Heat Transfer in Slow Granular Flows

慢速颗粒流中的传热

• 批准号: 0331352
• 负责人: Joseph McCarthy
• 金额: $ 14万
• 依托单位: University of Pittsburgh
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2003
• 资助国家: 美国
• 起止时间: 2003-10-01 至 2006-09-30
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=0331352&HistoricalAwards=false
• 关键词: Heat; Transfer; Slow; Granular; Flows

Slow granular flows where lasting contacts are common play an important role in industries ranging from food to paper to pharmaceuticals to ceramics. Despite the fact that the companion case of conduction in (micro-structurally static) porous materials has been well studied, heat transfer in even the simplest slow particle flows is poorly understood. While it is clear that the conductivity depends strongly on the micro-structure of the bulk material, in these slow flows, the micro-structure changes with time so that the contact duration becomes critical and the role of particle mixing/segregation (i.e., "convective" heat transfer) quickly comes to the fore.This work uses simple experiments and Thermal Particle Dynamics (TPD) to examine heat flow in two prototypical slow granular flows: a simple shear cell and (to a limited extent) a tumbler. TPD is a recently introduced computational technique that has been shown to be capable of capturing both thermal and mechanical behavior of particles from a Lagrangian viewpoint in static beds. In this work, we extend this technique to slowly flowing granular beds in order to addresses the fundamental issue of how particle-particle contacts/collisions affect both the uniformity and magnitude of the conductance in macroscopic particulate systems. The primary intellectual merit of the proposal lies in addressing the fundamental issue of the competition between conduction and convection in granular systems, as well as the industrial relevance of examining heat transfer rates in specific devices.

持久接触的缓慢颗粒流在食品、造纸、制药和陶瓷等行业中发挥着重要作用。尽管事实上（微观结构静态）多孔材料中的传导的伴随情况已经得到了很好的研究，但即使是最简单的慢速颗粒流中的传热也知之甚少。虽然很明显，电导率很大程度上取决于散装材料的微观结构，但在这些缓慢的流动中，微观结构随时间变化，因此接触持续时间变得至关重要，颗粒混合/分离（即“对流”传热）的作用很快就凸显出来。这项工作使用简单的实验和热粒子动力学 (TPD) 来检查两种典型的缓慢颗粒流中的热流：简单的剪切 细胞和（在有限程度上）玻璃杯。 TPD 是最近推出的一种计算技术，已被证明能够从静态床中的拉格朗日观点捕获颗粒的热行为和机械行为。在这项工作中，我们将这项技术扩展到缓慢流动的颗粒床，以解决颗粒与颗粒接触/碰撞如何影响宏观颗粒系统中电导的均匀性和幅度的基本问题。该提案的主要智力价值在于解决颗粒系统中传导和对流之间竞争的基本问题，以及检查特定设备中传热率的工业相关性。