733 research outputs found
Enhanced visualisation of complex thermofluid data: Vertical and horizontal combined convection and microscale heat transfer cases
No full textCopyright @ 2000 UITIn general, convective heat transfer is an 'n-dimensional' problem where n is well in excess of 3 for steady flows. Traditionally, the method of dimensional analysis results in a small number of dimensionless groups. In the case of steady forced convection these can reduce to three, namely the Nusselt (Nu), Reynolds (Re) and Prandtl (Pr) numbers, for heat transfer, fluid flow regime and fluid properties respectively. Again, traditionally, data are presented on log-log graphs, say of Nu versus Re, with Pr being a possible third parameter. For natural convection, the Grashof number (Gr) expresses buoyancy effects in place of Re, while for combined (natural and forced) convection Gr becomes additional to, rather than replacing, Re. Using sets of data for: (a) vertical combined convection in nuclear safety, (b) horizontal combined convection review material, and (c) microchannel heat transfer, in the first part of this paper we survey this problem. We reach the following conclusions: that heat transfer data are presented in either 'holistic' or 'reductive' modes, and that other thermodynamic performance data are related to the generic scientific cases of (a) 3-dimensional space and (b) multi-dimensional space. In the second part of the paper we present a first attempt at applying design-type procedures to specifying this problem. Visualisation priorities are suggested from which particular solutions will be developed in future
Non-Newtonian and flow pulsatility effects in simulation models of a stented intracranial aneurysm
No full textPermission to redistribute provided by publishers.Three models of different stent designs implanted in a cerebral aneurysm, originating from the Virtual Intracranial Stenting Challenge'07, are meshed and the flow characteristics simulated using commercial computational fluid dynamics (CFD) software in order to investigate the effects of non-Newtonian viscosity and pulsatile flow. Conventional mass inflow and wall shear stress (WSS) output are used as a means of comparing the cfd simulations. In addition, a WSS distribution is presented, which clearly discriminates in favour of the stent design identified by other groups. It is concluded that non-Newtonian and pulsatile effects are important to include in order to avoid underestimating wss, to understand dynamic flow effects, and to discriminate more effectively between stent designs. © Authors 2011
"Vera effigies Francisci". Un ritratto del Serafico nella chiesa di San Francesco a Brescia
No full textLa chiesa di San Francesco a Brescia, sede principale dell'Ordine dalla metà del XIII secolo, custodisce un ritratto di San Francesco a figura intera, riconducibile stilisticamente ad un arco cronologico che va dalla fine del XVI secolo all'inizio del XVII, ma iconograficamente accostabile alle molte tavole medievali dedicate al Serafico. Sulla sommità della tavola campeggia un’iscrizione a capitali maiuscole dorate: “VERA ET.(origi)NALIS EFFIGIES D.(ivi) P.(atris) FRANCISCI DU(m) VIVERET MCCXI”. Il ritratto è, con ogni probabilità, copia seicentesca di un'antica tavola medievale, il dossale attribuito a Giunta Pisano, oggi custodito nel Museo di San Matteo a Pisa, di cui i Conventuali di Brescia si procurarono copia per mostrare ai fedeli un ritratto autentico del fondatore, concorde con l'ideologia dell'Ordine
Detailed reconstruction and safety analysis of a pre–Seveso accident
No full textIndustrial safety has been a topic of growing interest during the last decades, mainly because of the increased awareness and knowledge about safety issues. In this framework, the detailed reconstruction of the dynamics of an explosion (1 killed and 8 injured) occurred, on the 26th of June 1971, at Noury Italy (a plant dedicated to the production of chemicals for hardening plastics) is worth of interest and it could be used to improve actual safety guidelines related to the storage of peroxides. The accident happened before whatever Seveso Directive release. Therefore, root-causes reconstruction and related risk assessment were carried out making a comparison between a hypothetical plant layout at that time and a modern plant layout implemented with minimum safety systems, such as acoustic alarms and adequate bypass lines. The accident reconstruction was carried out by doing a deep literature research, mainly based on newspaper clippings of the time, to both remodel the accident at best and draw the most likely layout of the plant. The latter is of fundamental importance to carry out a risk assessment procedure by applying the Recursive Operability Analysis (ROA), which allows for a direct generation of the fault trees that can provide an easy estimation of the probability of occurrence of all unwanted events. This method was applied to the Noury Italy case study to show the criticalities of the storage equipment also underlining the possible improvements which could be implemented also in the ‘70s, therefore preventing the fatal explosion
Recursive operability analysis as a tool for ATEX classification in plants managing explosive dusts
No full textSafety and prevention in workplaces are important issues, especially regards to risks with serious consequences for health and infrastructures, such as dust explosions, which have caused several industrial accidents during the last centuries and, actually, represent a critical issue in the industrial framework. The current European legislation, referred to as ATEX directive, identifies ATEX zones as parts of the plant where explosive atmospheres can be generated. In this work, a modified version of the classic Recursive Operability Analysis method, specifically tailored to define with an automatic procedure the ATEX zones related to flammable dust clouds, is proposed. The method is fast and effective, allowing for an automatic generation of fault trees from which the probability of occurrence defining the specific ATEX zone type can be estimated. This technique was successfully implemented in a chemical plant dedicated to the mixing of inert powders with a stearate powder, a hazardous dust classified as strongly explosible. The extent of all the ATEX zones identified within the plant was simulated with the ALOHA software, treating the dispersed dust cloud of stearate as a dense gas cloud. From the results, it was possible to identify not only type and extension of all the ATEX zones but also either the most critical parts of the plant or the most dangerous activities (e.g. human errors in the use of the forklift was found to account for about 97.7% to explosion probability in this type of plant)
Combined convection and wall conduction effects in laminar pipe flow: numerical predictions and experimental validation under uniform wall heating
No full textLaminar combined convection in horizontal circular ducts is investigated both numerically and experimentally, under uniform wall heating. A series of experiments for the heating of water in a long horizontal copper tube are simulated numerically in order to assess the reliability of the theoretical results. Peripheral and axial wall conduction effects, inherently present in the experiments, are accounted for in the numerical model. The cross validation of experimental and numerical data allows significant conclusions to be reached on conjugate conduction and convection with buoyancy effects in horizontal duct flows. Buoyancy is considered for values of the modified Rayleigh number, Ra-q0, up to 5 . 10(6); the forced convection contribution is considered for two values of the entry Reynolds number, Re-0 = 500 and 1000
Francesco di Giorgio nella trattatistica rinascimentale. XXIII.3. Giacomo Barozzi da Vignola
No full textIl contributo illustra la valutazione dell'opera teorica e architettonica di Francesco di Giorgio Martini nel trattato di Giacomo Barozzi da Vignola Le due regole della prospettiva pratica, e nel commento di Egnazio Danti al testo vignolesco
Integrating Recursive Operability Analysis with Different Risk Assessment Methods: Analysis of the Historical BP American Refinery Explosion
No full textThe British Petroleum (BP) American Refinery accident, back in 2005, was one of the most severe explosions recorded in any industrial accident database. According to both the reconstruction and the interviews with the company, it was found that the causes of the accident where both technical, with the failure of a level controller, which was also badly designed for the isomerization unit, and human, with a very stressed and undersized personnel. In this work, a Quantitative Risk Assessment (QRA) based on the Recursive Operability Analysis (ROA), as hazards and accidental scenarios identification tool, was performed on the unit (BP isomerization unit) involved in the accident. The analysis was carried out exploiting many different techniques, to provide a proper assessment. The quantification of all node-deviation-variables (necessary to establish the real behaviour of the system) was performed by implementing the BP plant in CoCo simulator. Basic events were identified using a simplified Failure Mode and Effects Analysis (FMEA). Then, the magnitude of fire and explosion was estimated basing on the simulation results provided by the ALOHA software. Finally, a Fault Tree Analysis for the BP isomerization unit was performed, quantifying the probability of occurrence of all the most credible scenarios. Probabilities, magnitudes, and risk indexes (function of the distance with respect to the source point) were also estimated. From the analysis, the importance of redundant measurements of the most crucial variables, such as liquid level, and the impact of human errors was highlighted
Aspetti di sostenibilità ambientale nelle strutture ospedaliere: il benessere visivo
No full textL'articolo tratta delle questioni relative al progetto del comfort visivo per il luoghi di cura. In particolare, l'oggetto è quello della progettazione degli spazi per la degenza. Nell'ultima parte dell'articolo vengono riportate le risultanze sperimentali di alcune prove tese a comparare modelli fisici all'interno di "cielo artificiale" e modelli numerici (Ecotect, Radiance) nella simulazione della luce naturale. Si è preso in considerazione il cpmportamento di "light shelves" nel miglioramento della qualità della luce
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