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Jeffrey A. Sondrup

Bio: Jeffrey A. Sondrup is an academic researcher. The author has contributed to research in topics: Water conservation & Advanced Test Reactor. The author has an hindex of 1, co-authored 1 publications receiving 6 citations.

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ReportDOI
01 Aug 2013

6 citations


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Dissertation
01 Jan 2014
TL;DR: In this paper, the single and two-phase heat transfer in high aspect ratio mini-channels has not been well-characterized, especially in regard to the onset of nucleate boiling.
Abstract: Heat transfer in high aspect ratio mini-channels has important applications for materials test reactors using plate-type fuel. These fuel plates typically possess coolant channels with hydraulic diameters on the order of 4 mm or less. The single and two-phase heat transfer in such channels has not been well-characterized, especially in regard to the onset of nucleate boiling. While surface effects are known to dramatically influence the incipience of boiling, they have not been widely considered under forced convection. Since the limiting safety system setting for the MITR is the onset of nucleate boiling, there is considerable interest in better characterizing the phenomenon in such channels. This study presents a first-of-a-kind, two-phase flow facility designed to measure the singlephase heat transfer coefficient and onset of nucleate boiling in a high aspect ratio mini-channel over a wide range of flow conditions while also permitting high speed visualization of the entire surface. The single-phase heat transfer coefficient is measured for mass fluxes ranging from 750 kg/m2-sec up to 6000 kg/m2-sec and for subcoolings ranging from 20 °C to 70 °C. The onset of nucleate boiling superheat and heat flux are measured for mass fluxes ranging from 750 kg/m2sec to 3000 kg/m2-sec and for subcoolings ranging from 10 °C to 45 °C. Measurements are supported with high speed videography to visualize bubble incipience when conditions permit. The influence of surface wettability on the incipience point is also investigated by performing tests on a surface oxidized at high temperature in air. Using a boundary layer analysis along with experimental data obtained in the study, a semianalytical correlation is developed to predict the single-phase heat transfer coefficient in high aspect ratio rectangular channels. The correlation accounts for effects from secondary flows and heating asymmetry, and is suitable for both the transition and fully turbulent flow regimes. The new correlation predicts the Nusselt number with a mean absolute error of 4.9% in the range of 2.2

17 citations

01 Jan 2016
TL;DR: In this article, the time evolution of the release of the dynamically retained deuterium from tungsten after plasma exposure is investigated and possible analytical dependencies in fully de-trapping-, diffusion-and recombination-limited regimes are reviewed.
Abstract: The time evolution of the release of the dynamically retained deuterium from tungsten after plasma exposure is investigated. Possible analytical dependencies in fully de-trapping-, diffusionand recombination-limited regimes are reviewed. Detailed parameter studies with respect to various parameters, such as the material temperature during exposure and release, the exposure flux and fluence, the binding energy and the depth distribution of traps, as well as the diffusivity and recombination properties of deuterium, are performed using reaction-diffusion modelling without pre-imposed limitations on the rate limiting process. To judge the conformity of the time evolution of the released flux F to the power law decay F(t) ~ t , the time dependent parameter α(t), namely the local slope of the log10FF-log10tt dependence, is introduced. It is demonstrated that a good power law fit of the outgassing flux with average parameter α in the range of experimental observations is possible even in a fully diffusion-limited regime for nonuniform initial depth profiles when the actual time evolution α(t) demonstrates an oscillatory behavior. For conditions of plasma exposures in the linear plasma device PSI-2 where a power law flux decay with α varying in the range of 0.8 – 1.2 depending on exposure conditions in a pure deuterium plasma was observed, none of the investigated parameter combinations result in a strict power law decay of the outgassing flux (α does not remain constant over time). It is demonstrated, however, that in some cases and for certain time intervals, the flux decay can be reasonably well fitted by a power law with values of α in the range of experimental observations. It is indicated that also experimental data from JET and PSI-2 exhibit deviations from a power law.

4 citations

01 Jan 2018
TL;DR: Krumwiede et al. as mentioned in this paper compared macroscopic tensile (σy, σflow, and σuts) and shear punch (τy and τmax) test results to nanoindentation hardness data (H) obtained on a number of different neutron-irradiated materials in order to understand the relationship and scaling behavior on radiation-damaged samples.
Abstract: Author(s): Krumwiede, David Lewis | Advisor(s): Hosemann, Peter | Abstract: Nanoindentation has been used for decades to assess materials on a local scale and to obtain fundamental mechanical property parameters. Nuclear materials research often faces the challenge of testing rather small samples due to the hazardous nature, limited space in reactors, and shallow ion-irradiated zones, fostering the need for small-scale mechanical testing (SSMT). As such, correlating the results from SSMT to bulk properties is particularly of interest. This thesis compares macroscopic tensile (σy, σflow, and σuts) and shear punch (τy and τmax) test results to nanoindentation hardness data (H) obtained on a number of different neutron-irradiated materials in order to understand the relationship and scaling behavior on radiation-damaged samples. Various empirical relationships are employed and compared. In addition, multiple methods for obtaining hardness numbers from the load-displacement (LD) curves generated during instrumented indentation testing (IIT) are analyzed. After investigating many permutations of LD curve analysis methods and empirical relationships, combinations for specific cases are suggested based on expected material behavior. Utilizing these suggestions, efficacious relationships are found between hardness, tensile yield, tensile flow, and shear max.

3 citations

01 Jan 2016
TL;DR: In this article, the authors present a series of experiments on the effects of the proposed algorithm on the performance of the algorithm and the results of the experiments are presented....
Abstract: . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . xiii CHAPTER

2 citations