Experimental Characterization of Airflow Within a Clean HEPA Filter Used for the Containment of Radioactive Contamination in Nuclear Facilities

2016 ◽  
Author(s):  
Alilou Youssef ◽  
Bourrous Soleiman ◽  
Thomas Dominique ◽  
Bardin-Monnier Nathalie ◽  
Nérisson Philippe ◽  
...  
Keyword(s):  
Pressure Drop ◽  
High Efficiency ◽  
Filter Design ◽  
Physical Models ◽  
Airflow Rate ◽  
Nuclear Facilities ◽  
Airborne Contamination ◽  
Pleated Filters ◽  
The Impact

In hazardous industrial activities such as in nuclear facilities, High Efficiency Particulate Air filters (HEPA filters) are essential to ensure the containment of airborne contamination. Most of the filters used in ventilation networks are pleated, in order to offer a larger surface of filtration. For industrial risks likely to lead to an important release of particles (e.g. fire), predicting the evolution of the pressure drop of pleated filters is very important, in order to anticipate any dysfunction, failure or breaking of these devices. Pressure drop variations are linked to airflow rate variations and to clogging process of the medium by airborne particles. Thus, the airflow pattern in a pleat channel is essential for optimizing the filter design and enhancing its lifetime. Particles are transported by the airflow and deposited at the filter surface; hence, the geometry of the dust cake (shape and location) is partially determined knowing the velocity streamlines. The present paper focuses on the characterization of airflows in a clean HEPA filter. The difficulty to perform fine measurement on a real scale filter led us to develop an experimental device, consisting in the reproduction of a single pleat, identical to a real pleat constituting industrial filters. The small dimension of the pleat makes the velocity measurement difficult to establish. That is why μ-PIV method has been adapted to measure the velocity field inside the filter for different filtration velocities at the first moments of the experiment, in order to avoid the impact of clogging by particles used to seed the flow. These particles are DEHS droplets 0.01 < St < 0.05. In the future, these well-characterized airflows will be the basis for CFD computation of particle transport and deposition inside the pleats. Ultimately, the aim is to develop or upgrade physical models predicting the pressure drop evolution of pleated filters, during clogging process in accidental situations.

Active Air Control System Development Using Charge Air Integrated Manifold Engine Numerical Simulation (CAIMENS)

2007 ◽  
Author(s):  
Diana K. Grauer ◽  
Kirby S. Chapman ◽  
Ali Keshavar
Keyword(s):  
Numerical Simulation ◽  
Pressure Drop ◽  
Flow Rate ◽  
Pressure Wave ◽  
Equivalence Ratio ◽  
Peak Pressure ◽  
Intake Manifold ◽  
Airflow Rate ◽  
Engine System ◽  
The Impact

The natural gas transmission industry integrates turbochargers into the engine system to strategically increase airflow for the purpose of decreasing pollutant emissions, such as Nitrogen Oxide (NOX). Regulations are expected to be tightened in the coming years, forcing transmission companies to look past turbochargers for compliance. The solution to further decreasing emissions lies not in further retrofit, but focusing on the physics of the current system. The flow rate physics of the intake and exhaust manifolds impede equal distribution of air from the turbocharger to each cylinder. Imbalance in airflow creates a discontinuity in the trapped equivalence ratio from cylinder to cylinder. The trapped equivalence ratio is directly proportional to NOX production and a function of the fuel flow rate, airflow rate, and, in two-stroke cycle engines, the scavenging efficiency. Only when these three characteristics are balanced cylinder to cylinder will the combustion and the NOX production in each cylinder be equal. The engine NOX production will be disproportionately high if even one cylinder operates less lean relative to the other cylinders. Balancing the NOX production between cylinders can lower the overall NOX production of the engine. This paper reports on an investigation into the transient, compressible flow physics that impact the trapped equivalence ratio. A comprehensive, variable geometry, multi-cylinder Turbocharger-Reciprocating Engine Computer Simulation (T-RECS) has been developed to illustrate the effect of airflow imbalance on an engine. A new model, the Charge Air Integrated Manifold Engine Numerical Simulation (CAIMENS), is a manifold flow model coupled with the T-RECS engine processor that uses an integrated set of fundamental principles to determine the crank angle-resolved pressure, temperature, burned and unburned mass fractions, and gas exchange rates for the cylinder. CAIMENS has the ability to show the transient impact of one cylinder firing on each successive cylinder. The pulsation model also describes the impact of manifold pressure drop on in-cylinder peak pressure and the pressure wave introduced to the intake manifold by uncovering the intake ports. CAIMENS provides the information necessary to quantify the impact of airflow imbalance, and allows for the visualization of the engine system before and after airflow correction. The model shows that not only does the manifold pressure drop have a significant impact on the in-cylinder peak pressure, but it also has an impact on the pressure wave introduced to the intake manifold as the ports are opened. Also, each cylinder has a considerable impact on the airflow into each successive cylinder.

Evaluation of Air Filtration Options for an Industrial Gas Turbine

2015 ◽  
Author(s):  
Christopher A. Perullo ◽  
Josh Barron ◽  
Dale Grace ◽  
Leonard Angello ◽  
Tim Lieuwen
Keyword(s):  
Pressure Drop ◽  
Gas Turbines ◽  
Life Cycle Cost ◽  
High Efficiency ◽  
Air Filtration ◽  
Unit Output ◽  
Almost All ◽  
The Cost ◽  
The Impact ◽  
Unit Performance

Gas turbines ingest large quantities of air during operation. As a result, large quantities of foreign particles ranging in size from smoke (0.01 to 1.0 micron) to pollen (10 micron) enter the unit and can contribute to both fouling and erosion depending on particle size. Fouling and erosion both lead to reductions in unit output and efficiency resulting in increased operational cost. Operators have historically combatted fouling through a combination of online water washes, more effective off-line water washes, and air filtration. As is the case with almost all engineering problems, the trade-off between the cost and effectiveness of these methods must be evaluated. Online washing is somewhat effective but has led to first stage blade erosion and unit trips in some cases. Off-line washing is more effective at cleaning the unit, but requires the unit to be shut down for extended periods of time. Air filtration can help prevent foreign particles from entering the unit, but higher efficiency filters are generally associated with a larger inlet pressure drop, leading to decreased unit output; this is balanced against reduced fouling rates. These tradeoffs between the costs associated with higher efficiency filters and the frequency of compressor washing need to be evaluated on a plant-by-plant basis to determine the best combination of air filtration and compressor washing programs. This paper presents a field study carried out to determine the effectiveness of high efficiency filters in preventing compressor fouling. Fourteen units at four sites were monitored over a 9 month to 3 year time period to determine the changes in unit performance and the impact of water washes on unit performance for both pre and final filters of lower and higher efficiency ratings. Results to date indicate that higher efficiency filters are effective at reducing the need for off-line water washes and potentially reduce life-cycle cost. Reduced output from the higher pressure drop, high efficiency filters is offset by the better performance retention offered from reduced fouling rates.

Influence of Pleat Deformation on Pressure Drop for a High-Efficiency Particulate Air Filter: A Small-Scale Experimental Approach

2016 ◽  
Vol 3 (1) ◽  
Author(s):  
S. Bourrous ◽  
L. Bouilloux ◽  
P. Nerisson ◽  
D. Thomas ◽  
J. C. Appert-Collin
Keyword(s):  
Pressure Drop ◽  
Particle Deposition ◽  
Complex Analysis ◽  
High Efficiency ◽  
Numerical Approach ◽  
Small Scale ◽  
Contamination Level ◽  
Wide Range ◽  
Pleated Filters ◽  
Filtration Surface

For industrial or domestic applications, the wide range of use of pleated filters makes the understanding of their airflow behavior a major issue for designer and users. In all industrial installations dealing with radioactive matter, the containment of pollutants must be ensured. High-efficiency particulate air (HEPA) filters are used as the last purification stage before the air is rejected in the environment. These filters can be used either alone, in the case of nonsensible installation, or coupled with other filtration devices disposed before it where contamination level could be important. The prediction of their pressure drop is very important in nuclear safety to be able to anticipate any dysfunction or rupture of these devices. It has been observed that geometry of the medium has an influence on the pressure drop of a pleated filter. In the case of HEPA filters, no convincing explanation has been brought to explain their airflow behavior. The pressure drop evolution of the filter during the clogging remains difficult to explain by assuming constant pleat geometry. Some studies show that deformation occurs during the filter use, which could induce an increase of the available volume in the pleat and a reduction of the efficient filtration surface. The increase in computation capacity introduces nowadays the possibility to perform complex simulation, taking into account the effect of fluids on sensible devices. This can be the case for simple structural analysis or for more complex analysis such as vibration induced by gas or fluid flow. It is mostly applied to avoid breaking or deformation of safety devices, and this can also be applied to anticipate the fluid behavior of some special devices such as filters. In classical filtration application, properties of the filter are coupled with particle deposition (e.g., changes in geometry and permeability depend on the thickness of the deposit). The studies concerning mechanical properties of filters are mainly performed for liquid filtration and clean filters. For pleated filters, the complexity of this kind of analysis remains the modification of the link between geometry, pressure drop, mechanical strength, and particle transport and accumulation inside the pleat. As a first approach, it has been chosen to combine an experimental and a numerical approach to improve the understanding of filter behavior. In this paper, the pleat deformation will be investigated using a direct nonintrusive laser measurement performed on a single pleat experiment. The rate of filtration surface lost will be estimated using these data and taken into account to evaluate the pressure drop against the filtration velocity. Results obtained show that the pleat deformation is an important parameter, which influences the geometry of the pleat.

Preparation and Characterization of Fibrillated Nanofibrous Filter Material

2014 ◽  
Vol 936 ◽  
pp. 327-331 ◽  
Author(s):  
Tian Yu ◽  
Yan Bin Jiang ◽  
Jian Hu
Keyword(s):  
High Efficiency ◽  
Fiber Material ◽  
Filter Material ◽  
Air Permeability ◽  
Filtration Efficiency ◽  
Structure And Properties ◽  
Nanofiber Morphology ◽  
Opposite Trend ◽  
The Impact

The nanofiber, which diameter less than 1000 nm, has been discovered as advanced fiber material for high efficiency filtration. Tencel fiber is a new kind of regenerated fiber which can be easily fibrillated by a mechanical beating process to form nanofiber morphology. The present study shows the nanofiber morphology of Tencel fiber and investigates how the structure and properties of filter material change with the impact of fibrillated nanofiber. The results show a mass of nanofibril appeared after the Tencel fiber is intensively beat. At the same time, the air permeability and pore size of filter material is decreased with the decrease of fibrillated nanofiber content while the strength gets an opposite trend. Whats more, the filtration efficiency of the filter material is significantly enhanced by fibrillated nanofiber which filtration rate achieves 6.3 for particles bigger than 4 μm at 20 wt%. This paper has shed some light on the application of fibrillated fibrillated nanofiber to enhance the efficiency of filter material effectively.

scholarly journals CFD and Experimental Characterization of a Bioreactor: Analysis via Power Curve, Flow Patterns and k L a

Processes ◽  
2020 ◽  
Vol 8 (7) ◽  
pp. 878
Author(s):  
Luis A. Ramírez ◽  
Edwar L. Pérez ◽  
Cesar García Díaz ◽  
Dumar Andrés Camacho Luengas ◽  
Nicolas Ratkovich ◽  
...  
Keyword(s):  
Lower Energy ◽  
Scaling Up ◽  
Airflow Rate ◽  
Biological Processes ◽  
Experimental Characterization ◽  
Cfd Simulations ◽  
Transfer Rates ◽  
Curve Flow ◽  
The Impact

Mixing operations in biological processes is of utmost importance due to its effect on scaling-up and heat and mass transfer. This paper presents the characterization of a bench-top bioreactor with different impeller configurations, agitation and oxygen transfer rates, using CFD simulations and experimental procedures. Here, it is demonstrated that factors such as the type of impeller and the flow regime can drastically vary the operation as in the preparation of cultures. It was observed that the bioreactor equipped with a Rushton generates a k L a of 0.0056 s−1 for an agitation velocity and airflow rate of 250 RPM and 5 L/min, respectively. It is suitable result for the dissolved oxygen (DO) but requires a considerable amount of power consumption. It is here where the importance of the agitator’s diameter can be observed, since, in the case of the two propeller types studied, lower energy consumption can be achieved with a smaller diameter, as well as a much smaller shear cup 2.376 against 0.723 s−1 by decreasing by 4 cm the standard diameter of an agitated tank (10 cm). Finally, the k L a values obtained for the different configurations are compared with the maximum shear rate values of different cell cultures to highlight the impact of this study and its applicability to different industries that use agitation processes for cell growth.

scholarly journals Changes in Fan Energy Consumption According to Filters Installed in Residential Heat Recovery Ventilators in Korea

2021 ◽  
Vol 13 (18) ◽  
pp. 10119
Author(s):  
Kyungjoo Cho ◽  
Chang-U Chae ◽  
Dongwoo Cho ◽  
Taeyeon Kim
Keyword(s):  
Energy Consumption ◽  
Pressure Drop ◽  
Power Consumption ◽  
Ultrafine Particles ◽  
Heat Recovery ◽  
High Efficiency ◽  
Airflow Rate ◽  
Fan Performance ◽  
Air Volume

In recent years, because of outdoor ultrafine particles, residential heat recovery ventilators (HRVs) have been used with high efficiency filters by residents in Korea. However, as pre-filters are primarily used in residential HRVs, when a high-efficiency particulate air (HEPA) filter is installed, the filter pressure drop increases, reducing the airflow rate, which requires the fan to draw more power to maintain the airflow rate. Therefore, in this study, the change in power usage of HRVs installed in residential apartments in Korea with various air volumes and filters were analyzed. The results show that HEPA filters consumed 13.5–17.5% (16.1% on an average), 11.8–16.0% (13.8% on an average), and 16.8–41.3% (30.1% on an average) more power at 0.5, 1.0, and 1.5 air changes/h, respectively, than the pre-filter. These results indicate that unexpected power consumption increase could be caused if a pre-filter is replaced with a HEPA filter in residential small air-volume HRVs. This may lead to noise or failure due to fan overload. Thus, it is necessary to operate residential HRVs at the optimum air volume according to the fan performance.

scholarly journals Dynamic characterization of tungsten carbide behaviour at very high strain-rates

2018 ◽  
Vol 183 ◽  
pp. 02061
Author(s):  
Benjamin Erzar ◽  
Jean-Luc Zinszner
Keyword(s):  
Tungsten Carbide ◽  
High Efficiency ◽  
High Strength ◽  
Loading Path ◽  
Dynamic Characterization ◽  
Lagrangian Analysis ◽  
The Impact ◽  
Very High ◽  
Cemented Tungsten Carbide

Cemented tungsten carbide, with its very high density and high strength, is known to be the material composing several small calibre armour piercing ammunitions. The impact of a tungsten carbide core projectile onto a high efficiency armour often leads to the fracture of the tungsten carbide core. Thus, the pertinence of material models used in numerical simulations to describe the behaviour and the damage of the target is not sufficient to well predict a ballistic impact. In this work, the GEPI high-pulsed power generator is used to conduct dynamic characterization of the behaviour of a cemented tungsten carbide under both compressive and tensile loadings. The Hugoniot Elastic Limit of this material has been identified (HEL = 5.8 GPa). Moreover, Lagrangian analysis allowed the complete loading path to be identified up to 18 GPa.

Piezoelectric β-polymorph formation of new textiles by surface modification with coating process based on interfacial interaction on the conformational variation of poly (vinylidene fluoride) (PVDF) chains

2020 ◽  
Vol 91 (3) ◽  
pp. 31301
Author(s):  
Nabil Chakhchaoui ◽  
Rida Farhan ◽  
Meriem Boutaldat ◽  
Marwane Rouway ◽  
Adil Eddiai ◽  
...  
Keyword(s):  
High Efficiency ◽  
Vinylidene Fluoride ◽  
Research Work ◽  
Research Area ◽  
Interfacial Interaction ◽  
Tetraethyl Orthosilicate ◽  
Poly Vinylidene Fluoride ◽  
Carbon Nanofillers ◽  
The Impact ◽  
Advanced Applications

Novel textiles have received a lot of attention from researchers in the last decade due to some of their unique features. The introduction of intelligent materials into textile structures offers an opportunity to develop multifunctional textiles, such as sensing, reacting, conducting electricity and performing energy conversion operations. In this research work nanocomposite-based highly piezoelectric and electroactive β-phase new textile has been developed using the pad-dry-cure method. The deposition of poly (vinylidene fluoride) (PVDF) − carbon nanofillers (CNF) − tetraethyl orthosilicate (TEOS), Si(OCH2CH3)4 was acquired on a treated textile substrate using coating technique followed by evaporation to transform the passive (non-functional) textile into a dynamic textile with an enhanced piezoelectric β-phase. The aim of the study is the investigation of the impact the coating of textile via piezoelectric nanocomposites based PVDF-CNF (by optimizing piezoelectric crystalline phase). The chemical composition of CT/PVDF-CNC-TEOS textile was detected by qualitative elemental analysis (SEM/EDX). The added of 0.5% of CNF during the process provides material textiles with a piezoelectric β-phase of up to 50% has been measured by FTIR experiments. These results indicated that CNF has high efficiency in transforming the phase α introduced in the unloaded PVDF, to the β-phase in the case of nanocomposites. Consequently, this fabricated new textile exhibits glorious piezoelectric β-phase even with relatively low coating content of PVDF-CNF-TEOS. The study demonstrates that the pad-dry-cure method can potentially be used for the development of piezoelectric nanocomposite-coated wearable new textiles for sensors and energy harvesting applications. We believe that our study may inspire the research area for future advanced applications.

CHARACTERIZATION OF PRESSURE DROP AND VELOCITY FIELD IN A GAS-LIQUID CYCLONE SEPARATOR

2017 ◽  
Author(s):  
Juliana Loureiro ◽  
Atila Pantaleão Silva Freire ◽  
Gustavo Eduardo Oviedo Celis
Keyword(s):  
Velocity Field ◽  
Pressure Drop ◽  
Cyclone Separator

The Analyses of Learning Strategies in English as a Second Language: Theoretical Classification and Measurement Test

2020 ◽  
Vol 4 (2) ◽  
pp. 118-129
Author(s):  
Asti Gumartifa ◽  
◽  
Indah Windra Dwie Agustiani
Keyword(s):  
Language Learning ◽  
Learning Outcomes ◽  
Learning Strategies ◽  
Learning Process ◽  
English Learners ◽  
English Language ◽  
Point Of View ◽  
Effective Learning ◽  
The Impact

Gaining English language learning effectively has been discussed all years long. Similarly, Learners have various troubles outcomes in the learning process. Creating a joyful and comfortable situation must be considered by learners. Thus, the implementation of effective learning strategies is certainly necessary for English learners. This descriptive study has two purposes: first, to introduce the classification and characterization of learning strategies such as; memory, cognitive, metacognitive, compensation, social, and affective strategies that are used by learners in the classroom and second, it provides some questionnaires item based on Strategy of Inventory for Language Learning (SILL) version 5.0 that can be used to examine the frequency of students’ learning strategies in the learning process. The summary of this study explains and discusses the researchers’ point of view on the impact of learning outcomes by learning strategies used. Finally, utilizing appropriate learning strategies are certainly beneficial for both teachers and learners to achieve the learning target effectively.

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