Andrea Frattolillo

Flow conditioners efficiency a comparison based on numerical approach

Abstract Generally, flow conditioner efficiency is experimentally evaluated on the basis of the effects that these devices produce on a particular type of flowmeter. This approach, beside being very expensive, has certainly obstructed the development of a general theory and consequently the optimal design of flow conditioners. The present paper presents a comparison of the performance of different flow conditioners, independently from their effects on particular flowmeters. Therefore, the authors propose the use of several efficiency parameters to evaluate and compare flatness, uni-directionality and axi-symmetry of the velocity profiles produced downstream from the conditioners. In order to compare the main conditioners, a brief description of their characteristics is reported. Then, the numerical analysis is carried out using the finite volume technique. From the results obtained it was possible to calculate the efficiency of the conditioners under low-level disturbance conditions, such as those produced by an out of plane double elbow configuration.

Direct and indirect measurement of WBGT index in transversal flow

ISO 7243 considers the WBGT (Wet Bulb Globe Temperature) index as an index of thermal stress in hot environments. It can be evaluated directly by measuring the globe temperature, the natural wet bulb temperature, and the air temperature (only outside in the presence of solar radiation) or, indirectly, by measuring the air temperature, the air velocity, the humidity and the mean radiant temperature. The globe and natural wet bulb temperatures can only be estimated empirically, because they are not thermodynamic properties. The direct method, thus, permits neither very accurate measurements nor direct traceability. The aim of this study is to compare the above-mentioned methodologies experimentally. This analysis was carried out by varying the thermal and fluid dynamic parameters for transversal flow in the common measurement range.

Experimental design techniques for optimising measurement chain calibration

This paper tackles the design of a calibration using experimental design techniques. In particular, the optimum calibration plan for measurement chain is identified by suitably elaborating the error propagation law suggested by the ISO Guide. The main advantages of the proposed approach consist in: (i) calibration plans with a reduced number of calibration points; (ii) calibration curve applicable to the whole operating range; (iii) linear rather than complex regression technique always usable. Two different cases were analysed in order to show the efficiency of the proposed optimisation procedure: a psychrometer and an heat meter. The obtained theoretical results are verified on a number of real calibrations.

Indoor exposure to particles emitted by biomass-burning heating systems and evaluation of dose and lung cancer risk received by population

Homes represent a critical microenvironment in terms of air quality due to the proximity to main particle sources and the lack of proper ventilation systems. Biomass-fed heating systems are still extensively used worldwide, then likely emitting a significant amount of particles in indoor environments. Nonetheless, research on biomass emissions are limited to their effects on outdoor air quality then not properly investigating the emission in indoor environments. To this purpose, the present paper aims to evaluate the exposure to different airborne particle metrics (including both sub- and super-micron particles) and attached carcinogenic compounds in dwellings where three different heating systems were used: open fireplaces, closed fireplaces and pellet stoves. Measurements in terms of particle number, lung-deposited surface area, and PM fraction concentrations were measured during the biomass combustion activities, moreover, PM10 samples were collected and chemically analyzed to obtain mass fractions of carcinogenic compounds attached onto particles. Airborne particle doses received by people exposed in such environments were evaluated as well as their excess lung cancer risk. Most probable surface area extra-doses received by people exposed to open fireplaces on hourly basis (56 mm2 h-1) resulted one order of magnitude larger than those experienced for exposure to closed fireplaces and pellet stoves. Lifetime extra risk of Italian people exposed to the heating systems under investigation were larger than the acceptable lifetime risk (10-5): in particular, the risk due to the open fireplace (8.8 × 10-3) was non-negligible when compared to the overall lung cancer risk of typical Italian population.

Ultrafine particle distribution and chemical composition assessment during military operative trainings

(1) Background: The assessment of airborne particulate matter (PM) and ultrafine particles (UFPs) in battlefield scenarios is a topic of particular concern; (2) Methods: Size distribution, concentration, and chemical composition of UFPs during operative military training activities (target drone launches, ammunition blasting, and inert bomb impact) were investigated using an electric low-pressure impactor (ELPI+) and a scanning electron microscope (SEM), equipped with energy-dispersive spectroscopy (EDS); (3) Results: The median of UFPs, measured for all sampling periods and at variable distance from sources, was between 1.02 × 103 and 3.75 × 103 particles/cm3 for drone launches, between 3.32 × 103 and 15.4 × 103 particles/cm3 for the ammunition blasting and from 7.9 × 103 to 1.3 × 104 particles/cm3 for inert launches. Maximum peak concentrations, during emitting sources starting, were 75.5 × 106 and 17.9 × 106 particles/cm3, respectively. Particles from the drone launches were predominantly composed of silicon (Si), iron (Fe) and calcium (Ca), and those from the blasting campaigns by magnesium (Mg), sulphur (S), aluminum (Al), iron (Fe), barium (Ba) and silicon (Si); (4) Conclusions: The investigated sources produced UFPs with median values lower than other anthropogenic sources, and with a similar chemical composition.