A Deeper Understanding of Small-Scale Phenomena in Heat Pipes through a Higher Order Lattice Boltzmann Method

通过高阶格子玻尔兹曼方法更深入地了解热管中的小尺度现象

• 批准号: 1233106
• 负责人: Laura Schaefer
• 金额: $ 25万
• 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: 2012
• 资助国家: 美国
• 起止时间: 2012-09-01 至 2016-07-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1233106&HistoricalAwards=false
• 关键词: Deeper; Understanding; Small; Scale; Phenomena

CBET-1233106PI: SchaeferHeat pipes are compact, reliable devices used for transporting heat, but there is a lack of understanding of their microscale fluid flow behavior. In order to gain deeper insights into the nature of these types of flows, which also often occur in complicated geometries, we will model the flows using a technique known as the lattice Boltzmann method. While that method is very useful in analyzing complicated flows, it still suffers from inadequate development on the inclusion of thermal effects. Therefore, we propose the development of advanced, higher order (more accurate) lattice Boltzmann-based numerical simulations that can further our knowledge of micro thermal-fluid phenomena in heat pipes. The intellectual merit of the proposed work comes both from developing a more rigorous, realistic, and versatile computational tool, and from the deeper understanding of complex flows that can be gained as a result. The fundamental underpinning of all lattice Boltzmann models are particle distribution functions that describe the density and momentum (and sometimes temperature) of the fluid elements. To develop a higher-order thermal lattice Boltzmann model, we will expand the equilibrium particle distribution function to the fourth order. In order to model multiple phases, we will incorporate fluid particle interactions using a better description of the effective mass. Combining these approaches means that the forces acting on the particles will need to be discretized over a large number of velocities, which is numerically complicated. However, while this is quite challenging, it will likely lead to additional insights into the contribution of the various aspects of the lattice Boltzmann formulation to instabilities and inaccuracies in the numerical simulations, thereby expanding the applicability of the lattice Boltzmann method. The model will be validated using the vast range of experimental data available in the literature. The resulting model will then be able to explore the effect of variations in geometry, fluid properties, etc., on heat pipe efficiency, and will lead to a better understanding of the underlying physics of the micro fluid phenomena that drive heat pipe systems.More accurate simulations of multiphase, multicomponent, thermal flows, particularly in small-scale and/or complicated geometries have many applications. Improving heat pipe performance can lead to increases in the overall energy efficiency of computer cooling systems, which currently consume huge amounts of power (a typical data center uses 1/3 of its energy consumption for cooling). The same is true for many other more conventional heat exchangers in the power generating and HVAC&R industries; it may be possible to design more efficient condensers, evaporators, generators, etc., by combining micromanufacturing processes with accurate simulations of the phase transitions that occur in those channels and surfaces. Improving the energy efficiency can directly lead to both economic and environmental savings. There are also educational benefits from the study of heat pipes. The devices will be used as demonstration units for undergraduate classes, in order to provide an impetus for discussion of phase change and heat transfer phenomena. Design teams of upper-level undergraduates will also help to translate heat pipe concepts (and their underlying principles) to the high-school and middle-school level, through designing and building demonstration units that examine different materials, working fluids, and configurations, as well as applications for heat pipes, such as cooling devices for overclocking processors and the creation of heat pipe boats.

CBET-1233106PI：Schaeferheat管道是紧凑的可靠设备，用于运输热量，但缺乏对它们的显微镜流体流动行为的了解。为了更深入地了解这些类型的流的性质，这些流量通常也会出现在复杂的几何形状中，我们将使用称为晶格玻尔兹曼方法的技术对流进行建模。尽管该方法在分析复杂的流动方面非常有用，但它仍然存在于纳入热效应的发展不足。因此，我们提出了基于高级，高阶（更准确）晶格玻璃体的数值模拟的发展，这些仿真可以进一步提高我们对热管中微热流体现象的了解。拟议工作的智力优点既来自开发更严格，更现实和多才多艺的计算工具，又是对可以获得的复杂流动的更深入的了解。所有晶格Boltzmann模型的基本基础是描述流体元素的密度和动量（有时温度）的粒子分布函数。为了开发高阶热晶格玻尔兹曼模型，我们将将平衡粒子分布函数扩展到第四阶。为了对多个阶段进行建模，我们将使用更好地描述有效质量来结合流体颗粒相互作用。结合这些方法意味着，作用在粒子上的力将需要在大量速度上离散，这在数值上是复杂的。但是，尽管这很具有挑战性，但它可能会导致对晶格Boltzmann配方对数值模拟中不稳定性和不准确性的各个方面的贡献的更多见解，从而扩大了Lattice Boltzmann方法的适用性。该模型将使用文献中可用的大量实验数据进行验证。然后，所得模型将能够探索几何，流体特性等变化对热管效率的影响，并可以更好地理解驱动热管系统的微流体现象的潜在物理学。更准确地模拟了多个酶，多组分，热流，尤其是在小尺度和/或复杂的地球上，许多应用程序都具有许多应用程序。改善热管性能会导致计算机冷却系统的整体能源效率提高，该系统目前会消耗大量功率（典型的数据中心使用1/3的能源消耗进行冷却）。对于发电和HVAC＆R Industries中的许多其他更常规的热交换器也是如此。通过将微制造过程与对这些通道和表面中发生的相变的准确模拟相结合，可以设计更有效的冷凝器，蒸发器，发电机等。提高能源效率可以直接导致经济和环境节省。热管的研究也有教育益处。这些设备将用作本科阶层的示范单位，以便为相变和传热现象的讨论提供动力。高级本科生的设计团队还将通过设计和建造示范单元来将热管概念（及其基本原理）转化为高中和中学水平，这些单元的设计和建造示范单元，这些单元检查不同的材料，工作液，配置，以及用于热管的热水管道（例如，用于过热式流程和热水管道的冷却式）的应用。