The present study has been conducted in the frame of BUMA (Prioritization of Building Materials Emissions as indoor pollution sources), a European funded project, aiming at assessing the exposure to ...emitted compounds in indoor air. Field campaigns in five (5) European cities (Milan, Copenhagen, Dublin, Athens and Nicosia) were carried out. These campaigns covered weekly winter and summer concentration measurements in two (2) public buildings and two (2) private houses in each city. BTEX, terpenes, and carbonyls were measured using passive sampling in two sites inside the building and one outside. VOC emission measurements on selected building material have also been performed using Field and Laboratory Emission Cell (FLEC). The results on indoor concentrations for compounds such as formaldehyde (1.2–62.6
μg
m
−3), acetaldehyde (0.7–41.6
μg
m
−3), toluene (0.9–163.5
μg
m
−3), xylenes (0.2–177.5
μg
m
−3) and acetone (2.8–308.8
μg
m
−3) have shown diversity and relatively significant indoor sources depending on the building type, age etc. Indoor concentrations of these substances are varied depending on the building age and type. The percentage of approximately 40% of the indoor air quality levels originated from building materials.
An indoor car park was appropriately equipped in order to test the de-polluting efficiency of a TiO(2)-containing paint in an indoor polluted environment, under real scale configuration. Depollution ...tests were performed in an artificially closed area of the parking, which was polluted by a car exhaust during the testing period. The ceiling surface of the car park was covered with white acrylic TiO(2)-containing paint (PP), which was developed in the frame of the EU project 'PICADA' (Photocatalytic Innovative Coverings Application for Depollution Assessment). The closed area was fed with car exhaust gases. As soon as the system reached steady state, the UV lamps were turned on for 5h. The difference between the final and the initial steady state concentration indicates the removal of the pollutants due to both the photocatalytic paint and car emission reduction. Results showed a significant photocatalytic oxidation of NO(x) gases. The photocatalytic removal of NO and NO(2) was calculated to 19% and 20%, respectively, while the photocatalytic rate (microgm(-2)s(-1)) ranged between 0.05 and 0.13 for NO and between 0.09 and 0.16 for NO(2).
Wind fields in the atmospheric surface layer (ASL) are highly three-dimensional and characterized by strong spatial and temporal variability. For various applications such as wind-comfort assessments ...and structural design, an understanding of potentially hazardous wind extremes is important. Statistical models are designed to facilitate conclusions about the occurrence probability of wind speeds based on the knowledge of low-order flow statistics. Being particularly interested in the upper tail regions we show that the statistical behaviour of near-surface wind speeds is adequately represented by the Beta distribution. By using the properties of the Beta probability density function in combination with a model for estimating extreme values based on readily available turbulence statistics, it is demonstrated that this novel modelling approach reliably predicts the upper margins of encountered wind speeds. The model’s basic parameter is derived from three substantially different calibrating datasets of flow in the ASL originating from boundary-layer wind-tunnel measurements and direct numerical simulation. Evaluating the model based on independent field observations of near-surface wind speeds shows a high level of agreement between the statistically modelled horizontal wind speeds and measurements. The results show that, based on knowledge of only a few simple flow statistics (mean wind speed, wind-speed fluctuations and integral time scales), the occurrence probability of velocity magnitudes at arbitrary flow locations in the ASL can be estimated with a high degree of confidence.
Application of the CFD methodology for risk assessment of hydrogen applications and associated support of regulation, codes and standards has been growing its momentum during the last years. The CFD ...tools applied should prove to be “adequately” validated for hydrogen applications. This contribution focuses on the hydrogen related validation work performed with the CFD code ADREA-HF. The code is a three dimensional transient fully compressible flow and dispersion CFD solver, able to treat highly complex geometries using the porosity formulation on Cartesian grids. The ADREA-HF validation effort was performed within various EC co-funded projects (EIHP, EIHP-2, HyApproval, HyPer, HySafe). Various types of hydrogen release scenarios were considered, including gaseous and liquefied releases, open, semi-confined and confined environments, sonic (under-expanded) and low momentum releases. In parallel to its validation the ADREA-HF code has been extensively used for regulations, codes and standards support.
The use of hydrogen as a fuel should always be accompanied by a safety assessment concerning the case of an accidental release. To evaluate the potential hazards in a spill accident both experiments ...and simulations are performed. In the present work, the CFD code, ADREA-HF, is used to simulate the liquefied hydrogen (LH2) spill experiments (test 5, 6, 7) conducted by the Health Safety Laboratory (HSL). Two horizontal releases, the one along the ground and the other one at a distance above the ground, and one vertical release are examined with spill rate 60 lt/min. The main focus of this study is on the presence of humidity in the atmosphere and its effect on the vapor dispersion. When humidity is present is cooled, condenses and freezes due to the low prevailing temperature (∼20 K near the release), and releases heat. In addition, during the release hydrogen droplets are formed due to mechanical and flashing break up, and water droplets and ice crystals due to humidity phase change. Therefore, two models are tested: the hydrodynamic equilibrium model, which assumes that the phases are in thermodynamic and kinematic equilibrium and the non hydrodynamic equilibrium model (slip model), which assumed that the phases are in thermodynamic equilibrium but they can obtain different velocities. The fluctuating wind direction was also taken into account, since it greatly affects the hydrogen dispersion. The computational results are compared with the experimental measurements, and it is concluded that humidity along with the slip effect influences the buoyancy of the cloud to a great extent. The best simulation case (humidity and slip effect) is consistent with the experiment for all three tests for the majority of the sensors.
•The dispersion of liquefied hydrogen is modeled based on the HSL experiments.•The effect of ambient humidity is examined.•The slip effect of H2 droplets, water droplets and ice crystals is examined.•The prediction with humidity and the slip effect is consistent with the experiments.•The fluctuated wind direction was modeled. Significant effect on gas dispersion.
•The statistical behavior of the variability of individual exposure is described with a beta function.•The extreme value in the beta function is properly addressed by 5 correlation.•Two different ...datasets gave clear support to the proposed novel theory and its hypotheses.
A key issue, in order to be able to cope with deliberate or accidental atmospheric releases of hazardous substances, is the ability to reliably predict the individual exposure downstream the source. In many situations, the release time and/or the health relevant exposure time is short compared to mean concentration time scales. In such a case, a significant scatter of exposure levels is expected due to the stochastic nature of turbulence. The problem becomes even more complex when dispersion occurs over urban environments. The present work is the first attempt to approximate on generic terms, the statistical behavior of the abovementioned variability with a beta distribution probability density function (beta-pdf) which has proved to be quite successful. The important issue of the extreme concentration value in beta-pdf seems to be properly addressed by the 5 correlation in which global values of its associated constants are proposed. Two substantially different datasets, the wind tunnel Michelstadt experiment and the field Mock Urban Setting Trial (MUST) experiment gave clear support to the proposed novel theory and its hypotheses. In addition, the present work can be considered as basis for further investigation and model refinements.
Within the framework of the EPHECT project (Emissions, exposure patterns and health effects of consumer products in the EU), irritative and respiratory health effects were assessed in relation to ...acute and long-term exposure to key and emerging indoor air pollutants emitted during household use of selected consumer products. In this context, inhalation exposure assessment was carried out for six selected ‘target’ compounds (acrolein, formaldehyde, benzene, naphthalene, d-limonene and α-pinene). This paper presents the methodology and the outcomes from the micro-environmental modelling of the ‘target’ pollutants following single or multiple use of selected consumer products and the subsequent exposure assessment. The results indicate that emissions from consumer products of benzene and α-pinene were not considered to contribute significantly to the EU indoor background levels, in contrast to some cases of formaldehyde and d-limonene emissions in Eastern Europe (mainly from cleaning products). The group of housekeepers in East Europe appears to experience the highest exposures to acrolein, formaldehyde and benzene, followed by the group of the retired people in North, who experiences the highest exposures to naphthalene and α-pinene. High exposure may be attributed to the scenarios developed within this project, which follow a ‘most-representative worst-case scenario’ strategy for exposure and health risk assessment. Despite the above limitations, this is the first comprehensive study that provides exposure estimates for 8 population groups across Europe exposed to 6 priority pollutants, as a result of the use of 15 consumer product classes in households, while accounting for regional differences in uses, use scenarios and ventilation conditions of each region.
Indoor air concentrations and 24-h exposure of housekeepers in West Europe to formaldehyde emitted from household consumer products, under different ventilation conditions. Display omitted
•For first time, exposure is assessed to 6 air pollutants from 15 consumer products•Estimates given for housekeepers and retired across 4 European geographical regions•Exposure to priority pollutants presents variability among population groups•No consistency for maximum exposure to all pollutants by only one population group•Product use, emissions, indoor activity and ventilation determine personal exposure
In this work a new approach for CFD RANS modelling of dispersion of airborne point source releases is presented. The key feature of this approach is the model capability to predict concentration time ...scales that are functions not only of the flow turbulence scales but also of the pollutant travel time. This approach has been implemented for the calculation of the concentration fluctuation dissipation time scale and the maximum individual exposure at short time intervals. For the estimation of travel time in the Eulerian grid the new ‘radioactive tracer method’ is introduced. The new approaches were incorporated in the CFD code ADREA. The capabilities of the new approaches are validated against the Mock Urban Setting Trial field experiment data under neutral conditions. The comparisons of model and observations gave quite satisfactory results.
This paper presents a computational investigation of the residence of atmospheric contaminants in the wake of an isolated cubical building under different stability conditions, using the ...computational fluid dynamics code ADREA-HF. Characteristic concentration decay times describing the detrainment behaviour of gas in the near-wake are assessed for different atmospheric stability conditions and the results are compared with experiments conducted in the field (Mavroidis et al., 1999). The flow and concentration fields are also investigated computationally. Two building orientations are examined, with the mean wind direction normal to or at 45° to the leading face of the cubical building. Characteristic decay time patterns calculated by the model agree in general with the experimental ones, while there is a tendency for the model to overestimate dilution rates for the wind direction normal to the face of the building. The residence time (Td), defined as the time it takes for gas concentration to decay to 1/e of its original value, depends on atmospheric stability, with higher values observed in general under stable conditions; Td is especially influenced by the prevailing wind speeds, with a tendency for higher values under lower wind speeds. On the other hand, the non-dimensional residence time (τ = UTd/H) is to a large extent independent of the atmospheric stability conditions, as also indicated by the experimental measurements. Residence times are in general larger when the cube is oriented at 45° to the wind than when it is normal to the wind. Finally, the spatial variability of the calculated residence time Td is also presented and discussed.
► Gas residence in the wake of an isolated cube was investigated using a CFD model. ► Residence times were compared with field results for different stability conditions. ► For the cube normal to the flow the model underestimated residence times. ► Non-dimensional residence times are in general independent of atmospheric stability. ► A power law dependence was observed between residence times and wind speed.
Materials that contain a photocatalyst have a semi-permanent capacity for removing harmful gases from the ambient air. It is the purpose of this study to investigate the photocatalytic activity of ...commercial paints containing TiO2 nanoparticles towards NO and NO2. Experiments were carried out in a stainless steel (30 m-3) walk-in type environmental chamber (Indoortron), under “real world setting” conditions of temperature, relative humidity, irradiation and pollutant concentrations. Two types of nanoparticle TiO2-containing paints were tested for their depolluting properties: a mineral silicate paint and a water-based styrene acrylic paint. The results showed a significant effect of TiO2-materials in reducing NOx. It was found that up to 74% of NO and 27% of NO2 were photo-catalytically degraded by the mineral silicate paint, while degradation percentage using the styrene acrylic paint reached 91% and 71% for NO and NO2, respectively. The photo-catalytic rate of NO on the mineral and styrene acrylic paint was calculated to 0.11 μg m-2 s and 0.18 μg m-2 s, respectively, indicating higher photocatalytic performance of the organic based material. The effect of relative humidity (RH) was also investigated. An increase of RH from 20% to 50% inhibited the NOx photocatalysis on the surface of the samples.
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