Simulation Of Solid-liquid Conjugate Heat Transfer With Electrohydrodynamic Flow

In recent years,based on the theory of Electrohydrodynamics(EHD),the phenomenon that the dielectric fluid overcomes its own viscous damping to form macroscopic flow in the present of the electric field force has attracted wide attention in the field of engineering technology.Among them,the enhanced heat transfer technology of EHD has been applied to many complex thermal energy systems and has a great development potential.The solid-liquid two-phase system has a good prospect in energy storage,electronic chip cooling,aerospace thermal control and other fields.For this purpose,this paper focuses on the solid-liquid two-phase system in a closed square cavity and carries out numerical simulation by using the Lattice Boltzmann Method(LBM),which is suitable for multi-field coupling problems,and combined with experimental research,the solid-liquid phase transition can be observed,the flow and heat transfer of the heat transfer system in the presence of EHD were investigated.The mathematical model is defined based on the physical problem,and the LB model of the system is established according to the fully coupled governing equations(including Navier-Stokes equations,electric potential equations,charge density conservation equations and energy equations).The influence of EHD effect on the heat transfer,flow field and charge transport in the solid-liquid two-phase phase transition process is explored in combination with numerical simulation and experimental research for the phase transition system.It is found that under the numerical simulation parameters,the enhancement efficiency of EHD effect on the Rayleigh-Benard convective phase change system is up to 62.81%,and the enhancement efficiency on the natural convective phase change system is up to 80.91%.Therefore,the effect of EHD on the natural convection system is more significant.In the square cavity-cylinder n-octadecane phase transition experiment,the high electric field can indeed strengthen the phase transition heat transfer,and with the increase of the electric field,the strengthening effect is more obvious,and the polarity of the electric field also has a certain effect on the phase transition rate,and the negative voltage will accelerate the melting of the solid phase.Considering the physical property difference between solid and liquid phases,the effects of electric field intensity,Rayleigh number Ra,solid medium size F and internal heat source intensity ?? on the heat transfer,flow field and charge transport of the conjugate heat transfer system are explored.It is found that under the condition of charge injection,the DC electric field has a significant strengthening effect on the conjugate heat transfer system for the calculation parameters,the strengthening effect becomes more obvious with the increase of electric Rayleigh number Ta.Rayleigh number Ra has an effect on the stability and heat transfer intensity of EHD conjugate heat transfer system.The larger Rayleigh number Ra increased the stronger the convective heat transfer,and the oscillation is more obvious.The size F of solid medium in the system will also affect the heat transfer of the system.When F = 0.3,EHD has the best strengthening effect on the system.When F = 0.7,EHD has no strengthening effect on the system.Finally,the influence of the intensity ?? of the internal heat source is investigated,and it is found that the enhancement effect of EHD reaches the maximum for 34.81% at ?? = 25.The combination of numerical simulation and experimental research in this paper focuses on the analysis of the enhanced heat transfer efficiency of EHD in different systems,and studies the influence of different parameters on the flow and heat transfer of the system,which not only provides theoretical support for the further application of EHD enhanced heat transfer technology in the solid-liquid two-phase system,but also lays the foundation for the development of the LB model of multiphase change thermal properties.