CAREER: Multiscale Simulation of Liquid-Vapor Phase Change Heat Transfer

在能源系统中，将微尺度的换热与大尺度的沸腾和冷凝流动联系起来，美国40%的能源消耗被用作加热沸腾蒸汽，用于发电。投入到蒸汽生产中的能源中，有72%通过气液冷凝排放到环境中。因此，沸腾和冷凝是能源领域的关键过程。提高对这些过程的了解可以提高发电、制冷和淡水蒸馏的效率。沸腾和冷凝是由发生在大范围大小尺度上的机制控制的，这些尺度之间的相互作用还没有被很好地理解。例如，在沸腾中，蒸汽泡在加热表面的微小空腔中形成，长大并分离到大块液体中，然后合并形成大的气态结构。这三个尺度上的流动和换热效应被认为是以一种复杂的方式相互作用的。在这个项目中，将开发计算方法来预测沸腾和冷凝过程中水垢之间的相互作用。将进行实验以评估和改进计算模型。由此产生的模型和获得的见解将指导增强型能源系统设备的工程设计，以提高传热性能和整体效率。作为补充外联工作，将在不同的区域中学开发和实施一个新的教学单元，介绍能源问题和计算机建模技能。作为这个项目的一部分，学生们将收集家用电器能源消耗的测量数据，并将其纳入一个网络工具，为公众提供家用电器效率和环境影响的指导。关于能源系统运输的研究将补充为不同区域社区的中学生编写和实施一个教学单元和课堂研究项目，介绍能源问题和计算机建模技能。中学生对家用电器能源消耗的测量将被纳入一个公共网络工具，该工具提供对效率和环境影响的估计，以及关于家用电器年龄和成本权衡的指导。在大学教学层面，将开发一门新的项目驱动的能源系统课程，在该课程中，学生将制作关键能源技术的公共教程视频。该项目旨在通过实验验证的多尺度模拟框架来表征流动沸腾和滴状冷凝中微尺度热传递和大尺度流体动力学之间的耦合。通过在平均意义上对小的、分散的特征进行建模，直接跟踪中间气体和液体特征的轨迹，以及解析大的结构，该方法将捕捉已被独立理解的尺度之间的相互作用。对于流动沸腾，这将用于研究大汽泡尾迹与气泡成核之间的相互作用以及两相流动结构的发展。对于滴状冷凝，该方法将量化输运性质对瞬变冷凝的影响以及流体动力对传热的贡献。该方法将通过实验高速摄影和热成像研究进行验证和补充。模拟软件将开源发布，以支持在发电、吸收冷却、水蒸馏和电子冷却方面的应用研究。

Connecting microscale heat transfer and large-scale flows in boiling and condensation in energy systems40% of US energy consumption is used as heat to boil steam for power production. 72% of this energy invested in steam production is rejected to the environment through gas-to-liquid condensation. Boiling and condensation are therefore critical processes in the energy landscape. Improved understanding of these processes can lead to increased efficiencies in power generation, refrigeration, and freshwater distillation. Boiling and condensation are governed by mechanisms that occur over a wide range of size scales, and the interplay between these scales is not yet well understand. For example, in boiling, vapor bubbles form in minute cavities on heated surfaces, grow and detach into the bulk liquid, and merge to form large gaseous structures. Flow and heat transfer effects at these three scales have been postulated to interact in a complex fashion. In this project, computational methods will be developed to predict interactions between scales in boiling and condensation. Experiments will be performed to assess and refine computational models. Resulting models and gained insights will guide engineering of enhanced energy system equipment to improve heat transfer performance and overall efficiency. In a complementary outreach effort, a new teaching module will be developed and implemented in diverse regional secondary schools, introducing energy issues and computer modeling skills. As part of this project, students will collect measurements of residential appliance energy consumption to be incorporated into a web-tool that provides guidance on appliance efficiency and environmental impacts for the public. Research on transport in energy systems will complement development and implementation of a teaching module and classroom-based research project for secondary school students in diverse regional communities introducing energy issues and computer modeling skills. Secondary school student measurements of residential appliance energy consumption will be incorporated into a public web-tool that provides estimates of efficiency and environmental impacts, and guidance on appliance age and cost tradeoffs. At the university teaching level, a new project-driven Energy Systems course will be developed in which students will develop public tutorial videos on key energy technologies.This project seeks to characterize the coupling between micro-scale heat transfer and large-scale fluid dynamics in flow boiling and dropwise condensation through an experimentally validated multiscale simulation framework. By modeling small, dispersed features in an averaged sense, directly tracking trajectories of intermediate vapor and liquid features, and resolving large structures, this approach will capture interactions between scales, which have been understood independently. For flow boiling, this will be applied to study interactions between large vapor bubble wakes and bubble nucleation and the development of two-phase flow structures. For dropwise condensation, this approach will quantify the effects of transport properties on transient condensation and hydrodynamic contributions to heat transfer. The approach will be validated and complemented with experimental high-speed photography and thermal imaging studies. Simulation software will be released open-source to support research for applications in power generation, absorption cooling, water distillation, and electronics cooling.