Effect of wall thermal conductivity on the heat transfer process in heterogeneous steam reforming reactor systems for hydrogen production
Description
The dimensionless Nusselt number data are presented to illustrate the effect of wall thermal conductivity on the heat transfer process in heterogeneous steam reforming reactor systems for hydrogen production. The wall thermal conductivity and exterior convective heat loss coefficient are taken as independent parameters to understand how important thermal management is. In fluid dynamics, the dimensionless Nusselt number is the ratio of convective to conductive heat transfer at a boundary in a fluid. Convection includes both advection and diffusion. The convection and conduction heat flows are parallel to each other and to the surface normal of the boundary surface, and are all perpendicular to the mean fluid flow in the simple case. An understanding of convection boundary layers is necessary to understanding convective heat transfer between a surface and a fluid flowing past it. The heterogeneous steam reforming reactor system is configured for simultaneous oxidation and steam reformation of methanol. The exothermic and endothermic processes are conducted at a pressure of 0.8 megapascals, with a methanol-air equivalence ratio of 0.8 and a steam-to-methanol molar ratio of 1.17. The channels are 0.7 millimeters in height and in width and 30.0 millimeters in length. To ensure the mechanical strength at elevated pressures, the thickness of the uncoated walls and the catalyst layers is 0.7 millimeters and 0.1 millimeters, respectively. The inlet temperature of the mixtures is 373 degrees kelvin. The temperature of the heterogeneous steam reforming reactor system can be regulated by the balance of the flow rates so that the catalyst is not overheated by the exothermic process. The oxidation catalyst consists essentially of oxides of copper, zinc and aluminum. The reforming catalyst consists essentially of copper and oxides of zinc and aluminum. To assure that adequate temperatures are provided for endothermic reforming, operating flow conditions are specified for the heterogeneous steam reforming reactor system by giving the gas velocity. 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. The energy released or consumed at each phase boundary is obtained using a summation over all gas-phase species. Geometric surface area does not include the additional surface area contributed by generally microscopic or small surface roughness or porosity. 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
The endothermic process is modeled in such a way as to take into account methanol steam reforming and decomposition and the water-gas shift reaction using a chemical kinetic model. Numerical simulations are performed using fluid mechanics. The mathematical formalism developed to describe transport phenomena and chemical kinetics is implemented into ANSYS FLUENT.