Lattice Boltzmann Simulation Of Electro-thermo-convection Under The Dissociation-recombination Mechanism In Dielectric Fluids

By applying a potential difference between the electrodes,the charge in the nonisothermal liquid will be subjected to the thermal buoyant force and the Coulomb force,causing the process of fluid flow and heat transfer,which is called electro-thermoconvection?ETC?.This problem can effectively control the flow and heat transfer by coupling the electricity,heat with the convection effect,which is an urgent problem to be solved in many industrial sectors and also the significance of this paper.Charge injection and dissociation-recombination are two main charge generation mechanisms in dielectric liquids,which exist simultaneously in the actual physical process,but there is a primary and secondary relationship under different electric field intensity.When the electric field intensity is low,the dissociation-recombination mechanism plays a leading role.In this paper,the electro-thermo-convection under the dissociation-recombination mechanism is studied.Lattice Boltzmann Method?LBM?is easy to program,suitable for complex shapes and easy to realize parallel computation,and is especially suitable for multi-physical field coupling problem.In this paper,LBM is used to simulate and analyze the electro-thermoconvection under the dissociation-recombination mechanism.Firstly,the governing equation is dimensionless and the related dimensionless parameters are listed.Then,the lattice Boltzmann model is established for each physical field.Then,the electro-thermo-convection problems in two electrode structures of the parallel plate and the inner cylinder-square cavity are simulated by LBM.The LBM results of pure natural convection and pure electro-convection obtained by simulation are consistent with those obtained by literature,which verifies the correctness of LBM model and program.Then,the electro-thermo-convection process under different working conditions is simulated,and the mechanism of electro-thermo-convection enhancing heat transfer is emphatically analyzed.The results show that the increase of T increases the flow intensity greatly,so the heat transfer efficiency can be improved obviously.The dissociation parameter W₀ is related to the thickness of the dissociation layer,and changes the flow pattern and heat transfer.We analyze the Dissociation Layer?DSL?effect and find that the increase of W₀ leads to the weakening of DSL effect and the enhancement of bulk effect,during which the flow field changes and the heat transfer effect changes.In addition,the influence of geometric parameters on heat transfer enhancement is also studied in the inner cylinder-square cavity model.The results show that with the increase of the offset and radius side length ratio,the electro-convection is more and more intense,and the heat transfer enhancement effect is obviously improved.The shift of the inner electrode directly downward is more conducive to heat transfer.Finally,the change of heat transfer intensity caused by different physical properties of fluids is explored.In this paper,LBM is used to study the electro-thermo-convection in two typical electrode structure.The control and influence of the electro-thermo-convection on the flow and heat transfer under the dissociation-recombination mechanism are emphatically analyzed.It not only has high academic research value,but also can provide specific guidance for relevant practical application.