Simulations of reactive flows in COMSOL

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Original Title: Simulating Reacting Flows in COMSOL In recent versions of COMSOL Multiphysics ®, we have added several new multiphysics interfaces, decomposed the basic physics interfaces into separate interfaces, and predefined the coupling between multiphysics fields in the "Multiphysics" node of the model tree. This update perfectly combines the flexibility of the basic physical field interface with the convenience of predefined multi-physical field coupling. Study of fluid flow and reactions in gases and liquids The Chemical Reaction Engineering, CFD, and Plasma modules contain various forms of equations to describe the transport of chemicals in concentrated solutions, including Maxwell-Stefan equations and mixed-average models. For a concentrated solution, the model equation must take into account the interaction between all substances in the solution, while the model for a dilute solution involves only the interaction between the solute and the solvent. The above two descriptions are illustrated in the schematic below. Dilute solution (left) and concentrated solution (right). Dilute solution mainly includes solute and solvent, as well as the interaction between different solvents. A concentrate solution contains all that interaction between the substances. The velocity field of a concentrated solution is defined as the sum of the fluxes of each species I, accompanied by the interactions of the species: Expand the full text (1) Where n is the flux in kg/ (m m ² 2; s) and ρ is the density in kg/m m ² 3;. For a dilute solution, the velocity field depends on the velocity of the solvent: (2) From the above figure and equation (1), we can see that the mass transfer and fluid flow in the concentrated solution are tightly coupled. Use the new "reactive flow" multiphysics interface in COMSOL Multiphysics ® In previous versions of COMSOL Multiphysics, the Reaction Flow interface was a stand-alone multiphysics interface with its own domain settings and boundary conditions, specifically designed to handle flow coupling and the transfer and reaction of chemicals. Because all settings are predefined, the interface is easy to use. However, on the other hand, such predefined physical field interfaces lose some flexibility to some extent. Suppose that when you want to make more drastic changes to the dense mass transfer equation and the flow equation separately, the predefined multiphysics interfaces are not adequate for this, and you must define the problem by adding both types of physics interfaces separately, and then manually create the multiphysics coupling. When using the new Reactive Flow interface for strong solution problems, jacketed glass reactor ,wiped film evaporator, you can change the transport equation and fluid flow settings separately to handle such tightly coupled problems. The coupling itself is defined in the Multiphysics node. Many operations can be performed with this capability, such as changing from laminar to turbulent flow, or changing the transport model from the Maxwell-Stefan equation to a mixed-average model. Let's take a look at how this can be implemented in the model tree and in the "multi-physics" node setup. As shown in the screenshot below, all the regular nodes in this basic physical interface allow the user to modify them at any time after the couplings are predefined in the "Multi-Physical" node. The predefined coupling controls the mass flux and agrees with the continuity equation of the flow when the mass flux of all substances is summed. In this way, the two sets of equations are fully coupled in both directions. Model tree with the Reactive Flow multiphysics node enabled. Not only can we choose the physical field interfaces to be coupled, but we can also change the flow model to include turbulent reacting flows. Compared with the previous multi-physical field interface, this method has greater flexibility while retaining ease of use. Another advantage of the new Reactive Flow multiphysics interface is in the Research node. By solving the fluid flow equations, we can obtain a more accurate initial guess of the total flux. In Step 2, we have only solved the mass transfer problem, where the velocity field is calculated from the previous fluid flow equations. We have obtained a satisfactory solution for the fluid flow and solution composition, which can now be used as a preliminary estimate for the fully coupled problem. The final research step (Step 3) involves solving the fluid flow and chemical mass transfer in the fully coupled system. It should be noted that in the case of a large number of three-dimensional substances, although the fully coupled system itself may also follow a certain order, all the cycles of substance and fluid flows are performed automatically. The three research steps (1,2,3) solve the fluid flow, chemical species transfer, and fully coupled problems, respectively. The automatically generated solver configuration shows that the intermediate step is used to store the flow and concentration fields, and the final step uses the stored solutions as initial estimates and solves the fully coupled problem. With the new Reactive Flow multiphysics interface, you can solve a range of interesting problems, such as the case below. Images show flow and concentration in a tubular reactor used to convert methane to hydrogen. The model combines mass transfer in a concentrated solution, fluid flow in a free porous medium, and heat transfer phenomena between an endothermic reaction and a heated jacket on the outer wall of the reactor cylinder. The concentration of hydrogen in the reactor used to convert methane to hydrogen. The reaction in the reactor is endothermic, and the heat comes from the wall of the column, so the amount of hydrogen produced near the wall is high. Learn more Carbon deposition in isomerization catalysis Syngas combustion in a round jet burner If you would like to learn more about using the new Reactive Flow multiphysics interface in your own simulation studies,wiped film evaporator, please contact us today Carbon deposition in isomerization catalysis Syngas combustion in a round jet burner Carbon deposition in isomerization catalysis Syngas combustion in a round jet burner If you would like to learn more about using the new Reactive Flow multiphysics interface in your own simulation studies, please contact us today In the menu bar at the bottom of the homepage of COMSOL official account, click "Support Center-Selected Simulation Articles" to view more simulation articles. Return to Sohu to see more Responsible Editor:. toptiontech.com

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