Effect of flow velocity on the dimensionless Nusselt number of continuous flow reactors configured with segmented steam reforming catalyst layers

The dimensionless Nusselt number data are presented to illustrate the effect of flow velocity on the heat transfer operation of continuous flow reactors configured with segmented steam reforming catalyst layers. 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 conductive component is measured under the same conditions as the convective but for a hypothetically motionless fluid. The Nusselt number is a dimensionless number, closely related to the fluid's Rayleigh number. The mass transfer analogue of the Nusselt number is the Sherwood number. The dimensionless Nusselt number is the ratio of convective to conductive heat transfer across a boundary. 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. A thermal boundary layer develops if the fluid free stream temperature and the surface temperatures differ. A temperature profile exists due to the energy exchange resulting from this temperature difference. The continuous flow reactor is configured for simultaneous oxidation and steam reformation of methanol. 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 oxidation catalyst consists essentially of oxides of copper, zinc and aluminum. 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. The catalyst segments have a uniform distribution of length, and the spacing between catalyst segments is equal to their length. Contributor: Junjie Chen, E-mail address: [e-mail], 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

本数据集提供无量纲努塞尔数（Nusselt number）数据，用以阐明流速对搭载分段式蒸汽重整催化剂层的连续流反应器传热过程的影响。在流体动力学领域，无量纲努塞尔数是流体边界处对流换热与导热换热的比值；对流过程包含平流与扩散两种形式。导热分量是在与对流换热完全一致的工况下，针对假想静止流体所测得的换热值。努塞尔数为无量纲参数，与流体的瑞利数（Rayleigh number）密切相关，其传质类比对应量为舍伍德数（Sherwood number）。无量纲努塞尔数可定义为边界两侧对流换热与导热换热的比值；在简化工况下，对流与传导热流彼此平行，且与边界表面的法向一致，同时均垂直于流体的平均流向。理解对流边界层是掌握固体表面与流经该表面的流体之间对流换热规律的核心前提：当流体主流温度与固体表面温度存在差异时，流场中会形成热边界层，该温差引发的能量交换会使得流场内形成特定的温度分布剖面。本研究所用连续流反应器可实现甲醇的同步氧化与蒸汽重整反应，反应器流道的高、宽均为0.7毫米，长度为30.0毫米；为保障高压工况下的机械结构强度，未涂层反应器壁与催化剂层的厚度分别为0.7毫米与0.1毫米。氧化催化剂的主要成分为铜、锌、铝的氧化物，重整催化剂则主要由铜以及锌、铝的氧化物组成。该放热与吸热反应过程均在0.8兆帕的压力下进行，甲醇-空气当量比为0.8，蒸汽-甲醇摩尔比为1.17；混合进料的入口温度为373开尔文。连续流反应器的温度可通过调节各物料的流量平衡进行调控，避免放热反应过程使催化剂发生过热；为确保吸热重整反应获得充足的反应温度，本数据集通过指定气体流速来确定连续流反应器的运行工况。催化剂分段单元的长度分布均匀，且相邻催化剂分段之间的间距与分段单元自身长度相等。贡献者：陈俊杰，电子邮箱：[e-mail]，ORCID：0000-0002-5022-6863，河南省焦作市世纪大道2000号河南理工大学机械与动力工程学院能源与动力工程系，邮编454000，中华人民共和国。