Author(s):

Theodore M. Chu, & Lane B. Carasik.

Abstract:

In sodium-cooled fast reactors, transient thermal stratification of the sodium coolant within the reactor components can cause severe thermal stresses. This thermal stress phenomena after related occurrences and/or during severe accident conditions can lead to vessel/component structure failure. Therefore, a thorough understanding of thermal stratification phenomena is critical to operational reliability and licensing efforts.

Turbulent scaling theories can be used to describe the underlying mechanics contributing to stratification. In particular, Bolgiano-Obukhov (BO59) scaling is of interest in liquid-metal flows for its inclusion of buoyancy in the flow. However, the instantaneous velocity and temperature time series data required for investigating the presence of BO59 scaling is lacking. In an effort to augment the data sets available, the use of high-fidelity computational fluid dynamics (CFD) simulations to generate data capable of observing BO59 scaling is of interest.

This study focuses on efforts in modeling the Gallium Thermal-hydraulic Experiment (GaTE) facility using large eddy simulations in Nek5000. The GaTE facility was designed as a scaled-down model of the Advanced Burner Test Reactor plenum to investigate thermal stratification within liquid-metal flows under a variety of operational conditions. Instantaneous temperature and velocity data are generated by the CFD model of GaTE during a forced flow transient exhibiting mixed convection with Ri = 0.722.

In general, the data have shown evidence of BO59 scaling throughout the plenum, especially with the momentum spectra and cospectra, indicating that the simulation is likely capable of generating the necessary instantaneous velocity and temperature data required for observing the BO59 microscale in liquid-metal flows. It has been determined that future investigation is needed to understand the lack of agreement in the spectra for the lower plenum height region and to assess the presence of BO59 scaling in mixed convection regimes with greater influence of natural convection effects.

Full Article:

https://www.tandfonline.com/doi/full/10.1080/00295639.2026.2688037#abstract 

Author(s):

Sierra A. Tutwiler, Dillon R. Shaver, & Lane B. Carasik.

Abstract:

With the push for clean energy systems such as nuclear reactors, fusion energy systems, and concentrated solar power, novel heat exchanger designs that incorporate the use of heat transfer enhancements (HTEs) are being investigated to optimize performance. One particular heat transfer enhancement is the twisted elliptical tube used to modify standard shell and tube heat exchangers in a novel manner. The twisting geometry of the tube causes increased mixing of the fluid, inducing turbulence at lower Reynolds numbers and allowing for improved heat transfer characteristics. This occurs with marginal to major increases in the frictional pressure drop for higher Prandtl number fluids (i.e. molten salts and heat transfer oils) and lower Prandtl fluids (e.g. gases and liquid metals) intended for advanced power conversion systems. Currently, the existing twisted elliptical tube Nusselt number and friction factor correlations only include the dependence of Reynolds number, Prandtl number, and the modified Froude number or swirl number while not reporting a Prandtl number range. The modified Froude number has been used previously to characterize the effects of the tube diameter and torsional pitch on heat transfer. However, we have found evidence that those two geometric characteristics should be treated separately from one another. In this study, we performed a Buckingham-Pi analysis that presented the cross-sectional aspect ratio (Ra) and Prandtl number (Pr) as Pi groups for twisted elliptical tube bundles. Using large eddy simulations of twisted elliptical tube bundle unit cells, we confirmed the importance of both Pi groups on Nusselt number and friction factor. As we increased the Prandtl number from 0.001 to 1, we observed a corresponding non-linear increase that was not able to be collapsed to one exponential fit. From our findings, we suggest two different functional forms to account for Prandtl number. When linearly increasing the aspect ratio, a non-linear increase in both the Nusselt number and friction factor was observed that is not captured by existing correlations. For the aspect ratio, we observed that the Nusselt number had a logarithmic dependence that was independent of the Prandtl number.

Full Article:

https://www.sciencedirect.com/science/article/pii/S0142727X24002194 

Author(s):

Cody S. Wiggins, Arturo Cabral, Adam Mafi, Jerel Houston & Lane B. Carasik.

Abstract:

A combined positron emission particle tracking (PEPT) and X-ray computed tomography (CT) technique is presented, and its utility is demonstrated through investigation of flow in a pipe with twisted tape swirl insert with varying flow conditions (diameter-based Reynolds numbers 16,300–63,300). A description of this technique is given, as well as data handling practices used to relate geometric information captured by CT to fluid flow data gathered via PEPT. It is found that the CT component is readily capable of capturing the stainless steel insert geometry in this present system, but the use of combined plastic and metal materials leads to artifacts in imaging of the plastic surface. Nonetheless, CT data are related to PEPT flow measurements, and average velocity fields are calculated via a pseudo-framing and interpolation scheme and used to visualize and interrogate key flow phenomena within the system. Radial velocity profiles of the mean flow characteristics are seen to collapse to a nearly common form across all flow conditions considered. Helical vortices are seen propagating through the flow field, generated by bypass flow around the gap between the insert and pipe wall, with additional coherent secondary flow structures seen in the higher Reynolds number cases. These findings enhance the understanding of the mixing mechanisms in these swirl flows and encourage the continued development of PEPT-CT methodologies for 3D flow measurements in optically inaccessible systems.

Full Article:

https://link.springer.com/article/10.1007/s00348-024-03860-7 

Author(s):

Trevor Franklin, Casey Icenhour, Pierre-Clément A. Simon, Paul Humrickhouse, Fande Kong, Lane B. Carasik.

Abstract:

Multiphysics modeling capabilities have a crucial role to play in the accelerated deployment of fusion energy. To that end, we developed new Multiphysics fusion blanket simulation capabilities in the Multiphysics Object-Oriented Simulation Environment (MOOSE). Firstly, we expanded on the existing capabilities of the previously published work, by coupling 3D tritium transport modeling capabilities using the Tritium Migration Analysis Program, version 8 (TMAP8) to an existing tool including thermal hydraulics, fully three-dimensional (3D) heat transfer, and loosely coupled neutronics analysis. Secondly, we performed a thorough verification of the new capabilities and increased testing code coverage to meet MOOSE’s software quality standards. The MOOSE framework follows a strict software quality assurance plan to be Nuclear Quality Assurance, Level 1 compliant. The new Multiphysics fusion blanket simulation capabilities are now held to the same standard. Thirdly, to demonstrate MOOSE’s new fusion blanket modeling capabilities, we performed a fully integrated, Multiphysics simulation of a 3D solid ceramic breeder blanket design. This proof-of-concept simulation provides the temperature and tritium distribution across the blanket. The combined efforts towards software quality and the development of Multiphysics coupling capabilities provide an effective and reliable framework for modeling solid ceramic fusion blankets using MOOSE.

Full Article:

https://www.sciencedirect.com/science/article/pii/S0920379625003254 

Author(s):

Briana R. Schrage, Joshua E. Leach, Ethan Villarreal, Jisue Braatz, Kristian G. Myhre.

Abstract:

Mediated electrochemical oxidation (MEO) is a low-temperature, low-pressure, aqueous mineralization process used to treat organic waste. A powerful metal oxidant is used as a mediator in an acidic solution. Although Ce and Co are thoroughly studied mediators, Ag is a preferred choice because of the higher efficiency rates of mineralization observed with this system. Importantly, the quantification methodology and spectroscopic characteristics of the Ag(ii) ion must be obtained. In this study, we determined molar extinction coefficients of the primary absorption band associated with the Ag(ii) ion in 2–9 M HNO3 solution. The optimization of Ag(ii) electrooxidation was also determined by altering parameters such as HNO3 concentration, mediator concentration, and temperature. The optimization studies and extinction coefficient data provide parameters for implementation of Ag as a suitable mediator for MEO processing of organic waste.

The extinction coefficient of silver(ii) has been obtained. Titration quantification methods were then used to optimize electrochemical silver(ii) generation as a function of temperature, silver(i) concentration, and HNO3 concentration.

Full Article:

Optimization and quantification of silver(ii) for mediated electrochemical oxidation applications | Dalton Transactions | The Royal Society of Chemistry 

Author(s):

Colin Bailey, Connor Donlan, Matthew Glace, Gabrielle Broussard, Someshwar Nagamalla, Lane B. Carasik, Thomas D. Roper.

Abstract:

This study presents a kinetic model that simulates the consumption of 4-hydroxybenzoic acid (4-HBA), the formation of di-isopropyl benzoic acid (DIPBA) via a Friedel–Crafts alkylation reaction, and the generation of key impurities. The model provides valuable insights into reaction dynamics by capturing the intricate interplay between reaction kinetics and competing pathways. In addition, we introduce a cost-effective, scalable reactor design that overcomes the limitations of traditional laboratory-based reactor systems. The reactor system enhances safety, efficiency, and adaptability, making it ideal for large-scale, highly acidic reactions in laboratory settings. Together, this work underscores the insights and limitations of conventional kinetic modeling for solvolysis-mediated Friedel–Crafts reactions and lays the foundation for more efficient and innovative approaches to chemical process development.

This study presents a kinetic model that simulates the consumption of 4-hydroxybenzoic acid (4-HBA), the formation of di-isopropyl benzoic acid (DIPBA) via a Friedel–Crafts alkylation reaction, and the generation of key impurities.

Full Article:

https://pubs.rsc.org/re/article/11/3/757/1225405/Reactor-and-kinetic-study-advances-for-highly