scholarly journals Influence of Hydrodynamic Conditions on Micromixing in Microreactors with Free Impinging Jets

Fluids ◽  
2020 ◽  
Vol 5 (4) ◽  
pp. 179
Author(s):  
Rufat Sh Abiev ◽  
Alexey A Sirotkin
Keyword(s):  
Flow Rate ◽  
Weighted Average ◽  
Weight Fraction ◽  
Impinging Jets ◽  
Liquid Sheet ◽  
Average Concentration ◽  
Reaction Products ◽  
Intensive Formation ◽  
Nonmonotonic Character

An experimental study and mathematical modeling of micromixing in a microreactor with free impinging jets (MRFIJ) with a diameter of 1 mm was carried out. In the experimental part, the iodide-iodate technique was used (involving parallel competing Villermaux–Dushman reactions with the formation of I3−). Theoretical assessment revealed that more than 50% of the introduced energy is dissipated in the jets collision region. Through the use of differentiated sampling, an uneven quality distribution of micro mixing in the central and peripheral zones of the reactor was found: at moderate flow rates (700–1000 mL/min, jets velocity of 15–21 m/s) the micromixing in the central part of reactor is up to 12 times better than that in the periphery. Furthermore, the weight fraction of the probes in the central zones of MRFIJ is reduced with increasing jet velocity; this effect is attributed to a more intense formation of ligaments and droplets upon collision of jets and their secondary mixing on the walls of the apparatus. In terms of the weighted average concentration, the best quality of micromixing in the samples is achieved at a flow rate of 300 mL/min. With an increase in the flow rate (and velocity) of the jets, the dependence of the I3− concentration on the flow rate has a nonmonotonic character, which is explained by a change in the nature of the flow in the collision zone of the jets: the transition from the formation of a liquid sheet to the intensive formation of ligaments and drops and secondary mixing of the liquid film formed on the walls of the reactor. The effect of “freshness” of solutions on the concentration of reaction products was studied.

HOLOGRAPHY EXPERIMENTS IN THE BREAKUP REGION OF A LIQUID SHEET FORMED BY TWO IMPINGING JETS

1995 ◽  
Vol 5 (4-5) ◽  
pp. 387-402 ◽  
Author(s):  
B. S. Kang ◽  
Y. B. Shen ◽  
D. Poulikakos
Keyword(s):  
Impinging Jets ◽  
Liquid Sheet

Radon removal by aeration: observations on testing, installation and maintenance of domestic treatment units

2009 ◽  
Vol 9 (4) ◽  
pp. 469-475
Author(s):  
T. Turtiainen
Keyword(s):  
Water Quality ◽  
Water Flow ◽  
Removal Efficiency ◽  
Flow Rate ◽  
Test Protocol ◽  
Household Water ◽  
Medium Flow ◽  
Removal Efficiencies ◽  
Frequent Sampling

Radon is one of the contaminants that sometimes impair the water quality of wells, especially those drilled in bedrock. Domestic radon removal units based on aeration have been commercially available for more than ten years. In order to determine how effectively these units remove radon a new test protocol applying frequent sampling while letting 100 litres of water flow, was developed. This way, removal efficiencies can be more accurately calculated and possible malfunctions detected. Seven models of domestic aerators designed for removing radon from household water were tested. The aerators were based on diffused bubble aeration, spray aeration or jet aeration. The average removal efficiencies for 100 litres with a medium flow rate were 86–100% except for a unit that circulated the aerated water back to the well that had removal efficiency of 80% at the maximum. By conducting a questionnaire study usual problems related to the aeration units were localized and recommendations on maintenance and installation are given accordingly.

First flush effects in an urban catchment area in Aalborg

1998 ◽  
Vol 37 (1) ◽  
pp. 251-257 ◽  
Author(s):  
Torben Larsen ◽  
Kirsten Broch ◽  
Margit Riis Andersen
Keyword(s):  
Water Quality ◽  
Catchment Area ◽  
Quality Parameters ◽  
Average Concentration ◽  
First Flush ◽  
Storm Events ◽  
Urban Catchment ◽  
Discharge Measurements ◽  
Quality Measurements

The paper describes the results of measurements from a 2 year period on a 95 hectare urban catchment in Aalborg, Denmark. The results of the rain/discharge measurements include 160 storm events corresponding to an accumulated rain depth of totally 753 mm. The water quality measurements include 15 events with time series of concentration of SS, COD, BOD, total nitrogen and total phosphorus. The quality parameters showed significant first flush effects. The paper discusses whether either the event average concentration or the accumulated event mass is the most appropriate way to characterize the quality of the outflow.

scholarly journals The influence of temperature and TMGa flow rate on the quality of p-GaN

AIP Advances ◽  
2021 ◽  
Vol 11 (3) ◽  
pp. 035109
Author(s):  
Zikun Cao ◽  
Xiaowei Wang ◽  
Degang Zhao ◽  
Feng Liang ◽  
Zongshun Liu
Keyword(s):  
Flow Rate ◽  
Influence Of Temperature

scholarly journals Simple fistula-in-ano: is it all simple? A systematic review

2021 ◽  
Author(s):  
F. Litta ◽  
A. Parello ◽  
L. Ferri ◽  
N. O. Torrecilla ◽  
A. A. Marra ◽  
...  
Keyword(s):  
Systematic Review ◽  
Surgical Treatment ◽  
Fecal Incontinence ◽  
Anal Fistula ◽  
Randomized Clinical Trials ◽  
Weighted Average ◽  
Anal Fistulas ◽  
Postoperative Continence ◽  
Average Success Rate

Abstract Background Simple anal fistula is one of the most common causes of proctological surgery and fistulotomy is considered the gold standard. This procedure, however, may cause complications. The aim of this systematic review was to assess the surgical treatment of simple anal fistula with traditional and sphincter-sparing techniques. Methods A literature research was performed using PubMed, Cochrane, and Google Scholar to identify studies on the surgical treatment of simple anal fistulas. Observational studies and randomized clinical trials were included. We assessed the risk of bias of included studies using the Jadad scale for randomized controlled trials, and the MINORS Scale for the remaining studies. Results The search returned 456 records, and 66 studies were found to be eligible. The quality of the studies was generally low. A total of 4883 patients with a simple anal fistula underwent a sphincter-cutting procedure, mainly fistulotomy, with a weighted average healing rate of 93.7%, while any postoperative continence impairment was reported in 12.7% of patients. Sphincter-sparing techniques were adopted to treat 602 patients affected by simple anal fistula, reaching a weighted average success rate of 77.7%, with no study reporting a significant postoperative incontinence rate. The postoperative onset of fecal incontinence and the recurrence of the disease reduced patients’ quality of life and satisfaction. Conclusions Surgical treatment of simple anal fistulas with sphincter-cutting procedures provides excellent cure rates, even if postoperative fecal incontinence is not a negligible risk. A sphincter-sparing procedure could be useful in selected patients.

scholarly journals Machining Ti-6Al-4V Alloy Using Nano-Cutting Fluids: Investigation and Analysis

2021 ◽  
Vol 5 (2) ◽  
pp. 42
Author(s):  
Abdelkrem Eltaggaz ◽  
Ibrahim Nouzil ◽  
Ibrahim Deiab
Keyword(s):  
Surface Finish ◽  
Minimum Quantity Lubrication ◽  
Weight Fraction ◽  
Contact Length ◽  
Al2o3 Nanoparticles ◽  
Compressive Stresses ◽  
Cutting Zone ◽  
The Impact ◽  
Cooling And Lubrication

Minimum Quantity Lubrication nanofluid (MQL-nanofluid) is a viable sustainable alternative to conventional flood cooling and provides very good cooling and lubrication in the machining of difficult to cut materials such as titanium and Inconel. The cutting action provides very difficult conditions for the coolant to access the cutting zone and the level of difficulty increases with higher cutting speeds. Furthermore, high compressive stresses, strain hardening and high chemical activity results in the formation of a ‘seizure zone’ at the tool-chip interface. In this work, the impact of MQL-nanofluid at the seizure zone and the corresponding effects on tool wear, surface finish, and power consumption during machining of Ti-6Al-4V was investigated. Aluminum Oxide (Al2O3) nanoparticles were selected to use as nano-additives at different weight fraction concentrations (0, 2, and 4 wt.%). It was observed that under pure MQL strategy there was significant material adhesion on the rake face of the tool while the adhesion was reduced in the presence of MQL-nanofluid at the tool-chip interface, thus indicating a reduction in the tool chip contact length (TCCL) and reduced seizure effect. Furthermore, the flank wear varied from 0.162 to 0.561 mm and the average surface roughness (Ra) varied from 0.512 to 2.81 µm. The results indicate that the nanoparticle concentration and the reduction in the seizure zone positively influence the tool life and quality of surface finish.

CHANGES IN THE TECHNICAL AND TECHNOLOGICAL LEVEL OF STEAM CULTIVATORS IN THE XXI CENTURY

2021 ◽  
Vol 2 (143) ◽  
pp. 174-183
Author(s):  
Andrey Yu. Nesmiyan ◽  
◽  
Anastasiya S. Kaymakova ◽  
Yuliya S. Tsench ◽  
Keyword(s):  
Weighted Average ◽  
Specific Weight ◽  
Research Purpose ◽  
Utilization Rate ◽  
Average Value ◽  
Technological Level ◽  
Short Test ◽  
Specific Material ◽  
The Cost

Most modern agricultural machines and tools consist of components, the main parameters, design features of which were justified in the first half of the twentieth century. Slowly and evolutionarily, these technical means are developing. (Research purpose) The research purpose is in identifying general trends in the technical and technological level of steam cultivators in the first quarter of the XXI century. (Materials and Methods) For the study there was analyzed the data of the short test reports of the selected machines. The production of steam cultivators in the Russian Federation is gradually increasing. (Results and discussion) For ten years of the beginning of the XXI century, only 27 machines were provided for testing, and from 2014 to 2017 – more than 40, while for "old" cultivators, the weighted average value of the tractor traction class was 2.8, for new ones it is about of four. For the study period (on average 10 years) the quality of soil cultivation in terms of such parameters as deviation from the specified depth of cultivation, crumbling and combing of the field surface has not changed much. The productivity of cultivator units increased by 7-21 percents, which is explained not only by an increase in the power of tractors, but also by an increase in the utilization rate of charge time on average from 0.72 to 0.77. The specific weight of the "new" cultivators was on average 22 kilogram-meters less than that of the "old" analogues, which can be explained by the evolution of their designs. (Conclusions) Increasing the class of tractors by one "level" the specific material consumption of the cultivators aggregated with them increases by about 58 kilogram-meters for both "old" and " new " cultivators. With an increase in the width of the tools from 4 to 16 meters, their weight will increase by 8 times, which affects the cost and operational and environmental characteristics of wide-reach cultivators.

Research in Different Categories of UK Universities

1997 ◽  
Vol 11 (5) ◽  
pp. 304-313
Author(s):  
W. O. George ◽  
A. N. Hill
Keyword(s):  
Weighted Average ◽  
Unit Group ◽  
Research Quality ◽  
Average Score ◽  
Social Sciences And Humanities ◽  
Peer Rating ◽  
Subject Areas ◽  
Broad Subject ◽  
The Impact

In this paper, the origins and characteristics of the 102 current UK universities are briefly traced and the outcomes of recent assessments of research quality are summarized for all universities and for the 69 subject units within which assessment was made. The quality of research in a subject unit, group of subject units or complete institution is measured by a weighted average score based on a peer rating of submitted subject units from each university and the numerical values obtained are described within the limitations of the methodology developed. The authors consider the scores in terms of the characteristics of each university and the broad subject areas, science, engineering, social sciences and humanities. They then discuss the industrial link with research in terms of recent government policy inputs, university research outcomes and the impact of market forces on universities from diminishing patterns of some income streams.

Effect of working pressure, travel speed and nozzle wear rate on spray quality of different flat fan nozzles

2011 ◽  
Vol 7 (1) ◽  
pp. 17-31
Author(s):  
Eleonóra Kecskés-Nagy ◽  
Milan Koszel ◽  
István Sztachó-Pekáry
Keyword(s):  
Wear Rate ◽  
Flow Rate ◽  
Liquid Flow ◽  
Liquid Flow Rate ◽  
Travel Speed ◽  
Coverage Rate ◽  
Working Pressure ◽  
Nozzle Wear ◽  
Mean Diameter

The objective of the work was to determine the influence of working pressure and working speed on drop tracks size and changes in flow rate of flat fan nozzles. New nozzles and nozzles after laboratory wear were tested. The influence of nozzles wear on drop tracks size was tested. It was found that the increase in liquid flow rate resulted in higher values of mean diameter of the droplet track. The increase in working pressure or working speed causes decrease in drop tracks size and reduction in merging of droplets on sprayed surface. The increase of the wear was followed by increased coverage rate. This phenomenon is especially dangerous when using nozzles with a considerable wear for agricultural spraying since this causes ecological threat to environment.

scholarly journals Exposure to Ultrafine Particles in the Ferroalloy Industry Using a Logbook Method

Nanomaterials ◽  
2020 ◽  
Vol 10 (12) ◽  
pp. 2546
Author(s):  
Rikke Bramming Jørgensen ◽  
Ida Teresia Kero ◽  
Aleksander Blom ◽  
Esten Eide Grove ◽  
Kristin von Hirsch Svendsen
Keyword(s):  
Exposure Assessment ◽  
Ultrafine Particles ◽  
Weighted Average ◽  
Average Concentration ◽  
Respirable Particles ◽  
Exposure Estimation ◽  
Close Proximity ◽  
Personal Sampling ◽  
Time Weighted Average ◽  
Stationary Sampling

Background: It is difficult to assess workers’ exposure to ultrafine particles (UFP) due to the lack of personal sampling equipment available for this particle fraction. The logbook method has been proposed as a general method for exposure assessment. This method measures the time and concentration components of the time-weighted average concentration separately and could be suitable for investigation of UFP exposure. Objectives: In this study, we have assessed workers’ exposure to UFP in a ferrosilicon plant. The main tasks of the furnace workers were identified, and the logbook method was used in combination with stationary measurements of UFP taken as close to the identified task areas as possible. In order to verify the results, respirable particles were collected using stationary sampling in close proximity to the UFP measuring instrument, and personal full-shift sampling of respirable particles was performed simultaneously. Thus, exposure to respirable particles determined using the logbook method could be compared to the results of standard measurement. Methods: The particle number concentration of ultrafine particles was determined using a NanoScan SMPS. Respirable particle concentration and exposure were determined using a sampling train consisting of a pump, filter, filter cassettes, and SKC Cyclone for the respirable fraction. Attendance times for workers at each work location were registered via thorough observations made by the research team. Results: The logbook method for exposure estimation based on stationary sampling equipment made it possible to calculate UFP exposure for workers operating the furnaces at a ferrosilicon plant. The mid-size furnace and the large furnace were evaluated separately. The workers operating the largest furnace were exposed to 1.47 × 104 particles/cm3, while workers operating the mid-size furnace were exposed to 2.06 × 104 particles/cm3, with a mean of 1.74 × 104 particles/cm3. Substantial contributions from the casting area, ladle transport corridor, and both tapping areas were made. Exposure to respirable particles was 2.04 mg/m3 (logbook); 2.26 mg/m3 (personal sampling) for workers operating the large-sized furnace, 3.24 mg/m3 (logbook); 2.44 mg/m3 (personal sampling) for workers operating the medium-sized furnace, and 2.57 mg/m3 (logbook); 2.53 mg/m3(personal sampling) on average of all tappers. The average ratio of these two methods’ results was 1.02, which indicates that the logbook method could be used as a substitute for personal sampling when it is not possible to perform personal sampling, at least within this industry. Conclusions: The logbook method is a useful supplement for exposure assessment of UFP, able to identify the most polluted areas of the workplace and the contribution of different work tasks to the total exposure of workers, enabling companies to take action to reduce exposure.

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