Effect of Joule heating on the electroosmotic microvortex and dielectrophoretic particle separation controlled by local electric field

Dielectrophoresis(DEP)technology has become important application of microfluidic technology to manipulate particles.By using a local modulating electric field to control the combination of electroosmotic microvortices and DEP,our group proposed a device using a direct current(DC)electric field to achieve continuous particle separation.In this paper,the influence of the Joule heating effect on the continuous separation of particles is analyzed.Results show that the Joule heating effect is caused by the local electric field,and the Joule heating effect caused by adjusting the modulating voltage is more significant than that by driving voltage.Moreover,a non-uniform temperature distribution exists in the channel due to the Joule heating effect,and the temperature is the highest at the midpoint of the modulating electrodes.The channel flux can be enhanced,and the enhancement of both the channel flux and temperature is more obvious for a stronger Joule heating effect.In addition,the ability of the vortices to trap particles is enhanced since a larger DEP force is exerted on the particles with the Joule heating effect;and the ability of the vortex to capture particles is stronger with a stronger Joule heating effect.The separation efficiency can also be increased because perfect separation is achieved at a higher channel flux.Parameter optimization of the separation device,such as the convective heat transfer coefficient of the channel wall,the length of modulating electrode,and the width of the channel,is performed.

Joule heating effect of electroosmosis in a finite-length microchannel made of different materials

This paper presents a numerical analysis of Joule heating effect of electroosmo- sis in a finite-length microchannel made of the glass and polydimethylsiloxane （PDMS） polymer. The Poisson-Boltzmann equation of electric double layer, the Navier-Stokes equation of liquid flow, and the liquid-solid coupled heat transfer equation are solved to investigate temperature behaviors of electroosmosis in a two-dimensional microchannel. The feedback effect of temperature variation on liquid properties （dielectric constant, vis- cosity, and thermal and electric conductivities） is taken into account. Numerical results indicate that there exists a heat developing length near the channel inlet where the flow velocity, temperature, pressure, and electric field rapidly vary and then approach to a steady state after the heat developing length, which may occupy a considerable portion of the microchannel in cases of thick chip and high electric field. The liquid temperature of steady state increases with the increase of the applied electric field, channel width, and chip thickness. The temperature on a PDMS wall is higher than that on a glass wall due to the difference of heat conductivities of materials. Temperature variations are found in the both longitudinal and transverse directions of the microchannel. The increase of the temperature on the wall decreases the charge density of the electric double layer. The longitudinal temperature variation induces a pressure gradient and changes the behavior of the electric field in the microchannel. The inflow liquid temperature does not change the liquid temperature of steady state and the heat developing length.

Studying on the increasing temperature in IT-SOFC:Effect of heat sources

The dimensions and the materials type limit the performance of fuel cell. The increase of the temperature in electrodes and electrolyte of the cell,is due to the over potential of activation (transfer of load),the over potential Ohmic (resistance of polarization),the over potential of reaction (heat released by the chemical reaction) and the over potential of diffusion. In this paper,we studied the thermo-electrical performance of an intermediate temperature solid oxide fuel cell (IT-SOFC) with electrode supported. The aim of this work is to study this increasing temperature of a single cell of an IT-SOFC under the influence of the following parameters: heat sources,functioning temperature and voltages of the cell,geometric configuration and materials type. The equation of energy in one dimension is numerically resolved by using the method of finite volumes. A computing program (FORTRAN) is developed locally for this purpose in order to obtain fields of temperature in every element of the cell.

Effect of an electrostatic field on gas adsorption and diffusion in tectonic coal

The characteristics of adsorption, desorption, and diffusion of gas in tectonic coal are important for the prediction of coal and gas outbursts. Three types of coal samples, of which both metamorphic grade and degree of damage is different, were selected from Tongchun, Qilin, and Pingdingshan mines. Using a series of experiments in an electrostatic field, we analyzed the characteristics of gas adsorption and diffusion in tectonic coal. We found that gas adsorption in coal conforms to the Langmuir equation in an electrostatic field. Both the depth of the adsorption potential well and the coal molecular electroneg- ativity increases under the action of an electrostatic field. A Joule heating effect was caused by changing the coal-gas system conductivity in an electrostatic field. The quantity of gas adsorbed and AP result from competition between the depth of the adsorption potential well, the coal molecular electronegativ- ity, and the Joule heating effect. △P peaks when the three factors control behavior equally. Compared with anthracite, the impact of the electrostatic field on the gas diffusion capacity of middle and high rank coals is greater. Compared with the original coal, the gas adsorption quantity,△P, and the gas diffusion capacity of tectonic coal are greater in an electrostatic field. In addition, the smaller the particle size of tectonic coal, the larger the△P.

Electrifying Ba_(0.5)Sr_(0.5)Co_(0.8)Fe_(0.2)O_(3-δ) for focalized heating in oxygen transport membranes

Industry decarbonization requires the development of highly efficient and flexible technologies relying on renewable energy resources,especially biomass and solar/wind electricity.In the case of pure oxygen production,oxygen transport membranes(OTMs)appear as an alternative technology for the cryogenic distillation of air,the industrially-established process of producing oxygen.Moreover,OTMs could provide oxygen from different sources(air,water,CO_(2),etc.),and they are more flexible in adapting to current processes,producing oxygen at 700^(-1)000℃.Furthermore,OTMs can be integrated into catalytic membrane reactors,providing new pathways for different processes.The first part of this study was focused on electrification on a traditional OTM material(Ba_(0.5)Sr_(0.5)Co_(0.8)Fe_(0.2)O_(3-δ)),imposing different electric currents/voltages along a capillary membrane.Thanks to the emerging Joule effect,the membrane-surface temperature and the associated O_(2) permeation flux could be adjusted.Here,the OTM is electrically and locally heated and reaches 900℃on the surface,whereas the surrounding of the membrane was maintained at 650℃.The O_(2)permeation flux reached for the electrified membranes was~3.7 NmL min^(-1)cm^(-2),corresponding to the flux obtained with an OTM non-electrified at 900℃.The influence of depositing a porous Ce_(0.8)Tb_(0.2)O_(2-δ) catalytic/protective layer on the outer membrane surface revealed that lower surface temperatures(830℃)were detected at the same imposed electric power.Finally,the electrification concept was demonstrated in a catalytic membrane reactor(CMR)where the oxidative dehydrogenation of ethane(ODHE)was carried out.ODHE reaction is very sensitive to temperature,and here,we demonstrate an improvement of the ethylene yield by reaching moderate temperatures in the reaction chamber while the O_(2) injection into the reaction can be easily fine-tuned.

PARTIAL REGULARITY FOR THE NAVIER-STOKES-FOURIER SYSTEM

This paper addresses a nonstationary flow of heat-conductive incompressible Newtonian fluid with temperature-dependent viscosity coupled with linear heat transfer with advection and a viscous heat source term, under Navier/Dirichlet boundary conditions. The partial regularity for the velocity of the fluid is proved for each proper weak solution, that is, for such weak solutions which satisfy some local energy estimates in a similar way to the suitable weak solutions of the Navier-Stokes system. Finally, we study the nature of the set of points in space and time upon which proper weak solutions could be singular.

Combined effects of Joule heating and nonuniform heat source/sink on unsteady MHD mixed convective flow over a vertical stretching surface embedded in a Darcy-Forchheimer porous medium

This paper deals with an unsteady magnetohydrodynamics(MHD)heat and masstransfer for a viscous incompressible fluid through a vertical stretching surface embedded ina Darcy-Forchheimer porous medium in the presence of a non-uniform heat source/sink andfirst-order chemical reaction.The porous surface is subjected to a uniform transverse magneticfield.The influence of velocity,thermal,and concentration slip is also investigated.The governing equations are coupled non-linear partial differential equations,which have been converted via similarity transformation into a set of ordinary differential equations.The resultantsystem of non-linear ordinary differential equations has been solved numerically with the helpof the“MATLAB”BVP4C Solver.Results are presented graphically to analyze the effects ofvarious physical parameters discovered in the problem such as Hartmann number(M),Forchheimer number(Fr),Grashof number(Gr),solutal Grashof number(Gc),suction parameter(S),porosity parameter(el),dimensionless velocity slip(Sv),Prandtl number(Pr),dimensionless thermal slip(St),space-dependent heat source/sink parameter(eA
1),temperature-dependent heat source/sink(eB)1),Eckert number(Ec),Schmidt number(Sc),chemical reaction parameter(g),unsteadiness parameter(A),and dimensionless concentration slip(Sc)on non-dimensionalvelocity ec0ðhÞ,temperature zðhÞ,and concentration efðhÞprofiles.The influence of these parameters on skin-friction coefficient(C)f),Nusselt number(Nu)x),and Sherwood number(Sh)x)areexpressed in tabular form.It is observed that an enhancement in Fr and el results in the declination of the velocity profile.There is an enhancement in temperature with an increment in theeA)1 and eB)1.The physical representation of flow characteristics that appeared in the problem ispresented using various graphs to depict real-world applications in industrial and engineeringoperations.The results were compared to previous studies,revealing that the two are in goodagreement.The novelty of the present investigation is:To interpret the combined effects ofviscous dissipation and Joule heating on a vertical stretching surface embedded in a highlyporous medium modeled using the Darcy-Forchheimer model.The findings could be valuablein understanding the flow of oil,gas,and water through an oil or gas field reservoir,as well asgroundwater migration and filtering and purification procedures.

Influence of the Gas Temperature in Ozone Production of Mixture N2-O2

The ozone occurs naturally in the atmosphere and presents a filter of protection, absorbing the radiations wavelengths lower than 310 nm. The industrial generation of ozone is the classical application of the non-equilibrium air plasmas at the atmospheric pressure. A low temperature is needed because the ozone quickly decays at the high temperature. This study is based on a temporal kinetic model for the production of ozone. The chemical kinetics take into account 96 reactions with 19 species atomic and molecular created in the discharge. In this work, the model allows to calculate the temporal evolution of neutral, ionized and excited species concentrations in plasma. The results show the influence of the kinetic on the ozone production yield and on the gas heating by Joule effect.

Quantum Fluctuation of a Mesoscopic Inductance Coupling Circuit at Finite Temperature

We study the quantization of mesoscopic inductance coupling circuit and discuss its time evolution. Bymeans of the thermal field dynamics theory we study the quantum fluctuation of the system at finite temperature.

Biomimetic,fire-resistant,ultralight and porous carbon fiber sponges enabling safe and efficient remediation of crude oil spills in harsh environments

Advanced absorbents must meet the requirements of superior hydrophobic/oleophilic behavior,favorable adsorption efficiency,and high photothermal and Joule heating performance to handle frequent crude oil spills.However,current carbon-based absorbents suffer from poor fire resistance,thus severely limiting their application in harsh environments.Herein,inspired by a bird’s nest,a polymer“welding”strategy is proposed to design a versatile absorbent in which the polymer serves as a“binder”to interconnect discontinuous fibers together to form a 3D welded structure.The continuous conductive networks endow the absorbent with high photothermal and Joule heating effect,thus achieving all-weather adsorption,and improving the adsorption efficiency of crude oil via the self-heating function.Compared with other absorbents,the absorbent prepared via polymer welding technology exhibited preferable comprehensive performance,such as superhydrophobicity,high fire resistance,and high absorption efficiency.Specially,the noninflammable absorbent can restrain the combustion of crude oil,thereby reducing its combustion in case of fire.The versatile absorbent is expected to provide a promising solution for the safe and effi-cient cleanup of crude oil spills in harsh environments.Overall,the unique polymer welding strategy can be developed into a universal strategy for other material systems to expand their applications.