Particle/Wall and Partical/Boundary-Layer Interactions

粒子/壁和粒子/边界层相互作用

• 批准号: 8814368
• 负责人: Massoud Kaviany
• 金额: $ 18.72万
• 依托单位: Regents of the University of Michigan - Ann Arbor
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 1988
• 资助国家: 美国
• 起止时间: 1988-09-01 至 1992-02-29
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=8814368&HistoricalAwards=false
• 关键词: Particle; Wall; Partical; Boundary; Layer

Two phenomena occurring in particulate flows, namely, heat transfer during collisions between particles and surfaces, and the interaction of the particles with the momentum and thermal boundary layers will be studied. Experiments will be performed using particle diameters between 1 to 10 mm, low and high thermal conductivity particles, and laminar and turbulent flows. Flow visualization, particle tracing, and Laser Doppler Anemometry will be used for the velocity measurements. The rate of change of sensible heat of a collector (particle/wall interaction) and the change in local rate of surface heat transfer (particle/boundary-layer interaction) will be measured in the heat transfer experiments. In addition, analytical/numerical study of the elastic impact will be made by allowing for variable surface areas, heat transfer through the surrounding gas (gap contribution), material property differences between the particle and the surface, particle spin, and surface roughness. These studies will determine the role of particles in heat transfer from dilute particulate flows (such as in drying and the freeboard portion of the fluidized beds) and will supply the fundamental knowledge needed for understanding and prediction of dense phase systems. Many particle systems, such as dryers, fluidized beds and particle processing (mechanical or chemical loops) require transfer of heat between fluid/particle mixtures and confining or submerged surfaces. Two of the major heat transfer mechanisms are the direct transfer of heat between the particles and these surfaces (conduction), and direct heat between the fluid and the surfaces. The latter is influenced by the motion of the particles. Presently, the conduction contribution is not known for practical cases where the particle surface is not smooth, and when the particle undergoes a spin and arrives at the surface obliquely. The extent of the disturbances caused in the flow field, by the motion of the particles, is also not yet known. This study aims at furnishing these needed fundamental data on the influence of particles on surface heat transfer rates.

颗粒流中出现的两种现象，即热 在颗粒和表面之间的碰撞期间转移，以及 粒子与动量和热量的相互作用 将研究边界层。 将进行实验 使用1至10 mm的颗粒直径，低和高热量 导电性颗粒以及层流和湍流。 流 可视化、粒子追踪和激光多普勒风速测量 将用于速度测量。 变化率 收集器的显热（颗粒/壁相互作用）， 局部表面传热率的变化 （粒子/边界层相互作用）将在 传热实验 此外，分析/数字 弹性冲击的研究将通过考虑可变的 表面积，通过周围气体（间隙）的热传递 贡献），颗粒之间的材料性质差异 以及表面、粒子自旋和表面粗糙度。 这些 研究将确定颗粒在传热中的作用 从稀释的颗粒流（如在干燥和 流化床的自由空间部分），并将供应 理解和预测所需的基本知识 密相系统 许多颗粒系统，如干燥器、流化床和流化床， 颗粒处理（机械或化学循环）需要 流体/颗粒混合物之间的热传递和限制或 水下表面 两种主要的传热机制 是粒子之间的直接传热 表面（传导），以及流体和 表面。 后者是由运动的影响， 粒子 目前，传导贡献是未知的 对于颗粒表面不光滑的实际情况，以及 当粒子旋转到达表面时 间接地。 在流动中引起的扰动程度 场，通过粒子的运动，也是未知的。 这项研究旨在提供这些所需的基本数据， 颗粒对表面传热率的影响。