| The main heat transfer mode of the microchannel heat exchanger is convection heat transfer,but as the channel size decreases,the various force contrasts change,which makes many physical phenomena in the microscale field very different from the macro world.In the microscale field,the relative effects of inertial force,electromagnetic force,etc.,which are proportional to the higher power of the feature size are reduced,while the effects of viscous force,surface tension,electrostatic force,etc.,which are proportional to the lower power of the dimension are relatively increased.This causes some new phenomena in the flow in the micro-scale channel.These phenomena are obviously different from the traditional theory of conventional flow channels,which makes the research of this subject have important practical significance and scientific value.The first chapter of this paper introduces the background and significance of the research,and introduces the research status of microchannel electroosmotic flow and roughness.The second chapter introduces some basic knowledge of pressure electroosmotic flow,including the principle of electroosmotic flow formation and Stern electric double layer model,Poisson-Boltzmann(P-B)equation,Laplace equation of applied electric field,continuity equation of fluid flow,momentum equation,The energy equation,and hence the momentum equation for the pressure-electroosmotic drive flow.Furthermore,the fully developed laminar flow equations in the infinitely long rectangular square tube are further solved,which lays a theoretical foundation for future research.The third chapter introduces the relevant knowledge of CFD,completes the grid-independent verification,and verifies the accuracy of the model.It determines that the mesh size of the simulation needs to be less than 2μm.It is found that the FLUENT simulates the micron order by comparing the simulation with the experimental data.Microchannels are reliable.The fourth and fifth chapters are based on the P-B equation,the Laplace equation of the applied electric field and the NS equation describing the electroosmotic-pressure-driven flow field distribution,and the energy equation of convective heat transfer.The continuity equation and momentum of the electroosmotic-pressure-driven flow are established.A series of equations such as equations and energy equations.The analytical solution of the dimensionless velocity,the dimensionless Nu number,the fluid temperature and the wall temperature difference Tw-T of the electroosmotic-pressure-driven flow field between two infinite plates is solved.The molar concentration of solution C,the applied electric field strength E,and the double are studied.The effects of electric layer potential ζ,unit pressure drop,scale effect,etc.on the dimensionless velocity distribution,bed shear stress ratio,Nu number and Tw-T of the pressure-electroosmotic drive flow between plates.The sixth chapter is based on the finite volume method calculation software FLUENT numerical simulation of the electric double layer potential ζ distribution and the applied electric field strength E distribution.It is found that the analytical solution is similar to the numerical simulation results,and the analytical solution has higher reliability.At the same time,the effects of different solution molar concentration C,applied electric field strength E and electric double layer potential ζ on the flow and convective heat transfer characteristics in three-dimensional rectangular microchannels were numerically simulated.The seventh chapter is based on the finite volume method calculation software FLUENT numerical simulation of the flow and convective heat transfer in the three-dimensional rectangular microchannel,and the effects of different aspect ratios on flow and heat transfer are studied.The effects of the height and spacing of triangular rectangular roughness elements on the flow and heat transfer in a rectangular microchannel with an aspect ratio of 4 were investigated. |
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