Title: Thermal Transport and Chemical Phenomena in Solar Reactors: Enabling Sun to Heat, Fuels and Nutrients
Understanding transport phenomena—mass, momentum, energy, radiative intensity, and charge—and chemical reactions is crucial to boost the performance of a host of solar energy technologies. I will discuss our discoveries and knowledge gained from thermal transport models and measurements for two applications: (a) particle-based concentrated solar power and (b) (photo)electrochemical hydrogen production and nutrient recovery. For the first application, low-cost ceramic particles are leading contenders as heat-transfer and thermal storage media for the next generation of concentrated solar power plants. My group's focus has been to understand, predict and manipulate radiative and multimode heat transfer in granular flows with these particles. We have developed unique modeling capabilities that combine data-driven radiative transport models with Lagrangian particle tracking to capture the flow behavior. This framework gives us unparalleled capabilities to probe materials—morphology—flow—radiation coupling in these systems. To further quantify multimode heat-transfer behavior, we measure high-temperature radiative material properties and leverage this knowledge to perform operando and non-contact thermal measurements for granular flows. For the second application, I will highlight a unique framework developed to model the effects of competing electron-transfer reactions in Z-scheme photocatalytic systems for solar hydrogen production. For this application, we have also identified a powerful strategy to achieve selective reaction interfaces by controlling mass transport of aqueous ions to reaction sites. Finally, I will touch on some recent work where we propose and analyze a new solar-driven approach to transform wastewater nitrates to ammonia to recover nitrogen nutrients. Collectively, these innovations can inform new and improved materials and reactor design/operation for solar to heat, fuel, and nutrient technologies.
Rohini Bala Chandran is an Assistant Professor in Mechanical Engineering at the University of Michigan since January 2018. Previously, she was a postdoctoral research fellow at Lawrence Berkeley National Lab and obtained an M.S. (2010) and Ph.D. (2015) from the University of Minnesota, Twin Cities, in Mechanical Engineering. At Michigan, Prof. Bala Chandran leads the Transport and Reaction Engineering for Sustainable Energy Lab (TREE Lab) to pursue multidisciplinary research in the areas of thermal and fluid sciences, multiscale computational modeling, electrochemical engineering, and semiconductor physics.
Dr. Bala Chandran is a recipient of the NSF-CAREER award (2022), a Doctoral New Investigator award from the American Chemical Society Petroleum Research Fund (2021), and one of 100 selected attendees at the US Frontiers of Engineering meeting organized by the National Academy of Engineering (2020). Research in her group has been funded by the US Advanced Research Projects Agency – Energy (ARPA-E), US Department of Energy Solar Energy Technologies Office (DOE-SETO) and the Fuel Cell Technologies Office (DOE-FCTO), and startup funding from the University of Michigan, Ann Arbor.
Title: Overview of the theory and experimental characterization of heat conduction in highly anisotropic materials
I will present a broad overview of the theory and experimental characterization of heat conduction in highly anisotropic materials, ranging from layered (e.g., graphite) to chain-like (e.g. highly-drawn polyethylene). Beginning with modeling, Neumann's principle relates the symmetries of a material's crystal unit cell to the symmetries of its thermal conductivity tensor used in the anisotropic form of Fourier's law. For highly anisotropic crystals, the concept of phonon focusing leads to useful intuitions about the crystal's minimum thermal conductivity as well as thermal boundary conductance. Effective-medium averaging rules for polycrystals made of randomly oriented anisotropic grains will also be discussed. Turning to experimental techniques, I will show several examples of how the geometry of the heat input and temperature measurement locations can be jointly adjusted to improve the measurement sensitivity to various components of a sample's unknown thermal conductivity tensor. This discussion will cover traditional techniques that use one heater and measure one temperature response at a time, like the electrothermal "3 omega" and laser-based "FDTR" methods, as well as our more recent work developing a "structured illumination, thermal imaging" (SITI) method with thousands of pixels of optical heating and thermometry.
Chris Dames is Department Chair and Howard Penn Brown Professor of Mechanical Engineering at UC Berkeley, with a joint appointment at the Lawrence Berkeley National Laboratory in the Materials Science Division. His research focuses on fundamental aspects of the thermal sciences at the nanoscale and other challenging regimes. He earned his PhD from MIT in 2006 under Gang Chen, following a BS and MS (under Arun Majumdar) from UC Berkeley. Prof. Dames’ recognitions include an NSF CAREER Award, DARPA Young Faculty Award, Viskanta Fellowship and heat transfer lectureship at Purdue University, and selection to the Faculty Leadership Academy at UC Berkeley.
Title: Smart Buildings and Neighborhoods Enabling a Sustainable Energy Future
Residential and commercial buildings account for almost one-third of total global energy consumption worldwide. Recent IEA analysis has suggested that energy intensity in the buildings industry must decrease five times more quickly over the next 10 years than it did in the previous 5 years to reach targets in the Net Zero Emissions by 2050 Scenario. To achieve these aggressive goals, significant development and deployment of smart, connected, and efficient buildings and communities are required. Even more, these buildings and communities must synergistically interact in real time with the electric grid to provide demand flexibility that enables a more optimized, resilient, reliable, and affordable energy system. However, because significant energy inequities are persistent throughout the buildings sector, as a science and engineering community, we must prioritize a transition to a sustainable energy future where the benefits, as well as costs, are equitably distributed.
This talk will discuss smart building and neighborhood technologies and solutions that can enable a sustainable energy future for all communities. It will highlight current Department of Energy and national laboratory research, development, and deployment efforts that advance these clean energy goals. The talk will conclude by challenging the scientific community to look through a lens of equity that prioritizes an equitable distribution of benefits and costs for a sustainable energy future for all.
Dr. Roderick Jackson is the laboratory program manager for buildings research at NREL. He sets the strategic agenda for NREL's buildings portfolio, while working closely with senior laboratory management. The portfolio includes all research, development, and market implementation activities, which aim to improve the energy efficiency of building materials and practices. He also guides discussions with the U.S. Department of Energy (DOE) Building Technologies Office to expand research ranging from grid-interactive efficient buildings to mechanical and thermal properties of building materials. He helps identify industry partnership opportunities to advance building envelope and equipment technologies.
At NREL, Dr. Jackson was recognized as a Distinguished Member of Research Staff. In 2022, he received a Black Engineer of the Year Award (BEYA), recognized with a BEYA Professional Achievement in Government Award.
He is serving a three-year appointment to the American Council for an Energy-Efficient Economy (ACEEE) Research Advisory Board, which began in 2021. He has been a member of the American Society of Heating, Refrigerating and Air-Conditioning Engineers and has received several awards in his career, including the National GEM Consortium Alumni of the Year and Greater Knoxville Business Journal's 40 under 40. In 2022, he joined the board of directors for the Southwest Energy Efficiency Project (SWEEP).
Dr. Jackson came to NREL from Oak Ridge National Laboratory, where he was the group manager for Building Envelope Systems Research. He was on the forefront of connected communities research, leading an effort that established Alabama Power’s Smart Neighborhood. Working with Southern Company and DOE, it was the first project in the southeastern United States to connect high-performance homes with a community microgrid, deploying a transactive microgrid approach.
Another of Dr. Jackson's notable industry accomplishments is a result of his role as the technical lead for the Additive Manufacturing Integrated Energy (AMIE) demonstration project at Oak Ridge National Laboratory. With his leadership, AMIE brought together experts from multiple research teams across the lab, 20 partners from industry, and DOE scientists to design, develop, and demonstrate a 3D-printed house that shares power wirelessly with a 3D-printed electric vehicle. The first-of-its-kind research was completed in just nine months.
Title: Role of Thermal and Fluids Technologies in Support of National Security and Energy Applications
Sandia National Laboratories is a multi-program national laboratory run for the United States Department of Energy. While Sandia's roots hail from the Manhattan Project of the 1940's, the Laboratories have evolved into providing support for a wide variety of national security and energy related areas of interest to the Nation. This talk will review Sandia's history and highlight the role that Sandia plays in the development of state-of-the-art thermal and fluids capabilities that address a variety of engineering applications of national importance, including energy, homeland security, and defense.
Dr. Hassan is a native of Raleigh, North Carolina. He earned his bachelor's degree in 1988, his master's degree in 1990, and his Doctorate in Aerospace Engineering from North Carolina State University in 1993. He is currently the Director of the Chief Research Office and serves as Sandia's Deputy Chief Research Officer. In this role, Dr. Hassan leads Sandia's research strategy development including the execution of the Laboratory Directed Research and Development program and oversees Sandia's external partnership and technology transfer programs. Dr.
Hassan has been employed at Sandia since 1993 and has managed all phases of research, development, and applications work. He has focused predominately on the thermal, fluid, and aero science technology areas helping Sandia to accomplish its national security mission.
Dr. Hassan has served in a variety of positions in research and development (R&D) in the areas of aerodynamics and aerothermodynamics of high-speed flight vehicles, drag reduction for low-speed ground transportation vehicles, and high- velocity oxygen fuel thermal sprays. He has overseen all aspects of engineering sciences R&D and applications work at Sandia. Most notably, he helped support National Aeronautics and Space Administration (NASA) in determining the cause of the Space Shuttle Columbia accident in 2003 and was part of the team that shutdown the Deepwater Horizon oil well after the explosion and spill in 2010.
Dr. Hassan is a Fellow of the American Institute of Aeronautics and Astronautics (AIAA) and serves on the Institute's Board of Trustees as the Immediate Past President (2022-2023). Previously, he served on AIAA's Board as Director and Vice President from 2008-2017, President-Elect from 2019-2020, and President from 2020-2022. He currently serves as the Chair of the AIAA Foundation Board of Trustees. In addition, Dr Hassan has served on several national review boards for the National Academies, NASA, DARPA, and Air Force Office of Scientific Research, and has participated as an external member of the NASA Engineering and Safety Center since 2004. Dr. Hassan currently serves on the North Carolina State University's Engineering Foundation Board and the Mechanical and Aerospace Engineering Educational Advisory Board and has served on similar boards for New Mexico State University, Texas A&M University, the University of Texas at Austin, the University of New Mexico, and the Georgia Institute of Technology. He was the 2008 recipient of the AIAA Sustained Service Award and a 2017 recipient of North Carolina State University's Distinguished Engineering Alumnus Award.
Title: Coupled heat transfer processes of materials in extreme environments
The heat transfer processes in materials when subjected to extreme heat fluxes, electromagnetic fields, oxidizing species, and ion irradiation play the critical role in the performance and efficacy in a wide range of materials and technologies, from nano-to-macro scales. In these environments, the large perturbations in energy density imparted on materials lead to coupled thermal transport processes that play a major role in thermal dissipation and management. For example, the high temperatures and power fluxes typical in hypersonic flight and jet engines can lead to coupled radiative and conductive processes that are critical to enhance for leading edge cooling or restrict for thermal barriers of turbine blades, respectively. At surfaces and interfaces, coupled processes also dictate thermal resistances on the nanoscale. As another example, nonequilibrium thermal processes induced by plasma or short pulsed irradiation of materials are critical for manufacturing, catalysis and material synthesis.
Clearly, coupled thermal transport processes dictate the thermal transport of materials ranging from nano-to-macro scales in extreme environments. In this talk, I will discuss our recent research efforts in developing experimental metrologies to measure the heat transfer processes of materials and across interfaces when subjected to thermal and environmental fluxes typical in extreme environments, from nanoscales to macroscales and picoseconds to seconds. I will focus on the following directions:
-Measuring the thermal conductivity and emissivity of materials up through their melting point: Derived from our recently developed Steady-State Thermoreflectance (SSTR) technique, we have developed a method to simultaneously measure the thermal conductivity, hemispherical emissivity and melting temperature of materials up to 4,000 K. We demonstrate this on W and Mo standards, and extend these measurements to a novel high entropy carbide of interest for hypersonic applications, demonstrating the near-record setting melting temperature of this high entropy ceramic.
-Thermal transport at surfaces during plasma irradiation and “plasma cooling”: Using thermoreflectance-based metrologies, we measure the temperature change on the surface of a metal irradiated with a plasma flux. The complex plasma environment consisting of high energy photons, ions, and neutrals leads to a transiently varying source of energy during the plasma irradiation. We show the possibility of “plasma cooling”, in which the initial flux of energy delivered by a plasma, which is primarily photonic, leads to a transient evaporative cooling-like effect that results in a transient temperature drop at a surface. This cooling effect is followed by subsequent heating when the sluggish heavy particles in the plasma impart their energy to the material.
-Electron-phonon nonequilibrium at interfaces for mid-IR plasmonics and polaritonics: Ultrafast laser pulses give rise to extreme conditions of nonequilibrium between the electrons and phonons in a material, often resulting in thousands of degrees in the temperature difference between these two thermal systems. At interfaces, differences in photon-electron-phonon coupling can lead to the emergence of a novel process, “Ballistic Thermal Injection” (BTI), in which nonequilibrium electrons can deposit their excess energy across an interface without the net flow of charge. We show that BTI can be used to unidirectionally control heat flow across interfaces (i.e., a transient thermal diode effect), and lead to thermally driven control of plasmon and phonon-polariton absorption in the mid-IR, paving the wave for novel method to control mid-IR responses of materials with heat.
Patrick E. Hopkins is a Professor in Department of Mechanical and Aerospace Engineering at the University of Virginia, with courtesy appointments in the Department of Materials Science and Engineering and the Department of Physics. Patrick received his Ph.D. in Mechanical and Aerospace Engineering at the University of Virginia in 2008 under the mentorship of Professor Pamela Norris. After his Ph.D., Patrick was one of two researchers in the nation to receive a Truman Fellowship from Sandia National Laboratories in 2008, working under the mentorship of Dr. Leslie Phinney. In 2011, Patrick returned to the University of Virginia and joined the faculty. Patrick’s current research interest are in energy transport, charge flow, laser-chemical processes and photonic interactions with condensed matter, soft materials, liquids, vapors and their interfaces. Patrick’s group at the University of Virginia uses various optical thermometry-based experiments to measure the thermal conductivity, thermal boundary conductance, emissivity, thermal accommodation, strain propagation and sound speed, and coupled electron, phonon, and photon mechanisms in a wide array of bulk materials and nanosystems. In 2021, Patrick co-founded Laser Thermal, Inc., a company based in Charlottesville Virginia that is commercializing thermal conductivity measurement systems that provide non-contact, automated metrologies for thermal properties of thin films, coatings and bulk materials.
In the general fields of nanoscale heat transfer, laser interactions with matter, and energy transport, storage and capture, Patrick has authored or co-authored over 285 technical papers (peer reviewed) and been awarded 5 patents focused on materials, energy and laser metrology for measuring thermal properties. Patrick has been recognized for his accomplishments in these fields via AFOSR and ONR Young Investigator Awards, the ASME Bergles-Rohsenhow Young Investigator Award in Heat Transfer, and a Presidential Early Career Award for Scientists and Engineering (PECASE). Patrick is a fellow of ASME and was recently awarded the ASME Gustus L. Larson Memorial Award. During 2021-2022, Patrick was awarded a Humboldt Fellowship to work on laser thermometry of materials in extreme environments at the Joint Research Center in Karlsruhe, Germany.
Title: Thermal Transport in Li-ion Batteries
Li-ion cells offer high-efficiency electrochemical energy storage, and therefore, may play a central role in meeting the energy challenges of the future such as storage of renewable energy and electric vehicles. Li-ion cells pose several interesting scientific questions related to thermal and fluid transport that directly affect their performance and safety. Understanding and optimizing the nature of multiscale heat transfer in Li-ion cell materials, components and systems remains a critical challenge.
This talk will summarize ongoing experimental and theoretical research on thermal transport in Li-ion cells. Multiscale thermal conduction measurements that identify poor thermal transport across the cathode-separator interface as the fundamental root cause of the low thermal conductivity of Li-ion cells will be discussed. A molecular bridging technique that improves this interfacial thermal transport by 4X will be discussed. System-level multiphysics simulations that model and predict the highly non-linear thermal runaway phenomenon in a battery pack will be discussed. Finally, motivated by thermal runaway in Li-ion cells, stability analysis of multilayer diffusion-reaction problems will be discussed. Key outcomes of this theoretical work include derivation of a new non-dimensional number to predict the occurrence of thermal runaway, and analysis of the existence of multiple but finite number of imaginary eigenvalues in such problems.
Ankur Jain is an Associate Professor in the Mechanical and Aerospace Engineering Department at the University of Texas, Arlington. His research interests include energy conversion in Li-ion batteries, additive manufacturing, electrochemistry and theoretical heat/mass transfer. He has published 118 journal papers, and given over 62 invited talks, seminars and tutorials. His research has helped better understand key thermal transport processes in battery materials and during polymer additive manufacturing. He has also helped develop new analytical techniques for heat/mass diffusion and convection problems, including the concept of imaginary eigenvalues in certain multilayer problems. He received the UT Arlington President's Award for Excellence in Teaching (2022), UT Arlington College of Engineering Lockheed Martin Excellence in Teaching Award (2018), UT Arlington College of Engineering Outstanding Early Career Award (2017), NSF CAREER Award (2016) and the ASME EPP Division Young Engineer of the Year Award (2013). He received his Ph.D. (2007) and M.S. (2003) in Mechanical Engineering from Stanford University, where he received the Stanford Graduate Fellowship, and B.Tech. (2001) in Mechanical Engineering from Indian Institute of Technology, Delhi with top honors.
Title: Thermal management of electric machines for Sustainable Green Transportation
Stringent greenhouse gas emission legislations have accelerated the need for the electrification of ground and air transportation. Since electric motors are one of the electric drivetrain's core components, improving their performance is a key enabler of better performance metrics. High heat generation in electric motors, especially at high power density, as a consequence of electromagnetic losses, limits motor efficiency and longevity by ultimate aging of the winding wire insulation and premature demagnetization of the magnets. Therefore, enhanced cooling technology is essential to increase motor power and torque density while keeping the peak winding temperature below the winding insulation temperature threshold. In this presentation, liquid cooling concepts to extract heat directly from the winding of electric motors will be discussed, which dramatically reduces the thermal resistances between the winding and the coolant, leading to significantly higher current density while operating within the thermal limit of materials employed in the electric motor.
Dr. Satish Kumar is currently a Professor at George W. Woodruff School of Mechanical Engineering at Georgia Tech. Prior to joining Georgia Tech in 2009 as an Assistant Professor, he worked at IBM Corporation, where he was responsible for the thermal management of electronic devices. Kumar received his Ph.D. in Mechanical Engineering and M.S. degree in Electrical and Computer Engineering from Purdue University, West Lafayette in 2007; and B.Tech. degree in Mechanical Engineering from the Indian Institute of Technology, Guwahati in 2001. His research interests include electro-thermal transport study in electronic devices and materials, e.g., wide band-gap devices, electric motors, etc. He is the author or co-author of over 150 journal or conference publications. Dr. Kumar is an ASME Fellow and recipient of the 2005 Purdue Research Foundation Fellowship, 2012 Summer Faculty Fellow from Air Force Research Lab, 2014 Sigma Xi Young Faculty Award, 2014 DARPA Young Faculty Award, 2017 Woodruff Faculty Fellow, and 2020 ASME K-16 Clock Award.
Title: Turbulent mixing in shock-driven variable-density flow—from supernova explosion to fusion system
Mixing is central to several important phenomena in nature and engineering. Rayleigh-Taylor (RT) and Richtmyer-Meshkov (RM) driven wrinkles at the interface of materials lie at the heart of an overarching science for material mixing that stretches from oil trapping salt domes, that develop over tens of millions of years, to degradation of Inertial Confinement Fusion (ICF) capsule performance in 10 -12 ns. RT and RM are insidious instabilities that start with exponential growth (power-law function of time for RM) of small-scale perturbations, and end in a fully turbulent mixing process. Shock tube experiments allow us to explore the effects of Mach number and initial conditions on unsteady variable-density mixing. I will describe here the results from recent experiments which quantifies the effect of initial conditions on the transition to turbulence in RMI driven flows The evolving density and velocity fields are measured simultaneously using high spatial resolution planar laser-induced fluorescence (PLIF) and particle image velocimetry (PIV) techniques. For the first time, we have acquired simultaneous PIV-PLIF measurements at 60KHz in such a transient flow system. Density, velocity, and density–velocity cross-statistics are calculated using ensemble averaging to investigate the effects of additional modes on the mixing and turbulence quantities. The density and velocity data show that a distinct memory of the initial conditions is maintained in the flow before interaction with reshock.
Devesh Ranjan is the Eugene C. Gwaltney Jr. School Chair in the Woodruff School of Mechanical Engineering at Georgia Institute of Technology. Ranjan joined the faculty at Georgia Tech in 2014. Ranjan also served as Interim Vice-President for Interdisciplinary Research (Feb 2021-June 2021) at Georgia Tech. Before coming to Georgia Tech, he was a director's research fellow at Los Alamos National Laboratory (2008) and Morris E Foster Assistant Professor in the Mechanical Engineering department at Texas A&M University (2009-2014). He earned a bachelor's degree from the NIT-Trichy (India) in 2003, and master's and Ph.D. degrees from the UW-Madison in 2005 and 2007 respectively, all in mechanical engineering.
Ranjan’s research focuses on the interdisciplinary area of power conversion, complex fluid flows involving shock and hydrodynamic instabilities, and the turbulent mixing of materials in extreme conditions, such as supersonic and hypersonic flows. Ranjan is a Fellow of the American Society of Mechanical Engineers (ASME), and has received numerous awards for his scientific contributions, including the DOE-Early Career Award (first GT recipient), the NSF CAREER Award, and the US AFOSR Young Investigator award. He was invited to participate in the National Academy of Engineering’s 2016 US Frontiers in Engineering Symposium. At Georgia Tech, Ranjan served as a Provost’s Teaching and Learning Fellow (PTLF) from 2018-2020, and was named 2021 Governor’s Teaching Fellow. He was also named Diversity, Equity and Inclusion (DEI) Fellow for 2020-21.
Title: Next Generation Heat Exchangers for Sustainable Decarbonization/Electrification of Energy Conversion Systems
Heat exchangers are critical to efficient thermal energy exchange in numerous industrial applications and everyday life, with significant applications in building energy systems, transportation, petrochemical processing, electricity generation, waste heat recovery, among others. Meanwhile, the urgent need for substantial reducing/elimination of CO2 and other greenhouse gases is now a global high priority across industries and at all levels. Decarbonization of energy conversion systems through technologies such as energy efficiency, electrification, renewable energy and/or carbon neutral fuels requires novel technologies that may not exist today. Of particular interest are heat exchangers that are light and compact offering reduction of size, weight, and power consumption, and ultimately the cost (SWAP-C) for wide-spread next-generation high efficiency and light energy conversion systems. This presentation will offer a review of recent progress, a vision on future needs for select key energy conversion processes, and the respective research gaps, challenges, and opportunities.
MICHAEL OHADI is the Minta Martin Professor of Mechanical Engineering at the University of Maryland, College Park. Ohadi's research has involved active and passive process intensification of fluid/thermal processes utilizing multi-scale design optimization, materials, and manufacturing techniques. In 1991 Prof. Ohadi co-founded the Center for Environmental Energy Engineering (CEEE) to advance innovative solutions in support of energy efficiency and carbon emission reduction. For more than 25 years he has led an industrial consortium in Advanced Heat Exchangers and Process Intensification techniques within the CEEE, with member companies from the U.S., Europe, and Asia. From 2016 to 2020, Ohadi served as Program Director (PD) at the U.S. Department of Energy, Advanced Research Project Agency-energy (ARPAE) where he led the development of programs in advanced heat exchangers and energy conversion systems, and lightweight and ultra-efficient electric motors, drives, and associated thermal management systems. Prof. Ohadi is a Fellow of the American Society of Mechanical Engineers (ASME) and the American Society of Heating, Refrigeration, and Air-Conditioning Engineers (ASHRAE). He has published more than 300 peer reviewed technical articles in his fields of expertise.
Title: Thermal Engineering to Enable Advanced Spacecraft Power Generation Technologies
Historically, spacecraft have operated with relatively low power density sources, such as solar photovoltaics, electrochemical batteries, and radioisotope thermoelectric generators (RTGs). New mission concepts call for mass-efficient power solutions to operate in extreme environments, such as the cryogenic lunar night cycle or on the 470°C Venus surface. Emerging space power technologies, including nuclear fission lunar surface power (FSP) and nuclear electric propulsion (NEP) will operate at unprecedented power densities, requiring efficient and low mass heat rejection technologies. This presentation will share two collaborative projects aligned with these needs: (1) Development of alkali-metal chemical-fueled spacecraft power systems and (2) Demonstration of additively manufactured radiators with embedded heat pipe networks for mass-optimized high temperature heat rejection.
Alkali-metal fueled combustion spacecraft power systems: The Advanced Lithium-Powered Venus Explorer (ALIVE) lander concept would employ a combustion heat engine for power generation and refrigeration, enabling surface missions up to 120 hours. A key feature of this technology is that the Venus atmosphere (~95% CO2) spontaneously reacts with lithium at temperature, allowing in-situ resource utilization for the oxidizer. However, the underlying Li-CO2 batch reaction process has been poorly characterized. In this project, an experimental campaign was performed to quantify feasible reaction yields, system specific energy, and heat delivery temperatures. Based on these findings, matched heat engine and refrigeration cycles were identified. In collaboration with the NASA Jet Propulsion Laboratory, this concept is being extended to a self-contained Li-SF6 heat and power system for lunar night survival. Initial reactor designs have been experimentally assessed, and future efforts seek to couple these with high-efficiency free-piston Stirling converters.
Monolithic additively manufactured heat-pipe-radiators for high temperature heat rejection: Emerging spacecraft power and propulsion technologies require new solutions for high temperature radiative heat rejection. For example, the Kilopower liquid-metal cooled nuclear reactor will reject heat at 500 – 600 K; intensified free-piston Stirling engines could approach cold-side temperatures of 700 – 800 K. State-of-the-art radiators have been demonstrated based on Ti-H2O heat pipes bonded to metal panels at 400 K. However, new higher temperature concepts are sought that can avoid thermal stress failures at bond-interfaces and minimize mass.
In this collaborative project, we are exploring additively manufactured monolithic heat pipe radiators (HPRs). These HPRs can be produced from high temperature corrosion-resistant materials (e.g., Inconel, Monel, Ti) in a single additive process (e.g., powder-bed fusion) that forms vapor-flow passages, porous liquid-wicking structures, and fin sections. Embedded heat pipes would operate with high temperature phase-change fluids (e.g., pressurized H2O, alkali metals). This eliminates material interfaces and can achieve nearly isothermal surface temperatures with branching heat pipes. Progress will be shared on computational modeling and prototype fabrication. Initial artifacts have been tested in vacuum environments with heat input up to 508 K, validating this concept for thermal- and mass-efficient spacecraft heat rejection.
Alexander Rattner is an Associate Professor of Mechanical Engineering at Penn State University and the principal investigator of the Multiscale Thermal Fluids and Energy Lab. He received the 2016 Frederick A Howes Scholar award in computational science and an NSF CAREER grant (2017-2023). His research expertise includes waste heat recovery, absorption refrigeration, supercritical CO2 power cycles, spacecraft thermal management and power systems, and experimental and computational multiphase flow heat and mass transfer.