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.

Deposition of Suspensions in the Entrance of a Channel

1977 ◽  
Vol 99 (2) ◽  
pp. 365-370 ◽  
Author(s):  
S. M. Eldighidy ◽  
R. Y. Chen ◽  
R. A. Comparin
Keyword(s):  
Gravitational Force ◽  
Deposition Process ◽  
Electrostatic Charge ◽  
Analytical Investigation ◽  
The Other ◽  
Channel Inlet ◽  
Surface Adhesion ◽  
Static Charge ◽  
Transfer Number ◽  
Dilute Suspensions

An analytical investigation of the mechanics of deposition in a channel from the channel inlet to a distance of 7 channel depths has been made and a mathematical model developed for the deposition process from which the most significant parameters affecting the deposition can be identified. The analysis is restricted to laminar flow of dilute suspensions with electro-static charge and surface adhesion and without gravitational force. The results show that the electrostatic charge has the most effect on deposition. The other parameters included in the study are Knudsen number, momentum-transfer number, Reynolds number, diffusive Peclet number.

Laminar Flow of Suspensions in the Entrance Region of a Diffuser

1979 ◽  
Vol 101 (3) ◽  
pp. 309-311 ◽  
Author(s):  
R. Y. Chen ◽  
S. M. Eldighidy ◽  
R. A. Comparin
Keyword(s):  
Laminar Flow ◽  
Fine Particles ◽  
Electrostatic Charge ◽  
Analytical Investigation ◽  
Two Dimensional ◽  
Governing Equations ◽  
Dilute Suspensions ◽  
Implicit Finite Difference ◽  
Charge Parameter ◽  
Diffuser Angle

An analytical investigation of the mechanics of deposition of fine particles in a two-dimensional diffuser from the diffuser to inlet to the point of separation has been made. The deposition of suspensions in a diffuser was found to depend strongly on the electrostatic charge parameter and the diffuser angle. The analysis is restricted to laminar flow of dilute suspensions with diffusive, electrostatic, and surface adhesive effects. The implicit finite difference method was utilized to obtain a solution of the governing equations.

Effect Of Phosphorus On Ge/Si(001) Island Formation

2002 ◽  
Vol 737 ◽  
Author(s):  
Theodore I. Kamins ◽  
Gilberto Medeiros-Ribeiro ◽  
Douglas A. A. Ohlberg ◽  
R. Stanley Williams
Keyword(s):  
Deposition Rate ◽  
Strain Energy ◽  
Competitive Adsorption ◽  
Lattice Mismatch ◽  
Three Dimensional ◽  
Deposition Process ◽  
Thin Layers ◽  
Island Size ◽  
Partial Pressures ◽  
Intermediate Size

ABSTRACTWhen Ge is deposited epitaxially on Si, the strain energy from the lattice mismatch causes the Ge in layers thicker than about four monolayers to form distinctive, three-dimensional islands. The shape of the islands is determined by the energies of the surface facets, facet edges, and interfaces. When phosphorus is added during the deposition, the surface energies change, modifying the island shapes and sizes, as well as the deposition process. When phosphine is introduced to the germane/hydrogen ambient during Ge deposition, the deposition rate decreases because of competitive adsorption. The steady-state deposition rate is not reached for thin layers. The deposited, doped layers contain three different island shapes, as do undoped layers; however, the island size for each shape is smaller for the doped layers than for the corresponding undoped layers. The intermediate-size islands are the most significant; the intermediate-size doped islands are of the same family as the undoped, multifaceted “dome” structures, but are considerably smaller. The largest doped islands appear to be related to the defective “superdomes” discussed for undoped islands. The distribution between the different island shapes depends on the phosphine partial pressure. At higher partial pressures, the smaller structures are absent. Phosphorus appears to act as a mild surfactant, suppressing small islands.

scholarly journals Numerical Prediction of Heat Transfer Characteristics of Nanofluids in a Minichannel Flow

2014 ◽  
Vol 2014 ◽  
pp. 1-7 ◽  
Author(s):  
Arjumand Adil ◽  
Sonam Gupta ◽  
Pradyumna Ghosh
Keyword(s):  
Heat Transfer ◽  
Brownian Motion ◽  
Pressure Drop ◽  
Laminar Flow ◽  
Computational Model ◽  
Flow Regime ◽  
Cfd Simulation ◽  
Computational Results ◽  
Heat Transfer Characteristics ◽  
Simulation Process

CFD simulation of the heat transfer and pressure drop characteristics of different nanofluids in a minichannel flow has been explained using FLUENT version 6.3.26. Different nanofluids with nanoparticles of Al2O3, CuO, SiO2, and TiO2have been used in the simulation process. A comparison of the experimental and computational results has been made for the heat transfer and pressure drop characteristics for the case of Al2O3-water nanofluid for the laminar flow. Also, computations have been made by considering Brownian motion as well as without considering Brownian motion of the nanoparticles. After verification of the computational model with the experimental results for Al2O3-water nanofluid, the simulations were performed for the same experimental readings for different nanofluids in the laminar flow regime to find out the heat transfer and pressure drop characteristics.

Numerical Investigation on Heat Transfer and Oxidation Deposition of Aviation Fuel in a Rotatory U-Channel

2021 ◽  
Vol 143 (2) ◽  
Author(s):  
Zekun Zheng ◽  
Xinyan Pei ◽  
Siqian Yan ◽  
Lingyun Hou
Keyword(s):  
Heat Transfer ◽  
Deposition Rate ◽  
Turbulent Transport ◽  
Hydrocarbon Fuel ◽  
Deposition Process ◽  
Outer Edge ◽  
Aviation Fuel ◽  
Regenerative Cooling ◽  
Turbine Cooling ◽  
Rotation Numbers

Abstract Liquid-fuel regenerative cooling is a promising turbine cooling technology. We developed a numerical model of heat transfer coupled with oxidation deposition in a rotatory channel for regenerative cooling applications. Source terms for the centrifugal and Coriolis forces caused by rotation were added to the momentum equations and turbulent transport equations. A kinetic model for the thermal oxidation and deposition of supercritical hydrocarbon fuel was used to predict the oxidation deposition process. Coupled fluid–solid simulations of the heat transfer and oxidation deposition of hydrocarbon fuel in a U-shaped channel at five rotation numbers showed that the rotation improves convective heat transfer in the cooling channel and prevents the occurrence of a heat transfer deterioration zone. The average deposition rate in the channel decreased with increasing rotation number. In the centrifugal section of the rotatory channel, the Coriolis force caused the temperatures of the leading wall to be higher than those of the trailing wall, but the differences became smaller and nearly disappeared in the elbow and centripetal sections. The deposition rate on the leading wall was higher than that on the trailing wall in the straight centrifugal channel. In the bending section, the oxidation deposits were more prone to form on the inner edge than on the outer edge.

Mathematical Model of In-Flight Oxidation of Metallic Particles in Thermal Spraying

2000 ◽  
Author(s):  
A.M. Ahmed ◽  
R.H. Rangel ◽  
V.V. Sobolev ◽  
J.M. Guilemany
Keyword(s):  
Mathematical Model ◽  
Thermal Behavior ◽  
Spray Deposition ◽  
Particle Surface ◽  
Thermal Spraying ◽  
Deposition Process ◽  
Conservation Equation ◽  
Spherical Particles ◽  
Energy Conservation Equation ◽  
Acceleration And Deceleration

Abstract This paper presents a mathematical model of the in-flight oxidation of spherical particles during thermal spray deposition process. The model includes analysis of the mechanical and thermal behavior of the powder particles. The former accounts for acceleration and deceleration of the particles at the spray distance under different fluid velocities. The thermal behavior takes into account heating, melting, cooling and possible solidification as the particle travel towards the substrate. A finite-difference method is used to solve the thermal energy conservation equation of the particles. The model includes nonequilibrium calculations of the phase change phenomena in the liquid-solid (mushy) zone. The growth of the oxide layer at the particle surface is represented by a modified boundary condition, which includes finite-rate oxidation. The results obtained give the interrelations between various process parameters and the oxidation phenomenon and agree with experimental observation.

scholarly journals Analysis of the Binding of Analyte-Receptor in a Micro-Fluidic Channel for a Biosensor Based on Brownian Motion

Micromachines ◽  
2020 ◽  
Vol 11 (6) ◽  
pp. 570
Author(s):  
Sunghak Choi ◽  
Woo Il Lee ◽  
Gyu Hee Lee ◽  
Yeong-Eun Yoo
Keyword(s):  
Mathematical Model ◽  
Brownian Motion ◽  
Flow Rate ◽  
Channel Height ◽  
Micro Channel ◽  
Analyte Concentration ◽  
Fluidic Channel ◽  
Binding Characteristics ◽  
Detection Characteristics ◽  
The Mathematical Model

This study experimentally analyses the binding characteristics of analytes mixed in liquid samples flowing along a micro-channel to the receptor fixed on the wall of the micro-channel to provide design tools and data for a microfluidic-based biosensor. The binding or detection characteristics are analyzed experimentally by counting the number of analytes bound to the receptor, with sample analyte concentration, sample flow rate, and the position of the receptor along the micro-channel length as the main variables. A mathematical model is also proposed to predict the number of analytes transported and bound to the receptor based on a probability density function for Brownian motion. The coefficient in the mathematical model is obtained by using a dimensionless mathematical model and the experimental results. The coefficient remains valid for all different conditions of the sample analyte concentration, flow rate, and the position of the receptor, which implies the possibility of deriving a generalized model. Based on the mathematical model derived from mathematical and experimental analysis on the detection characteristics of the microfluidic-based biosensor depending on previously mentioned variables and the height of the micro-channel, this study suggests a design for a microfluidic-based biosensor by predicting the binding efficiency according to the channel height. The results show the binding efficiency increases as the flow rate decreases and as the receptor is placed closer to the sample-injecting inlet, but is unaffected by sample concentration.

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