The Application Of Lattice Boltzmann Method In Convective Heat Transfer And Chemical Reaction

Lattice Boltzmann method in recent years has been developed into a power tool for modeling fluid flow and complex physical phenomenon. The lattice Boltzmann method is different from the traditional computational fluid dynamic based on the micro continuous equation, which is based on the micro-fluid dynamic model and mesoscopic kinetics equations. At present, the lattice Boltzmann method has been found a great successful application on many academic areas, such as multiphase flow, porous media flow, suspended particulates flow, reaction flow, magnetic fluid dynamic, bio-mechanics, and etc., and has become a kind of important methods of fluid dynamic simulation.However, there still exist some difficulties in the application of the lattice Boltzmann method, such as in chemical reaction, treatment to the interaction between the different phases on a non-uniform grid, the coupling of gas-solid two-phase flows, which are rarely studied. In order to promote the application of lattice Boltzmann method in chemical reaction, the lattice Boltzmann method was employed to investigate the transport characteristics in the methanol stream reforming.First, the LBGK equation was derived from Boltzmann equation and the prerequisite conditions for application were obtained. Starting from LBGK equation, the macroeconomic dynamic equations were deduced by using Champan-Enskog method, thereby, the relationship between macro physical parameters and the model ones ware established. Then the D2G9 model and the D2Q9 model were employed to simulate numerically the lid-driven cavity flow, Poiseuille flow, Couette flow, respectively, by comparison of the simulated results, the advantages of D2G9 model over others were analysed. To the end, the D2G9 model was used to simulate the flow around a cylinder, and simulation results for analysis.Furthermore, the thermal lattice model was introduced in detailed, the latest theoretical model was also given. By using this model and TD2G9 model, negligibly heat dissipation, the natural convection in an enclosure channel was simulated, respectively, and the computed results showed good consistency of compared with that of benchmarks. In order to verify the advantages of the new model, the new model and the HE-LUO model were used to simulate the incompressible flow and heat transfer between the two parallel plates, and the results of two models were very similar with each other. However, the new model showed easy dealing with, less computation time and good numerical stability compared with other models.On this basis, the chemical reaction model was established and used to simulate the methanol steam reforming reaction between the two parallel plates. The model broke through restrictions of HE-LUO model, and the temperature and composition fields were solved with lattice Boltzmann method evolution equations, respectively. It means that the advantages of lattice Boltzmann method ware maintained. By employing the model, the effects of inlet velocity, boundary temperature and the length of the channel on the reaction process and reaction production of the outlet channel were investigated. The simulated results showed very good consistency compared with that computed with the traditional CFD method, which implied that the chemical reaction model is correct.