[en] To develop the understanding and predictive measures of the post 'loss of water inventory' hazardous conditions as a result of the natural and/or terrorist acts to the spent fuel pool of a nuclear plant. This includes the thermal cooling limits to the spent fuel assembly (before the onset of the zircaloy ignition and combustion), and the ignition, combustion, and the subsequent propagation of zircaloy fire from one fuel assembly to others.

[en] We consider turbulent channel flows computed with DNS and LES employing a Fourier-Galerkin method. We show that the balance of total mean shear stress, a measure of conservation of the numerical method, is satisfied only weakly (i.e., in an integral sense), rather than strongly (i.e., pointwise). A study of filters induced by projectors reveals that a certain filter, the Dirichlet filter, provides a tool for extracting shear stresses that are strongly conservative. Numerical results support the theory and demonstrate that spurious oscillations, present in the unfiltered stresses, are also suppressed

[en] Highlights: • A robust technique for determining melting temperatures in hydrocarbon mixtures by DSC has been established. • Melting temperatures determined via the endset scanning method were found to be consistent with cryoscopic measurements and the stepwise method. • The impact of any sample de-mixing that may have occurred over multiple freeze-melt cycles was negligible. • New SLE data for heptane + hexadecane, hexane + hexadecane and hexane + para-xylene + hexadecane. - Abstract: There is a lack of consistency in the literature about how to determine the melting (liquidus) temperature in a hydrocarbon mixture from thermograms recorded by differential scanning calorimetry (DSC). This paper establishes a robust technique for determining liquidus temperatures by DSC by testing two methods detailed in the literature and assessing the potential for de-mixing to preclude repeatable measurements. Liquidus temperatures determined via the end set scanning method were found to be consistent with literature measurements of the same mixture obtained visually, and with a liquidus temperature measured for a fresh sample using the step method. In contrast, use of the thermogram’s peak temperature produced inconsistent results that often could not be reasonably extrapolated to zero scan rate. The impact of any sample de-mixing that may have occurred over multiple freeze-melt cycles was negligible, as demonstrated by the consistency of the thermograms repeated at the same scan rate, and the consistency of liquidus temperatures obtained with different sample loadings into the DSC. New (solid + liquid) equilibrium results are reported for {heptane + hexadecane (C₁₆)} and (hexane + hexadecane) binaries as well as a (hexane + para-xylene + hexadecane) ternary over a temperature range from (260.80 to 279.17) K at atmospheric pressure. Comparisons of the binary measurements against both literature data and the calculations with a property package implemented in commercial software showed deviations of less than 1 K for mixtures with C₁₆ solute mole fractions around 0.3, and −3 K for the mixture with a C₁₆ solute mole fraction around 0.1, due to the increasing sensitivity of the liquidus temperature on composition as the solute fraction decreases. The ternary mixture, with a C₁₆ solute mole fraction of around 0.1, showed a deviation of −5 K, suggesting the property package does not adequately capture the interactions associated with the presence of an aromatic component.

[en] The standard envelope equation for charged particle beams (e.g., Lee-Cooper) neglects self-field contributions from the beam rotation and the slope of the beam envelope. We have carried out an expansion that includes these effects to first order, resulting in a new equation for the edge radius. The change in beam kinetic energy due to space-charge depression as the beam radius varies is also included. For the centroid equation, we have included the 'self-steering' effect due to the curvature of the beam orbit. To leading order, there is a cancellation between the self-steering effect and the space-charge depression of the beam energy, so that a more accurate centroid equation is obtained by using the undepressed value of the energy (i.e., the total beam energy) to calculate the orbit. We have implemented the envelope and centroid equations in the Lamda code. The effect of the new terms will be illustrated with calculations for the DARHT accelerators at the Los Alamos National Laboratory

[en] Highlights: • Computational fluid dynamics analysis of Peltier cooling of downhole tools. • CFD analysis of the performance of Colsiblo and Nibron has been presented. • A curve fitting technique best predicts thermal performance of Peltier cooling. • Peltier cooling and CFD designs improve downhole tool performance up to 25 K. Downhole tools encounter harsh environmental conditions due to pressure and elevated temperatures. Use of Peltier cooling in down-hole seismic tooling has been restricted by the performance of such devices at elevated temperatures. Present paper analyses the performance of Peltier cooling in temperatures suited for down-hole measuring equipment using measurements, predicted manufacturer data and computational fluid dynamic analysis. A critical analysis of Peltier performance prediction techniques is presented with measurements. Validity of the extrapolation of thermoelectric cooling performance at elevated temperatures has been tested using computational models for thermoelectric cooling device. This method has been used to model cooling characteristics of a prototype downhole tool and the computational technique used in has proven valid. Further, an CFD analysis of the performance of two heat sink metals has been presented. The experimental and modelling exercise was targeted at achieving cooling performance that would enable the tool withstand temperatures near 200 $°$C.

[en] We have demonstrated successful operation of a 3.35- m-diameter insulator stack at 158 kV/cm on five consecutive Z-accelerator shots. The stack consisted of five +45 deg;-profile 5.715-cm-thick cross-linked-polystyrene (Rexolite- 1422) insulator rings, and four anodized- aluminum grading rings shaped to reduce the field at cathode triple junctions. The width of the voltage pulse at 89% of peak was 32 ns. We compare this result to a new empirical flashover relation developed from previous small-insulator experiments conducted with flat unanodized electrodes. The relation predicts a 50% flashover probability for a Rexolite insulator during an applied voltage pulse when E_maxe^-0.27/d(t_effC)^1/10 = 224, where E_max is the peak mean electric field (kV/cm), d is the insulator thickness (cm), t_eff is the effective pulse width (ps), and C is the insulator circumference (cm). We find the Z stack can be operated at a stress at least 19% higher than predicted. This result, and previous experiments conducted by Vogtlin, suggest anodized electrodes with geometries that reduce the field at both anode and cathode triple junctions would improve the flashover strength of +45 deg; insulators

[en] Highlights: • VLE data for (CH_4 (1) + C_6H_6 (2)) and (CH_4 (1) + C_6H_5CH_3 (3)) were measured. • LLE was observed at T = 198.15 K, a T higher than expected, for (CH_4 + C_6H_5CH_3)_. • Inconsistences in the literature data were identified and assessed. • More data at x_1 > 0.3 for both systems are needed to investigate discrepancies. - Abstract: New isothermal pTxy data are reported for (methane + benzene) and (methane + methylbenzene (toluene)) at pressures up to 13 MPa over the temperature range (188 to 313) K using a custom-built (vapor + liquid) equilibrium (VLE) apparatus. The aim of this work was to investigate literature data inconsistencies and to extend the measurements to lower temperatures. For (methane (1) + benzene (2)), measurements were made along six isotherms from (233 to 348) K at pressures to 9.6 MPa. At temperatures below 279 K there was evidence of a solid phase, and thus only vapor phase samples were analyzed at these temperatures. For the (methane (1) + methylbenzene (3)) system, measurements were made along seven isotherms from T = (188 to 313) K at pressures up to 13 MPa. Along the 198 K isotherm, a significant change in the data’s p,x slope was observed indicating (liquid + liquid) equilibria at higher pressures. The data were compared with literature data and with calculations made using the Peng–Robinson (PR) equation of state (EOS). For both binary systems our data agree with much of the literature data that also deviate from the EOS in a similar manner. However, the data of Elbishlawi and Spencer (1951) for both binary systems, which appear to have received an equal weighting to other data in the EOS development, are inconsistent with the results of our measurements and data from other literature sources

[en] Highlights: • The GERG-2008 EOS was tested against recently published low temperature data for (methane + butane). • A simpler departure function reduced the maximum c_p deviation at T = 120 K from (110 to 7) %. • Improved BIPs for (methane + butane) were determined by re-fitting to an extended data set. • Deviations for high pressure VLE data at T = 244 K were reduced from (9 to 1.4) %. - Abstract: The Groupe Européen de Recherches Gazières (GERG) 2008 multi-parameter equation of state (EOS) is considered the reference model for the prediction of natural gas mixture properties. However, the limited quality of thermodynamic property data available for many key binary mixtures at the time of its development constrained both its range of validity and achievable uncertainty. The data situation for the binary system (CH_4 + C_4H_1_0) in particular was identified previously as limiting the ability of the GERG-EOS to describe rich natural gases at low temperatures. Recently, new vapour-liquid equilibrium (VLE) and liquid mixture heat capacity data measured at low temperatures and high pressures have been published that significantly improve the data situation for this crucial binary, allowing erroneous literature data to be identified and the predictive behaviour of the GERG-EOS when extrapolated to be tested. The 10 basis functions in the generalised departure function used by the GERG-EOS for several binaries including (CH_4 + C_4H_1_0) were examined to eliminate the term causing a divergence between measured and predicted liquid mixture isobaric heat capacities at T < 150 K. With a simplified nine-term departure function, the maximum relative deviation between the measured and predicted heat capacities was reduced from nearly (110 to 7) %. The interaction parameters in the GERG equation were also re-determined by including, for the first time for this binary, reliable low temperature VLE data together with most of the other high temperature data used in the original development of the model. The new interaction parameters for (CH_4 + C_4H_1_0) reduced the relative deviation of bubble point pressures measured and calculated at T = 244 K from (9 to 1.4) %, without affecting the accuracy of property predictions at higher temperatures.

[en] Highlights: • High quality multi-component natural gas vapor-liquid equilibrium (VLE) presented. • Data measured for mixtures and at conditions relevant to LNG scrub columns. • Predicted VLE of GERG equation of state (EOS) better than Peng-Robinson EOS. • GERG EOS reoptimized for CH₄ + C₄H₁₀ better predicted multi-component VLE. • Reoptimization of GERG EOS for other binaries may further improve VLE predictions. - Abstract: Accurate simulations of scrub columns in liquefied natural gas (LNG) plants are challenging, requiring frequent solution of the non-linear equations governing vapor-liquid equilibrium (VLE), material, and energy balances for multi-component mixtures. Reliable fluid property predictions at high pressures and low temperatures are thus crucial; however, no high-quality multi-component VLE data at conditions relevant to the LNG scrub column are available to test commonly-used equations of state (EOS). Here we report VLE measurements at pressures to 9 MPa and temperatures from (203 to 273) K for mixtures containing CH₄, C₂H₆, C₃H₈, iC₄H₁₀, nC₄H₁₀ and/or N₂. Far from the mixture’s critical point, the GERG-2008 EOS predictions were more accurate than the Peng-Robinson EOS predictions. Above 7 MPa both EOS under-predicted the liquid phase’s methane content and over-predicted its butane content by 10–50 times the experimental uncertainty. Rowland et al.’s recent revision of the GERG model reduced the maximum deviations by (17–35)%. Further optimizations should improve the constituent binary departure functions and hence improve the description of multicomponent VLE data, particularly at conditions relevant to LNG production.

[en] This paper presents a general theory and isogeometric finite element implementation for studying mass conserving phase transitions on deforming surfaces. The mathematical problem is governed by two coupled fourth-order nonlinear partial differential equations (PDEs) that live on an evolving two-dimensional manifold. For the phase transitions, the PDE is the Cahn–Hilliard equation for curved surfaces, which can be derived from surface mass balance in the framework of irreversible thermodynamics. For the surface deformation, the PDE is the (vector-valued) Kirchhoff–Love thin shell equation. Both PDEs can be efficiently discretized using C¹-continuous interpolations without derivative degrees-of-freedom (dofs). Structured NURBS and unstructured spline spaces with pointwise C¹-continuity are utilized for these interpolations. The resulting finite element formulation is discretized in time by the generalized-α scheme with adaptive time-stepping, and it is fully linearized within a monolithic Newton–Raphson approach. A curvilinear surface parameterization is used throughout the formulation to admit general surface shapes and deformations. The behavior of the coupled system is illustrated by several numerical examples exhibiting phase transitions on deforming spheres, tori and double-tori.