Experimental Study of Water and Air Based Permeabilities of Washed and Screened Sands

2005 ◽  
Author(s):  
Shu-Ye Lei
Keyword(s):  
Experimental Data ◽  
Experimental Study ◽  
Porous Media ◽  
Particle Diameter ◽  
Velocity Slip ◽  
Slip Effect ◽  
Slip Effects ◽  
Water Based ◽  
The Mean ◽  
Mean Particle Diameter

The permeability of narrow screened washed sands of granularity 100–450 μm was measured experimentally using water and air to investigate the effect of slip on the gas based permeability. The experimental data show that the air based permeability of the unconsolidated particle media is not proportional to the square of the mean particle diameter and that slip significantly affects the air based permeability measurements for unconsolidated porous media. The velocity slip effect is significant even for Kn<10−3. Slip effects were not found in the water based permeability measurements with the same sand samples. All of the experimental data lay around the curve k/d=0.283φ2.67 within ± 4.1%. However, the water based permeability was not below all of the air based permeability as expected. The air based permeability eliminated slip effects was about 59 % lower than that water based one, much larger than possible measurement. The experimental results showed that the standard air viscosity value in the handbooks was not its actual, the actual air viscosity may be over twice of that in handbooks.

Prediction of the deflagration index for organic dusts as a function of the mean particle diameter

2017 ◽  
Vol 50 ◽  
pp. 67-74 ◽  
Author(s):  
Anna Fumagalli ◽  
Marco Derudi ◽  
Renato Rota ◽  
Jef Snoeys ◽  
Sabrina Copelli
Keyword(s):  
Particle Diameter ◽  
Deflagration Index ◽  
The Mean ◽  
Mean Particle Diameter

Influence of nucleating agent type on the morphology of extruded polyetherimide foam for printed circuit boards*

2019 ◽  
Vol 56 (3) ◽  
pp. 317-341 ◽  
Author(s):  
Clemens Keilholz ◽  
Daniel Raps ◽  
Thomas Köppl ◽  
Volker Altstädt
Keyword(s):  
Surface Tension ◽  
Printed Circuit Boards ◽  
Particle Diameter ◽  
Nucleating Agent ◽  
Nucleating Agents ◽  
Circuit Boards ◽  
Printed Circuit ◽  
Foam Morphology ◽  
The Mean ◽  
Mean Particle Diameter

This work focuses on the development of foamed high temperature thermoplastic substrates for printed circuit boards. For this application it is necessary to achieve mean cell diameters smaller than 30 µm in order to be able to realize vias and high packaging densities (miniaturization). Different additives as nucleating agents, namely macro- and micro-crystalline talc, silica, calcium carbonate, and wollastonite, were melt-compounded with polyetherimide using a twin-screw extruder. Foamed samples are prepared by foam extrusion using a slit die and CO2 as physical blowing agent. The aim of this study is to analyze the influence of the mean particle size and the particle surface tension on the mean cell diameters. Therefore, the shape of the additives, the foam morphology, and the elongational viscosity were considered. The additives with a suitable particle size and surface tension exhibit a positive influence on the foam morphology, resulting in smaller cell diameters (<30 µm), a narrower cell size distribution and a foam density lower than 900 kg/m3. If the mean particle diameter of the nucleating agents is lower than 0.6 µm in this study, no nucleation effect could be observed. This is related to the fact that no heterogeneous nucleation occurs, if the particle diameter is too small. If the mean particle diameter of the used additives is larger than 1.5 µm, which could be demonstrated in this study in case of polyetherimide, then the additive acts as nucleating agent and heterogeneous nucleation occurs. Furthermore, it was observed that the mean cell diameter was affected by the different surface tensions of the studied nucleating agents.

scholarly journals The role of mixing layer on changes of particle properties in lower troposphere

2009 ◽  
Vol 9 (4) ◽  
pp. 16483-16525
Author(s):  
L. Ferrero ◽  
E. Bolzacchini ◽  
M. G. Perrone ◽  
S. Petraccone ◽  
G. Sangiorgi ◽  
...  
Keyword(s):  
Size Distribution ◽  
Mixing Layer ◽  
Particle Diameter ◽  
Lower Troposphere ◽  
Atmospheric Particulate Matter ◽  
Vertical Profiles ◽  
Stable Conditions ◽  
The Mean ◽  
Hierarchical Statistical Model ◽  
Mean Particle Diameter

Abstract. Vertical profiles of atmospheric particulate matter number concentration, size distribution and chemical composition were directly measured in the city of Milan, over three years (2005–2008) of field campaigns. An optical particle counter, a portable meteorological station and a miniaturized cascade impactor were deployed on a tethered balloon. Mixing layer height was estimated by PM dispersion along height. More than 300 PM vertical profiles were measured both in the winter and summer, mainly in clear and dry sky conditions. Under these conditions, no significant changes in NO3−, SO42− or NH4+ into or over the mixing layer were found. From experimental measurements we observed changes in size distribution along height. An increase of the mean particle diameter, in the accumulation mode, passing through the mixing layer under stable conditions was highlighted; the mean relative growth was 2.1±0.1% in the winter and 3.9±0.3% in the summer. At the same time, sedimentation processes occurred across the ML height for coarse particles leading to a mean particle diameter reduction (14.9±0.6% in the winter and 10.7±1.0% in summer). A hierarchical statistical model for the PM size distribution has been developed to describe the aging process of the finest PM fraction along height. The proposed model is able to estimate the typical vertical profile that characterises launches within pre-specified groups. The mean growth estimated on the basis of the model was 1.9±0.5% in the winter and 6.1±1.2% in the summer, in accordance with experimental evidence.

scholarly journals Experimental study of forced convection heat transport in porous media

2017 ◽  
Author(s):  
Nicola Pastore ◽  
Claudia Cherubini ◽  
Dimitra Rapti ◽  
Concetta I. Giasi
Keyword(s):  
Heat Transfer ◽  
Experimental Data ◽  
Experimental Study ◽  
Porous Medium ◽  
Porous Media ◽  
Heat Transport ◽  
Forced Convection ◽  
Convection Heat Transfer ◽  
Convection Heat ◽  
Forced Convection Heat Transfer

Abstract. The knowledge of the dynamics of forced convection heat transfer in porous media is relevant in order to optimize the efficiency of geothermal installations in aquifers. In some applications groundwater is used directly as thermal fluid. The system uses one or several drilling holes to pump and deliver groundwater with a heat exchange system at surface (open loop). Other applications use vertical borehole heat exchangers without injection or extraction of groundwater (closed loop). In both systems the convection flow dynamics in porous media play an important role on the heat production. The present study is aimed at extending this thematic issue through heat transport experiments and their interpretation at laboratory scale. An experimental study to evaluate the dynamics of forced convection heat transfer in a thermally isolated column filled with porous medium has been carried out. The behavior of two porous media having different grain sizes and specific surfaces has been observed. The experimental data have been compared with an analytical solution for one dimensional heat transport for local non thermal equilibrium condition. The interpretation of the experimental data shows that, the heterogeneity of the porous medium affects heat transport dynamics causing a channeling effect which has consequences on thermal dispersion phenomena and heat transfer between fluid and solid phases limiting the capacity to store or dissipate heat in the porous medium.

Number concentration dependence of ultrasonic disruption ratio of diameter-sorted microcapsules

2022 ◽  
pp. 095441192110703
Author(s):  
Junsyou Kanashima ◽  
Naohiro Sugita ◽  
Tadahiko Shinshi
Keyword(s):  
Drug Delivery Systems ◽  
Focused Ultrasound ◽  
Particle Number ◽  
Particle Diameter ◽  
Number Concentration ◽  
The Mean ◽  
And Control ◽  
Polymer Shells ◽  
Filtration Technique ◽  
Mean Particle Diameter

The use of ultrasound to destroy microcapsules in microbubble-assisted drug delivery systems (DDS) is of great interest. In the present study, the disruption ratios of capsule clusters were measured by observing and experimentally analyzing microcapsules with polymer shells undergoing disruption by ultrasound. The microcapsules were dispersed in a planar microchamber filled with a gelatin gel and sonicated using 1 MHz focused ultrasound. Different capsule populations were obtained using a filtration technique to modify and control the capsule sizes. The disruption ratio as a function of the concentration of capsules was obtained through image processing of the recorded photomicrographs. We found that the disruption ratio for each population exponentially decreases as the particle number concentration (PNC) increases. The maximum disruption ratio of the diameter-sorted capsules was larger than that of polydispersed capsules. Particularly, for resonant capsule populations, the ratio was more than twice that of polydispersed capsules. Furthermore, the maximum disruption ratio occurred at higher concentrations as the mean particle diameter of the capsule cluster decreased.

Numerical and experimental study on knocking combustion in turbocharged direct-injection engines for a wide range of operating conditions

2021 ◽  
pp. 146808742110601
Author(s):  
Magnus Kircher ◽  
Emmeram Meindl ◽  
Christian Hasse
Keyword(s):  
Experimental Data ◽  
Experimental Study ◽  
Numerical Study ◽  
Direct Injection ◽  
Operating Conditions ◽  
Auto Ignition ◽  
Spark Timing ◽  
Crank Angle ◽  
Wide Range ◽  
The Mean

A combined experimental and numerical study is conducted on knocking combustion in turbocharged direct-injection spark-ignition engines. The experimental study is based on parameter variations in the intake-manifold temperature and pressure, as well as the air-fuel equivalence ratio. The transition between knocking and non-knocking operating conditions is studied by conducting a spark timing sweep for each operating parameter. By correlating combustion and global knock quantities, the global knock trends of the mean cycles are identified. Further insight is gained by a detailed analysis based on single cycles. The extensive experimental data is then used as an input to support numerical investigations. Based on 0D knock modeling, the global knock trends are investigated for all operation points. Taking into consideration the influence of nitric oxide on auto-ignition significantly improves the knock model prediction. Additionally, the origin of the observed cyclic variability of knock is investigated. The crank angle at knock onset in 1000 consecutive single cycles is determined using a multi-cycle 0D knock simulation based on detailed single-cycle experimental data. The overall trend is captured well by the simulation, while fluctuations are underpredicted. As one potential reason for the remaining differences of the 0D model predictions local phenomena are investigated. Therefore, 3D CFD simulations of selected operating points are performed to explore local inhomogeneities in the mixture fraction and temperature. The previously developed generalized Knock Integral Method (gKIM), which considers the detailed kinetics and turbulence-chemistry interaction of an ignition progress variable, is improved and applied. The determined influence of spark timing on the mean crank angle at knock onset agrees well with experimental data. In addition, spatially resolved information on the expected position of auto-ignition is analyzed to investigate causes of knocking combustion.

Experimental and Numerical Investigations of Air Flow Characteristics Through Microporous Media

2006 ◽  
Author(s):  
Ruina Xu ◽  
Peixue Jiang
Keyword(s):  
Experimental Data ◽  
Porous Media ◽  
Flow Regime ◽  
Air Flow ◽  
Slip Flow ◽  
Particle Diameter ◽  
Flow Characteristics ◽  
Average Particle ◽  
Friction Factors ◽  
Slip Flow Regime

The effect of particle diameter on the air flow characteristics in various micro-porous media test sections was studied experimentally and numerically. The test sections were made of bronze particles with average diameters of 200 μm, 125 μm, 90 μm and 40 μm. The experimentally measured friction factors in the porous media with average diameters of 200 μm and 125 μm agree well with the known correlation. However, the experimental values for the friction factors in the micro-porous media with 90 μm a and 40 μm average diameters are much less than the known correlation. Also, the differences between the experimental results and the known correlation increase with decreasing average particle diameter. Numerical simulations of the air flow in micro-porous media including rarefaction were performed using the CFD code FLUENT 6.1 to predict the pressure drop characteristics in the four test sections. The calculated friction factors for the non-slip flow regime in the micro-porous media agree well with the known correlation and the experimental data. The numerically predicted friction factors for the slip flow regime in the micro-porous media with 90 μm and 40 μm diameter particles were less than the known correlation and close to the experimental data. The results show that rarefaction effects occur in air flows in the micro-porous media with particle diameters less than 90 a and that numerical calculations with velocity slip on the boundary can simulate the slip flows in micro-porous media.

scholarly journals EXPERIMENTAL STUDY OF THE INLET FLOW IN A NON-PREMIXED COMBUSTION CHAMBER

2020 ◽  
Vol 19 (1) ◽  
pp. 72
Author(s):  
B. P. Trevisan ◽  
W. M. C. Dourado
Keyword(s):  
Fluid Dynamics ◽  
Experimental Data ◽  
Experimental Study ◽  
Combustion Chamber ◽  
Equivalence Ratio ◽  
Premixed Combustion ◽  
Laser Doppler Velocimeter ◽  
Mean Flow ◽  
Inlet Flow ◽  
The Mean

The evaluation, validation and development of the models used in computation fluid dynamics requires the availability of experimental data for which the boundary conditions, especially the conditions of the inlet flow, are well defined. Laser diagnostics techniques provide experimental data used in computational fluid dynamics and are a powerful tool for measurements of the mean properties and fluctuations of the turbulent flow because they are non-intrusive methods, with high repetition rate and high spatial and temporal resolution. Therefore, in the present work an experimental study of the inlet flow (inert and combusting flows) in a non-premixed combustion chamber is presented. The velocity measurements were carried out using a laser Doppler velocimeter at the entrance region of the combustion chamber. An asymmetry on the mean flow and an increase on the total velocity fluctuations with the increase of the equivalence ratio was observed. The major effect on the increase of the equivalence ratio was a presence of a coherent movement on large scales associated to the flame brush dynamics.

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