116 research outputs found
Direct Numerical Simulation and Wall-Resolved Large Eddy Simulation in Nuclear Thermal Hydraulics
International audienceThe critical review discusses the most accurate methods for description of turbulent flows: the computationally very expensive direct numerical simulation (DNS) and slightly less accurate and slightly less expensive large eddy simulation (LES) methods. Both methods have found their way into nuclear thermal hydraulics as tools for studies of the fundamental mechanisms of turbulence and turbulent heat transfer. In the first section of this critical review, both methods are briefly introduced in parallel with the basic properties of the turbulent flows. The focus is on the DNS method, the so-called quasi-DNS approach, and the coarsest turbulence modeling approach discussed in this work, which is still on the very small-scale, wall-resolved LES. Other, coarser turbulence modeling approaches (such as wall-modeled LES, Reynolds Averaged Navier-Stokes (RANS)/LES hybrids, or RANS) are beyond the scope of the present work. Section II answers the question: "How do the DNS and LES methods work?" A short discussion of the computational requirements, numerical approaches, and computational tools is included. Section III is about the interpretation of the DNS and LES results and statistical uncertainties. Sections IV and V give some examples of the DNS and wall-resolved LES results relevant for nuclear thermal hydraulics. The last section lists the conclusions and some of the challenges that might be tackled with the most accurate techniques like DNS and LES
Estudio de prefactibilidad técnico-económico para construcción de residencial para el adulto mayor en la ciudad de Santiago
Tesis (Ingeniero Civil Industrial)El objetivo de este estudio es contribuir al mejoramiento de la
calidad de vida del adulto mayor en la Región Metropolitana a través de
la construcción de una comunidad residencial. Para la elaboración de
este estudio, se toma como base un completo estudio de segmento de
personas mayores a 60 años, a través de fuentes de información de tipo
estadístico, principalmente del Instituto Nacional de Estadísticas (INE),
del Ministerio de Desarrollo Social y del Servicio Nacional de Adultos
Mayores (SENAMA). Éstos proporcionarán importantes datos y
conclusiones que serán relevantes para la confección de la propuesta
planteada. A pesar de tener un formato tipo, cabe destacar que será un
trabajo desde lo general a lo particular.
Las empresas de servicios de hoy en día buscan y necesitan
diferenciarse de sus competidores, de esa forma pueden lograr una
mayor sustentabilidad económica en el tiempo. En esta línea, un gran
número de ellas se encuentran continuamente investigando y
desarrollando nuevos proyectos, previo análisis y realización de estudios
de perfil, prefactibilidad y factibilidad, otorgando información relevante
sobre invertir en el proyecto a ejecutar.
Para ello, se llevará a cabo un estudio de pre factibilidad de
proyecto en el cual se requiere realizar ciertas delimitaciones, para así
segmentar el tipo de personas que eventualmente harán uso de las
instalaciones que se propondrán más adelante avanzado el proyecto,
definiendo aspectos relevantes, el proceso, las características del
servicio, oportunidades y grado de diferenciación asociados al proyecto,
entre otros
Homogeneous bubble nucleation limit of mercury under the normal working conditions of the planned European Spallation Source
In spallation neutron sources, liquid mercury is the subject of big thermal
and pressure shocks, upon adsorbing the proton beam. These changes can cause
unstable bubbles in the liquid, which can damage the structural material. While
there are methods to deal with the pressure shock, the local temperature shock
cannot be avoided. In our paper we calculated the work of the critical cluster
formation (i.e. for mercury micro-bubbles) together with the rate of their
formation (nucleation rate). It is shown that the homogeneous nucleation rates
are very low even after adsorbing several proton pulses, therefore the
probability of temperature induced homogeneous bubble nucleation is negligible.Comment: 22 Pages, 11 figures, one of them is colour, we plan to publish it in
Eur. Phys. J.
An experimental and numerical investigation of the use of liquid flow in serpentine microchannels for microelectronics cooling
This paper presents a combined experimental and numerical investigation of single-phase water flow and heat transfer in serpentine rectangular microchannels embedded in a heated copper block. The performance of four different microchannel heat sink (MCHS) configurations are investigated experimentally, the first having an array of straight rectangular microchannels (SRMs), while the other have single (SPSMs), double (DPSMs) and triple path multi-serpentine rectangular microchannels (TPSMs). Three-dimensional conjugate heat transfer models are developed for both laminar and turbulent single-phase water flows in each of these MCHSs and the governing flow and energy equations solved numerically using finite elements. The numerical predictions of pressure drop (∆P) and average Nusselt number (〖Nu〗_avg) are in good agreement with experimental data, and indicated that the single path serpentine microchannel (SPSM) leads to a 35% enhancement of the 〖Nu〗_avg at a volumetric flow rate of 0.5 l/min and a 19% reduction in total thermal resistance (R_th) compared to the conventional SRM heat sink. However, this enhancement is at the expense of a large (up to ten-fold) increase in ∆P compared to the SRM heat sink, so that a suitable compromise must be struck between heat transfer and pressure drop in practical MCHS designs
Direct Numerical Simulation of Turbulent Heat Transfer Modulation in Micro-Dispersed Channel Flow
The object of this paper is to study the influence of dispersed micrometer
size particles on turbulent heat transfer mechanisms in wall-bounded flows. The
strategic target of the current research is to set up a methodology to size and
design new-concept heat transfer fluids with properties given by those of the
base fluid modulated by the presence of dynamically-interacting,
suitably-chosen, discrete micro- and nano- particles. We run Direct Numerical
Simulation (DNS) for hydrodynamically fully-developed, thermally-developing
turbulent channel flow at shear Reynolds number Re=150 and Prandtl number Pr=3,
and we tracked two large swarms of particles, characterized by different
inertia and thermal inertia. Preliminary results on velocity and temperature
statistics for both phases show that, with respect to single-phase flow, heat
transfer fluxes at the walls increase by roughly 2% when the flow is laden with
the smaller particles, which exhibit a rather persistent stability against
non-homogeneous distribution and near-wall concentration. An opposite trend
(slight heat transfer flux decrease) is observed when the larger particles are
dispersed into the flow. These results are consistent with previous
experimental findings and are discussed in the frame of the current research
activities in the field. Future developments are also outlined.Comment: Pages: 305-32
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