Effect of catalyst layer thickness on the dimensionless Nusselt number in reacting flow systems designed with oxidation catalyst segments
Description
The dimensionless Nusselt number data under different catalyst layer thickness conditions are presented associated with the oxidation catalyst segmentation methods employed for reacting flow systems. The reacting flow system is configured for simultaneous oxidation and steam reformation of methanol. The reacting flow system comprises two separate sets of flow channels, which are located between spaced, highly heat-conductive metal or ceramic separating walls. The medially located, bi-catalytic separating walls have different catalysts on opposed surfaces. These catalysts are selected for the particular reaction taking place in the adjacent reaction zone. The reacting flow system provides for continuous and simultaneous reaction of two different process reaction streams in the channels defined between the walls, wherein a first process reaction stream undergoes a high temperature exothermic reaction in the first set of flow channels and a second process reaction stream undergoes an endothermic heat-consuming reaction in the second set of flow channels separated from the first set of flow channels by the heat transfer separating walls. More specifically, the reacting flow system includes a set of reforming channels for steam reformation of methanol and a set of oxidation channels for heating the reactor system to operating temperature. A separating wall therefore separates two adjacent reaction zones and also functions to transfer heat from the oxidation occurring at the catalyst surface in the oxidation zone directly to the reforming catalyst coated on the opposed surface. The channels are 0.7 millimeters in height and in width and 30.0 millimeters in length. Channel height refers to the inside height of a channel. 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 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 continuous flow reactor can be regulated by the balance of the flow rates so that the catalyst is not overheated by the exothermic process. To assure that adequate temperatures are provided for endothermic reforming, operating flow conditions are specified for the continuous flow reactor by giving the gas velocity. 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
ANSYS FLUENT is applied to define the terms in the equations relating to conservation, thermodynamics, chemical production rates, and equation of state, and then combine the results to define the problem involving surface chemistry. The under-relaxation factors are reduced for all variables. The residuals decrease by at least six orders of magnitude.