1,721,040 research outputs found
The role of particle resuspension within PM concentrations in underground subway systems
No full textHigh particulate matter (PM) concentrations have been measured on subway networks worldwide, with serious implications for human health. Such concentrations are known to be mainly produced by wear and friction of the metal parts and can accumulate in subways over time, causing a sort of age effect. Surveys have also shown that particle resuspension, caused by train arrivals and departures, significantly increases particulate matter concentrations. The research aim was threefold: (1) to provide a literature review on particulate matter concentrations in urban subway systems; (2) to measure the influence/incidence of the resuspension of PM2.5 and PM10 caused by subway train transit; and (3) to investigate the presence of a subway age effect. A sampling campaign was carried out on the station platforms of the Naples (Italy) Subway Line. The results show that particle resuspension significantly influences PM concentrations, reaching daytime values up to + 1200% greater than those at nighttime. Furthermore, to investigate any age effect, the results were compared with those of a previous study performed in 2014, concluding that, in the absence of tunnel cleaning and/or washing and with a standard ventilation system on station platforms, no statistically significant difference was observed between PM concentrations over the two measurement periods. These results suggest that the particles generated by mechanical wear-and-tear and friction processes constitute a very slow phenomenon. A useful solution could be tunnel washing, thereby removing fine particles that would no longer be available for resuspension
LA MISURA DELLA PORTATA DI MASSA TRAMITE L'EFFETTO CORIOLIS
No full textAn exhaustive description of the application of the Coriolis acceleration to the mass flow measurement is presented. After a survey of the existing Coriolis acceleration mass flowmeters and of their metrological performances, the operating principle of a new type of mass flowmeter based on the Coriolis effect is described. It has been designed at the Department of Mechanical Engineering for Energy, at the University of Naples
The Coriolis effect in mass flow measurement
No full textAn exhaustive description of the application of the Coriolis acceleration to the mass flow measurement is presented. On the basis of a survey of the existing Coriolis acceleration mass flowmeters and of their metrological performances, in this work is also presented the operation principle of a new type of mass flowmeter based on the coriolis effect, which was realized in the Department of Mechanical Engineering for Energy University of Naples
Application of nanofluids in industrial processes. The case of food processing
No full textA crossflow heat exchanger for drying purposes integrated in a pasta manufacturing process is considered in the present work. Different nanofluids, i.e., Al2O3, TiO2, and CuO, are considered with particle dimensions ranging from 20 to 60 nm and volumetric concentration in the range of 0 %–5%. Base fluid is water. An analytical model of the heat exchanger is developed and the energy performance is evaluated from a Life Cycle Analysis perspective by considering the embodied energy of the different nanoparticles. The utilization of the nanofluids allows to reduce the dimensions of the device. In particular, a reduction in length of 26 %, 25 %, and 27 % is estimated for Al2O3, TiO2, and CuO respectively. Oppositely, there is not an enhancement of the energy performance. In particular, an increase of the operating energy is detected since the reduction of the dimension increases pressure losses and the saving in embodied energy due to the use of less material is not sufficient to offset the increase in embodied energy due to the utilization of the nanoparticles
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
Analysis of technology diffusion policies for renewable energy. The case of the Italian solar photovoltaic sector
No full textThe scope of the work is to depict a solid framework to interpret the capacity development of solar PV in Italy. To this aim the pivotal roles of public incentives is addressed and a vis a vis analysis of the regulatory framework and corresponding quantitative data is provided. The Italian regulatory framework did not provide an adequate focus on operational requirements for developing solar PV and allowed the speculative behavior of many investors. This is demonstrated by the correlation index between installed capacity and level of incentive equal to 0.988. Additionally, LCOE is calculated and from 2009 onward it is half of the average incentive level. Furthermore, the role of “followers” assumed by large power generators in the first phase of the PV development determined the absence of an industrial leadership. Oppositely, in a second phase, large utilities became more active on the PV market since they realized the impact on power market price. The linear correlation index between market price and PV capacity is found to be equal to −0.68, therefore price decreases at the increase of PV installed capacity and this is detrimental for large power utilities, thus they were pushed to be active in the PV sector
Cold potable measurement by means of a combination meter
No full textIn this paper an accurate description of a combination water meter is provided. Therefore, the main results of calibration tests are presented. Final considerations about the reliability of a combination meter in very wide flow range applications are also reported
Analysis of ageing effects on static gas meters
No full textStatic gas meters are currently being installed in increasing quantities within gas distribution networks across Europe due to their up-to-date technology which intrinsically allows to comply with current requests from Normation and fiscal bodies; on the other hand, the technology on which such meters are based is still relatively new, therefore confidence in it must be built. In particular, for instance in Italy, regulation agencies require more frequent verification of static meters with respect to “classical” technology meters due to the lack of information about their long-term stability. In the present paper, we present a study about the effects of ageing on static gas meters, that was performed based on the calibration of over 1500 G25 gas meters based on thermal (CTTMF - Capillary Type Thermal Mass Flowmeter) technology after 8 years from their installation; the size of the sample and its remarkable homogeneity provides a good level of confidence in the validity of the conclusions. We will show that most of the meters provided a response within legal limits, and that a very high percentage of them largely outperformed the requests. The technical reasons behind this performance and its implications for the evaluation of the capabilities of CTTMF technology will be discussed
Description of Velocity Fields in Front of Exhaust Axisymmetric Inlets by means of New Empirical Equations
No full textNew empirical equations for the prediction of air velocity in a symmetry plane offreety suspended
circular exhaust openings are presented. The new equations here introduced are derived from experimental studies carried out by the authors. In consideration of the difficulty in describing simply and accurately the velocity field by means of a single equation, velocity gradients are provided along lines parallel to the opening axis (i.e. perpendicular to the plane
containing the circular suction aperture). These velocity decays allow the user/designer to predict
with satisfactory accuracy the air velocity also outside the hood axis, by means of easy-to-use equations
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