Joshua P. Schlegel

Flow Characteristics and Void Fraction Prediction in Large Diameter Pipes

Two phase flows in large diameter pipes have immense importance in a wide variety of industrial applications. As a first approximation for the prediction of a two-phase flow and as a beginning for the development of more complex models, the drift-flux model is often used to characterize and predict flows for many geometries and flow conditions. In this chapter, the flow characteristics in flows in large diameter pipes are illustrated based on the experimental data. The flow regimes and their transition criteria are discussed. The existing drift-flux models are summarized, their strengths and weaknesses are noted and the data that can be used to evaluate these models are presented. Based on the flow regime transitions in large diameter pipes, all of the available drift-flux models are evaluated systematically in both low (bubbly) and high (cap and churn-turbulent) void fraction flows. The drift-flux type correlations of Hibiki and Ishii [14] and Kataoka and Ishii [24] are found to be able to give the best predictions for the existing low and high void fraction databases respectively and are recommended for void fraction predictions in flows in large diameter pipes.

Prediction of interfacial area transport in a coupled two-fluid model computation

ABSTRACT A computer code has been written to predict interfacial area transport within the framework of the two-fluid model. The suitability of various constitutive models was evaluated from a scientific and numerical standpoint, and selected models were used to close the two-fluid model. The resulting system was then used to optimize the empirical constants in the interfacial area transport equation for large diameter pipes. The optimized model was evaluated based on comparison with the data of Shen et al. and Schlegel et al. The optimization shows agreement with previous research conducted by Dave et al. and Talley et al. using TRACE-T, and reduced the RMS error in the interfacial area concentration prediction for the large diameter pipe data from 52.3% to 34.9%. The results also highlight a need for additional high-resolution data at multiple axial locations to provide a more detailed picture of the axial development of the flow. The results also indicate a need for improved modeling of the interfacial drag, especially for Taylor cap bubbles under relatively low void fraction conditions.

Direct Synthesis of Radioactive Gold Nanoparticles Using a Research Nuclear Reactor

We report the single-step synthesis of radioactive gold nanoparticles with an activity and size appropriate for potential use in cancer treatment and diagnosis. Methods: A solution of 2 mM gold chloride (HAuCl4⋅3H2O), 1 mM polyvinylpyrrolidone (molecular weight, 360,000), and 60 mM 2-propanol was prepared in deionized water. Seven different samples of the solution were irradiated in a neutron flux of 7.45 × 1012 n/cm2⋅s in a research reactor for 0.5, 1, 3, 5, 10, 30, or 60 min. The resulting nanoparticles were characterized for morphology and chemical composition using a transmission electron microscope and ImageJ. Results: The obtained nanoparticles were 3–450 nm in size. The average size depended on the length of irradiation, with a longer irradiation producing smaller nanoparticles. Irradiation for 10 min produced nanoparticles with characteristics suitable for potential cancer treatment and diagnosis (average size, 50 nm; activity, 6.85 MBq/mL). Conclusion: Direct production of chemically stable radioactive gold nanoparticles was successfully accomplished using the Missouri University of Science and Technology reactor. The nanoparticles had physical and radioactive characteristics potentially useful for cancer treatment and diagnosis.