CRS4 Report

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https://hdl.handle.net/11050/59
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Mostra il contenuto di CRS4 Report per Subject "3D simulation"

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    A thermal fluid-dynamic steady state analysis of the EADF downcomer channel
    (2000-04-04) Aragonese, Cosimo; Buono, Stefano; Fotia, Giorgio; Maciocco, Luca; Moreau, Vincent; Sorrentino, Luca
    In this work a numerical simulation of the Energy Amplifier Demonstration Facility (EADF) [1, 2] downcomer channel is presented. The simulation is fully three-dimensional (3D) and is focused on a Steady-State Analysis. All relevant heat transfer phenomena are taken into account. The Intermediate Heat eXchangers (IHX) of the EADF reference configuration are immersed in the lead-bismuth eutectic of the downcomer and no physical barrier separates the hot and cold collectors. As expected, the simulation shows a thermal stratification outside the IHX, whose characteristics mainly depend on the IHX pressure loss. A parametric study of the effects of the IHX pressure loss coeficient on the thermal stratification pattern is presented.
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    A thermal fluid-dynamic transient analysis of the EADF down-comer channel
    (2000-12-05) Aragonese, Cosimo; Buono, Stefano; Fotia, Giorgio; Maciocco, Luca; Moreau, Vincent; Sorrentino, Luca
    In this work a numerical simulation of the downcomer channel of the Energy Amplifier Demonstration Facility (EADF) [1, 2] is presented. The simulation is fully three-dimensional (3D) and is focused on a transient analysis. All relevant heat transfer phenomena are taken into account. Starting from the nominal power configuration, we have simulated the response of the system to a power shutdown of the core for a period of 60 s. The core shutdown is simulated imposing a linear variation of the inlet flow temperature from 400°C to 305°C in 10 s. The simulation shows the evolution of the thermal stratification outside the IHX and the evolution of the IHX operation.
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    CFD simulation of an isothermal water flow in the EADF-target geometry in dynamical similarity (COULI experiment)
    (2001-07-17) Maciocco, Luca; Sorrentino, Luca
    The results of the numerical simulation of an isothermal water-flow in a geometry typical of the spallation target of the Energy Amplifier Demonstration Facility (EADF) are presented, and compared with the experimental results obtained at CEA-Cadarache (COULI experiment). All the calculations were performed with the Star-CD finite-volume commercial code. Basically, a 2D axisymmetric model was adopted, although a full 3D simulation was carried out as well, as explained below. The Chen k-ε high-Reynolds model was used, joined with a Norris & Reynolds Two-Layer model for the simulation of the near-wall turbulence. The grid-independence of the solution has been verified, and the results obtained with two different convection schemes (QUICK and MARS) has been compared, in order to minimise numerical uncertainties. No appreciable differences were found in the results. Because of the fact that experimental measurements revealed a high non-axisymmetric and non stationary flow behaviour, the possible presence of instabilities intrinsic in the flow topology has been analysed through a full 3D simulation, obtained with the circumferential extrusion of the 2D model. The simulation yielded a steady solution, with results in perfect agreement with the 2D case. It is worth to notice that it was possible to obtain a converged solution in the 3D case only using the MARS scheme, while the QUICK scheme had numerical problems. In spite of the above-mentioned lack of axial symmetry in the experimental set-up, the comparison with computational results showed the capability of Star-CD to correctly simulate the main flow characteristics.
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    Optimisation of the pin cooler design for the megapie target using full 3D numerical simulations
    (2002-01-18) Buono, Stefano; Maciocco, Luca; Moreau, Vincent; Sorrentino, Luca
    The MEGAwatt PIlot Experiment (MEGAPIE) project has been recently proposed to demonstrate the feasibility of a liquid lead bismuth target for spallation facilities at a beam power level of 1 MW. The target will be put into operation at the Paul Scherrer Institut (PSI, Switzerland) in 2004 and will be used in the existing target block of SINQ. About 650 kW of thermal power has to be removed through a bunch of 12 pin-coolers. In order to improve the heat exchange, it was decided to investigate the possibility of accelerating the oil coolant by introducing a spiral in the oil cylindrical channel. This forces the flow to rotate while rising, thus increasing the Reynolds number and the heat transfer coefficient. We show some numerical simulations, which have supported the dimensioning of the pins as well as the choice of the secondary coolant, that is Diphyl THT. The spiral option has been confirmed. The spiral diameter must be a little smaller than the channel width, to allow the effective mechanical assemblage of the pin. The existence of a gap between the spiral and the external wall adds complexity to the numerical simulation, being fully 3D with several orders of magnitude of length scales involved. A single pin has been tested by Enea-Brasimone and entirely simulated by CRS4 for a matrix of various operational settings. Results are shown and compare.