Prediction of Thermophoretic Deposition Efficiency of Particles in a Laminar Gas Flow along a Concentric Annulus： A Comparison of Developing and Fully Developed Flows

Thermophoresis is an important mechanism of micro-particle transport due to temperature gradients in the surrounding medium.It has numerous applications,especially in the field of aerosol technology.This study has numerically investigated the thermophoretic deposition efficiency of particles in a laminar gas flow in a concentric annulus using the critical trajectory method.The governing equations are the momentum and energy equations for the gas and the particle equations of motion.The effects of the annulus size,particle diameter,the ratio of inner to outer radius of tube and wall temperature on the deposition efficiency were studied for both developing and fully-developed flows.Simulation results suggest that thermophoretic deposition increases by increasing thermal gradient,deposition distance,and the ratio of inner to outer radius,but decreases with increasing particle size.It has been found that by taking into account the effect of developing flow at the entrance region,higher deposition efficiency was obtained,than fully developed flow.

Bioconvective nanofluid flow over an exponential stretched sheet with thermophoretic particle deposition

The current work is being done to investigate the flow of nanofluids across a porous exponential stretching surface in the presence of a heat source/sink,thermophoretic particle deposition,and bioconvection.The collection of PDEs(partial differential equations)that represent the fluid moment is converted to a system of ODEs(ordinary differential equations)with the use of suitable similarity variables,and these equations are then numerically solved using Runge Kutta Fehlberg and the shooting approach.For different physical limitations,the numerical results are visually represented.The results show that increasing the porosity characteristics reduces velocity.The mass transfer decreases as the thermophoretic limitation increases.Increases in the porosity parameter reduce skin friction,increases in the solid volume fraction improve the rate of thermal distribution,and increases in the thermophoretic parameter increase the rate of mass transfer.

Multi-solitons of Thermophoretic Motion Equation Depicting the Wrinkle Propagation in Substrate-Supported Graphene Sheets

The paper addresses the thermophoretic motion(TM) equation, which is serviced to describe soliton-like thermophoresis of wrinkles in graphene sheet based on Korteweg-de Vries(KdV) equation. The generalized uni?ed method is capitalized to construct wrinkle-like multiple soliton solutions. Graphical analysis of one, two, and threesoliton solutions is carried out to depict certain properties like width, amplitude, shape, and open direction are adjustable through various parameters.

Evaluation of thermophoretic effects on graphite dust coagulation in high-temperature gas-cooled reactors

In high-temperature gas-cooled reactors,graphite dust particles within the reactor core and the heat transfer equipment experience large temperature gradients.Under such conditions,thermophoresis may play an important role in determining aerosol evolution.This study presents a theoretical and numerical analysis of the thermophoretic effects on aerosol coagulation within these reactors.The coagulation rates for Brownian versus thermophoretic coagulation are calculated and compared for various temperature gradients.Our results show that thermophoretic coagulation dominates over Brownian coagulation for large temperature gradients.We defined an enhancement factor to evaluate the role of thermophoretic coagulation under various reactor conditions.The enhancement factor increased dramatically with increasing temperature gradient,decreasing pressure and increasing particle diameter,but was not very sensitive to temperature change.The time evolution of the particle size distribution related to combined Brownian and thermophoretic coagulation was simulated using a log-skew-normal method of moments.The simulation results indicate that aerosol evolution can be strongly accelerated by thermophoretic coagulation under large temperature gradients.

A nanofluid MHD flow with heat and mass transfers over a sheet by nonlinear boundary conditions: Heat and mass transfers enhancement

In this paper,we have numerically examined the steady boundary layer of a viscous incompressible nanofluid and its heat and mass transfers above a horizontal flat sheet.The boundary conditions considered were a nonlinear magnetic field,a nonlinear velocity and convection.Such nonlinearity in hydrodynamic and heat transfer boundary conditions and also in the magnetic field has not been addressed with the great details in the literature.In this investigation,both the Brownian motion and thermophoretic diffusion have been considered.A similarity solution is achieved and the resulting ordinary differential equations (nonlinear) are worked numerically out.Upon validation,the following hydrodynamic and heat and mass transfers parameters were found:the reduced Sherwood and Nusselt numbers,the reduced skin friction coefficient,and the temperature and nanoparticle volume fraction profiles.All these parameters are found affected by the Lewis,Biot and Prandtl numbers,the stretching,thermophoretic diffusion,Brownian motion and magnetic parameters.The detailed trends observed in this paper are carefully analyzed to provide useful design suggestions.

Quadratic convective flow of radiated nano-Jeffrey liquid subject to multiple convective conditions and Cattaneo-Christov double diffusion

A nonlinear flow of Jeffrey liquid with Cattaneo-Christov heat flux is investigated in the presence of nanoparticles. The features of thermophoretic and Brownian movement are retained. The effects of nonlinear radiation, magnetohydrodynamic(MHD), and convective conditions are accounted. The conversion of governing equations into ordinary differential equations is prepared via stretching transformations. The consequent equations are solved using the Runge-Kutta-Fehlberg(RKF) method. Impacts of physical constraints on the liquid velocity, the temperature, and the nanoparticle volume fraction are analyzed through graphical illustrations. It is established that the velocity of the liquid and its associated boundary layer width increase with the mixed convection parameter and the Deborah number.

DEPOSITION OF PARTICLES IN TURBULENT PIPE FLOW

The deposition of particles in turbulent pipe flow was investigated in terms of two mechanisms, turbulent and thermophoretic. A general equation incorporating these two mechanisms was formulated to calculate the deposition efficiency of aerosol particles in turbulent pipe flow together with thermophoretic deposition. The validity of the equation was confirmed by good agreement between calculated and measured results.

Significance of Stefan blowing effect on flow and heat transfer of Casson nanofluid over a moving thin needle

The current mathematical model explains the influence of non-linear thermal radiation on the Casson liquid flow over a moving thin needle by considering Buongiorno’s nanofluid model.The influences of Stefan blowing,Dufour and Soret effects are also considered in the model.The equations which represent the described flow pattern are reduced to ordinary differential equations(ODEs)by using apt similarity transformations and then they are numerically solved with Runge–Kutta-Fehlberg’s fourth fifth-order method(RKF-45)with shooting process.The impacts of pertinent parameters on thermal,mass and velocity curves are deliberated graphically.Skin friction,rate of heat and mass transfer are also discussed graphically.Results reveal that,the increase in values of Brownian motion,thermophoresis,Dufour number,heating and radiative parameters improves the heat transfer.The increasing values of the Schmidt number deteriorates the mass transfer but a converse trend is seen for increasing values of the Soret number.Finally,the escalating values of the radiative parameter decays the rate of heat transfer.

Effects of thermal boundary conditions on the joule heating of electrolyte in a microchannel

Joule heating effects on a slit microcharmel filled with electrolytes are comprehensively investigated with emphasis on the thermal boundary conditions. An accurate analytical expression is proposed for the electrical field and the temperature distributions due to Joule heating are numerically obtained from the energy balance equation. The results show that a thermal design based on the average electric potential difference between electrodes can cause severe underestimation of Joule heating. In addition, the parame- tric study of thermal boundary conditions gives us an insight into the best cooling scenario for microfluidic devices. Other significant thermal characteristics, including Nusselt number, thermophoretic force, and entropy generation, are discussed as well. This study will provide useful information for the optimization of a bioMEMS device in relation to the thermal aspect.

Impact of Joule heating and multiple slips on a Maxwell nanofluid flow past a slendering surface

This manuscript presents a study of three-dimensional magnetohydrodynamic Maxwell nanofluid flow across a slendering stretched surface with Joule heating.The impact of binary chemical reactions,heat generation,thermal radiation,and thermophoretic effect is also taken into consideration.The multiple slip boundary conditions are utilized at the boundary of the surface.The appropriate similarity variable is used to transfer the flow modeled equations into ODEs,which are numerically solved by the utilization of the MATLAB bvp4c algorithm.The involved parameter's impact on the concentration,velocity,and temperature distribution are scrutinized with graphs.The transport rates(mass,heat)are also investigated using the same variables,with the results reported in tabulated form.It is seen that the fluid relaxation,magnetic,and wall thickness characteristics diminish the velocities of fluid.Further,the velocity,concentration,and temperature slip parameters reduce the velocities of fluid,temperature,and concentration distribution.The results are compared to existing studies and shown to be in dependable agreement.