The dimensionless Sherwood number data pertaining to the steam reforming catalyst segmentation methods used in microchannel reactors
Description
The dimensionless Sherwood number data are obtained for illustrating the steam reforming catalyst segmentation methods used in microchannel reactors. The Sherwood number, also called the mass transfer Nusselt number, is a dimensionless number used in mass-transfer operation. It represents the ratio of the convective mass transfer to the rate of diffusive mass transport. Using dimensional analysis, it can also be further defined as a function of the Reynolds and Schmidt numbers. It is particularly valuable in situations where the Reynolds number and Schmidt number are readily available. Since Reynolds number and Schmidt number are both dimensionless numbers, the Sherwood number is also dimensionless. The microchannel reactor is configured for simultaneous oxidation and steam reformation of methanol. The reforming process proceeds in one set of the channels through which the endothermic reactants flow, and the exothermic oxidation process proceeds in the second set of the channels. Exothermic and endothermic reactions take place simultaneously whereby the heat required for the latter is supplied by the former. 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. The ratio of the height of the channels to the width of the channels may vary. The channels are 0.7 millimeters in height and in width and 30.0 millimeters in length. The oxidation catalyst consists essentially of oxides of copper, zinc and aluminum. The oxidation catalyst allows for initial start-up and the heat-up of the reactor system. The reforming catalyst consists essentially of copper and oxides of zinc and aluminum. 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 inlet temperature of the mixtures is 373 degrees Kelvin. The temperature of the reactor can be regulated by the balance of the flow rates so that the catalyst is not overheated by the exothermic process and thus damaged. The gas velocity is 2.0 meters per second at the reforming channel inlets and 0.6 meters per second at the oxidation channel inlets, thereby assuring sufficient heat in the reactor to carry out endothermic reforming of methanol. The boundary conditions relate macroscopic fluid flow at a catalytically active surface to the rates of surface reactions. 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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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. Physical properties depend on temperature and composition.