Study On Agglomeration And Deposition Characteristics Of Nanoparticles Under Electric Field

Nanofluid is a new type of heat transfer medium with high heat transfer coefficient.Due to the large specific surface area and high surface energy of nanoparticles,agglomeration is easy to occur.Therefore,agglomeration of nanoparticles is the key factor affecting the stability of nanofluids,and also an important factor for their wide application.In this paper,molecular dynamics simulation method is used to study the characteristics of particle agglomeration and deposition in nanofluids under the influence of electric field,and explain the mechanism from the microscopic perspective.The results showed that:For the agglomeration of Cu nanoparticles,the effect of electric field intensity and electric field form on the agglomeration of Cu nanoparticles in water-based solution was simulated by molecular dynamics method.The potential energy,kinetic energy,diffusion coefficient and radial distribution function of the system were analyzed and studied by statistics.Results show that the electric field is always delay the collision for the first time,which happen delay particles together with the electric field.In the presence of an electric field,the diffusion coefficient is always smaller than that in the case of electric field intensity of 0 V/nm.In other words,the motion resistance of particles increases after the electric field is applied,and the collision of particles is inhibited,which is the same as the time rule of particle collision for the first time.The difference is that under the action of parallel uniform electric field,the collision time of delayed particles increases first and then decreases with the increase of electric field intensity.The sinusoidal alternating electric field has no specific rule for the collision time of delayed particles,but the collision time of delayed particles always occurs.For the deposition of nanoparticles,molecular dynamics method was used to simulate the deposition characteristics of Cu nanoparticles on the wall under different electric field intensity,different directions and different electric field forms.The potential energy,kinetic energy,diffusion coefficient and radial distribution function of the system were analyzed and studied by statistics.The results show that the application of parallel uniform electric field along the y direction always delays the particle's first collision with the wall surface,and the application of electric field has the effect of delaying particle deposition.A parallel electric field is applied along the x direction.When the electric field intensity is less than 0.6V/nm,the electric field can delay particle deposition.When the electric field intensity is greater than 0.6V/nm,the electric field is applied to promote particle deposition.The diffusion coefficient is relatively small under the action of electric field,and the total potential energy decreases with each Cu nanoparticle collision.By comparing electric fields in different directions,it is found that the effect of electric field applied in y direction on particle deposition is more obvious.Therefore,the effect of alternating electric field applied in y direction on particle deposition is studied.The results show that the alternating electric field promotes the deposition of particles,and with the increase of the applied electric field frequency,the total deposition time of particles decreases.The diffusion coefficient increases with the increase of the frequency of the applied electric field,and the kinetic energy of the system increases with the increase of the frequency,which promotes the deposition of particles.According to the radial distribution function,with the increase of electric field frequency,the aggregation of water molecules on the surface and wall of particles decreases,which promotes the deposition of particles.