1,721,067 research outputs found
Review of a dust explosion modeling
No full textA single particle model developed for dust explosion is here reviewed. The model describes the behaviour of a reacting particle which undergoes different steps during reaction: heating, devolatilization and homogeneous combustion. The model predicts the maximum values of the deflagration index, also including the role of turbulence. Four explosion regimes have been introduced to take into account the effect on the KSt value of the dust diameter and of the dust shape (different from sphere). These regimes are defined as function of dimensionless numbers (Bi, Da, Th) which contain the chemico-hysical properties of the dust-air mixtures. The effect of fuel gas addition to dust was also included in the model by calculating an equivalent gas mixture composition given by the flammable gas present in the hybrid mixture and the pyrolysis products generated from the dust pyrolysis. Finally, a guideline for the dust explosion simulations is proposed and modeling perspective discussed. © 2013, AIDIC Servizi S.r.l
Explosibility and flammability characteristics of nicotinic acid-lycopodium/air mixtures
No full textPowder products are frequently meet as dust mixtures in industrial processes. However the effect of mixing combustible dusts on the flammability and explosion behaviour of their mixture is still unclear. This work dealing with the explosibility and flammability of dust mixtures made of Nicotinic acid and Lycopodium. Explosion tests on the 20-L explosion vessel at different dust concentrations and relative amounts were performed. The two dusts showed the same minimum explosion concentration (MEC), but different explosibility parameters (KSt and Pmax). The predominant influence of the most reactive compound (Nicotinic acid) on the explosibility of the dust mixture was found. This effect was not encountered for the minimum explosion concentration. © Copyright 2014, AIDIC Servizi S.r.l
Un nuovo codice miniato da Cristoforo Majorana (Berlino, Staatsbibliothek zu Berlin - Preussischer Kulturbesitz, ms. Ham. 466)
No full text
HEAT AND MASS TRANSFER IN MONOLITHS IN THEPRESENCE OF AN EXOTHERMIC SUPERFICIAL REACTION
No full textHeat and mass transfer phenomena are investigated in a catalytic monolith with a fast exothermic superficial reaction at fully developing laminar flow for different values of the kinetic parameters.
The behavior of a channel of the monolith reactor is simulated with a three-dimensional model with cylindrical symmetry, whose unsteady Navier-Stokes equations, discretized by adopting the control volume approach, are solved by means of the CFD-ACE+ package.
The perturbation generated by heat production associated with the reaction of the flow field, temperature and concentration profiles determines at the ignition of the reaction a new entrance
effect with consequent enhancement of mass and heat transfer.
Hence Nu and Sh curves exhibit a not monotonic trend along the dimensionless axial coordinate, with a spike in correspondence of the ignition. Such enhancement is strongly dependent on the kinetic parameters of the surface reaction, and is not predictable with available correlations.
Mass and heat transfer coefficients collapse only if a different definition of Nu and Sh, expressed as functions of the actual driving force, embedding the adiabatic temperature rise and the kinetic parameters, is used
I capisaldi dell'estetica neoclassica: Johan Joachim Winckelmann, Anton Raphael Mengs e Charles-Nicolas Cochin
No full textFluid flow and dust dispersion in an agitated 20 L explosion vessel
No full textA CFD model was developed to simulate the turbulent flow field and the associated dust dispersion in an agitated spherical explosion vessel. Simulations were performed in the presence of a fan at the bottom of the sphere. Numerical results show that a helicoidal flow pattern is established. The dust entrained by the fluid flow accumulates at the wall and mainly at the top of the sphere
Una proposta di identificazione per il ritratto di ecclesiastico di Pier Francesco Foschi nel Musée Fesch di Ajaccio: Pierfrancesco Riccio, il maggiordomo del Duca Cosimo I de' Medici
No full textThe Design of Duct Venting of Gas Explosions
No full textVenting systems are useful for the mitigation of ac- cidental explosions. Vent ducts should be used if equipment is located indoors, as NFPA 68 (2007) suggests, for discharging combustion products to safe location. However, the presence of a duct is likely to increase the severity of the explosion with respect to simply vented vessels.
Up to now, no reliable correlations are available for the sizing of ducted vented systems. The only cor- relation available was developed by Bartknecht in 1993 for gas explosion, also acknowledged by NFPA 68.
In this study, we propose an engineering correla- tion based on semi-empirical engineering methodolo- gies, which is able to quantify the relations between geometric properties and the peak pressure occurring in the combustion chamber in the presence of a duct fitted on the vent panel. To this aim, we have regressed all the available experimental data on gas explosion in ducted-vented vessels
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