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RISS 인기검색어
- 검색키워드
- 저자 : Rossouw, D.J. (검색결과 3 건)
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The thermal interaction of a buoyant plume from a calandria tube with an oblique jet
Rossouw, D.J.,Atkins, M.D.,Beharie, K.,Kim, T.,Rhee, B.W.,Kim, H.T. Elsevier 2016 Nuclear engineering and design Vol.310 No.-
<P><B>Abstract</B></P> <P>Severe reactor core damage may occur from fuel channel failure as a consequence of excessive heat emitted from calandria tubes (CTs) in a pressurised heavy water (D<SUB>2</SUB>O) reactor (CANDU). The heating of the CTs is caused by creep deformation of the pressure tubes (PTs), which may be ballooning or sagging depending on the internal pressure of the PTs. The deformation of the pressure tube is due to overheating as a result of a loss-of-coolant accident (LOCA) and emergency core cooling system (ECCS) failure. To prevent the exacerbation of the LOCA, circulating D<SUB>2</SUB>O in the moderator tank may be utilized by forming a secondary jet that externally cools the individual CTs. The buoyant plume develops around the CTs and interacts with the secondary jet at a certain oblique angle with respect to the gravitational axis, depending on the spatial location of the hot calandria tubes (or the hot reactor core region). This study reports on how the local and overall heat transfer characteristics on a calandria tube where the buoyant plume develops, are altered by the obliqueness of the external secondary jet (from a co-current jet to a counter-current jet) in a simplified configuration at the jet Reynolds number of <I>Re<SUB>j</SUB> </I> =1500 for the Archimedes number of <I>Ar<SUB>D</SUB> </I> =0.11 and Rayleigh number of <I>Ra<SUB>D</SUB> </I> =1.6×10<SUP>6</SUP> (modified Rayleigh number of 3.0×10<SUP>7</SUP>).</P> <P><B>Highlights</B></P> <P> <UL> <LI> A crucial role of relative orientation between mixed convection modes is observed. </LI> <LI> The extent of thermal interaction strongly depends on the relative orientation. </LI> <LI> Coolant flow is substantially diffused by a buoyant plume if counter-acting. </LI> <LI> Slightly oblique coolant flow to the gravitational axis provides the best cooling. </LI> </UL> </P>
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Multimarker Prediction of Coronary Heart Disease Risk
Kim, H.C.,Greenland, P.,Rossouw, J.E.,Manson, J.E.,Cochrane, B.B.,Lasser, N.L.,Limacher, M.C.,Lloyd-Jones, D.M.,Margolis, K.L.,Robinson, J.G. Elsevier Biomedical 2010 JOURNAL OF THE AMERICAN COLLEGE OF CARDIOLOGY - Vol.55 No.19
Objectives: The aim of this study was to investigate whether multiple biomarkers contribute to improved coronary heart disease (CHD) risk prediction in post-menopausal women compared with assessment using traditional risk factors (TRFs) only. Background: The utility of newer biomarkers remains uncertain when added to predictive models using only TRFs for CHD risk assessment. Methods: The Women's Health Initiative Hormone Trials enrolled 27,347 post-menopausal women ages 50 to 79 years. Associations of TRFs and 18 biomarkers were assessed in a nested case-control study including 321 patients with CHD and 743 controls. Four prediction equations for 5-year CHD risk were compared: 2 Framingham risk score covariate models; a TRF model including statin treatment, hormone treatment, and cardiovascular disease history as well as the Framingham risk score covariates; and an additional biomarker model that additionally included the 5 significantly associated markers of the 18 tested (interleukin-6, d-dimer, coagulation factor VIII, von Willebrand factor, and homocysteine). Results: The TRF model showed an improved C-statistic (0.729 vs. 0.699, p = 0.001) and net reclassification improvement (6.42%) compared with the Framingham risk score model. The additional biomarker model showed additional improvement in the C-statistic (0.751 vs. 0.729, p = 0.001) and net reclassification improvement (6.45%) compared with the TRF model. Predicted CHD risks on a continuous scale showed high agreement between the TRF and additional biomarker models (Spearman's coefficient = 0.918). Among the 18 biomarkers measured, C-reactive protein level did not significantly improve CHD prediction either alone or in combination with other biomarkers. Conclusions: Moderate improvement in CHD risk prediction was found when an 18-biomarker panel was added to predictive models using TRFs in post-menopausal women.
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The isothermal-fluidic field of a secondary moderator jet in a ¼ scale CANDU-6 reactor model
Kim, Hyoung Tae,Rhee, Bo Wook,Im, Sunghyuk,Sung, Hyung Jin,Atkins, Michael D.,Rossouw, Dillon J.,Kim, Tongbeum North-Holland Pub. Co 2017 Nuclear engineering and design Vol.323 No.-
<P><B>Abstract</B></P> <P>The steady, isothermal-fluidic field of forced moderator streams in a ¼ scaled moderator circulation tank (MCT) of a CANDU-6 reactor is analysed. Particular focus is placed on characterizing a secondary jet formed by the collision of symmetric, counter flowing wall jets discharged upwards by nozzles installed at each side of the MCT’s horizontal axis. Two separate sets of experiments have been conducted employing water and air as the working fluids with different nozzle configurations (i.e., discrete dove-tail nozzles for water and two-dimensional slot jet nozzles for air). Then, cross validation of the fluidic data sets from these two different test facilities have been made where the fluidic similarity of the secondary jet generated by the inlet nozzles (particularly its rate of dissipation as it interacts with the calandria tubes (CTs)) has been established. Based on the established fluidic similarity, a series of numerical simulations have been performed according to the boundary conditions obtained extensively from the two-dimensional MCT experiments. Subsequently, the numerical results have been validated against the experimental data to assess the capability of a commercial code (ANSYS CFX V15.0) to resolve the moderator interaction with the CTs. It has been demonstrated that a monotonic decay of the secondary jet whose peak (having roughly 50% of the nozzle’s exit mean vertical velocity component) exists at the throat of the first row of the calandria tubes in the MCT takes place. After which, the momentum of the secondary jet is substantially reduced along its centreline. The rate of dissipation of the secondary jet is under-predicted by the default <I>k-ω</I> SST turbulence model, leading to a dramatic over-prediction of the penetration distance of the secondary jet into the core region. However, the accuracy of the numerical results can be substantially improved with turbulence model parameter tuning to achieve a closer fit with the reference experimental data.</P> <P><B>Highlights</B></P> <P> <UL> <LI> There exist secondary jet Reynolds number independence and fluidic similarity. </LI> <LI> Secondary jet peaks roughly at 50% of the nozzle’s exit means vertical velocity. </LI> <LI> The momentum of the secondary jet is substantially reduced along its centreline. </LI> <LI> The rate of dissipation of the secondary jet is under-predicted by the default <I>k-ω</I> SST turbulence model. </LI> <LI> The accuracy of the numerical results can be improved with turbulence model parameter tuning. </LI> </UL> </P>
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