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

Connecting microscale heat transfer and large-scale flows in boiling and condensation in energy systems 40% 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.