Presidential Young Investigators Award: Convective Transport Complex Flows

总统青年研究员奖：对流传输复杂流

• 批准号: 8958347
• 负责人: Melany Hunt
• 金额: $ 22.89万
• 依托单位: California Institute of Technology
• 依托单位国家: 美国
• 项目类别: Continuing Grant
• 财政年份: 1989
• 资助国家: 美国
• 起止时间: 1989-09-01 至 1996-02-29
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=8958347&HistoricalAwards=false
• 关键词: Presidential; Young; Investigators; Award; Convective

Heat and mass transfer in fluid-solid flows encompasses many engineering disciplines from handling and processing of granular material to chemical synthesis using packed and fluidized beds. Though petrochemical, process, and energy industries have extensively used these technologies, models governing the bulk fluid-solid transport rates are based largely on empirical data. To simplify the analysis the fluid-solid systems are often viewed as macroscopically homogeneous; however, on the microscopic or pore level, the medium consists of a random distribution of individual particles in a surrounding fluid. The pore-level transport depends on the bed structure, frequency of the particle collisions, heat, mass and momentum exchange between the particles and fluid, and interactions with bounding surfaces. Though exact descriptions incorporating these local or microscopic effects appear inextricable, the current efforts focus on understanding the local mechanisms with the intent of furthering development of the industrially-important macroscopic relations. The planned analytical and experimental research will investigate transport in the bulk and in the boundary regions of the particle flows. In the bulk region, the overall flow appears uniform, but locally the individual particles rotate and translate laterally. This local motion increases the cross-stream heat and mass diffusion and yields higher transport rates. Near a bounding surface, the particles are not uniformly distributed but contact the surface at distinct points causing a near-wall alignment of particles. The distribution depends on the surface conditions of the wall, the type of particle, and the flow rate and affects the velocity profile, molecular diffusivity and local particle convection. The work performed with this PYI grant will emphasize fluid-solid transport involving heat and mass transfer in contact-dominated granular flows. This field has many industrial applications in energy, process, and food industries, and also combines aspects of the simpler fixed-bed problems with the more complex moving- particle flows. These aspects of granular flows are poorly understood and yet they comprise the mechanisms that govern the heat, mass and momentum transport. Continued research in these areas will advance the modeling of granular material flows and may lead to other fluid-solid research areas such as fluidized beds and suspension flows.

流体-固体流动中的传热和传质包括许多 工程学科从处理和加工 颗粒状材料的化学合成， 流化床。 虽然石化、加工和能源 工业界广泛使用这些技术、模型 控制散装流体-固体传输速率的基础是 主要基于经验数据。 为了简化分析， 流体-固体系统通常被视为宏观的 均匀;然而，在微观或孔隙水平上， 介质由随机分布的个体组成 周围流体中的粒子。 孔隙水平输运 取决于床层结构，粒子的频率 碰撞，热量，质量和动量之间的交换 粒子和流体，以及与边界表面的相互作用。 虽然准确的描述包含这些当地或 微观影响似乎无法解决，目前的努力 重点了解当地机制， 进一步发展工业上重要的 宏观关系。 计划的分析和 实验研究将调查运输散装 以及颗粒流的边界区域。 在 整体区域，整体流动似乎均匀，但局部 单个粒子旋转并横向平移。 这 局部运动增加了横流的热量和质量 扩散并产生更高的传输速率。 在边界附近 表面上，颗粒不是均匀分布的， 在不同的点接触表面， 粒子的排列。 分布取决于 壁的表面条件，颗粒的类型，以及 流速和影响速度分布，分子 扩散率和局部粒子对流。 保华基金的工作重点是 流体-固体传输，包括传热和传质， 接触主导的颗粒流 这个领域有很多 能源、加工和食品工业应用 工业，也结合了更简单的固定床的方面， 更复杂的运动粒子流的问题。 这些 颗粒流的各个方面都知之甚少， 包括控制热量、质量和 动量输运 在这些领域的持续研究将 推进颗粒物质流动的建模，并可能导致 其他流固研究领域，如流化床， 悬浮液流动。