Effect of Viscosity Ratio on the Electric-Field-Driven Enhancement of Heat/Mass Transfer to a Spherical Drop

2012 ◽  
Author(s):  
Mohamed R. Abdelaal ◽  
Milind A. Jog
Keyword(s):  
Mass Transfer ◽  
Electric Field ◽  
Mass Transport ◽  
Heat Mass Transfer ◽  
Viscosity Ratio ◽  
Continuous Phase ◽  
Uniform Electric Field ◽  
Dielectric Fluid ◽  
Periodic Electric Field ◽  
Time Periodic

The effect of viscosity ratio on the electric-field-driven enhancement of heat/mass transfer to a spherical liquid drop of one dielectric fluid from another immiscible dielectric fluid is computationally investigated in this paper. The flow field is considered to be in the Stokes regime and the energy (species) conservation equations in the continuous phase are solved numerically using a fully implicit finite volume method. Results for flow outside the drop, transient temperature distributions, Nusselt number variations, and heat/mass transfer enhancement are presented for Peclet numbers varying from 10 to 500, dimensionless electric field frequency from 50 to 1000, and the ratio of viscosity of the continuous to the dispersed phase varying from 0.1 to 50. Steady and non-uniform unsteady electric fields are considered. The computational simulations show that when viscosity of the drop is lower than the viscosity of the surrounding fluid, a steady uniform electric field is more effective in enhancement of heat/mass transport compared to a non-uniform time periodic electric field. Conversely, when the continuous phase is less viscous than the drop, the non-uniform time periodic electric field provides improved heat/mass transport than the steady uniform electric field.

Heat/Mass Transfer to a Drop Translating in a Perpendicular Electric Field

2015 ◽  
Author(s):  
Mohamed R. Abdelaal ◽  
Omar A. Huzayyin ◽  
Milind A. Jog
Keyword(s):  
Mass Transfer ◽  
Electric Field ◽  
Mass Transport ◽  
Time Scale ◽  
Peclet Number ◽  
Heat Mass Transfer ◽  
Surface Velocity ◽  
Dielectric Fluid ◽  
Péclet Number ◽  
Transport Enhancement

Enhancement of heat or mass transport in a spherical drop of a dielectric fluid translating in another dielectric fluid in the presence of uniform electric field is investigated. The internal problem or the limit of the majority of the transport resistance being in the dispersed phase is considered. The transient energy conservation equation is solved using a fully implicit finite volume method. In the literature, there is a plenty of studies that had been carried out when the electric field acts in the same plane of translation. In this paper, considering creeping flow regime, numerical computations have been conducted when the electric field acts perpendicular to the plane at which translation acts. As such the flow is no longer a two dimensional flow as a third component velocity comes to picture. At the first glance, thoughts of transport enhancement come to mind on the presence of a third velocity component that might promote mixing and consequently enhance transport effectiveness. Results are expressed in terms of the Nusselt number. Nusselt numbers are plotted in terms of Peclet number, Fourier number and the parameter L which is defined as the ratio of the maximum electric-field-induced surface velocity to translation-induced surface velocity. The code was validated by comparing, results for Peclet numbers of 500 and 1000 to corresponding cases available in literature. Results showed good agreement with previous results. A 3-D grid of 20×40×60 has been considered to cover the computational domain. A grid independence study has been carried out by doubling the whole grid. Results show acceptable results compromising accuracy and code running time. The effect of electric field is expressed in terms of parameter L. For low Peclet numbers (Pe ≤ 250), the application of electric field perpendicular to the plane at which translation acts leads to enhancement of heat/mass transport compared to that in pure translation. Such enhancement is about the same when the electric field and translation act in the same plane. On the other hand, for moderate Peclet numbers (Pe= 250∼1000), the transport enhancement is significant when compared to the enhancement obtained by an electric field acts in the same plane of action of translation as well as pure translation. These results can be understood by comparing time scales for diffusion and convection. When Peclet number is low the convection time scale is very large and hence mixing is not that effective in promoting heat / mass transfer. Whereas for moderate Peclet number, when the convection time scale gets smaller, heat/mass transfer is considerably enhanced compared to low Peclet numbers.

scholarly journals Electric Field Control of the Polluting Emissions from a Propane Flame

2013 ◽  
Vol 3 (2) ◽  
pp. 95-108
Keyword(s):  
Mass Transfer ◽  
Electric Field ◽  
Heat Mass Transfer ◽  
Carbon Capture ◽  
Flame Temperature ◽  
Fuel Combustion ◽  
Electric Field Effect ◽  
Electric Field Effects ◽  
Field Effects ◽  
Polluting Emissions

The present study is performed with the aim to reduce the levels of polluting emissions from fuel combustion that produce acid rains and the greenhouse effect (NOx, CO2). The electric field effects on the processes of heat/mass transfer and propane combustion are studied in order to perform electric control of the levels of polluting emissions from the flame. The results of experimental studies show the direct influence of the electric field's enhanced mass transfer on local variations of the flame composition and fuel combustion. The related variations of the flame temperature, processes of soot formation, carbon capture and deposition along the flame channel flow are studied by varying the field strength and the equivalence ratio of the propane-air mixture. The results show that the electric field effect on soot for- mation, carbon capture and sequestration, for fuel-rich flame flow, can be used to reduce the levels of CO2 emissions from the flame. In addition, the field-enhanced heat/ mass transfer to the channel walls, for fuel-lean conditions, can be used to control the fuel combustion, flame temperature and temperature- sensitive levels of NOx emissions. The most pronounced electric field effects on fuel combustion and composition of the products are observed in the limit of the weak fields (U<1,2 kV, E<105 V m-1).

Numerical Study of Dynamic Behavior of Dielectric Fluid Bubbles Within Diverging, External Electric Fields

2006 ◽  
Author(s):  
Matthew R. Pearson ◽  
Jamal Seyed-Yagoobi
Keyword(s):  
Electric Field ◽  
Electric Fields ◽  
Numerical Study ◽  
Pool Boiling ◽  
Spherical Shape ◽  
Past Research ◽  
Bubble Surface ◽  
Uniform Electric Field ◽  
Dielectric Fluid ◽  
Uniform Field

Past research in the area of pool boiling within the presence of electric fields has generally focused on the case of uniform field intensity. Any numerical or analytical studies of the effect of non-uniform fields on the motion of bubbles within a dielectric liquid medium have assumed that the bubbles will retain their spherical shape rather than deform. These studies also ignore changes to the electrical field caused by the presence of the bubbles. However, these assumptions are not necessarily accurate as, even in the case of a nominally uniform electric field distribution, bubbles can exhibit considerable physical deformation and the field can become noticeably affected in the vicinity of the bubble. This study explores the effect that a non-uniform electric field can have on vapor bubbles of a dielectric fluid by modeling the physical deformation of the bubble and the alteration of the surrounding field. Numerical results show that the imbalance of electrical stresses at the bubble surface exerts a net dielectrophoretic force on the bubble, propelling the bubble to the vicinity of weakest electric field, thereby enhancing the separation of liquid and vapor phases during pool boiling. However, the proximity of the bubble to one of the electrodes can considerably alter the bubble trajectory due to an attractive force that arises from local distortions of the potential and electric fields. This phenomenon cannot be predicted if bubble deformation and field distortion effects are neglected.

scholarly journals Macroscopic Modeling of In Vivo Drug Transport in Electroporated Tissue

2016 ◽  
Vol 138 (3) ◽  
Author(s):  
Bradley Boyd ◽  
Sid Becker
Keyword(s):  
Electric Field ◽  
Mass Transport ◽  
Drug Transport ◽  
Irreversible Electroporation ◽  
Drug Uptake ◽  
Macroscopic Model ◽  
Uniform Electric Field ◽  
Macroscopic Modeling ◽  
Reversible Electroporation

This study develops a macroscopic model of mass transport in electroporated biological tissue in order to predict the cellular drug uptake. The change in the macroscopic mass transport coefficient is related to the increase in electrical conductivity resulting from the applied electric field. Additionally, the model considers the influences of both irreversible electroporation (IRE) and the transient resealing of the cell membrane associated with reversible electroporation. Two case studies are conducted to illustrate the applicability of this model by comparing transport associated with two electrode arrangements: side-by-side arrangement and the clamp arrangement. The results show increased drug transmission to viable cells is possible using the clamp arrangement due to the more uniform electric field.

Breakup of a conducting drop in a uniform electric field

2014 ◽  
Vol 754 ◽  
pp. 550-589 ◽  
Author(s):  
Rahul B. Karyappa ◽  
Shivraj D. Deshmukh ◽  
Rochish M. Thaokar
Keyword(s):  
Steady State ◽  
Numerical Analysis ◽  
Electric Field ◽  
Viscosity Ratio ◽  
Uniform Electric Field ◽  
Shape Prior ◽  
Capillary Stress ◽  
Electric Stress ◽  
Dc Electric Field ◽  
Axisymmetric Shape

AbstractA conducting drop suspended in a viscous dielectric and subjected to a uniform DC electric field deforms to a steady-state shape when the electric stress and the viscous stress balance. Beyond a critical electric capillary number $\def \xmlpi #1{}\def \mathsfbi #1{\boldsymbol {\mathsf {#1}}}\let \le =\leqslant \let \leq =\leqslant \let \ge =\geqslant \let \geq =\geqslant \def \Pr {\mathit {Pr}}\def \Fr {\mathit {Fr}}\def \Rey {\mathit {Re}}\mathit{Ca}$, which is the ratio of the electric to the capillary stress, a drop undergoes breakup. Although the steady-state deformation is independent of the viscosity ratio $\lambda $ of the drop and the medium phase, the breakup itself is dependent upon $\lambda $ and $\mathit{Ca}$. We perform a detailed experimental and numerical analysis of the axisymmetric shape prior to breakup (ASPB), which explains that there are three different kinds of ASPB modes: the formation of lobes, pointed ends and non-pointed ends. The axisymmetric shapes undergo transformation into the non-axisymmetric shape at breakup (NASB) before disintegrating. It is found that the lobes, pointed ends and non-pointed ends observed in ASPB give way to NASB modes of charged lobes disintegration, regular jets (which can undergo a whipping instability) and open jets, respectively. A detailed experimental and numerical analysis of the ASPB modes is conducted that explains the origin of the experimentally observed NASB modes. Several interesting features are reported for each of the three axisymmetric and non-axisymmetric modes when a drop undergoes breakup.

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