COMPARISON OF FOUR PARTICLE DEPOSITION RATE FORMULAE IN LAMINAR FLOW

2021 ◽  
Vol 21 (84) ◽  
Author(s):  
Muhammad Isnaeni
Keyword(s):  
Laminar Flow ◽  
Deposition Rate ◽  
Particle Deposition

scholarly journals Airflow and Particle Deposition in Acinar Models with Interalveolar Septal Walls and Different Alveolar Numbers

2018 ◽  
Vol 2018 ◽  
pp. 1-18 ◽  
Author(s):  
Jinxiang Xi ◽  
Mohamed Talaat ◽  
Hesham Tanbour ◽  
Khaled Talaat
Keyword(s):  
Deposition Rate ◽  
Particle Deposition ◽  
Orientation Angle ◽  
Structural Complexity ◽  
Particle Dispersion ◽  
Breath Holding ◽  
Complex Models ◽  
Tracking Model ◽  
Lagrangian Tracking ◽  
Collateral Ventilation

Unique features exist in acinar units such as multiple alveoli, interalveolar septal walls, and pores of Kohn. However, the effects of such features on airflow and particle deposition remain not well quantified due to their structural complexity. This study aims to numerically investigate particle dynamics in acinar models with interalveolar septal walls and pores of Kohn. A simplified 4-alveoli model with well-defined geometries and a physiologically realistic 45-alveoli model was developed. A well-validated Lagrangian tracking model was used to simulate particle trajectories in the acinar models with rhythmically expanding and contracting wall motions. Both spatial and temporal dosimetries in the acinar models were analyzed. Results show that collateral ventilation exists among alveoli due to pressure imbalance. The size of interalveolar septal aperture significantly alters the spatial deposition pattern, while it has an insignificant effect on the total deposition rate. Surprisingly, the deposition rate in the 45-alveoli model is lower than that in the 4-alveoli model, indicating a stronger particle dispersion in more complex models. The gravity orientation angle has a decreasing effect on acinar deposition rates with an increasing number of alveoli retained in the model; such an effect is nearly negligible in the 45-alveoli model. Breath-holding increased particle deposition in the acinar region, which was most significant in the alveoli proximal to the duct. Increasing inhalation depth only slightly increases the fraction of deposited particles over particles entering the alveolar model but has a large influence on dispensing particles to the peripheral alveoli. Results of this study indicate that an empirical correlation for acinar deposition can be developed based on alveolar models with reduced complexity; however, what level of geometry complexity would be sufficient is yet to be determined.

Measured Effects of Reduced Flow Velocity in a Laminar Flow Cleanroom

1994 ◽  
Vol 37 (3) ◽  
pp. 41-46
Author(s):  
Peter Carr ◽  
Angelo Rapa ◽  
William Fosnight ◽  
Robert Baseman ◽  
Douglas Cooper
Keyword(s):  
Laminar Flow ◽  
Particle Deposition ◽  
Deposition Velocity ◽  
Equivalent Diameter ◽  
Surface Deposition ◽  
Deposition Velocities ◽  
Airborne Concentration ◽  
Class 1 ◽  
Surface Particle ◽  
Contamination Levels

Vertical laminar flow (VLF) cleanrooms generally operate with airflows between 60 feet per minute (fpm) and 110 fpm. Tests were performed to evaluate the effects on particle contamination levels when the airflow velocity in a FED-STD-209 Class 1 VLF cleanroom was reduced. The cleanroom normally operates at 90 fpm. Measurements of surface particle concentrations were made on settling monitor wafers and on wafers carried in an open cassette. Optical particle counters measured the airborne particle concentrations at several locations. Results at 100 fpm and 50 fpm, respectively, for particles larger than or equal to 0.3 μm in optical equivalent diameter were −0.0002 and +0.0029 particles/sq cm/hr for the settling wafers and 0.009 and 0.024/sq cm total for the wafers carried for 5 hr in the open cassettes. Summary statistics are provided for the airborne and surface particle counts. Deposition velocity is the ratio of surface deposition rate to airborne concentration. For the monitor wafers at the lower flow, the calculated particle deposition velocities were near 0.003 cm/sec, which is within the range expected from theory and experiments in the literature.

Diffusive, Electrostatic, and Gravitational Deposition of Suspensions in the Entrance of a Nozzle

1983 ◽  
Vol 50 (1) ◽  
pp. 1-7
Author(s):  
T. A. Korjack
Keyword(s):  
Mathematical Model ◽  
Brownian Motion ◽  
Laminar Flow ◽  
Gravity Field ◽  
Deposition Rate ◽  
Flow Parameter ◽  
Deposition Process ◽  
Electrostatic Charge ◽  
Analytical Investigation ◽  
Nozzle Inlet

An analytical investigation of the mechanics of deposition affected by gravity, electrostatic charge, and Brownian motion in an effuser from the nozzle inlet to a distance where incompressible effects are still valid has been made and a mathematical model developed for the deposition process. The analysis was restricted to laminar flow of dilute, nonreactive suspensions contained within an incompressible, viscous carrier. The results show that increasing the nozzle angle causes a decrease in deposition rate regardless of the diffusive Peclet number and gravity flow parameter. Furthermore, an increase in gravity field causes an increase in bottom deposition rate and decrease in top deposition rate.

Effect of Brownian Diffusion and Particle Size on Thermophoretic Flow

1995 ◽  
Author(s):  
S. Jayaraj
Keyword(s):  
Particle Size ◽  
Laminar Flow ◽  
Aerosol Particle ◽  
Particle Deposition ◽  
Brownian Diffusion ◽  
Particle Sizes ◽  
Deposition Mechanism ◽  
Hot Gas ◽  
Grid Adaptation ◽  
Schmidt Numbers

Abstract This work attempts to analyse the aerosol particle deposit on in laminar flow over a flat plate with hot gas flowing over it. Solution is obtined by a finite difference marching procedure with grid adaptation. Prediciton were made about aerosol particle deposition due to Brownian diffusion and also due to the phenomenon of thermophoresis. The regions of importance of the two different mechanisims are approximately predicted by analysis the results for different particle sizes. The results are validated by comparision with similarity solution. It is observed that thermophoresis is the predominant deposition mechanism for Schmidt numbers ranging from 100 to 106, whereas for Schmidt numbers ranging from 100 to 103 Brownian diffusion has a strong effect on the deposition rate.

Simulation of Submicron Particle Deposition in Laminar and Turbulent Stagnation Point Flows

1991 ◽  
Author(s):  
Salem Abuzeid ◽  
Ahmed A. Busnaina
Keyword(s):  
Brownian Motion ◽  
Stagnation Point ◽  
Deposition Rate ◽  
Particle Deposition ◽  
Aerosol Particles ◽  
Laminar Flows ◽  
Wafer Surface ◽  
Particle Sizes ◽  
Mean Flow ◽  
Gaussian Random Process

Abstract The two dimensional laminar and turbulence stagnation-point flow over a wafer surface within a cleanroom environment are numerically simulated. This study shows the relationship between particle capture area on the wafer and the particle size and flow conditions. The mean flow field is simulated using a two equation k-ϵ turbulence model. Trajectories of aerosol particles are evaluated by solving the corresponding Lagrangian equation of motion that includes effects of drag, gravity, lift force, Brownian motion and turbulence fluctuations. The Brownian motion is modeled as a white noise process and turbulence fluctuation is assumed to behave as Gaussian random process. Simulations are carried out for aerosol particles (of various sizes) released at different locations over the surface. Depositions of particles on the wall are evaluated and a capture area which varies with particle sizes is produced. The results show that Brownian motion becomes very significant when turbulence fluctuations start to disappear near the wall for particles smaller than 1 μm in diameter. The results also show that, deposition of particles in turbulent flows are usually higher than that in laminar flows for all particle sizes considered. The effect of fluid on particle deposition rate is predicted for fluid of air and water. The results show that, particles deposition rate in air is higher than that in water.

Blower-door estimates of PM2.5 deposition rates and penetration factors in an idealized room

2020 ◽  
pp. 1420326X2094442 ◽  
Author(s):  
Yonghang Lai ◽  
Ian Ridley ◽  
Peter Brimblecombe
Keyword(s):  
Deposition Rate ◽  
Coefficient Of Variation ◽  
Particle Deposition ◽  
Experimental Methods ◽  
Test Cell ◽  
Deposition Rates ◽  
Penetration Factor ◽  
Surface Materials ◽  
Novel Method ◽  
Indoor And Outdoor

Particle deposition and penetration in buildings has been widely studied, but the effect of indoor characteristics merits further investigation, so improved experimental methods may be needed. The present study measured indoor and outdoor concentrations of PM2.5 and estimated PM2.5 deposition rates and penetration factors under a variety of different indoor situations, with a novel method (blower-door method). The blower-door method is compared with the standard decay and rebound method for an idealized room (a portable building test cell; 6.08 m [Formula: see text] 2.40 m [Formula: see text] 2.60 m) under eight testing scenarios (empty, cardboard boxes in three arrangements, terry cloth wall covering, and three sets of window holes); run three times to establish the coefficient of variation representing precision. Results show that higher induced indoor–outdoor pressure differences cause a larger variation of estimated effective deposition rate on different indoor surfaces. The deposition rate and penetration factor may be influenced by indoor surface materials. The blower-door method gives higher precision for the estimates, and detects subtle differences in penetration factors, which may be difficult using the decay and rebound method.

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