Constructions And Applications Of Microscopic Transfer Models Coupled With Fluid Structures

The development of modern chemical engineering is speeding up in the direction of green,miniaturization,intelligence and integration.Compared with macroscopic transfer processes,the confinement effect is remarkable due to the existence of interfaces under micro/nano-sacle,and the fluid shows highly heterogeneity both in spatial density and orientation.Therefore,the fluid structure has great influence on transfer processes.Experimentally,in general,it is difficult to make in-situ observations of the transfer processes.While theoretically,since most of the macroscopic transfer theories are based on the continuity hypothesis,they do not take the fluid structure into consideration.Therefore,these theories are not appropriate for dealing with transfer processes of micro/nano confined fluids.In addition,most of the existing non-equilibrium theories are developed on the basis of the local-equilibrium assumptions,so they are generally not applicable to the dynamic processes far-from-equilibrium.Therefore,it is of great significance to develop a new non-equilibrium theoretical framework coupled with fluid structure for micro/nano-scopic transfer processes in modern chemical engineering.Herein,we first propose the concept of "structured thermodynamics".Under the framework of structured thermodynamics,combine non-equilibrium statistical mechanics and maximum path information entropy principle,we further propose a theoretical framework for microscopic transfer processes coupled with fluid structure.The theoretical framework is then applied for the investigations of several interfacial transfer processes.This dissertation is composed of the following several parts:(1)Construct the theoretical framework of non-equilibrium structured thermodynamics.Start from Kramers equation,a set of dynamical equations is derived.These equations,involving the local density,local momentum and local kinetic energy,are coupled with each other and eventually depend on the two-body probability distribution function,whose least-biased prediction is given by applying the maximum path information entropy principle.We show that the proposed dynamical governing equations are self-consistent,and can recover to the existing relevant theories upon various local-equilibrium assumptions.The simplified forms of these equations are also discussed for several types of systems with geometrical symmetries.This work provides a theoretical framework at molecular level for investigating dynamical behaviors of multi-component systems far-from-equilibrium.(2)Clarify the intrinsic relationship between Navier-Stokes equation and DDFT equation.Navier-Stokes equations are widely applied to deal with non-equilibrium fluid dynamics such as the flow field on nanoscale.On the other category,dynamical density functional theory(DDFT)has recently been recognized as a robust tool to investigate the non-equilibrium processes such as molecular diffusion and adsorption dynamics.Both approaches have achieved great success while their intrinsic correlation remains ambiguous.Herein,we prove that DDFT can be derived from the general Navier-Stokes equations with approximate evaluation of pressure tensor.Motivated by this procedure,we introduce the flow effect on pressure tensor,and then propose extensions of DDFT for addressing the coupling between dynamic adsorption and fluid flow.This work,revealing the relation between DDFT and Navier-Stokes equations,not only casts novel insights into the extension of DDFT,but also highlights a potential route to overcome the Navier-Stokes analytic solution problem.(3)Further construct the theoretical framework of fluid flow-adsorption coupling,and systematically investigate the dynamical adsorption of ions from confined flows onto the surfaces of nanoscale pores.It is found that a competition relation exists between the adsorption and flow.Promoting flow speed suppresses the adsorption amount,while enhancing adsorption strength reduces the flow speed.With the increase of flow speed,the contact density of co-ion is enhanced while that of counter-ion is suppressed,leading to overall enhanced accumulation charge densities at pore surfaces.Besides,the accumulation charge density increases monotonically with the applied voltage in large pores,while displays a non-trivial relation with the applied voltage in small pores of several ion sizes.This work not only extends the theoretical framework of non-equilibrium molecular theories,but also provides novel insights into the regulation of interfacial dynamic processes.(4)Construct the microscopic heat transfer model across interfaces coupled with fluid structure.Start from the self-consistent dynamical governing equations,a molecular model is proposed to describe the interfacial heat transfer coupled with local fluid structure.It is validated that this model is consistent with the homogeneous limit and agrees well with relevant work.The temperature drop is observed at the solid-liquid interface due to the thermal property mismatch of different phases.It is found that the layering effect of fluid molecules near the wall surface has great effect on temperature evolution through interfacial heat resistance.In addition,confinement effect also has non-negligible effect.The interfacial thermal resistance is reduced with the decrease of the pore size and the promotion of the surface wettability.This work provides a new theoretical framework for investigating the coupling relation between interfacial heat transfer and fluid structure,and offers fundamental perspective for realizing interfacial thermal management in chemical reactions and other applications.(5)Propose a theoretical framework of interfacial reaction-diffusion-heat transfer coupling.Combine the self-consistent dynamical governing equations and collision theory,a set of dynamical equations describing the coupling amoung interfacial reaction,molecular diffusion and interfacial heat transfer.The fluid microscopic structure evolution is driven by the chemical potential gradient,molecular transport and chemical reaction.The theoretical prediction agrees well with the relevant experimental observations.Then we design a programmed heating and cooling to effectively regulate the reaction heat.We find the system temperature is oscillated between the upper and lower boundary temperatures.Further we design the electro-catalysis model to regulate the reaction temperature via pulse current applied on electrodes.This theoretical framework extends the reaction-diffusion coupling model,and it provides a platform for investigating the matching relationship between reaction heat and heat transfer of micro-nano interfacial systems.In this dissertation,several kinds of microscopic transfer models coupled with fluid structure are constructed and applied to different transfer processes,including adsorption/diffusion dynamics,fluid flow,heat transfer across interfaces,etc.These theoretical models provide a platform for the mechanism investigation of the mass,momentum and heat transfer processes of inhomogeneous fluid systems.In addition,this work extends the non-equilibrium fluid structure thermodynamics,and provides a theoretical support for the developments and applications of micro-nano chemical engineering technologies.