The Investigation Of Ion Transport And Energy Conversion In Nanochannels Considering The EDL Effect

Based on the ion channels on the cell membrane,biological cells carry out metabolic activities constantly and exchange materials with the surrounding environment.Inspired by biological ion channels,bionic micro-nano fluidic devices have been used widely in various fields.With the progress of science and technology,bionic intelligent nanochannels are increasingly being developed for the clean energy conversion due to the good tunable geometry and chemical properties,the internal ion transport and energy conversion characteristics have attracted wider attention.Based on this,the ion transport and energy conversion characteristics in nanochannels are studied systematically by numerical simulation in this paper.Its main contents are as follows:(1)An ion transport and flow heat transfer model in the overlapping electric double layer nanochannel is established,and the corresponding ion distribution,potential distribution,conductivity,flow heat transfer characteristic are investigatted.The results show that the solution concentration dependent surface charge and boundary slip significantly affect the ion transport,conductivity and velocity distribution,thus affect the corresponding fluid behavior and heat transfer in the nanochannel.In addition,the physical mechanism of ion transport with overlapping electric double layer is analyzed in detail.(2)An ion transport model in asymmetric bilayer nanochannels is established,the ion rectification performance of four types bilayer nanochannels are compared.The results show that the presence of asymmetric geometry alone cannot induce ion rectification,and the presence of surface charge is necessary.In addition,when the left nanopore is charged with negative charge and the right nanopore is charged with positive charge,it has the best ion rectification performance,which can be further improved by adjusting surface charge density,geometric parameters and ion concentration: The ion rectification ratio increases with the increase of surface charge density.When the total length of the bilayer nanochannel is fixed,the ion rectification ratio has an optimal value with the change of left nanopore length.In addition,low ion concentration is benefited to improve ion rectification performance.(3)The ion transport and energy conversion models under the pressure and temperature difference are conducted.The energy conversion performance difference under the three electric boundary conditions and the power output performance of the nanochannel under the action of temperature difference are comprehensively studied.The results show that the energy conversion performance has obvious deviation under three different electric boundary conditions.In addition,the output power is weakened at low and high solution concentrations /p H,so an optimized solution concentration /p H exists.Under the action of temperature difference,the output power increases significantly due to the enhancement of ion migration ability and the decrease of fluid viscosity.When further study the influence of soret effect and viscous dissipation effect on nanochannel power generation,it is found that soret effect plays an important role on ion transport,while the viscous dissipation effect can be ignored.(4)The multi-physics coupling model of ion transport and energy conversion in charged conical nanopore is established,the effect of the conical nanopore direction,temperature difference direction and its magnitude on ions transport and energy conversion characteristics is studied in depth.The results show that both positive and negative temperature differences improve the output power within the research range,and the negative temperature difference has more significant enhancement on the output power and energy conversion efficiency than the positive temperature difference.In the further study of the temperature difference effect,it is found that the energy conversion characteristics such as current,diffusion potential and output power show approximately linear thermal response characteristics with the increase of temperature difference.In addition,an interesting competitive mechanism between the concentration difference and the temperature difference effect is found,which determines the preferred orientation of the conical nanopore for better output performance.