Carbon dioxide mole fraction data with different porosities pertaining to the coupling of endothermic and exothermic reactions in chemical reactors
Description
The carbon dioxide mole fraction data with different porosities are obtained for the coupling of endothermic and exothermic reactions in chemical reactors. The porosity is isotropic. The porosity does not vary with space and therefore the porous media are homogeneous. Exothermic and endothermic reactions take place simultaneously whereby the heat required for the latter is supplied by the former. Heat transfer occurs via conduction through the walls of the reactor. For the endothermic reaction, the structure is especially effective because both the internal surfaces of the walls are coated with structured catalysts, which is capable of providing more efficient heat exchange and minimizing the problem of loss of catalytic activity. Such a reactor system is typically adiabatic in nature, meaning no heat is added in addition to the exothermic reaction heat release. The reactor system is in the form of a catalytic coating on a substrate composed of ceramic or metal walls defining straight reforming or oxidation channels which are parallel to each other and to the axis of the reactor. Relatively high mass transfer is provided by using low hydraulic diameter channels. The design increases the number of boundary layers between a fluid and a reactor wall by a factor of one hundred or more, and boundary layers are known to impede heat transfer. To facilitate computational modeling of transport phenomena and chemical kinetics in the flowing system of complex chemical reactions involving gas-phase and surface species, steady-state analyses are performed and computational fluid dynamics is used. ANSYS FLUENT is applied to the problem involving surface chemistry. Two types of species are defined: gas-phase and surface. The first type is a species in the gas phase above the surface. A surface species is defined to be the chemical species at the gas-solid interface. A surface does not necessarily have to be flat, and each surface species occupies one surface site. A site is considered to be a position or location on the surface at which a species can reside. A site does not necessarily have a composition itself or have to be a particular atom, and the total number of sites per unit area is conserved. The contribution of homogeneous reactions involving gas-phase species is insignificant under the conditions of interest. The heat release and consumption due to a surface reaction must be included in the model. Endothermicity or exothermicity of surface reactions contribute to the energy balance at an interface. Heat fluxes in the solid phase are balanced by chemical heat release at the surface. Contributor: Junjie Chen, E-mail address: koncjj@gmail.com, ORCID: 0000-0002-5022-6863, Department of Energy and Power Engineering, School of Mechanical and Power Engineering, Henan Polytechnic University, 2000 Century Avenue, Jiaozuo, Henan, 454000, P.R. China
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Steps to reproduce
To solve the conservation equations, a segregated solution solver with an under-relaxation method is used. The segregated solver first solves the momentum equations, then solves the continuity equation, and updates the pressure and mass flow rate. The energy and species equations are subsequently solved and convergence is checked.