scholarly journals Short-term <sup>222</sup>Rn activity concentration changes in underground spaces with limited air exchange with the atmosphere

2011 ◽  
Vol 11 (4) ◽  
pp. 1179-1188 ◽  
Author(s):  
L. Fijałkowska-Lichwa ◽  
T. A. Przylibski
Keyword(s):  
Mechanical Ventilation ◽  
Radiation Protection ◽  
Activity Concentration ◽  
Residential Buildings ◽  
Ventilation System ◽  
The Other ◽  
Uranium Mine ◽  
Activity Concentrations ◽  
Concentration Changes ◽  
Air Exchange

Abstract. The authors investigated short-time changes in 222Rn activity concentration occurring yearly in two underground tourist facilities with limited air exchange with the atmosphere. One of them is Niedźwiedzia (Bear) Cave in Kletno, Poland – a natural space equipped with locks ensuring isolation from the atmosphere. The other site is Fluorite Adit in Kletno, a section of a disused uranium mine. This adit is equipped with a mechanical ventilation system, operated periodically outside the opening times (at night). Both sites are situated within the same metamorphic rock complex, at similar altitudes, about 2 km apart. The measurements conducted revealed spring and autumn occurrence of convective air movements. In Bear Cave, this process causes a reduction in 222Rn activity concentration in the daytime, i.e. when tourists, guides and other staff are present in the cave. From the point of view of radiation protection, this is the best situation. For the rest of the year, daily concentrations of 222Rn activity in the cave are very stable. In Fluorite Adit, on the other hand, significant variations in daily 222Rn activity concentrations are recorded almost all year round. These changes are determined by the periods of activity and inactivity of mechanical ventilation. Unfortunately this is inactive in the daytime, which results in the highest values of 222Rn activity concentration at the times when tourists and staff are present in the adit. Slightly lower concentrations of radon in Fluorite Adit are recorded in the winter season, when convective air movements carry a substantial amount of radon out into the atmosphere. The incorrect usage of mechanical ventilation in Fluorite Adit results in the most unfavourable conditions in terms of radiation protection. The staff working in that facility are exposed practically throughout the year to the highest 222Rn activity concentrations, both at work (in the adit) and at home (outside their working hours). Therefore, not very well considered solution for the ventilation system not only does not prevent radioactive exposure of the staff, but can even increase it. The authors have also observed comparable characteristics of the annual patterns of 222Rn activity concentration changes in underground spaces and residential buildings situated in the same or similar climatic zones.

The impact of mechanical ventilation operation strategies on indoor CO2 concentration and air exchange rates in residential buildings

2020 ◽  
pp. 1420326X2096076
Author(s):  
Pedro F. Pereira ◽  
Nuno M. M. Ramos
Keyword(s):  
Mechanical Ventilation ◽  
Air Quality ◽  
Exchange Rates ◽  
Indoor Air Quality ◽  
Indoor Air ◽  
Residential Buildings ◽  
Ventilation Strategy ◽  
The Impact ◽  
Mechanical Extraction ◽  
Air Exchange

In Portugal, residential buildings commonly have their ventilation strategy changed after commissioning. This occurs due to the building managers' willingness to reduce shared costs with the electricity needed for fan operation. However, this option is not technically supported, and the effects of such a strategy on indoor air quality-related to human pollutants are yet to be quantified. CO2 was monitored in 15 bedrooms and air exchange rates were calculated for each room. The air exchange rate values ranged from 0.18 to 0.53 h−1 when mechanical extraction ventilation was off, and from 0.45 to 0.90 h−1 when mechanical extraction ventilation was on, which represents an average increase of 119%. With the current intermittent ventilation strategy, all rooms remain above 1500 ppm for a given percentage of time, and 12 rooms presenting CO2 concentrations above 2000 ppm. Simulations of theoretical CO2 concentrations, for a non-interrupted mechanical ventilation strategy show that no rooms would accumulate CO2 concentrations above 2000 ppm, and only 25% would present CO2 concentrations above 1500 ppm. Pearson correlations between the monitored CO2 and human and spatial factors identified two relevant parameters. Those parameters correspond to ratios between CO2 generation and floor area ([Formula: see text]), and airflow with CO2 generation ([Formula: see text]). The proposed ratios could be used as ways to optimise ventilation costs and indoor air quality.

scholarly journals Experimental Investigation of the Air Exchange Effectiveness of Push-Pull Ventilation Devices

Energies ◽  
2020 ◽  
Vol 13 (21) ◽  
pp. 5817
Author(s):  
Sven Auerswald ◽  
Carina Hörberg ◽  
Thibault Pflug ◽  
Jens Pfafferott ◽  
Constanze Bongs ◽  
...  
Keyword(s):  
Heat Dissipation ◽  
Residential Buildings ◽  
Air Flow ◽  
Operation Mode ◽  
Ventilation System ◽  
Field Measurements ◽  
Gas Analysis ◽  
Decentralised Systems ◽  
Set Up ◽  
Air Exchange

The increasing installation numbers of ventilation units in residential buildings are driven by legal objectives to improve their energy efficiency. The dimensioning of a ventilation system for nearly zero energy buildings is usually based on the air flow rate desired by the clients or requested by technical regulations. However, this does not necessarily lead to a system actually able to renew the air volume of the living space effectively. In recent years decentralised systems with an alternating operation mode and fairly good energy efficiencies entered the market and following question was raised: “Does this operation mode allow an efficient air renewal?” This question can be answered experimentally by performing a tracer gas analysis. In the presented study, a total of 15 preliminary tests are carried out in a climatic chamber representing a single room equipped with two push-pull devices. The tests include summer, winter and isothermal supply air conditions since this parameter variation is missing till now for push-pull devices. Further investigations are dedicated to the effect of thermal convection due to human heat dissipation on the room air flow. In dependence on these boundary conditions, the determined air exchange efficiency varies, lagging behind the expected range 0.5 < εa < 1 in almost all cases, indicating insufficient air exchange including short-circuiting. Local air exchange values suggest inhomogeneous air renewal depending on the distance to the indoor apertures as well as the temperature gradients between in- and outdoor. The tested measurement set-up is applicable for field measurements.

scholarly journals Investigation of Ventilation Behaviors in Mechanically Ventilated Residential Buildings in China

2019 ◽  
Vol 111 ◽  
pp. 06048
Author(s):  
Yue Qi ◽  
Junjie Liu ◽  
Xilei Dai ◽  
Lei Zhao ◽  
Dayi Lai ◽  
...  
Keyword(s):  
Mechanical Ventilation ◽  
Energy Efficient ◽  
Natural Ventilation ◽  
Residential Buildings ◽  
Ventilation System ◽  
Outdoor Air ◽  
Climate Zones ◽  
Mechanically Ventilated ◽  
Ventilation Duration ◽  
Site Monitoring

Mechanical ventilation system provides a more reliable, controllable, and comfortable way of ventilation than natural ventilation through an opened window. However, the operation of mechanical ventilation system cost energy. This study investigated the usage of natural and mechanical ventilation in 46 apartments in ten cities across five different climate zones in China by on-site monitoring and questionnaire survey. On average, the daily natural and mechanical ventilation durations were 11 hours and 7.2 hours, respectively. Large differences existed among climate regions and seasons. From north to south, as the climate became warmer, the usage of natural ventilation increased. From seasonal perspectives, natural ventilation duration was the longest in summer and the shortest in winter. The trend of mechanical ventilation usage was opposite to that of natural ventilation. Generally, as the outdoor air temperature increased, the duration of natural ventilation increased and the duration of mechanical ventilation decreased. This study proposed an outline to use thermal comfort, health, and energy saving as three motivations to analyze ventilation behaviors. Based on the obtained results, suggestions were made for achieving healthy, thermally comfortable, and energy efficient ventilation in residential buildings.

APPLICABILITY OF VENTILATION SYSTEMS FOR REDUCING THE INDOOR RADON CONCENTRATION

2020 ◽  
Vol 191 (2) ◽  
pp. 202-208
Author(s):  
Martin Jiránek ◽  
Veronika Kačmaříková
Keyword(s):  
Mechanical Ventilation ◽  
Energy Consumption ◽  
Radon Concentration ◽  
Residential Buildings ◽  
Indoor Radon ◽  
Ventilation System ◽  
Supply Rate ◽  
Indoor Radon Concentration ◽  
Building Ventilation ◽  
Ventilation Systems

Abstract An analysis is presented of the ability of balanced mechanical ventilation systems to reduce the radon concentration in residential buildings efficiently. The analysis takes into account the following parameters: radon supply rate into the building, ventilation intensity, required indoor radon concentration and energy consumption. It is shown that the applicability of ventilation systems is limited mainly by energy consumption. Ventilation systems can be considered energetically acceptable if the ventilation intensity does not exceed 0.6 h−1, i.e. radon supply rate should not exceed 60 Bq/m3h for a required indoor radon concentration of 100 Bq/m3. Energy consumption can be significantly reduced by operating the ventilation system in a cyclic mode. Simulating the behavior of ventilation systems in time has been found as a useful tool for their design. In order to express by one parameter energy consumption and radon reduction, a completely new quantity—the ‘radon-related energy need’ has been proposed.

Experimental Quantification of Air Permeability of Building Envelope with Installed Controlled Ventilation System - Case Study

2019 ◽  
Vol 887 ◽  
pp. 571-578
Author(s):  
Boris Bielek ◽  
Daniel Szabó
Keyword(s):  
Exchange Rate ◽  
Residential Buildings ◽  
Ventilation System ◽  
Air Permeability ◽  
Building Envelope ◽  
Test Method ◽  
Air Exchange Rate ◽  
Controlled Ventilation ◽  
Air Infiltration ◽  
Air Exchange

To meet the increasingly stringent requirements of standard energy consumption and thus reducing operating costs of buildings, it is necessary to use energy-saving elements of technical equipment and eliminate heat loss through the building envelope. The biggest losses are caused by heat transmission and ventilation in the form of uncontrolled air infiltration through the building envelope. Their elimination can be achieved by improving the thermal technical quantification of building envelope and increase its airtightness. Determination of air permeability as a measure of quality building envelope is possible using the method of measuring devices Blower-Door test. Any defects can be detected by detection tools, then propose a suitable method for their removal and thus prevent unwanted unregulated air infiltration into the interior. On the other hand, are opposed to the health requirements required air exchange in the room, which is a significant reason for the transformation of this mode of ventilation by uncontrolled air infiltration to a controllable ventilation system. The subject of the paper is in-situ measurement of air permeability of specific apartment envelope by Blower-Door test method and comparison the efficacy of the installed controlled ventilation system and hygiene requirements of the ventilation intensity for residential buildings. Laboratory verification of façade ventilation unit parameters in big pressure chamber - measurement of inlet ventilation flap airflows at variable pressure differences. Methodology for the measurement by Blower-Door test method to determine the air permeability of building envelope structures and functionality of controlled ventilation system was based on a series of 10 measurements in 5 regimes. The overall air permeability of the building envelope or its integrated part may be verified using the total air exchange rate n50at 50 Pa pressure difference, determined experimentally according to STN EN 13829. Comparison of measured values with standard values recommended by some European countries with a similar climate with sealed and with unsealed ventilation flaps, which can determine the impact on the overall airtightness of the building envelope. Calculation of total hygiene required air exchange rate of the apartment and its comparison with actual measured values by Blower-Door test method.

scholarly journals Influence of Meteorological Parameters on the Variations of Atmospheric Radionuclides Concentration in Dar es Salaam, Tanzania

2020 ◽  
pp. 1-18
Author(s):  
Dorice Rashid Seif ◽  
Yusuf Ismail Koleleni
Keyword(s):  
Regression Analysis ◽  
Meteorological Parameters ◽  
Activity Concentration ◽  
Absolute Humidity ◽  
Dar Es Salaam ◽  
The Other ◽  
Atmospheric Conditions ◽  
Activity Concentrations ◽  
The Mean ◽  
Atmospheric Concentrations

Atmospheric concentrations of 7Be and 212Pb were measured for 11 years (2008 – 2018) in Dar es Salaam, Tanzania. The mean activity concentrations of 7Be and 212Pb were found to be within the range of 1.29 – 5.71 mBq/m3 and 10.85 – 50.06 mBq/m3, respectively. The annual mean activity concentrations of 7Be and 212Pb were 4.72 ± 1.18 mBq/m3 and 29.76 ± 13.63 mBq/m3, respectively. Distinct annual trends were depicted on 7Be and 212Pb, suggesting that the two radionuclides were affected differently with atmospheric conditions. Monthly atmospheric concentrations of 7Be showed a strong seasonal variation trend with the highest in January and February and lowest in April. 212Pb depicted the highest concentration during June and July and lowest in January and December. The regression analysis for 7Be and 212Pb activity concentrations together with number of meteorological parameters revealed that the relative humidity, rainfall, air temperature, absolute humidity and wind speed are the most significant parameters affecting radionuclides activity concentrations in the atmosphere. The sunspot numbers show 66.7% of its variability with 7Be activity concentration which further suggesting that other parameters may influence its variation. 212Pb, on the other hand, shows only 27.3% of its variability which clearly indicates that the existence of cosmic rays does not affect its activity concentration in the atmosphere.

scholarly journals RESEARCH OF APARTMENTS’ AIR REGIME IN THE PROCESS OF OPERATION AND RECONSTRUCTION

2019 ◽  
Vol 4 (10) ◽  
pp. 53-59
Author(s):  
О. Тирон ◽  
O. Tiron ◽  
Е. Попов ◽  
E. Popov
Keyword(s):  
Natural Ventilation ◽  
Residential Buildings ◽  
Ventilation System ◽  
Operating Mode ◽  
Cold Season ◽  
Air Permeability ◽  
Normal Operation ◽  
Scale Experiment ◽  
Comparison Of The Results ◽  
Air Exchange

Insufficient air exchange of apartments in gasified apartment residential buildings, as well as an apartment’s air balance when using mechanical ventilation can cause the formation and accumulation of carbon monoxide. This work is aimed at studying the air exchange of apartments when installing kitchen hoods in apartment buildings, as well as insufficient air permeability of windows in PVC (Polyvinyl chloride) bindings during the cold season. Analytical calculations and a full-scale experiment are carried out in two apartments with and without kitchen hood. The calculated air exchanges, actual air exchanges are determined: in normal operation by tenants and in conditionally maximum operating mode with open windows. The comparison of the results of analytical calculations with experimental data shows insufficient air permeability of PVC windows to maintain the necessary air exchange of natural ventilation. It becomes obvious that there are two ways to increase air exchange: regulated - opening vents and non-normative - installation of mechanical hoods. At the same time, the use of mechanical hoods can disrupt the operation of the natural ventilation system.

scholarly journals Effect of Mechanical Ventilation on Accidental Hydrogen Releases—Large-Scale Experiments

Energies ◽  
2021 ◽  
Vol 14 (11) ◽  
pp. 3008
Author(s):  
Agnieszka W. Lach ◽  
André V. Gaathaug
Keyword(s):  
Mechanical Ventilation ◽  
Mass Flow ◽  
Large Scale ◽  
Ventilation System ◽  
Hydrogen Gas ◽  
Forced Ventilation ◽  
British Standard ◽  
Confined Spaces ◽  
Series Of Experiments ◽  
Rate Limit

This paper presents a series of experiments on the effectiveness of existing mechanical ventilation systems during accidental hydrogen releases in confined spaces, such as underground garages. The purpose was to find the mass flow rate limit, hence the TPRD diameter limit, that will not require a change in the ventilation system. The experiments were performed in a 40 ft ISO container in Norway, and hydrogen gas was used in all experiments. The forced ventilation system was installed with a standard 315 mm diameter outlet. The ventilation parameters during the investigation were British Standard with 10 ACH and British Standard with 6 ACH. The hydrogen releases were obtained through 0.5 mm and 1 mm nozzles from different hydrogen reservoir pressures. Both types of mass flow, constant and blowdown, were included in the experimental matrix. The analysis of the hydrogen concentration of the created hydrogen cloud in the container shows the influence of the forced ventilation on hydrogen releases, together with TPRD diameter and reservoir pressure. The generated experimental data will be used to validate a CFD model in the next step.

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