Fault Trees for Minimum Flow Rates between Pairs of Nodes in Digraphs

1989 ◽  
pp. 266-266
Author(s):  
Dietmar Nentwig
Keyword(s):  
Flow Rates ◽  
Fault Trees ◽  
Minimum Flow

The minimum flow rate of electrosprays in the cone-jet mode

2019 ◽  
Vol 876 ◽  
pp. 553-572 ◽  
Author(s):  
Manuel Gamero-Castaño ◽  
M. Magnani
Keyword(s):  
Dielectric Constant ◽  
Reynolds Number ◽  
Flow Rate ◽  
Numerical Solutions ◽  
Viscous Stress ◽  
Flow Rates ◽  
Minimum Flow ◽  
Electric Stress ◽  
Work Done ◽  
Minimum Flow Rate

Stable electrospraying in the cone-jet mode is restricted to flow rates above a minimum, and understanding the physics of this constraint is important to improve this atomization technique. We study this problem by measuring the minimum flow rate of electrosprays of tributyl phosphate and propylene carbonate at varying electrical conductivity $K$ (all other physical properties such as the density $\unicode[STIX]{x1D70C}$, surface tension $\unicode[STIX]{x1D6FE}$ and viscosity $\unicode[STIX]{x1D707}$ are kept constant and equal to those of the pure liquids), and through the analysis of numerical solutions. The experiments show that the dimensionless minimum flow rate is a function of both the dielectric constant $\unicode[STIX]{x1D700}$ of the liquid and its Reynolds number, $Re=(\unicode[STIX]{x1D70C}\unicode[STIX]{x1D700}_{o}\unicode[STIX]{x1D6FE}^{2}/\unicode[STIX]{x1D707}^{3}K)^{1/3}$. This result is unexpected in the light of existing theories which, for the conditions investigated, predict a minimum flow rate that depends only on $\unicode[STIX]{x1D700}$ and/or is marginally affected by $Re$. The experimental dependency on the Reynolds number requires the viscous stress to be a factor in the determination of the minimum flow rate. However, the numerical solutions suggest that a balance of opposing forces including the fixing viscous stress, which at decreasing flow rates may lower the acceleration of the flow to the point of making it unstable, is unlikely to be the cause. An alternative mechanism is the significant viscous dissipation taking place in the transition from cone to jet, and which at low flow rates cannot be supplied by the work done by the tangential electric stress in the same area. Instead, mechanical energy injected into the system farther downstream must be transferred upstream where dissipation predominantly takes place. This mechanism is supported by the balance between the energy dissipated and the work done by the electric stress in the transition from cone to jet, which yields a relationship between the minimum flow rate, the Reynolds number and the dielectric constant that compares well with experiments.

Experimental Study of Low Concentration Sand Transport in Multiphase Air–Water Horizontal Pipelines

2015 ◽  
Vol 137 (3) ◽  
Author(s):  
Kamyar Najmi ◽  
Alan L. Hill ◽  
Brenton S. McLaury ◽  
Siamack A. Shirazi ◽  
Selen Cremaschi
Keyword(s):  
Experimental Study ◽  
Gas Flow ◽  
Intermittent Flow ◽  
Sand Transport ◽  
Physical Parameters ◽  
Internal Diameter ◽  
Flow Rates ◽  
Minimum Flow ◽  
Wide Range ◽  
Sand Size

The ultimate goal of this work is to determine the minimum flow rates necessary for effective transport of sand in a pipeline carrying multiphase flow. In order to achieve this goal, an experimental study is performed in a horizontal pipeline using water and air as carrier fluids. In this study, successful transport of sand is defined as the minimum flow rates of water and air at which all sand grains continue to move along in the pipe. The obtained data cover a wide range of liquid and gas flow rates including stratified and intermittent flow regimes. The effect of physical parameters such as sand size, sand shape, and sand concentration is experimentally investigated in 0.05 and 0.1 m internal diameter pipes. The comparisons of the obtained data with previous studies show good agreement. It is concluded that the minimum flow rates required to continuously move the sand increases with increasing sand size in the range examined and particle shape does not significantly affect sand transport. Additionally, the data show the minimum required flow rates increase by increasing sand concentration for the low concentrations considered, and this effect should be taken into account in the modeling of multiphase sand transport.

scholarly journals Determinación de caudales ecológicos en el río Cutuchi, Ecuador

2020 ◽  
Vol 5 (2) ◽  
pp. 33
Author(s):  
Mercy Llbay Yupa ◽  
Paola Albarrasín ◽  
Víctor M García
Keyword(s):  
Reference Method ◽  
Aquatic Life ◽  
Flow Rates ◽  
Minimum Flow ◽  
Tukey Test ◽  
Seasonal Flow ◽  
Ecological Flow ◽  
Del Rio ◽  
Hydrological Station ◽  
Ecological Flows

  La legislación del Ecuador obliga a mantener un caudal ecológico para preservar los ecosistemas y la biodiversidad. Sin embargo, son pocos los ríos en el país en los que se ha establecido el flujo mínimo. El objetivo de esta investigación fue determinar el caudal ecológico en el río Cutuchi, estación hidrológica Cutuchi A.J. Yanayacu (H792), mediante los métodos: Caudal de permanencia, Suizo, Tennant, Rafael Heras y Referencial. Adicionalmente, se comparó con el caudal ecológico al 10% del caudal medio mensual multianual establecido en la transitoria sexta de la ley ecuatoriana. También se analizó las tendencias del caudal y la precipitación en la cuenca alta del río Patate. Los resultados evidencian un caudal promedio anual de 9,64 m3/s para el río Cutuchi, con dos regímenes hidrológicos (avenidas y estiaje) que respondes a la distribución de las precipitaciones. La comparación de medias según la prueba de Tukey al 5%, determinó a los métodos Referenciales seguidos de Tennant, como adecuados para la sobrevivencia de la vida acuática en el río. De igual manera, los caudales estimados fueron superiores al caudal mínimo observado para el periodo 1990-2014. El análisis de tendencia mediante la prueba estadística de Mann-Kendall evidenció que el caudal anual y estacional presentaron cambios o tendencias significativas (p<0,01). Sin embargo, la precipitación no mostró cambios de aumento o disminución durante los 20 años (p<0,05=.   Palabras claves: Río Cutuchi, Caudales ecológicos, método Referencial, Tennant.   Abstract =Ecuador's legislation requires maintaining an ecological flow to preserve ecosystems and biodiversity. However, few rivers in the country where the minimum flow has been established. The objective of this research was to determine the ecological flow in the Cutuchi River, Cutuchi A.J. Yanayacu hydrological station (H792), using the methods: Permanence Flow, Swiss, Tennant, Rafael Heras and Referential. In addition, it was compared with the ecological flow to 10% of the average monthly multi-year flow established in the transitional sixth of Ecuadorian law. Flow and precipitation trends in the upper Patate River basin were also analyzed. The results show an average annual flow of 9.64 m3/s for the Cutuchi River, with two hydrological regimes (avenues and styling) that respond to the distribution of precipitation. The comparison of means according to the Tukey test at 5%, determined the Referential methods followed by Tennant, as suitable for the survival of aquatic life in the river. Similarly, the estimated flow rates were higher than the minimum flow observed for the period 1990-2014. Trend analysis using Mann-Kendall's statistical test showed that annual and seasonal flow showed significant changes or trends (p<0.01). However, precipitation showed no changes in increase or decrease during the 20 years (p<0.05=.   Keywords: Cutuchi River, Ecological flows, Reference method, Tennant.  

Способ управления давлением в системе водоснабжения

2020 ◽  
Author(s):  
R. Khadeev
Keyword(s):  
Water Supply ◽  
Control Systems ◽  
Pressure Control ◽  
Maximum Efficiency ◽  
Water Supply Systems ◽  
Flow Rates ◽  
Minimum Flow ◽  
Municipal Water Supply ◽  
Industrial Enterprises ◽  
Pumping Stations

Предложен способ управления напором в сети при работе насосных станций второго подъема. Устройство состоит из асимметричного планетарного дифференциала, соединенного с электроиндукционной силовой муфтой скольжения. Способ позволяет сохранить максимальный коэффициент полезного действия насоса и обеспечить экономичность его работы во всем диапазоне регулирования. Устройство регулятора напора в сети можно оценить, сравнив расчетную величину его коэффициента полезного действия, который составляет не менее 94 для минимальных значений расхода, при которых регулирование сильно затруднено. При оптимальных расходах системы ощутимые потери отсутствуют. Синхронный электродвигатель наиболее устойчив к перегрузкам, а при минимальных расходах обеспечивает необходимый напор, потребляя минимальное количество электроэнергии и сохраняя при этом свои номинальные обороты. Механизм был реализован в моделях и подтверждает заявленные параметры. Пока такая схема регулирования не была апробирована на реальных объектах, и не исследованы ее технико-экономические параметры. Она может быть применена в системах регулирования напора городской линии водоснабжения, в системах регулирования на предприятиях и в установках индивидуального обеспечения водой в частном доме.A method for pressure control in the network during the operation of pumping stations of the second elevation is proposed. The device consists of an asymmetric planetary differential connected to an eddy-current slip clutch. The method provides for maintaining the maximum efficiency and economic operation of the pump in the entire regulating range. The design of the pressure regulator in the network can be estimated by comparing the calculated efficiency value that is at least 94 for the minimum flow rates whereby the regulation is very difficult. At the optimal flow rates in the system there are no tangible losses. The synchronous electric motor is most resistant to overloads while at the minimum flow rates it provides for the required pressure consuming the minimum amount of electricity and at the same time maintaining the rated rpm. The mechanism was implemented in models and proved the claimed parameters. The presented control scheme neither has been approbated at existing facilities, nor its technical and economic parameters have been investigated, so far. It can be used in pressure control systems of a municipal water supply system, in control systems at industrial enterprises and in individual water supply systems in private houses.

Reactor concept for continuous reactions and extractions in supercritical fluids at minimum flow rates

2009 ◽  
Vol 48 (1) ◽  
pp. 33-35 ◽  
Author(s):  
Christoph Roosen ◽  
Jean-Luc Muller ◽  
Markus Kaever ◽  
Horst Kronenberg ◽  
Ralf Thelen ◽  
...  
Keyword(s):  
Supercritical Fluids ◽  
Flow Rates ◽  
Minimum Flow

Automation of Process Control in Chemical Plant

2015 ◽  
Vol 2 (1) ◽  
pp. 6-12
Author(s):  
Agus Sugiarta ◽  
Houtman P. Siregar ◽  
Dedy Loebis
Keyword(s):  
Process Control ◽  
Pid Control ◽  
Control Algorithm ◽  
Chemical Engineering ◽  
Chemical Plant ◽  
Raw Material ◽  
Flow Rates ◽  
Material Supply ◽  
Wide Range ◽  
Inherent Problem

Automation of process control in chemical plant is an inspiring application field of mechatronicengineering. In order to understand the complexity of the automation and its application requireknowledges of chemical engineering, mechatronic and other numerous interconnected studies.The background of this paper is an inherent problem of overheating due to lack of level controlsystem. The objective of this research is to control the dynamic process of desired level more tightlywhich is able to stabilize raw material supply into the chemical plant system.The chemical plant is operated within a wide range of feed compositions and flow rates whichmake the process control become difficult. This research uses modelling for efficiency reason andanalyzes the model by PID control algorithm along with its simulations by using Matlab.

A generic fluticasone propionate and salmeterol dry powder inhaler: Evidence of usability, function, and robustness

2021 ◽  
Vol 42 (1) ◽  
pp. 30-35 ◽  
Author(s):  
Donald P. Tashkin ◽  
Arkady Koltun ◽  
Róisín Wallace
Keyword(s):  
Chronic Obstructive Pulmonary Disease ◽  
Fluticasone Propionate ◽  
Healthy Volunteers ◽  
Pulmonary Disease ◽  
Dry Powder Inhaler ◽  
Chemical Degradation ◽  
Chronic Obstructive ◽  
Dry Powder ◽  
Obstructive Pulmonary Disease ◽  
Flow Rates

Background: A generic combination of fluticasone propionate and salmeterol xinafoate inhalation powder in a premetered, multidose, nonreusable inhaler was recently approved. Objective: To assess the performance of the generic device. Methods: Findings from three studies with regard to device usability, function, and robustness were reviewed. Results: In a study to assess device function in patients and healthy volunteers, the generic device was successfully used by patients with asthma and chronic obstructive pulmonary disease who were either dry powder inhaler users or dry powder inhaler‐naive, even though they were not trained beyond being provided the instructions for use. In a study to measure inhaled flow rates generated by patients and healthy volunteers, the generic device consistently simulated the delivery of a full dose of drug, even to patients with severe respiratory disease and reduced inspiratory flow rates. Although the generic device had a slightly higher airflow resistance, this study demonstrated that this difference did not result in any clinically meaningful differences in terms of drug delivery. Pressure drop, a key parameter that drives the fluidization and aerosolization of the powder dose, was found to be comparable between the devices. In an open-label study, the generic device met all U.S. Food and Drug Administration specifications for device robustness after 21.5 days of twice-daily dosing via oral inhalation among 111 participants with asthma or chronic obstructive pulmonary disease. All inhalers tested demonstrated conformity with a pharmacopeia with respect to key quality parameters (assay, delivered dose uniformity, aerodynamic size distribution). There was no evidence of chemical degradation of the active ingredients, nor of microbial or water ingress into the powder, as a result of inhaler use.

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