Effect of wall thermal properties on the dimensionless Sherwood number in transport phenomena in microchannel steam reforming reactors
Description
The dimensionless Sherwood number data are obtained for illustrating the effect of wall thermal conductivity on the mass transfer operation of microchannel steam reforming reactors. The dimensionless Sherwood number is a dimensionless number used in mass-transfer operation. The dimensionless Sherwood number represents the ratio of the convective mass transfer to the rate of diffusive mass transport. Using dimensional analysis, the dimensionless Sherwood number can also be further defined as a function of the Reynolds and Schmidt numbers. The dimensionless Sherwood number 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. 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. In each exothermic oxidation channel, the catalyst layer is reduced by half in amount. The catalyst segments have a uniform distribution of length, and the spacing between catalyst segments is equal to their length. To obtain the solution of the problem, numerical simulations are performed using fluid mechanics. 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 mathematical formalism developed to describe transport phenomena and chemical kinetics is implemented into ANSYS FLUENT. More specifically, 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.