between June 2020 and June 2023 were conveniently sampled.We used the Hospital Anxiety and Depression Scale’s(HADS)anxiety subscale(HADS-A)to determine patients’anxiety at four time points(T1-T4):Patients’preoperative visit,waiting period in the surgical waiting room,after entering the operating room,and before anesthesia induction,respectively.The Riker Sedation-Agitation Scale(RSAS)examined EA after surgery.Scatter plots of HADS-A and RSAS scores assessed the correlation between patients’pre-anesthesia anxiety status and EA.We performed a partial correlation analysis of HADS-A scores with RSAS scores.RESULTS NSCLC patients’HADS-A scores gradually increased at the four time points:7.33±2.03 at T1,7.99±2.22 at T2,8.05±2.81 at T3,and 8.36±4.17 at T4.The patients’postoperative RSAS score was 4.49±1.18,and 27 patients scored≥5,indicating that 33.75%patients had EA.HADS-A scores at T3 and T4 were significantly higher in patients with EA(9.67±3.02 vs 7.23±2.31,12.56±4.10 vs 6.23±2.05,P<0.001).Scatter plots showed the highest correlation between HADS-A and RSAS scores at T3 and T4.Partial correlation analysis showed a strong positive correlation between HADS-A and RSAS scores at T3 and T4(r=0.296,0.314,P<0.01).CONCLUSION Agitation during anesthesia recovery in patients undergoing radical resection for NSCLC correlated with anxiety at the time of entering the operating room and before anesthesia induction.

Application of early enteral nutrition nursing based on enhanced recovery after surgery theory in patients with digestive surgery

BACKGROUND Postoperative nursing can improve the restlessness and gastrointestinal function of patients with tracheal intubation under general anesthesia in digestive surgery.Wide application of various nursing methods and routine nursing in periop-erative nursing of patients with general anesthesia in digestive surgery.AIM To investigate the impact of early postoperative enteral nutrition nursing based on the enhanced recovery after surgery(ERAS)theory on postoperative agitation and gastrointestinal recovery in patients undergoing general anesthesia that experienced tracheal intubation.METHODS The data of 126 patients with digestive surgery from May 2019 to February 2022 were retrospectively analyzed.According to different nursing methods,they were divided into control group and observation group,with 63 cases in observation group and 63 cases in control group.The patients in the control group had standard perioperative nursing care,whereas those in the observation group got enteral nourishment as soon as possible after surgery in accordance with ERAS theory.Both the rate and quality of gastrointestinal function recovery were compared between the two groups after treatment ended.Postoperative anes-thesia-related adverse events were tallied,patients'nutritional statuses were monitored,and the Riker sedation and agitation score(SAS)was used to measure the incidence of agitation.RESULTS When compared to the control group,the awake duration,spontaneous breathing recovery time,extubation time and postoperative eye-opening time were all considerably shorter(P<0.05).There was no significant difference in the recovery time of orientation force between the two groups(P>0.05);however,the observation group had a lower SAS score than the control group(P<0.05).The recovery time for normal intestinal sounds,the time it took to have the first postoperative exhaust,the time it took to have the first postoperative defecation,and the time it took to have the first postoperative half-fluid feeding were all faster in the observation group than in the control group(P<0.05);Fasting blood glucose was lower in the observation group compared to the control group(P<0.05),while the albumin and hemoglobin levels were higher on the first and third postoperative days;however,there was no statistically significant difference in the incidence of anesthesia-related adverse reactions between the two groups(P>0.05).CONCLUSION The extremely early postoperative enteral nutrition nursing based on ERAS theory can reduce the degree of agitation,improve the quality of recovery,promote the recovery of gastrointestinal function,and improve the nutritional status of patients in the recovery period after tracheal intubation under general anesthesia.

Effects of acupuncture on Alzheimer’s disease: the mechanistic study

Introduction Alzheimer’s disease(AD)is a degenerative disease of the central nervous system characterized by memory loss and cognitive impairment,often accompanied by emotional apathy,agitation,depression,delusions aggression,and other psychological symptoms[1–3].Psychological symptoms such as apathy,agitation,and depression tend to increase with the duration and severity of AD.

右美托咪定对老年患者七氟醚全麻苏醒期躁动的影响

全麻苏醒期躁动（emergence agitation,EA）是在麻醉苏醒期出现的躁动、兴奋和定向障碍等不恰当行为[1],可能对手术疗效产生极大的危害,常常造成手术切口的破裂和医疗资源配置的浪费。右美托咪定（dexmedetomidine,Dex）是α2肾上腺素能受体激动剂,可以抑制交感神经兴奋,兼具镇静和镇痛作用[2]本研究旨在评价Dex和咪达唑仑用于老年患者七氟烷全麻时对苏醒期躁动的影响,报告如下。

A METHOD OF PREPARING SPHERICAL NANO-CRYSTAL CELLULOSE WITH MIXED CRYSTALLINE FORMS OF CELLULOSE Ⅰ AND Ⅱ

A new kind of nano-crysta cellulose (NCC) prepared from natural cotton fiber has been obtained by the method ofacid hydrolysis. Compared to most other nanophase materials that derive from inorganic materials, our products are preparedfrom natural cotton fibers. The products are of spherical shape with mixed crystal forms of cellulose I and II. The preparationconditions determine the properties of the products. Prior treatment is a critical procedure. The properties of the products arealso strongly affected by such conditions as the kinds of acids used, the ratio of the acid mixture, the acid concentration, theultrasonic agitation time and hydrolysis temperature. The number average molecular weight of NCC is determined by gelpermeation chromatography (GPC). The particle size and shape were determined by transmission electron microscopy(TEM). X-ray diffraction was used to detect the crystallinity and average crystallite size of the panicle.

Agitation thrombolysis combined with catheter-directed thrombolysis for the treatment of non-cirrhotic acute portal vein thrombosis

AIM To evaluate the safety and efficacy of agitation thrombolysis(AT) combined with catheter-directed thrombolysis(CDT) for the treatment of non-cirrhotic acute portal vein thrombosis(PVT). METHODS Nine patients with non-cirrhotic acute PVT who underwent AT combined with CDT were analyzed retrospectively. Portography was carried out via the transjugular intrahepatic portosystemic(commonly known as TIP) or percutaneous transhepatic(commonly known as PT) route, followed by AT combined with CDT. Complications of the procedure, and the changes in clinical symptoms, hemodynamics of the portal vein and liver function were recorded. Follow-up was scheduled at1, 3 and 6 mo after treatment, and every 6 mo thereafter, or when the patients developed clinical symptoms related to PVT. Color Doppler ultrasound and contrast-enhanced computed tomography/magnetic resonance imaging were performed during the follow-up period to determine the condition of the portal vein.RESULTS AT combined with CDT was successfully performed. The portal vein was reached via the TIP route in 6 patients, and via the PT route in 3 patients. All clinical symptoms were relieved or disappeared, with the exception of 1 patient who died of intestinal necrosis 9 d after treatment. Significant differences in the changes in portal vein hemodynamics were observed, including the maximum lumen occupancy of PVT, portal vein pressure and flow velocity between pre-and posttreatment(P < 0.05). During the follow-up period, recurrence was observed in 1 patient at 19 mo after the procedure, and the portal vein was patent in the remaining patients.CONCLUSION AT combined with CDT is a safe and effective method for the treatment of non-cirrhotic acute PVT.

Predisposing factors, clinical assessment, management and outcomes of agitation in the trauma intensive care unit

BACKGROUND: Agitation occurs frequently among critically ill patients admitted to the intensive care unit(ICU). We aimed to evaluate the frequency, predisposing factors and outcomes of agitation in trauma ICU. METHODS: A retrospective analysis was conducted to include patients who were admitted to the trauma ICU between April 2014 and March 2015. Data included patient's demographics, initial vitals, associated injuries, Ramsey Sedation Scale, Glasgow Coma Scale, head injury lesions, use of sedatives and analgesics, head interventions, ventilator days, and ICU length of stay. Patients were divided into two groups based on the agitation status.RESULTS: A total of 102 intubated patients were enrolled; of which 46(45%) experienced agitation. Patients in the agitation group were 7 years younger, had significantly lower GCS and sustained higher frequency of head injuries(P<0.05). Patients who developed agitation were more likely to be prescribed propofol alone or in combination with midazolam and to have frequent ICP catheter insertion, longer ventilatory days and higher incidence of pneumonia(P<0.05). On multivariate analysis, use of propofol alone(OR=4.97; 95% CI=1.35–18.27), subarachnoid hemorrhage(OR=5.11; 95% CI=1.38–18.91) and ICP catheter insertion for severe head injury(OR=4.23; 95% CI=1.16–15.35) were independent predictors for agitation(P<0.01).CONCLUSION: Agitation is a frequent problem in trauma ICU and is mainly related to the type of sedation and poor outcomes in terms of prolonged mechanical ventilation and development of nosocomial pneumonia. Therefore, understanding the main predictors of agitation facilitates early risk-stratification and development of better therapeutic strategies in trauma patients.

Process Intensification in Pneumatically Agitated Slurry Reactors

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.

Characterization of the Engineering Flow in a Miniaturised Bioreactor by Computational Fluid Dynamics

Three approaches based on computational fluid dynamics(CFD) techniques have been assessed for their ability to describe the engineering flow environment in a miniaturized mechanically agitated bioreactor. The three approaches tested were the source-sink(SS), the multiple reference frames(MRF) and the sliding grids(SG). In all the cases, the predictions of the velocity components agree with reported experimental data. However, the analysis of the results of the turbulent intensities predicted by the three approaches indicates the MRF and the SG techniques under predicted turbulent intensities are comparable to both experimental measurements and the SS method. The predicted power number and pumping number based on the SS approach are closer to typical reported experimental values compared to those obtained from the MRF and SG methods.

Individualized music for dementia:Evolution and application of evidence-based protocol

The theory-based intervention of individualized music has been evaluated clinically and empirically leading to advancement and refinement of an evidence-based protocol, currently in its 5th edition. An expanded version of the protocol was written for professional health care providers with a consumer version tailored for family caregivers. The underlying mid-range theory is presented along with a seminal study that was followed by further research in the United States, Canada, Great Britain, France, Sweden, Norway, Japan and Taiwan. Key studies are summarized. Given its efficacy when implemented by research staff, studies have advanced to testing the intervention under real-life conditions when implemented and evaluated by trained nursing assistants in long-term care facilities and visiting family members. In addition, one study evaluated the implementation of music by family members in the home setting. Initial research focused on agitation as the dependent variable with subsequent research indicating a more holistic response such as positive affect, expressed satisfaction, and meaningful interaction with others. The article advances by describing on-line programs designed to train health care professionals in the assessment, implementation and evaluation of individualized music. In addition, Gerdner has written a story for apicture book intended for children and their families(in press). The story models principles of individualized music to elicit positive memories, reduce anxiety and agitation, and promote communication. The article concludes with implications for future research.

Effect of agitation speed on the morphology of Aspergillus niger HFD5A-1 hyphae and its pectinase production in submerged fermentation

AIM: To investigate the impact of agitation speed on pectinase production and morphological changing of Aspergillus niger(A. niger) HFD5A-1 in submerged fermentation. METHODS: A. niger HFM5A-1 was isolated from a rotted pomelo. The inoculum preparation was performed by adding 5.0 m L of sterile distilled water containing 0.1% Tween 80 to a sporulated culture. Cultivation was carried out with inoculated 1 × 107 spores/m L suspension and incubated at 30 ℃ with different agitation speed for 6 d. The samples were withdrawn after 6 d cultivation time and were assayed for pectinase activity and fungal growth determination. The culture broth was filtered through filter paper(Whatman No. 1, London) to separate the fungal mycelium. The cell-free culture filtrate containing the crude enzyme was then assayed for pectinase activity. The biomass was dried at 80 ℃ until constant weight. The fungal cell dry weight was then expressed as g/L. The 6 d old fungal mycelia were harvested from various agitation speed, 0, 50, 100, 150, 200 and 250 rpm. The morphological changing of samples was then viewed under the light microscope and scanning electron microscope.RESULTS: In the present study, agitation speed was found to influence pectinase production in a batch cultivation system. However, higher agitation speeds than the optimal speed(150 rpm) reduced pectinase production which due to shear forces and also collision among the suspended fungal cells in the cultivation medium. Enzyme activity increased with the increasing of agitation speed up to 150 rpm, where it achieved its maximal pectinase activity of 1.559 U/m L. There were significant different(Duncan, P < 0.05) of the pectinase production with the agitation speed at static, 50, 100, 200 and 250 rpm. At the static condition, a well growth mycelial mat was observed on the surface of the cultivation medium and sporulation occurred all over the fungal mycelial mat. However with the increased in agitation speed, the mycelial mat turned slowly to become a single circular pellet. Thus, it was found that agitation speed affected the morphological characteristics of the fungal hyphae/mycelia of A. niger HFD5A-1 by altering their external as well as internal cell structures.CONCLUSION: Exposure to higher shear stress with an increasing agitation speed could result in lower biomass yields as well as pectinase production by A. niger HFD5A-1.

CFD investigation of the agitation in the desupersaturation during the wet-process phosphoric acid(WPPA)process

Desupersaturation is a complex cooling operation that involves hydrodynamic,thermal and mechanical phenomena.This process requires continuous agitation to avoid fouling problems and sludge deposition.The current work aims to investigate the well mixedness in the desupersaturation tank for optimal performance.For this purpose,a multi-fluid CFD study was conducted based on the Euler–Euler modeling approach,considering a multiphase flow involving a liquid phase(phosphoric acid)and a poly-dispersed solid phase,i.e.a sludge with three different sizes where each size is considered as a separate phase.First,the hydrodynamic behavior of the flow within the agitated desupersaturator is analyzed through the investigation of the velocity fields as well as the power and pumping numbers,to determine both the agitator capacity to pump the flow and its power consumption during the operation.Then,in order to assess the mixture homogeneity,we evaluated the solid suspension in the desupersaturation reactor following conventional methods and two new proposed methodologies:the first approach is to evaluate the suspension quality in the mixing system by compartment and the second consists on the assessment of the uniform convergence of the solid concentration.Furthermore,we calculated the time required to achieve a full suspension at different solid concentrations.On other hand,we conducted a detailed analysis of the solid distribution dependency on the impeller rotational speed at different solid volume fraction,which allows a good understanding of the parameters controlling the homogenization in the desupersaturator.

CFD Simulation of Local and Global Mixing Time in an Agitated Tank

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.

A Study on a Gas Agitated Extractor with Static Mixer

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-