Analysis of electrodynamic fluidization

2018 ◽  
Vol 854 ◽  
pp. 261-292
Author(s):  
F. J. Higuera
Keyword(s):  
Applied Voltage ◽  
Gas Flow ◽  
Hydrodynamic Instability ◽  
Suspended Particles ◽  
Normal Operation ◽  
Electric Force ◽  
Lower Electrode ◽  
Electrode Area ◽  
Electrically Conducting ◽  
Interparticle Collisions

Electrodynamic fluidization is a technique to generate suspensions of electrically conducting particles using electric forces to overcome their weight. An analysis of electrodynamic fluidization is presented for a monodisperse aerosol of non-coalescing particles of infinite electrical conductivity and negligible inertia suspended in a gas in the gap between two horizontal plate electrodes. A DC voltage is applied between the electrodes that charges the particles initially deposited on the lower electrode and leads to a vertical electric force that lifts the particles and pushes them upwards across the gap. The direction of this force reverses when the particles reach the upper electrode, pushing them downwards until they fall onto the lower electrode and repeat the cycle. Stationary distributions of particles are computed for given values of the applied voltage and the number of suspended particles per unit electrode area. Interparticle collisions play a role when the second of these parameters is of the order of the inverse of the particle cross-section or larger. The electric field induced by the charge of the particles opposes the field due to the applied voltage at the lower electrode and thus sets an upper bound to the number of particles that can be suspended for a given voltage. This bound is attained in the normal operation of a fluidization device, in which there is an excess of particles deposited at the lower electrode, and is computed as a function of the applied voltage. The predictions are compared to experimental results in the literature. A linear stability analysis for dilute aerosols with negligible collision effects shows that the stationary solution becomes unstable when the deposition threshold is approached with a number of suspended particles per unit electrode area larger than a certain critical value. A hydrodynamic instability appears near the lower electrode, where the electric force on a localized accumulation of charged particles leads to an upward gas flow that helps carrying the particles away from the electrode and increases the amplitude of the initial particle accumulation. The instability gives rise to electrohydrodynamic plumes whose dynamics involves collisions, mergers and generation of new plumes.

Control of the Flow Direction Induced by Plasma Actuator

2012 ◽  
Author(s):  
Yu Ikoshi ◽  
Satoshi Ogata ◽  
Takehiko Segawa ◽  
Ryota Yamatani
Keyword(s):  
Applied Voltage ◽  
Reverse Flow ◽  
Flow Direction ◽  
Plasma Actuator ◽  
Lower Electrode ◽  
Barrier Discharge Plasma ◽  
Induced Flow ◽  
Piv Analysis ◽  
Asymmetric Electrodes ◽  
Aerodynamic Flow Control

It is known that a dielectric barrier discharge plasma actuator (DBD-PA) induces tangential flow in the vicinity of the wall. In the conventional studies the induced flow was generated in the direction from the upper electrode to the lower electrode. The direction of the induced flow was one-way using DBD-PA composed of asymmetric electrodes. However, in this experiment, it was found that the flow induced by DBD-PA can be generated in the opposite direction in contrast with conventional results. In this study, effects of DBD induced flow on applied voltage characteristics were investigated by means of PIV analysis. When square wave voltages biased negative are applied to the electrodes of DBD-PA, the flow is generated in the direction from the lower electrode to the upper electrode. It should be noted that it is not reversed by sine waves even with same amplitudes and frequencies when the reverse flow was generated by DBD-PA, a vortex is induced above the area of plasma. The vortex height was about 10 mm, and it tended to change slightly its shape based on the electrode width. It seems that the vortex on the plasma area play an important role in the mechanism of the reverse flow. The plasma actuator has been focused as an actuator for aerodynamic flow control. If it becomes possible to control the flow direction as well as the velocity by changing the applied voltage, the applications of the plasma actuator can be spread across a wide area of industry.

Dynamic Actuation of Electro-Elastic Spherical Membranes Using Dielectric Elastomers

Aerospace ◽  
2005 ◽  
Author(s):  
Nakhiah Goulbourne ◽  
Eric Mockensturm ◽  
Mary Frecker
Keyword(s):  
Dynamic Response ◽  
Applied Voltage ◽  
Gas Flow ◽  
Applied Pressure ◽  
Material Model ◽  
Dielectric Elastomer ◽  
Inertial Effects ◽  
Mechanical Pressure ◽  
Material Parameters ◽  
Dielectric Elastomer Actuators

This paper presents dynamic results for spherical dielectric elastomer actuators subject to an inflating mechanical pressure and an applied voltage. Different equilibria modes arise during dynamic operation due to inertial effects. In previous work, the inertial effects have been studied for the limited case of a constant applied pressure during membrane deformation [1]. Here, novel results are presented in which the dynamic response of spherical dielectric elastomer actuators to a pressure-time loading history as well as a more realistic constant gas flow rate are considered. The results are calculated for both the damped and the zero-damped cases. The spherical membrane is assumed to follow the Mooney material model where various inflation modes arise depending on the material parameters. The range of Mooney material parameters considered, the driving pressure and the applied voltage all affect the dynamic response.

Traceability of real-time reference gas generation for reactive gaseous compounds

2020 ◽  
Author(s):  
Timo Rajamäki ◽  
Sari Saxholm
Keyword(s):  
Real Time ◽  
Gas Flow ◽  
Cost Savings ◽  
Normal Operation ◽  
Mercury Chloride ◽  
Atmospheric Measurements ◽  
Trace Impurities ◽  
Gas Generation ◽  
Gas Concentration ◽  
Uncertainty Calculation

<p>For reactive gaseous compounds, limited availability of bottled standard gases often limits their measurement accuracy and comparability. Typically, an available reference gas concentration range for the specific compounds may be limited to even orders of magnitude higher than the levels normally measured at atmospheric measurements and most often only dry reference gases in inert matrices, typically nitrogen, are available. This means that when applying test gases from cylinders humidity in measurement system may cause significantly longer measurement response than in normal operation.</p><p> </p><p>A real-time reference gas generation is an effective method to circumvent these obstacles. Controlled evaporation of the reference solution enables flexible and reliable generation of test gases in wide concentration and flow ranges as well as in different gas matrices. The method is useable in field conditions and it may provide cost savings since necessary consumables include solely pure carrier gas and solution of the studied chemical with know concentration.</p><p> </p><p>We validate this method for different reactive gaseous compounds and key impurities. For mercury chloride, the most typical form of oxidised mercury in process emissions and atmosphere, reference gas with concentration ranging from sub-ng/m<sup>3</sup> to tens of µg/m<sup>3</sup> is generated. In case of typical base and acid trace impurities, ammonia, hydrogen chloride and hydrogen fluoride, the reference gases are generated in (bio-) methane and air matrices. In all cases studied, the stabilization time of generating gas flow is no longer, than some minutes. Accuracy and traceability of the generated gas concentration are estimated based on full uncertainty calculation as well as comparison with traceable reference gas standards.</p>

CFD Simulation of a Coolant Flow and a Heat Transfer in a Pebble Bed Reactor

2008 ◽  
Author(s):  
Wang-Kee In ◽  
Won-Jae Lee ◽  
Yassin A. Hassan
Keyword(s):  
Heat Transfer ◽  
Gas Flow ◽  
Cfd Simulation ◽  
Reverse Flow ◽  
Temperature Drop ◽  
Coolant Flow ◽  
Normal Operation ◽  
Fuel Temperature ◽  
Pebble Bed Reactor ◽  
Detailed Simulation

This CFD study is to simulate a coolant (gas) flow and heat transfer in a PBR core during a normal operation. This study used a pebble array with direct area contacts among the pebbles which is one of the pebbles arrangements for a detailed simulation of PBR core CFD studies. A CFD model is developed to more adequately represent the pebbles randomly stacked in the PBR core. The CFD predictions showed a large variation of the temperature on the pebble surface as well as in the pebble core. The temperature drop in the outer graphite layer is smaller than that in the pebble-core region. This is because the thermal conductivity of graphite is higher than the fuel (UO2 mixture) conductivity in the pebble core. Higher pebble surface temperature is predicted downstream of the pebble contact due to a reverse flow. Multiple vortices are predicted to occur downstream of the spherical pebbles due to a flow separation. The coolant flow structure and fuel temperature in the PBR core appears to largely depend on the in-core distribution of the pebbles.

scholarly journals Effects of Magnetic Field and Non-Uniform Basic Temperature Gradient

2002 ◽  
Vol 1 (1) ◽  
pp. 1-14
Author(s):  
S. Pranesh
Keyword(s):  
Magnetic Field ◽  
Temperature Gradient ◽  
Fluid Layer ◽  
Suspended Particles ◽  
Conducting Fluid ◽  
Wave Number ◽  
Uniform Temperature ◽  
Onset Of Convection ◽  
Electrically Conducting ◽  
Electrically Conducting Fluid

The effects of a non-uniform temperature gradient and magnetic field on the onset of convection in a horizontal layer of Boussinesq fluid with suspended particles confined between an upper free/adiabatic boundary and a lower rigid/isothermal boundary have been considered. A linear stability analysis is performed. The microrotation is assumed to vanish at the boundaries. The Galerkin technique is used to obtain the Eigen values. The influence of various parameters on the onset of convection has been analysed. Six different non-uniform temperature profiles are considered and their comparative influence on onset is discussed. It is observed that the electrically conducting fluid layer with suspended particles heated from below is more stable compared to the classical electrically conducting fluid without Suspended particles. The critical wave number is found to be insensitive to the changes in the parameters but sensitive to the changes in the Chandrasekhar number.

scholarly journals The Effect of Mass Transfer Rate-Time in Bubbles on Removal of Azoxystrobin in Water by Micro-Sized Jet Array Discharge

Catalysts ◽  
2021 ◽  
Vol 11 (10) ◽  
pp. 1169
Author(s):  
Feng Chen ◽  
Dezheng Yang ◽  
Feng Yu ◽  
Yang Kun ◽  
Ying Song
Keyword(s):  
Mass Transfer ◽  
Removal Efficiency ◽  
Flow Rate ◽  
Applied Voltage ◽  
Transfer Rate ◽  
Gas Flow ◽  
Mass Transfer Rate ◽  
Initial Solution ◽  
Solution Temperature ◽  
Gas Flow Rate

In this work, the azoxystrobin removal in water by using a micro-size discharge array was investigated, and the removal efficiency can reach as high as 98.1% after 9 min plasma treatment as well as the energy utilization being only 0.73 g/(kW·h). Based on the relationship between the generation of gas bubbles and parameters of gas-liquid discharge, it was found that the variation of applied voltage, gas flow rate and initial solution temperature could cause particle number change, mass transfer rate change and the mass transfer time change, which significantly affected the practical applications at last. The experimental results indicated that when gas flow rate was 0.7 SLM (Standard Liter per Minute) and the initial solution temperature was 297 K with the applied voltage of 8 kV and discharge frequency of 6 kHz, the removal efficiency of azoxystrobin achieved maximum. Based on the analysis results of liquid mass spectrometry, the removal pathways of azoxystrobin were supposed by the decomposed by-products. Toxicity tests indicated that the decomposed products were safe and non-toxic. So, this study may reveal an azoxystrobin degradation mechanism and provide a safe, reliable and effective way for azoxystrobin degradation.

OPTIMIZATION OF NON THERMAL PLASMA REACTOR PERFORMANCE FOR THE DECOMPOSITION OF XYLENE

2016 ◽  
Vol 78 (8) ◽  
Author(s):  
Nor Faraliana Shazwani Nor Azmi ◽  
Abdullahi Mohammed Evuti ◽  
Mohd Ariffin Abu Hassan ◽  
R. K. Raja Ibrahim
Keyword(s):  
Flow Rate ◽  
Thermal Plasma ◽  
Applied Voltage ◽  
Gas Flow ◽  
Plasma Reactor ◽  
Gas Flow Rate ◽  
Reactor Performance ◽  
Model Predictions ◽  
Non Thermal Plasma ◽  
Discharge Gap

Non Thermal Plasma (NTP) is an emerging method used for the decomposition of volatile organic compounds (VOCs). This research focuses on the optimization of NTP reactor performance for decomposition of xylene from wastewater using response surface methodology (RSM) by operating the NTP reactor at applied voltage of 12-15 kV, discharge gap of 2.0-3.0 cm and gas flow rate of 2.0-5.0 L/min. An optimum xylene removal efficiency of 81.98% was obtained at applied voltage 15kV, discharge gap 2.09cm and gas flow rate at 2.36 L/min. The experimental removal efficiencies and model predictions were in close agreement with an error of 0.63%. 

scholarly journals Thermal instability of compressible Walters’ (Model B′) fluid in the presence of Hall currents and suspended particles

2011 ◽  
Vol 15 (2) ◽  
pp. 487-500 ◽  
Author(s):  
Urvashi Gupta ◽  
Parul Aggarwal
Keyword(s):  
Magnetic Field ◽  
Dispersion Relation ◽  
Thermal Instability ◽  
Normal Modes ◽  
Suspended Particles ◽  
Elastic Parameter ◽  
Stationary Convection ◽  
Electrically Conducting ◽  
Permissible Range ◽  
Rayleigh Numbers

Effect of Hall currents and suspended particles is considered on the hydromagnetic stability of a compressible, electrically conducting Walters? (Model B?) elastico-viscous fluid. After linearizing the relevant hydromagnetic equations, the perturbation equations are analyzed in terms of normal modes. A dispersion relation governing the effects of visco-elasticity, magnetic field, Hall currents and suspended particles is derived. It has been found that for stationary convection, the Walters? (Model B?) fluid behaves like an ordinary Newtonian fluid due to the vanishing of the visco-elastic parameter. The compressibility and magnetic field have a stabilizing effect on the system, as such their effect is to postpone the onset of thermal instability whereas Hall currents and suspended particles are found to hasten the onset of thermal instability for permissible range of values of various parameters. Also, the dispersion relation is analyzed numerically and the results shown graphically. The critical Rayleigh numbers and the wavenumbers of the associated disturbances for the onset of instability as stationary convection are obtained and the behavior of various parameters on critical thermal Rayleigh numbers has been depicted graphically. The visco-elasticity, suspended particles and Hall currents (hence magnetic field) introduce oscillatory modes in the system which were non-existent in their absence.

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