List of Potential REU Projects

1-3.      Microdroplet Evaporation from Phase Routing Micro-Heat Exchangers for Extreme Heat Flux

Mentors: Damena Agonafer and J. Mark Meacham

Background: The objective of this research project is to realize an adaptable thermal management solution for emerging micro-/power electronics platforms by utilizing microstructural geometries to influence interface evolution, pinning, and evaporation of microdroplets. Advancement of micro-/power electronics demands greater package density. 3D chip stacking reduces the package footprint, decreases interconnect delay and power consumption, and supports component integration; however, associated localized hot spots require innovative and integrated thermal management solutions. Here, we focus on developing a 3D phase routing micro-heat exchange technology that exploits thin film evaporative cooling.

Projects: Student(s) will investigate aspects of thin film evaporation from individual and arrays of porous pillars using multiphase computational models (Project 1) and high-resolution visualization and experimental measurement (Project 2). Computational fluid dynamics (CFD) software will be used to model meniscus development, pinning, and evaporation of various liquids from micro-/mesoscale pillar geometries under adiabatic and heated conditions. The student(s) will develop fabrication processes in the Institute of Materials Science and Engineering clean room at Wash U to create structures for experimental investigation of how the transparency of graphene can affect the wettability of graphene-coated copper inverse opal structures in the presence of evaporation (Project 3).

  1. Exploring the Effect of Temperature on Capillary Condensation in Multiscale Porous Architecture Cathodes for Alkali Metal-Ambient Air Cells

Mentor: Vijay Ramani

Background: The high theoretical specific energy of secondary, metal-air batteries (Li-O2 – 3458 Wh/kg [3], Na-O2 -1108 Wh/kg [4], K-O2 – 935 Wh/kg [5]) has been the major motivator of research into these systems as a potential “beyond Li-ion” energy storage alternative. A major barrier to realizing this theoretical promise is to demonstrate ambient air, moisture tolerant operation of such systems. Balancing economical and engineering considerations [6], we believe systems that passively dehumidify ambient air input at the cathode have the greatest potential for achieving high system level specific energies  required for these batteries to be truly “beyond Li-ion”. We propose to use capillary condensation in multi-scale porous cathodes (carbon and conducting mixed metal oxides). The cathodes will contain a combination of macropores (for large air throughput) and mesopores (for capillary condensation). We will examine the dynamics of capillary condensation with variations in temperature.

Project: Capillary condensation is the phenomenon where water condenses at pressures () lower than the saturation pressure () inside sufficiently small pores. The dependence of the undersaturation () on pore radius is given by the Kelvin equation. While the Kelvin equation provides a static description, practical applications must account for the dynamics brought about by the decrease in temperature due to the latent heat of condensation. Thus, we propose for students to synthesize high area, mesoporous carbon and mixed metal oxides, and characterize the temperature dependent dynamics of capillary condensation within them using thermo-gravimetric analysis.

  1. Management of Radiative Heat Transfer for Next-Generation Carbon Capture and Storage

Mentor: Richard Axelbaum

Background: Carbon capture utilization and storage (CCUS) is presently too costly, and the efficiency penalty is too high to have large-scale impact on global carbon management. For CCUS to deliver the impact that is required to control CO2 concentrations in the atmosphere, dramatic improvements will be needed in our approach to generating power from fossil fuels. To this end, a number of transformative technologies have been proposed and many of these require operation of the combustion process under pressure (e.g., pressurized fluidized bed combustion, the Allam cycle, pressurized pulverized coal combustion). When combustion products are under pressure, the radiative heat transfer characteristics change, not just quantitatively but qualitatively, because the system transforms from being optically thin to optically thick as the radiatively-active species (CO2, H2O, soot, ash, and char) increase.

Project: The purpose of this REU project is to develop an understanding of radiative heat transfer in optically thick systems relevant to producing low-carbon power from fossil fuels and biomass. The student will be involved in pressurized combustion experiments and will assist in analyzing the results to understand how radiative heat transfer can be managed in these systems. By controlling radiative heat transfer, the performance and cost of these systems can be improved such that broad, international deployment of CCUS can be enabled.

6,7. Acoustic Stabilization of Flow Boiling and Condensation in Microchannels

Mentors: J. Mark Meacham and Patricia Weisensee

Background: The objective of this research project is to explore the potential of ultrasound actuation to stabilize inherently unstable phase-change heat transfer processes during boiling and condensation in microchannels. Flow instabilities represent a critical barrier to implementation of parallel microchannels (and their associated enhanced heat and mass transfer characteristics) for two-phase heating/‌cooling in high heat flux applications. Maldistribution owing to the significant disparity in liquid/‌vapor density yields less-desirable single-phase flow in some channels and dryout in others. Ultrasound enables manipulation and control of fluids based on otherwise problematic differences in density. We will apply existing knowledge of acoustic microfluidics to tune the microchannel/‌device geometry and ultrasound actuation parameters to stabilize phase change processes.

Project: The student(s) will design, model, and fabricate microchannel assemblies for investigation of acoustic stabilization of flow boiling and condensation. Like existing programs for undergraduate study of acoustic microfluidic devices, students will use COMSOL Multiphysics to predict system harmonic responses and the behaviors of simplified flows (e.g., gas/‌liquid versus vapor/‌liquid) (Project 5). Students will assist with fabrication, thermal measurement, flow visualization, and data analysis (Project 6).

  1. Management of Thermal Loads Induced by a Pneumatic System Integrated on an Electric Aircraft

Mentor: Emily Boyd

Background: Active flow control (AFC) aims to obtain desirable flow behavior by inducing large-scale changes in a flow field via low-energy input. AFC has numerous applications, such as: separation control to reduce fuel burn or increase payloads, high-lift systems, noise reduction, thermal management, mixing enhancement, etc. Integrating these systems into aerospace vehicles introduces additional power requirements that create thermal management challenges. Addressing the thermal management of these AFC systems integrated in a vehicle is an important step in preparing them for transition to aerospace products. It also provides broader opportunities for innovation in the thermal management of electric systems.

Project: The student(s) will utilize non-proprietary thermal management technology developed at The Boeing Company as well as state of the art solutions from technical literature to mitigate a thermal load induced by adding a pneumatic system to an electric aircraft, such as a drone, and analyze the net system efficiency that results.

  1. Experimental characterization of pool boiling of salt water on Lubricant Infused Surfaces

Mentor: Patricia Weisensee

Background: Pool boiling is a ubiquitous phenomenon in many industrial applications, ranging from the hot water kettle in our kitchen, to electronics cooling, to nuclear power plants. However, salt water or water with other impurities causes degradation of the surface due to build-up of a salt film. This film acts as a thermal resistance (or barrier) to heat transfer and decreases the heat transfer performance. Lubricant-Infused Surfaces (LIS or SLIPS) are surface-porous solids that are infused with a thin oil layer to create a non-sticky, atomically flat surface. These infused surfaces have been used for enhanced dropwise condensation, anti-freezing, and anti-fouling; however, they have not yet been explored for boiling, possibly due to the increased thermal resistance associated with the oil layer. Nevertheless, this oil layer is expected to have a significantly lower heat transfer penalty than salt built-up. Here, we will explore the anti-fouling, slippery lubricant-infused surface for pool boiling of salt water.

Project: As part of this REU, the student will fabricate lubricant-infused surfaces, conduct transient thermal and optical measurements during pool boiling for different salt concentrations (using the data acquisition software LabView and high speed imaging), and assist in data analysis (using Matlab).

  1. Laminar and Turbulent Forced and Free Convection Heat Transfer from Nanofluids in Pipes of Arbitrary Cross-section

Mentor: Ramesh Agarwal

Background: The objective of this research project is to develop a better understanding of heat transfer enhancement by nanofluids, i.e., fluids containing suspended nano-sized particles, flowing in noncircular pipes. The demand for high heat transfer rates in industrial systems and devices is ever increasing. As an example, steadily-increasing heat-flow demand has rendered thermal management the bottleneck in developing big data storage and high-performance computing units at a relatively small scale. Nanofluids are attractive candidates for next-generation heat transfer media due to their intrinsically high thermal conductivity, and there is a critical need to better understand their heat transfer enhancement properties.

Project: While the literature includes studies of circular pipe flow of nanofluids [7-12], there are few studies of laminar and turbulent flow in pipes with arbitrary cross-sections for entry and fully developed flow regimes. These complicated flows (and in particular, turbulent flow in a pipe of arbitrary cross-section) necessitate computational simulation. REU students will use ICEM software in ANSYS to model and mesh the pipe geometry, and Fluent will be used to compute the flow field and heat transfer. The turbulence models in Fluent (k-ε and SST k-ω) will be used to model turbulence in Reynolds-Averaged Navier-Stokes equations. Nanofluid property models will be included via User Defined Functions (UDF).

  1. Multiscale Modeling of Particle Formation in High Temperature Environments

Mentor: Pratim Biswas

Background: Particle formation and growth is an important aspect in many engineered systems such as materials synthesis and combustion. This study will focus on gas phase systems, thus emphasizing aerosol formation and growth aspects which are both important to make useful particles and prevent the emission of deleterious ones. An important aspect that drives the various aerosol phenomena of nucleation, condensation, and collisional growth is the temperature field in the system.

Project: The student will develop an integrated model that predicts particle size distribution, concentration information, shape, composition, and charge with temperature. The particle growth processes will be modeled over multiple spatial and temporal scales. This information will then be used to establish a desired temperature profile within a thermally managed system.

  1. Investigating the role of powder-melt pool thermal interactions on microstructural development during laser additive manufacturing

Mentor: Katherine Flores and Patricia Weisensee

Background: Additive manufacturing (AM) presents enormous opportunities for the production of geometrically complex structures, particularly for highly-specialized, low production volume components. Unlike traditional manufacturing methods, AM also offers the unique advantage of being able to vary and locally optimize the material microstructure or composition according to the expected service conditions, for instance creating gradient structures to increase ductility near stress concentrations while maintaining high strength elsewhere in the part. Achieving this requires improved understanding of the interplay of powder impact dynamics and thermal interactions in the melt pool, which remains largely elusive.

Project: The student will apply electron microscopy techniques to characterize the microstructure of metallic materials produced by a direct laser deposition AM method under a range of processing conditions (e.g. powder feed rates, laser power). They will correlate these observations with in situ thermal measurements of the melt pool during powder deposition. This will contribute to the development of a structure-processing model in an effort to controllably vary and produce desirable microstructures in additively manufactured parts.