1,721,057 research outputs found
CFD analysis of a realistic reduced-scale modeling equipped with axial jet fan
No full textTypically, in the experimental scale road tunnel model, the air flow induced by ventilation system is provided by an external fan. In this paper, the authors have numerically simulated full and reduced-scale tunnel in order to evaluate the possibility to realize a reduced scale of a road tunnel model with a realistic ventilation system consisting of impulsive jet fans. In particular, two different types of longitudinal ventilation systems were considered, traditional and alternative. The last one was equipped with jet fans that have the inlet/outlet sections inclined at a fixed pitch angle (α=6°) toward the tunnel floor. The jet fan was simulated as a simple momentum source that provides a pressure rise (pressure drop) across them as a function of the outflow air velocity. The analyzed tunnel consists in a 800 m one directional bore with circular cross section 5.05 m radius; the jet fans were installed at 5.67 m from the floor. Furthermore a burning Heavy Good Vehicle (HGV), placed at 450 m far away the tunnel entrance, was considered. To simulate numerically the burning vehicle, the species transport equation combustion model with Eddy-Dissipation-Concept (EDC) model was adopted. In order to create a reduced-scale model from a full scale, Froude method was applied to preserve geometrical, kinematical and dynamical similitude. Temperature and axial velocity profiles, in different tunnel sections for both considered models (full and scaled) and ventilation systems, were provided. The numerical results showed a good agreement for the both ventilation system
Numerical comparison of performance between traditional and alternative jet fans in tiled tunnel in emergency ventilation
No full textIn this paper a computational study was carried out to evaluate the performance of longitudinal ventilation
system equipped with an alternative jet fan with respect to traditional one in case of fire in tiled tunnel.
The alternative jet fan is equipped with inclined silencers (pitch angle a = 6) in order to reduce the
Coanda effect and consequently shear stress on the tunnel ceiling. The fire was simulated setting heat flux
on HGV surface. Computational fluid dynamic analysis was applied to simulate the ventilation in the unidirectional
tunnel through j–e model. The comparison conducted in terms of total thrust required to prevent
back-layering phenomena and numerical results were provided in terms of thrust of jet fan values,
average velocity values and temperature profiles, for different tunnel slope values. Furthermore the
authors have compared the critical velocity provided by CFD analysis with critical velocity provided in
the literature
Measurement of the compressed natural gas in automative application: a comparitive analysis between mass versus volumetric metering methods
No full textAlternative Gaseous Fuels are not new, but the fuel metering systems have become very sophisticated in order to control the flow of several products, such as Compressed Natural Gas (CNG), Liquefied Natural Gas (LNG), Liquefied Petroleum Gas (LPG), Hydrogen, Methanol and others. Alternative fuels and vehicles are now quite widespread, since they reduce emissions and dependence on foreign oil/energy supplies. In particular, CNG is currently being measured by means of a volumetric method when natural gas is supplied to a petrol pump, while is measured by a mass method when the gas is loaded into the vehicles. These different metering approaches can cause misalignments between the two metering systems, thereby causing arguments and disputes. In this paper, a metrological comparison between the two alternative CNG measurement approaches (volumetric vs. mass flow metering) is carried out.
In order to show and to stress the inconsistencies connected to these different measuring methods, the main results of a case study are presented and illustrated
Fondamenti di termometria (II edizione)
No full textRivolto agli allievi del corso di misure termofluidodinamiche, Fondamenti di misure per gli allievi di Ingegneria presso la Facoltà Federico II e Seconda Università degli studi di Napoli
Applicazioni numeriche di trasmissione del calore
No full textRaccolta di esercizi ed applicazioni numeriche sulla trasmissione del calor
ANALISI SPERIMENTALE SU SISTEMI CANALE-CAMINO ALIMENTATI ASIMMETRICAMENTE A FLUSSO TERMICO UNIFORME CON EFFETTI RADIATIVI
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Experimental analysis of chimney effect with radiation on an asymmetrically heated vertical channel
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