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This paper presents the use of large eddy simulations for calculating turbulent flows in the nuclear field. It focuses on the knowledge of temperature or pressure fluctuations, required to address issues such as thermal fatigue or vibrations. The different subgrid models used and their integration in the commercial CFD software STAR-CD are described. A representative set of applications performed – validation and industrial cases – in the last 15 years is presented. The flow configurations are mainly tee junctions, but also cross-flows over obstacles and shear layers, with water, sodium and...
Accurate simulation of subcooled boiling flow is essential for the operation and safety of nuclear power plants (NPP). In recent years, the use of computational fluid dynamics (CFD) codes has been extended to the analysis of multi-dimensional two-phase flow for the NPP. Among the applications of CFD code for the NPP analysis, the first target was selected as a mechanistic prediction of DNB (Departure from Nucleate Boiling) in PWR (Bestion et al, 2006). In DNB-type CHF (Critical Heat Flux), the expected flow regime is bubbly or churn turbulent flow in the high mass flux and high heat flux...
In order to demonstrate the potential of magnetic refrigeration which can provide cooling effects without affecting the environment, an experimental setup was built, in which a rotating regenerative gadolinium beds of 350 g were used. Water was used as a heat transfer fluid, and a magnetic field of 1.5 T was applied using permanent magnets. With this setup, the influence of the heat transfer fluid, the temperature drop was studied systematically. The analytical solution for entropy change as a function of enthalpy and temperature were obtained in MATLAB and compared with the experimental...
In the computational fluid dynamics (CFD) analysis of spray dryers, the Euler-Lagrange model is used to compute the motions of the spray droplets and the heat and mass transfers between the droplets and the air stream. Such calculations are performed for hundreds to tens of thousands of droplets to represent the spray in the dryer. One limiting factor in drying mass transfer is the internal diffusion of water moisture inside partially dried particles. In order to model this internal diffusion of water moisture, each particle is represented by a series of concentric spherical shells. A one-...
Background and Purpose —The ability to discriminate between ruptured and unruptured cerebral aneurysms on a morphological basis may be useful in clinical risk stratification. The objective was to evaluate the importance of inflow-angle (IA), the angle separating parent vessel and aneurysm dome main axes. Methods—IA, maximal dimension, height–width ratio, and dome–neck aspect ratio were evaluated in sidewall-type aneurysms with respect to rupture status in a cohort of 116 aneurysms in 102 patients. Computational fluid dynamic analysis was performed in an idealized model with variational...
Measurements have been done in order to obtain information concerning the effect of EGR for the smoke and NO x emissions of a heavy-duty diesel engine. Measured smoke number and NO x emissions are explained using detailed chemical kinetic calculations and CFD simulations. The local conditions in the research engine are analyzed by creating equivalence ratio - temperature (Phi-T) maps and analyzing the CFD results within these maps. The study uses different amount of EGR and the standard EN590 diesel fuel. The detailed chemical kinetic calculations take into account the different EGR rates...
In order to assess the accuracy and validity of subchannel, system, and computational fluid dynamics codes, the Paul Scherrer Institut has participated in the OECD/NRC PSBT benchmark with the thermal-hydraulic system code TRACE5.0 developed by US NRC, the subchannel code FLICA4 developed by CEA, and the computational fluid dynamic code STAR-CD developed by CD-adapco. The PSBT benchmark consists of a series of void distribution exercises and departure from nucleate boiling exercises. The results reveal that the prediction by the subchannel code FLICA4 agrees with the experimental data...
A major goal of fuel assembly design is a reliable prediction of the critical heat flux. Development and validation of CFD methods for predicting two-phase flows and CHF conditions is subject of ongoing research at AREVA-NP. This paper deals with numerical modeling of subcooled flow boiling of water in pipes and subchannels at flow conditions corresponding to the range of pressurized water reactor operation conditions. As simulation tool the commercial CFD software Star-CD is used in conjunction with its Extended Boiling Framework (EBF), a software package providing modeling tools for two-...
One of the major concerns of the gas diffusion layer (GDL) inside a proton exchange membrane fuel cell (PEMFC) is water management.Treatment of the pores of the GDL can affect the PEMFC performance due to the degree of water flooding inside the GDL. In this work, GDL flooding was investigated using a simplified approach in an established numerical model. The predictions are compared with experimental data of GDLs with different treatments. Local distributions inside the cell are given and the effect of homogenous GDL flooding on these is discussed.

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