scholarly journals About the Dependence of Breakthrough Curves on Flow Direction in Column Experiments of Transport across a Sharp Interface Separating Different Porous Materials

Geofluids ◽  
2019 ◽  
Vol 2019 ◽  
pp. 1-8
Author(s):  
Francesca Giacobbo ◽  
Mauro Giudici ◽  
Mirko Da Ros
Keyword(s):  
Porous Materials ◽  
Flow Direction ◽  
Breakthrough Curves ◽  
Coarse Grained ◽  
Low Flow ◽  
Flow Rates ◽  
Fine Grained ◽  
The Past ◽  
Asymmetric Behaviour ◽  
Flow Through

Conservative transport experiments with layered porous materials (coarse-grained vs. fine-grained) were performed through experimental cylindrical columns to assess the possible occurrence of interface processes at the discontinuity between media with different hydrodynamic and hydrodispersive properties, as proposed by some authors in the past based on modelling and experimental results. The outcomes of the present work show that, under certain conditions, the breakthrough curves (BTCs) obtained for flow through the coarse-grained and then through the fine-grained media (CtF) or vice versa (FtC) can differ. More specifically, an asymmetric behaviour is observed for cases when the ratio between the column and grain diameters is small. Moreover, the discrepancies between CtF and FtC BTCs are enhanced for low flow rates and low quantity of injected solute.

Assessment of the Use of Humidified Nasal Cannulas for Oxygen Therapy in Patients with Epistaxis

ORL ◽  
2021 ◽  
pp. 1-5
Author(s):  
Jingjing Liu ◽  
Tengfang Chen ◽  
Zhenggang Lv ◽  
Dezhong Wu
Keyword(s):  
Flow Rate ◽  
Oxygen Therapy ◽  
Preliminary Investigation ◽  
Nasal Cannula ◽  
Low Flow ◽  
Antiplatelet Drugs ◽  
Flow Rates ◽  
The Past ◽  
Oxygen Inhalation ◽  
Significant Difference

<b><i>Introduction:</i></b> In China, nasal cannula oxygen therapy is typically humidified. However, it is difficult to decide whether to suspend nasal cannula oxygen inhalation after the nosebleed has temporarily stopped. Therefore, we conducted a preliminary investigation on whether the use of humidified nasal cannulas in our hospital increases the incidence of epistaxis. <b><i>Methods:</i></b> We conducted a survey of 176,058 inpatients in our hospital and other city branches of our hospital over the past 3 years and obtained information concerning their use of humidified nasal cannulas for oxygen inhalation, nonhumidified nasal cannulas, anticoagulant and antiplatelet drugs, and oxygen inhalation flow rates. This information was compared with the data collected at consultation for epistaxis during these 3 years. <b><i>Results:</i></b> No significant difference was found between inpatients with humidified nasal cannulas and those without nasal cannula oxygen therapy in the incidence of consultations due to epistaxis (χ<sup>2</sup> = 1.007, <i>p</i> &#x3e; 0.05). The same trend was observed among hospitalized patients using anticoagulant and antiplatelet drugs (χ<sup>2</sup> = 2.082, <i>p</i> &#x3e; 0.05). Among the patients with an inhaled oxygen flow rate ≥5 L/min, the incidence of ear-nose-throat (ENT) consultations due to epistaxis was 0. No statistically significant difference was found between inpatients with a humidified oxygen inhalation flow rate &#x3c;5 L/min and those without nasal cannula oxygen therapy in the incidence of ENT consultations due to epistaxis (χ<sup>2</sup> = 0.838, <i>p</i> &#x3e; 0.05). A statistically significant difference was observed in the incidence of ENT consultations due to epistaxis between the low-flow nonhumidified nasal cannula and nonnasal cannula oxygen inhalation groups (χ<sup>2</sup> = 18.428, <i>p</i> &#x3c; 0.001). The same trend was observed between the 2 groups of low-flow humidified and low-flow nonhumidified nasal cannula oxygen inhalation (χ<sup>2</sup> = 26.194, <i>p</i> &#x3c; 0.001). <b><i>Discussion/Conclusion:</i></b> Neither high-flow humidified nasal cannula oxygen inhalation nor low-flow humidified nasal cannula oxygen inhalation will increase the incidence of recurrent or serious epistaxis complications; the same trend was observed for patients who use anticoagulant and antiplatelet drugs. Humidification during low-flow nasal cannula oxygen inhalation can prevent severe and repeated epistaxis to a certain extent.

THE FLOW OF FLUIDS THROUGH ACTIVATED CARBON RODS.

1952 ◽  
Vol 30 (4) ◽  
pp. 348-371 ◽  
Author(s):  
E. A. Flood ◽  
R. H. Tomlinson ◽  
A. E. Leger
Keyword(s):  
Activated Carbon ◽  
Relative Pressure ◽  
End Effects ◽  
Flow Rates ◽  
Frequency Distributions ◽  
Literal Sense ◽  
Fine Grained ◽  
Porous Bodies ◽  
Carbon Rods ◽  
Flow Through

The flow rates of the vapors of benzene, ethyl chloride, diethyl ether, methanol, and water through activated carbon rods have been found to exceed, considerably, flow rates calculated by classical equations. The excess flow rates show maxima in widely different relative pressure regions and are ascribed to flow of adsorbed material. An empirical equation is presented which correlates the observed flow rates with relevant adsorption isotherms. Classical equations of flow through elliptical and rectangular pipes are discussed with reference to flow through fine-grained porous materials. It is shown that equations of the Adzumi type are roughly valid as applied to fine-grained porous bodies, but that without a knowledge of the frequency distributions of pore sizes and shapes, flow data cannot be related to pore dimensions in any literal sense. End effects are discussed.

An LDV Study of the Influence of the Radiator on a Cooling Module Fan

2002 ◽  
Author(s):  
Robert J. Martinuzzi ◽  
Gregory A. Kopp ◽  
Brian Havel
Keyword(s):  
Laser Doppler Velocimetry ◽  
Reverse Flow ◽  
Low Flow ◽  
Doppler Velocimetry ◽  
Flow Conditions ◽  
Flow Rates ◽  
Cooling Fan ◽  
Outlet Flow ◽  
Flow Through ◽  
Cooling Module

The influence of the radiator on the flow through an automotive cooling fan module was investigated using Laser Doppler Velocimetry for three different flow conditions. It is found that at the nominal design point, the radiator acts as an effective flow straightener. At low flow rates, fan induced pre-swirl is significant, but the radiator helps reduce reverse flow through the fan. Under ram air conditions the upstream inlet distortions persist through the module resulting in a highly distorted outlet flow.

Compressible Simulation of Flow and Sound Around a Small Axial-Flow Fan With Flow Through Casing Slits

2020 ◽  
Vol 142 (10) ◽  
Author(s):  
Hiroshi Yokoyama ◽  
Katsutake Minowa ◽  
Kohei Orito ◽  
Masahito Nishikawara ◽  
Hideki Yanada
Keyword(s):  
Flow Field ◽  
Flow Rate ◽  
Aerodynamic Performance ◽  
Design Flow ◽  
Low Flow ◽  
Axial Fan ◽  
Flow Rates ◽  
Blade Tip ◽  
Flow Through ◽  
Design Flow Rate

Abstract Small axial fans are used for cooling electronic equipment and are often installed in a casing with various slits. Direct aeroacoustic simulations and experiments were performed with different casing opening ratios to clarify the effects of the flow through the casing slits on the flow field and acoustic radiation around a small axial fan. Both the predicted and measured results show that aerodynamic performance deteriorates at and near the design flow rate and is higher at low flow rates by completely closing the casing slits compared with the fan in the casing with slits. The predicted flow field shows that the vortical structures in the tip vortices are spread by the suppression of flow through the slits at the design flow rate, leading to the intensification of turbulence in the blade wake. Moreover, the pressure fluctuations on the blade surface are intensified, which increases the aerodynamic sound pressure level. The suppression of the outflow of pressurized air through the downstream part of the slits enhances the aerodynamic performance at low flow rates. Also, the predicted surface streamline at the design flow rate shows that air flows along the blade tip for the fan with slits, whereas the flow toward the blade tip appears for the fan without slits. As a result, the pressure distributions on the blade and the torque exerted on the fan blade are affected by the opening ratio of slits.

Transport Phenomena in Novel Microstructures for Use in Thermal Separation Processes

2009 ◽  
Author(s):  
Lukas E. Wiesegger ◽  
Ralf P. Knauss ◽  
Thomas Winkler ◽  
Stefan Maikowske ◽  
Ju¨rgen J. Brandner ◽  
...  
Keyword(s):  
Gaseous Phase ◽  
Phase Distribution ◽  
Flow Direction ◽  
Test System ◽  
Operating Conditions ◽  
Low Flow ◽  
Optimum Operating ◽  
Liquid Distribution ◽  
Flow Rates ◽  
Vof Model

In the present work novel microstructures are developed and studied by means of analytical and numerical methods. These microstructures form part of a demonstration microdevice to carry out a distillation without chemical reaction, two for the liquid and gaseous phase distribution/collection, and one for the liquid/gas mass transfer (“μTU-I,-II”). A solution for the 3D velocity field for the velocity component w in flow direction can be given for the rectangular and semicircular microchannel by using a lubrication approximation which gives good realistic values for the Reynolds number at low flow rates comparing to the common 2D approaches. The μTU-I is studied using the CFD code (6.3 FLUENT ® - 3ddp) by the approach of the VOF model. The simulations are performed with the test system methanol/water (distillation). By varying the flow rates of both phases and the contact angle, the condition until the occurrence of flooding of the microunit “μTU-I” is determined. The flooding and the optimum operating conditions of a new optimized configuration “μTU-II” -microunit are also investigated by means of numerical simulation (CFD). It can be shown that longitudinal instability is generated. Based on several concepts for liquid and gaseous phase distribution/collection by the Forschungszentrum Karlsruhe, novel microstructures (“Liquid-Distribution-Collection-Microstructure”, “Vapor-Distribution-Collection-Microstructure”) for both phases are developed, studied and optimized by using CFD. The results of all studies are verified based on the demonstration device in the laboratory.

Electroosmotic Flow Through Porous Materials

2014 ◽  
Author(s):  
Rakesh Saini ◽  
Matthew Kenny ◽  
Dominik P. J. Barz
Keyword(s):  
Porous Materials ◽  
Electroosmotic Flow ◽  
Capillary Flow ◽  
Cost Effective ◽  
Packed Bed ◽  
Flow Rates ◽  
Bed Porosity ◽  
Flow Through ◽  
Set Up ◽  
Air Liquid Interface

Electroosmotic flow can be employed in many microfluidic systems. Especially, highly porous materials are suitable since they generate significant flow rates and pressures. In the current research, we employ electroosmosis experiments using a relatively simple and cost-effective set-up including different sets of sintered packed beds of borosilicate micro spheres having a wider range of porosities. Various experiments are performed with varying applied electric field, and packed bed porosity. The flow rates are measured by tracking the air/liquid interface in a capillary which is connected to the packed bed. A mathematical model of the setup reveals the influence of the capillary flow on the flow rate of the electroosmotic flow.

Liquid Transport Properties in Sub-Micron Channel Flows

2001 ◽  
Author(s):  
K. Johan A. Westin ◽  
Kenneth S. Breuer ◽  
Chang-Hwan Choi ◽  
Peter Huang ◽  
Zhiqiang Cao ◽  
...  
Keyword(s):  
Flow Rate ◽  
Low Flow ◽  
Slip Boundary Conditions ◽  
Liquid Transport ◽  
Flow Rates ◽  
Slip Boundary ◽  
Laminar Channel Flow ◽  
Flow Through ◽  
Set Up ◽  
Good Agreement

Abstract An experimental set-up for pressure driven liquid flow through microchannels have been designed and tested. The flow rate is determined by tracking the free liquid surface in a precision bore hole using a laser distance meter. Measurements of the flow rate through silicon microchannels with a height of less than 0.9 μm show good results for Newtonian fluids (silicon oil, ethanol) at flow rates as low as 0.2 nl/s. The experimental results are also in very good agreement with predictions based on laminar channel flow using no-slip boundary conditions, indicating that standard macroscopic assumptions are still valid for these fluids under these conditions. However, experiments with aqueous solutions show anomalies in the form of unexpectedly low flow rates and time dependent variations. Possible explanations to these observations are discussed.

Solute Breakthrough Curves for Processed Kaolin at Low Flow Rates

1995 ◽  
Vol 121 (1) ◽  
pp. 17-32 ◽  
Author(s):  
Charles D. Shackelford ◽  
Patrick L. Redmond
Keyword(s):  
Breakthrough Curves ◽  
Low Flow ◽  
Flow Rates
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