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Proofs of well-functionning of an original hectometric magnetic bench, located in the South of France, at the Low Noise Underground Laboratory (LSBB for french acronym), Rustrel, are presented. Two different kinds of electrical measurements are justified and exposed. They are based on the monitoring of electrical quantities as characteristics and spontaneous induced bias, over the time and during periods of several weeks. A very first correlation with meteorological data is also presented. The technical as the scientific perspectives are exposed at the end.
Muography (or muon radiography) is an imaging technique that relies on the use of cosmogenic muons as a free and safe radiation source. It can be applied in various fields such as archaeology, civil engineering, geology, nuclear reactor monitoring, nuclear waste characterization, underground surveys, etc. In such applications, sometimes deploying muon detectors is challenging due to logistics, e.g. in a narrow underground tunnel or mine. Therefore, we are developing muon detectors whose design goals include portability, robustness, autonomy, versatility, and safety. Our portable muon detectors (or “muoscopes”) are based on Resistive Plate Chambers (RPC), planar detectors that use ionization in a thin gas gap to detect cosmic muons. Prototype RPCs of active area 16×16 cm² and 28 × 28 cm² were built in our laboratories at Louvain-la-Neuve (UCLouvain) and Ghent (UGent) to test and compare various design options. Benefiting from the experience gained in building and operating these prototypes, we are proceeding towards the development of improved prototypes with more advanced technical layout and readiness. In this paper we provide the status of our performance studies, including the cross-validation of the two types of prototypes in a joint data taking, and an outline of the direction ahead.
Located far from anthropical disturbances and with low seismic and magnetic background noise profiles, the LSBB facility is the ideal location for a new hybrid detector for the study of space-time strain. The MIGA infrastructure [1], utilizes an array of atom interferometers manipulated by the same beam, the resonant optical field of a 150 m long optical cavity. The infrastructure constitutes a new method for geophysics, for the characterization of spatial and temporal variations of the local gravity, and is a demonstrator for future decihertz gravitational wave observation. Such an infrastructure requires ultra-high vacuum (10⁻⁹ mbar) on a size (150 m) and scale (36 m³) not typically seen in underground laboratories other than CERN [2], and especially in underground environments with high humidity (up to 100%) and significant dust contamination (milimetric to micrometric porous rock particles). Here, we detail the status of the MIGA infrastructure and describe the ongoing generation and analysis of the vacuum works - this comes from tests of the prototype vacuum vessel, focusing on heating cycles, residual gas and heating analysis.
Samples from Vulcano hydrothermal system were incubated at hot temperatures with various electron donors and acceptors in order to isolate and characterize strains belonging from this environment. Eighteen strains were isolated, from which three seemed to belong to new species according to their 16S rRNA sequence. These strains are under phenotypic and genotypic characterization. Cultivation of representative taxa from an environment helps understanding ecological functions of microbial groups in these environments. Although cultivation often fails to isolate all representative prokaryotic taxa, effort of cultivation still can achieve the recovery of poorly characterized microorganisms.
The work proposed is part of a global project dealing with the characterization of heterogeneous media by both electromagnetic and mechanical full waveform inversions. Indeed Full Waveform Inversion of seismic reflection or Ground Penetrating Radar data is an efficient approach to reconstruct subsurface physical parameters with high resolution. This paper focuses on the mechanical part, and more specifically on quantitative imaging of nearsurface density. Processing field data is challenging because the nature of the source and the sensors used impact the signal-to-noise ratio as well as the frequency range appearing in the recorded data. From then it becomes interesting to process the data in the frequency domain and work on a few representative frequencies of the recorded temporal signal. In this article, field data are simulated by noisy synthetic data. Different frequency strategies are used and their results are compared with each other. The inverse problem consists in assessing the density in the probed medium from the data on the displacement field measured at the detectors. Such a problem is known to be nonlinear and ill-posed. It is solved iteratively by a regularized Gauss-Newton algorithm, which relies on the Fréchet derivatives obtained through the generalized reciprocity principle equivalent to the well-known adjoint method. The numerical results show an optimal strategy, for which the convergence rate and the computation time are reasonable, the spatial resolution is improved and the density is well reconstructed.
A person is in close contact with the natural environment throughout his life. In the interaction of nature and man, an important role is played by the preservation of ecological balance in the conditions of continuously growing needs of society. Environmental culture has a beneficial effect on the degree of development of the level of legal and environmental awareness in the society , as well as compliance by the members of the society with the requirements of environmental protection legislation. In the conditions of the rule of law, there is a great need for professional lawyers who are able to assist in the environmental and legal education of a person throughout his life. In order to raise the level of environmental and legal culture of the society , in our opinion, a special role should be assigned to professional lawyers, for whom this should be part of their professional activities. Within the framework of this research, we have proposed and implemented a case methodology on the subject of environmental law for law students.
Environmental education is one of the main tools for solving the problems of environmental management and environmental protection. In all highly developed countries, there is a tendency to develop technologies that contribute to reducing the harmful effects of human activities on the environment. The sustainable development of society and the economy in the face of growing demands for natural resources involves the careful treatment and transmission to future generations of clean air, genetic biodiversity and soil fertility. This can be achieved through the development of high-tech technologies based on environmental principles ,which largely depends on the quality of environmental education not only for specialists in the field of environmental management, but also for all people. We hold the view that environmental education has a great impact on the ability and skills of people to make decisions in accordance with environmental norms and standards. In order for environmental education to become an effective part of universal education, it is necessary first of all that every teacher has a competence in the field of ecology.
The main principles of personnel management of an agricultural enterprise.
Areas of work with the personnel of the agricultural enterprise.
In the context of the COVID-19 pandemic and the associated difficulties in the functioning of agricultural enterprises, in our opinion, new approaches are required to improve the efficiency of agricultural enterprises. The economic efficiency of an agricultural enterprise depends to a large extent on the efficiency of its personnel. In our opinion, human resources are one of the most important resources in the agricultural business.In this paper, we considered the use of grading to motivate employees of an agricultural enterprise. In our opinion, this will assist in the formation of a clear and transparent system of payment for work activities for the company's employees and, in addition, will optimize the size of the company's employee compensation fund.The system of management of labor resources of the agricultural enterprise should take into account the personality of the employee, knowledge of his features of motivation , and also be combined with the goals and objectives that the enterprise has.
In recent years, an integrated analysis of computational fluid dynamics (CFD) and computer simulation person (CSP), especially to reproduce the shape of the human body, has been conducted to estimate the interaction between the human body and its surrounding indoor environment. Meanwhile, clothing is often treated in a simplified manner, as a means of resistance to heat and pollutant transfer, and there is sufficient room for improvement in the hygrothermal and scalar transfer phenomena in and around clothing with a complex geometry. In this study, some garment models with complex geometry and others with simplified geometry were created with a CSP, and airflow, temperature, and humidity were investigated along with the CSP. It was assumed that only heat and water vapor were transported in the garment. As a result, the naked model was found to be over-or underestimated with respect to all airflow, temperature, and water vapor. It was also found that models with a simple garment shape produced the same results as models with a complex geometry on a macroscopic scale. Models with different regions and smaller air gaps between the clothes and the human body should be confirmed.
In this paper, taking 17 graduate male dormitories of a university in Shenyang as the research object, the relationship between the characteristics of internal personnel and pollutants, the relationship between pollutant concentration and air change rate in the winter dormitory is analyzed by means of questionnaire survey and measurement. Through test analysis, it was found that the number of students in the dormitory whose actual weight exceeded 10% of the normal weight was greater than or equal to 2 people, which would cause the indoor CO2 concentration to be significantly higher than that of the normal weight dormitory, and the smoking of students in the dormitory would cause an increase in indoor PM2.5 concentration; For indoor CO2 concentrations of more than 2000ppm in dormitories that are sealed all night, reasonable window ventilation is required to effectively reduce the concentration of gas pollutants; According to the questionnaire survey, it is known that students do not use doors and windows for ventilation, so that indoor air does not circulate, causing students to have drowsiness, lack of concentration, chest tightness and other symptoms. The results of the study provide a reference for improving air quality and ventilation strategies in university dormitories.
Tunnel fire smoke control is an important issue in the area of tunnel fire safety. Inspired by fire compartmentation in buildings, it is worth investigating whether a tunnel can be partitioned by a water mist system into a fire zone and safety zones. If so, people can move from the fire zone into a safe zone through the water mist system. Obviously, an essential question is to examine to what extent the fire-induced heat and smoke can be blocked by the water mist system. Thus, in present paper, CFD simulations were conducted to investigated the effectiveness of water mist systems on blocking fire-induced heat and smoke in a full-scale tunnel. We mainly focus on the impact of nozzle combination on smoke blocking effect. Simulation results show that the entrainment caused by the water mist system plays the main role on blocking fire-induced smoke, and the nozzle combination has small impact on heat blocking effect. Based on the momentum balance of the water mist system and ceiling jet smoke flow, a correlation of total water flow rate of the water mist system and fire heat release rate was proposed.
In order to protect the living environment and effectively control the harmful gas composition in the basement of civil air defense in wartime, this paper studies the pollutants of a civil air defense basement project in Jinan by CFD numerical simulation technology, and simulates the CO2 concentration distribution under three different air distribution forms in civil air defense. The results show that when the second-class shelter reaches the high-density population environment, the air conditions under the distribution form of side air supply and upper air return of the building meet the living conditions of the shelter personnel. The average CO2 concentration is 7200 ppm, but the central area forms a pollutant concentration area with an area of about 14.3%, and the highest concentration is 17000 ppm, which affects the physiological function of the shelter personnel. The CO2 concentration distribution simulated by the air distribution modes of upper air supply, side air return and upper air supply, lower air return is more uniform, and the average pollutant concentration is 6000 ppm and 5500 ppm. The air distribution effect of upper air supply and lower air return is the best, where the CO2 concentration is 23.6% lower than that of side air supply and upper air return scheme and 8.3% lower than that of upper air supply, side air return outlet scheme. The CO2 concentration distribution is uniform and there is no pollutant aggregation point. Under the special conditions of wartime, the air distribution of upper air supply and lower air return with uniform air outlet layout is more conducive to pollutant control.
The influences of the slope composition on both sides of the variable slope point and the opening numbers of the exhaust vent on the smoke diffusion and the smoke and heat exhaust efficiency in V-shaped tunnel were investigated by the numerical method. The results showed that for the asymmetric V-shaped tunnel, increasing the number of exhaust vents on the large slope side can improve the smoke and heat exhaust efficiency, but control the smoke in a smaller rang is relatively difficult. The corresponding smoke exhaust vent opening strategy should be drawn up in accordance with the composition of the slope of the V-shaped tunnel and the goal of the smoke control system in practice.
Building airflow characteristics can affect the indoor air environment, thereby affecting indoor air quality and building energy consumption. In recent years, the sunken square has increasingly designed and applied to underground transportation hub systems, because of their special advantages, such as improving the ventilation and lighting of the underground space, blurring the feeling of the ground and underground and improving the quality of the space. However, at present, there are few systematic and comprehensive researches on the airflow characteristics of the sunken squares to the underground metro station. In this study, the wind tunnel modeling experiment and the particle image velocity (PIV) technology are comprehensively used to study the influence of the sunken square on the airflow characteristics of the underground metro station, the influence of the sunken square on the flow field distribution and air exchange rate of underground metro station are obtained. The dimensionless average wind velocity at the large openings of the sunken square is 0.053-0.18, and the air exchange rate of the underground metro station is changed with the number and the relative positions of sunken squares. Conclusions of this research could provide useful reference to the design of airflow characteristics for underground buildings.
To evaluate the performance of RANS turbulence models, this study compares four different cavity flow benchmarks using the prevailing two-equation turbulence models for indoor airflows, namely the standard and RNG k-ε and the standard and SST k-ω models. A cavity flow consists of one air inlet and one outlet slot. The inlet slot is positioned on the upper left corner of the cavity, whereas the outlet slot is located in the lower right. This cavity flow is representative of mixing ventilation. These four cavity benchmarks differ by their geometry (i.e., the aspect ratio of the room), flow regime and whether the flow is isothermal or not. Measurements of the air velocity and temperature in these benchmarks are used to evaluate the accuracy of the RANS turbulence models. Many existing studies have investigated the airflow and heat transfer over these benchmarks. However, the numerical methods and other relevant CFD parameters are not always described in detail, reducing the transparency and reproducibility of these works. To compare the influence of the RANS turbulence model on the four cavity flows, a same CFD setup is adopted here for all benchmarks. This setup is based on the best practice in RANS, namely a steady second-order spatial discretization on a wall-resolved structured mesh and with a grid convergence analysis. The results show that k-ε models, particularly the standard k-ε model, are best suited in a fully turbulent flow regime without strong pressure gradients. On the opposite, the SST k-ω model performs best in the transitional regime while the k-ε models only give moderate to poor results.
Oil particles generated from metalworking fluids(MWFs) in machining process can lead serious health problem to operator. Local exhaust hood is an effective engineering method to capture oil particles and other contamination which is wildly used in manufacture workshop. In this paper, exhaust hood capture efficiency with various height, air volume and particle size was gotten by Computational Fluid Dynamic(CFD) technology. Though further analysis of the CFD result, feature air velocity was introduced. Then an equation of feature velocity and capture efficiency was established by multi regression method. According to this equation one improvement solution was studied: Set to flexible enclosure for up exhaust hood. The solution raised particle capture efficiency on each size significant, the result is equivalent to low down up exhaust hood for 60cm.
Accurate acquisition of real-time aerosol distribution indoors is crucial to both estimating real-time infection risk of indoor respiratory infectious diseases as well as rapidly optimizing the ventilation effectiveness of building structure during the design stage. Real-time prediction of aerosol distribution can hardly be achieved by CFD model due to its iterative solution strategy, while the Markov chain model can greatly reduce computing time by implementing the non-iterative state transfer process. In this study, a real-time visualization algorithm for aerosol dispersion in limited space is developed based on the Markov chain principle and pre-solved flow field. Then the reliability of the proposed algorithm is verified by experimental data. An interactive user interface is further constructed based on the validated algorithm to realize real-time simulation of the dynamic release process of multiple indoor pollution sources. Results show that the simulation outcomes agree well with the experimental validation data, and the dynamic real-time distribution of aerosols can be well visualized for steady-state airflow. The present study aims to provide a new effective prediction method for real-time visualization of indoor pollutant dispersion and rapid evaluation of the impacts of building structure on ventilation effectiveness.
The global pandemic of coronavirus disease 2019 (COVID-19) has posed a serious threat to human society on both perspectives of health and economy. Ultraviolet (UV) has been verified capable to damage the DNA and RNA of various microorganisms, including the new coronavirus. The parabolic reflector, a key component of the upper-room ultraviolet germicidal irradiation (UVGI) device, plays a vital role in collating and restraining ultraviolet light. In order to deeply understand the influence of the reflector in the device on the spatial distribution and numerical value of the ultraviolet radiation intensity, we measured and simulated the efficacy of the reflector equipped with a single-tube UV lamp. At a distance of 50cm from the reflector, a virtual plane with a side length of 40cm×40cm parallel to the exit port was introduced. At room temperature of 20 °C, measured and simulated reflectors were carried out at three heights A, B, and C, which were 25 cm, 20 cm, and 15 cm. We have concluded that as the height of the reflector increases, the irradiance value in the space also increases; then decreasing the height of the reflector is more conducive to the uniform distribution of the irradiance in the space. In conclusion, exploring the appropriate reflector height to obtain the balance of UV intensity and distribution is meaningful for improving the efficiency of the upper layer device
Semi-transparent photovoltaic double skin façade (STPV-DSF) is a novel structure which integrates photoelectric, photothermal, ventilation and energy-saving features, which proves to be extremely attractive and promising. In this study, a full-scale experimental system was built, airflow and heat transfer in a rectangular cavity with different transmittance (τ) and different ventilation modes in summer that studies a STPV-DSF and includes natural ventilation were examined experimentally. The Rayleigh number and Nusselt number of STPV-DSF is significantly higher than that of traditional DSF. This also means stronger intense flow. And the maximum temperature difference at night between mode 1 and mode 2 can reach 7.3°C. When the external air circulation mode is switched to the external and internal mode, the indoor temperature drops by 2.88°C in ten minutes. Therefore, making fully use of natural ventilation can effectively reduce the cooling load of air conditioning in summer. The solar radiation intensity is proved to have the greatest influence on the cavity temperature, followed by the transmittance, and the the ventilation mode least influence. Applying naturally ventilated STPV-DSF would be a new efficient way for the curtain wall buildings to meet the task of sustainable building design.
The performances of ventilation in the buildings with quadrate and cylindrical cross-sections are compared numerically. The incoming jet in the cylindrical unsheltered-building is more horizontal in comparison to the quadrate unsheltered-building. The dimensionless volume flow rates in the quadrate and cylindrical unsheltered-buildings are respectively 0.503 and 0.553. The incoming jet in the sheltered-buildings flows to the floors immediately. The velocity near the floor in the cylindrical sheltered-building is greater than that in the quadrate sheltered-building. The dimensionless volume flow rates in the quadrate and cylindrical sheltered-buildings are respectively 0.130 and 0.210.Comparing with the quadrate buildings, the ventilation rates in the cylindrical unsheltered and sheltered buildings increased by 10% and 61%.
To explore the coupling effect of open space temperature and air velocity in hot-arid and hot-humid climate regions in rural China, 1690 valid data were obtained by long-term field tests and questionnaires were carried out in hot-arid and hot-humid regions. Results indicated that when the operative temperature is below 33.5 °C, the mean thermal sensation decreases with the increase of air velocity in the hot-humid region. When the operative temperature rose to greater than 33.5 °C, the mean thermal sensation could be significantly reduced only when the air velocity is over 1.0 m/s. However, increasing air velocity in hot-arid regions can significantly improve the thermal sensation. In addition, residents in hot-humid regions were more willing to increase airflow than those in hot-arid regions. These results support the theory of climate adaptation and can provide a reference for the design of semi-open space buildings in rural regions.
The combined radiant floor and fan coil cooling (RFCAFC) system is widely used due to its high comfort and large energy saving potential. In this study, as an example, the combined RFCAFC system was studied in a high humidity environment in Jinan, Shandong Province, China. Days with similar outdoor meteorological conditions were grouped, and the comfort level and other evaluation indicators. The RFCAFC had good energy efficiency and comfort when the room was in a high humidity environment. This study showed that the radiant floor surface temperature uniformity coefficient (S) fluctuated between 0.7 and 1.0. The proportion of the total cooling capacity contributed by fan coil cooling under low temperature and high humidity (LH) is 68.0%. The combined cooling system used the LH operating strategy, the PMV value fluctuated from 0.12 to 0.49. Based on this study, the following recommendations for the combined cooling system can be made: (1) When the outdoor humidity is high, the radiant floor system should be turned on early to provide cooling capacity. (2) The operation strategy of the combined cooling system must be able to respond in real time to changes in outdoor meteorological conditions to prevent discomfort in times of extreme heat or humidity.
A vital question of how citizens expect to use the built environment is not fully addressed. This study aims to contribute to this question from the indoor and outdoor usage expectation. The potential influencing factors are examined via survey along with the meteorological data obtained from weather bureau. This study provides that the current location and the duration of indoor-stay serve as the influencing factors of the indoor and outdoor usage expectation. The indoor and outdoor usage expectation has an obvious influence on the thermal sensitivity of thermal environment. People who expect to use the outdoor environment showed the least thermal sensitivity, 42.3% weaker than those who do not expect to use. These findings help providing further understanding of the citizens’ thermal expectation and their thermal responses during the post-pandemic period.
For clear residential indoor pollutant concentration under different ventilation modes and contaminant distribution, to explore the emission efficiency of different ventilation way, choose suitable way of ventilation, different season in Shenyang, this article selects some typical residence as the research object, interior decoration materials commonly used as indoor pollutant source, based on CFD fluid mechanics principle, Airpak3.0.16 software was used to simulate indoor air flow field and indoor concentration distribution field of formaldehyde, benzene and VOC, and to compare and analyse indoor pollutant distribution law, air age and pollutant discharge efficiency under natural ventilation and mechanical ventilation in winter and summer. The results show that ventilation can effectively discharge most of indoor pollutants. 69% of indoor pollutants can be discharged by natural ventilation in summer, 46% of indoor pollutants can be discharged by natural ventilation in winter, 57% of indoor pollutants can be discharged by mechanical ventilation in summer, and 51% of indoor pollutants can be discharged by mechanical ventilation in winter. Under the condition of the same ventilation volume in the same season, natural ventilation has the best effect in summer, and considering that the energy consumption of mechanical ventilation is much higher than that of natural ventilation, natural ventilation is recommended in summer. The effect of mechanical ventilation is better in winter, and because Shenyang is not suitable to open Windows for ventilation for a long time in winter, mechanical ventilation should be used in winter.
Infectious respiratory diseases are known to have high levels of airborne transmissibility. However, traditional ventilation methods based on perfect mixing often lead to the diffusion of airborne pathogens. Multi-vent module-based adaptive ventilation (MAV) is a ventilation method designed to meet the needs of different indoor scenes and reduce air mixing. MAV combines multiple groups of multi-vent modules. The vent spacing of a single module is also an important factor, but the influence of the change of vent spacing on the effect of MAV in contaminant diffusion control has not been studied. Computational Fluid Dynamics (CFD) is applied to study the influence of air vent spacing of a single MAV module on contaminant diffusion control in a simple office. Three different vent spacing of 1.5m, 2.0m and 2.5m and four vent layout modes is selected. The results show that when the vent distance is 2.0m, the MAV system has the best control effect on contaminant diffusion. Up to 61.5% of the contaminants are limited in the control area.
The long-term evolution characteristics of the heat reservoir of soil have been analyzed by 15 years of simulation test with periodic indoor and outdoor air temperature conditions. A scale model test of the soil in the subway station sidewalls and software ANSYS fluid-structure coupling heat transfer model are built in this study, which are complementary and mutual authentication. In 1∼15 years, the results show that the maximal temperature rise of soil at 2 m buried depth is 3.9 °C, at 7 m buried depth is 1.6 °C, and at 12 m buried depth is 1.5 °C. On the sidewalls surface the average maximal endothermic heat flow density is 6.8 W/m ² in summer, and the average maximum exothermic heat flow density is 11.3 W/m ² in winter. It provides theoretical reference for the reasonable use of heat storage of the soil in the sidewalls of subway stations.
The farthest distance for aerosol diffusion in the Y direction
Boundary conditions in simulations of droplet dispersion (discrete phase).
The airport terminal with high numbers of occupied passengers has potentially become high risk region for aerosol transmission of COVID-19. In this paper, the Eulerian-Lagrangian approach and realizable k–ε turbulence model is used to numerically simulate the airflow organization and aerosol transmission when passengers move slowly in a line. During the aerosol transmission period, evaporation is also enrolled as it is a key factor influencing particle size distribution at the beginning of aerosol transmission from the human. In addition, the process of passenger moving in the airport terminal is realized by employing dynamic mesh algorithms. The results of the study show that people who are behind the infected person during the queuing movement have a higher risk of infection than those who are in front. In addition, the disturbance of people walking has an important influence on the distribution of aerosols.
Relative errors (RE) in temperature and flow velocity, both from CFD and CFD-EnKF.
Variation intervals of main parameters in different experimental conditions.
Accurately mastering the distribution of multi-physical field is an important prerequisite for rationally formulating building environment construction scheme. In practical engineering projects, sensor monitoring can obtain more accurate environmental state parameter values. However, due to the constraints of investment cost, spatial limitations and other factors, the number of on-site measured monitoring points is limited. On the contrary, CFD simulation can obtain global distribution information of the physical field, but the uncertainty of parameters such as boundary conditions seriously affects the reliability of simulation results. In view of the above problems, based on Ensemble Kalman Filter (EnKF), which is a sequential data assimilation algorithm, a technical framework for accurate indoor multiphysics simulation is established. We evaluated the performance of this method with reduced-scale model experiments, verifying that the simulation errors can be significantly reduced. The proposed method has a positive impetus for realizing the global monitoring of the physical field of the building space.
Heat exchange range of typical exposed parts(W/m²)
In this paper, the radiation heat exchange coefficient of the exposed parts of human body is firstly obtained through pre-experiment, which is used to separate the total output heat exchange amount of the manikin. Then the heat exchange amount of manikin under different airflow organizations of personal ventilation, mixed ventilation and seat ventilation are respectively studied. The value of convection heat exchange and radiation heat exchange of the face and head of human body are compared. And variable conditions are studied for different air temperatures and volumes. It is concluded that when the supply air temperature changes between 22? and 30°C with human body thermally comfortable, the total heat exchange of the face and head changes from 38 W/m ² to 137 W/m ² , and the range of the radiation heat exchange amount is 26 W/m ² to 67 W/m ² . The convection heat exchange amount changes between 6 W/m ² and 110 W/m ² , and the ratio of radiation heat exchange to convection heat exchange changes from 0.5 to 6.7.
The lay chamber.
Many factors such as human movement can weaken indoor temperature stratification and lead to the advantages of the displacement ventilation (DV) disappearing. Yet the investigation for the stratified destructive time during the human movement and the recovery time after human movement stops are still meagre so far. The concepts of dynamic steady-state and static steady-state are proposed to compute the stratified destructive time( T b ). The isothermal surface of 295K is engaged to explain the variation of T b . At last, the stratified restoring time( T c ) after human movement stops are inquiries in our paper. The conclusion is as follows: Firstly, the value of T b reaches a maximum value at the moving velocity of 1m/s, since the isothermal surface of 295K starts to be broken when the moving human velocity reaches 1.0m/s. However, the values of T b remains about 50s for the human moving velocities between 2.4m/s to 4.0m/s. The reason is that the temperature stratification are disappear completely when the human moving velocity exceeds 2.4m/s. Finally, The Tc keeps in the 250s when the human moving velocity is between 1.2m/s to 2.0m/s. The current study provides new insights into the design of the DV system.
Parameters used in Equations (1) and (2)
The environmental parameters in those sample sites (average ± sd)
Pearson two-tail correlation analysis between environmental parameters and HI for bioaerosols
The risk assessment of airborne bacteria and fungi between different-type buildings located in temperate climate zone is still unclear. We applied the culturable method to characterize the airborne bacteria and fungi in 10 residences, 1 school, 2 office buildings, 1 hospital, and 1 library during winter in Kunming, China. In a total of 79 rooms, 152 culturable microbial samples were investigated. Results showed that there were significant disparities in bacterial concentrations among various types of buildings. The highest culturable bacterial concentration was found in residences, while the lowest was in the library. In contrast, the fungal concentrations showed little difference. The risk assessment indicated that occupants in different types of buildings in Kunming had an acceptable exposure risk (hazard index < 1) for bioaerosols. The exposure risk for bacteria in residence was significantly higher than in the others, while the mean hazard index of fungi in residence was significantly higher than in schools, hospitals, and libraries. Ventilation could reduce the HI of bioaerosols in rooms. This study is helpful to give practical implications for assessing microbial characteristics in different types of buildings and highlight the significance of evaluating the microbial concentrations in residence in temperate climate zone in China.
Conditions for the model room.
Low energy consumption buildings with strong air tightness such as passive buildings are the development trend in the world. However, ventilation directly affects the emission and dynamic transport of indoor phthalates. A transient partition model considering the dynamic behavior of size-resolved particle was utilized to investigate the influence of ventilation on the airborne Di-2-ethylhexyl phthalate (DEHP). The air exchange rate ( a ) was set to 0.15 h ⁻¹ , 0.3 h ⁻¹ , 0.6 h ⁻¹ , 2h ⁻¹ for the different conditions. The predicted gas-phase concentration of DEHP in the initial 70 days is unaffected for different a and constant h ms , whereas it raises until the a increases to 2 h ⁻¹ . The equilibrium gas-phase concentration decreases from 0.257 to 0.203 μg/m ³ . Meanwhile, the higher a also reduced the particle-phase concentration of DEHP. Furthermore, the changes of airborne DEHP were analyzed by considering the impact of a on h ms caused by ventilation. The results indicates that more ventilation leads to higher gas-phase concentration for the whole stage. The gas-phase concentration at equilibrium increases from 0.237 to 0.440 μg/m ³ . The total airborne (gas-phase + particle-phase) concentration decreases with the higher ventitation rate, which indicates that the ventitation has a positive effect on indoor airborne DEHP.
Schematic of the greenhouses.
illustrates airborne fungal concentrations in the three greenhouses. The airborne fungal concentration in GS greenhouse before ventilation (CBV-S) was 24187.3 CFU/m 3 . After 40 minutes of ventilation, fungal concentration (CV-S) decreased to 12517.7 CFU/m 3 . The reduction ratio was 48.2%. The outdoor fungal concentration (CO-S) was 2221.7 CFU/m 3 , which was highly lower than indoor fungal concentrations. In GF greenhouse, CBV-F, CV-F and CO-F were 2609.5 CFU/m 3 , 3037.1 CFU/m 3 , 911.7 CFU/m 3 , respectively. The indoor concentration after 40 min of ventilation was slightly larger than it before ventilation. In GH greenhouse, it was 32756.2 CFU/m 3 , 12395.8 CFU/m 3 and 3257.9 CFU/m 3 of CBV-H, CV-H and CO-H. The reduction ratio of ventilation was 62.2%.
Taxonomic composition of airborne fungal genus in the three greenhouses.
Indoor and outdoor temperature and relative humidity in greenhouses during sampling time.
With the rapid development of greenhouses, the indoor air quality, particularly airborne microorganisms, is closely related to the health of farmers and needs more attention. In this study, the concentrations of airborne fungi at seedling, fruiting and harvesting stages in typical tomatoes greenhouses were tested. Temperature, relative humidity and the microbial concentrations were analysed. It was found that the dominant fungal genera are Aspergillus and Cladosporium , no matter it was in which growth stage. Ventilation is an effective way to reduce the concentrations of airborne fungi through dilution and decrease the relative humidity.
Plenum supply conditions of interest in this study. The top Figure shows the single-sided supply conditions and in addition it shows measurement points.
Measurement points for temperature and air speed room conditions.
Local mean air temperature measured at different heights and locations in the room.
Implementation of diffuse ceiling ventilation (DCV) is slowly gaining momentum and applications in building ventilation have taken off with countries like Denmark, Finland and Netherlands taking the lead in Europe. However, DCV is yet to gain a foothold in Sweden and so not many installations are known, and their performance in relation to Swedish building practice is not yet established. A school in southern Sweden was subsequently renovated and two classrooms were equipped with a sound-absorbent suspended ceiling compatible with DCV. DCV has possible benefits for educational environments including improved thermal comfort as well as lower costs and noise levels. However, it is currently still unknown how supply conditions in the plenum affect the diffusion of air and resulting conditions within the room. To assess airflow characteristics and whether these influence flow conditions in the classroom, we investigated and compared the performance of DCV with two different supply conditions in the plenum. Air speeds and temperature distribution measurements in the plenum and classroom were performed with constant temperature anemometers and thermocouples respectively. The general observation from this study and the system setup herein is that airflow and temperature characteristics in the classroom were independent of the airflow conditions in the plenum. Further investigations in a controlled climate chamber are recommended to investigate and optimise system performance in accordance with Swedish building practice.
In the future, the number of electric vehicles will increase significantly, promoting the integration of renewable energy into buildings and electric vehicles, which helps to achieve energy greening in transportation and architectural fields. The system includes renewable energy, buildings, electric vehicles, and energy storage systems. In this paper, the mathematical model of each system is established, and the electricity consumption of the building and the power generation of PV panels are predicted by the Energyplus software, and the economic evaluation index is proposed. In addition, the research analyses the effect of electric vehicles as electrical vectors in integrated PV panels and storage. The small solar residential data shows that through building-to-vehicle and vehicle-to-building solutions, on-site renewable energy utilization can be achieved, which is also conducive to building a zero-energyconsumption home.
Design improvement strategies (before & after)
Indoor ventilation of different elevations.
Airport control hall is the key organization of air traffic control system, mainly used to manage various flight activities of the airport. The control hall contains numerous control seats and control personnel. It is particularly important to create a comfortable indoor environment for the control personnel in a high-intensity working environment. But due to the current design code and standard lack for airport control hall and affiliated offices of the requirements of the physical environment, designers often excessive attention to functional requirements in the design and the facade, while ignoring the control hall indoor environment requirement, so the chaos such as plane layout, facade window problems such as unreasonable, As a result, natural ventilation is not smooth, air conditioning energy consumption increases, and indoor comfort is seriously affected.Sining AIR traffic control Support Building is one of the three major air traffic control projects in northwest China during the 13th Five-Year Plan period. In the preliminary design process of the scheme, the design team used Butterfly tool based on Grasshopper software to conduct computer simulation analysis on the natural ventilation condition of the scheme, comb out the optimization design method and conduct comparative verification. Improve indoor comfort, reduce building energy consumption, and finally summarize the air traffic control hall design strategy adapted to Sining’s unique natural environment, which provides reference for other air traffic control support building projects in northwest China.
Urban road tunnels with shafts have been applied in some cities in China. Field measurements of Mofan Road Tunnel show that ambient wind is widespread and its influence on the ventilation efficiency of shaft is unclear. In this paper, the physical model of a three-lane 210 m (length) *12 m (width) *6 m (height) tunnel is studied, with three vehicles in each lane and a speed of 60 km/h. Three-dimensional CFD simulations on a 210 m long tunnel with double shafts is carried out by Fluent 6.3.26. Momentum equation and k-ε equation turbulence model are used for simulation analysis and dynamic grid technology is used to simulate vehicles driving. It is found that the ambient wind in tunnel has great influence on the flow field in tunnel and shaft. Number Ri is defined as the ratio of horizontal inertia force to vertical inertia force, revealing the conversion of horizontal inertia force to vertical inertia force.
Adsorption isotherms
Deviations between predicated value and experimental data
People spend most of their time indoors. The volatile organic compounds (VOCs) in indoor air represented by toluene inevitably affect people's health. Activated carbon can effectively reduce indoor VOCs pollution. The experiments in the previous studies were carried out at the concentration of tens or hundreds of ppm, which could not reflect the actual adsorption performance of activated carbon in the actual conditions. In this study, a method was proposed to predict breakthrough curve of toluene at ~1 ppm. The method was based on Wheeler-Jonas model, the equilibrium adsorption capacity was predicted by the Freundlich equation, and the adsorption rate constant was obtained by Yoon-Nelson equation. The predicted breakthrough curves were in good agreement with the experimental data in the range of 0.5~4.0 ppm. The adsorption rate constant was predicted using the relationship with inlet concentration of toluene. When the breakout fraction was 20-85%, the relative deviation was 5.54% and 4.08% at 0.5 and 1.0 ppm. This method can predict the adsorption performance and service life of activated carbon for toluene at ppb~ppm level.
Pictures of two office buildings: (a) Technology Building; (b) Administration Building.
Microbial reproduction in air conditioning (AC) systems has caused increasing concern. When subject to airflow, microbes can be separated from substrates and spread into indoor air. This study investigated release of bacterial aerosols from AC systems with different service times in office buildings. Microbial aerosols were collected onto sterilized polycarbonate membranes using an air sampler. The concentration of total bacterial DNA was determined by 16S qPCR targeting universal bacterial genes. The most abundant genus was Lactobacillus before turning on the AC system. After turning on the AC system, the abundant genera were Pseudomonas and Agrobacterium with the service time of three and 12 years. When the AC system was put into use in the early stage, the microbial concentration after turning on the AC system was lower than that before turning on the AC system. However, after a long use of the AC system, the microbial concentration after turning on the AC system (7.50 × 103 copies/m ³ ) was higher than that before turning on the AC system (3.77 × 103 copies/m ³ ). The results show that the service time of AC system influences the community structure and content of indoor bacterial aerosols.
Response design matrix.
Tunnel widely exists in highway, subway and other underground buildings. Due to the structural limitations, the direction of evacuation is consistent with the main flow direction of smoke in the tunnel. For the design of smoke exhaust system, traditional methods aim at reducing the overall smoke concentration in the whole tunnel. However, when fire hazard occurs, rapid personnel escape requires higher visibility. In this paper, a novel air supply device designed for smoke-insulation passageway establishment and ventilation in tunnel fire is introduced. Wall-attached jet and orifice plate jet are combined in this device, which enables passageway to isolate smoke intrusion. In this study, an approach has been devised combining Response Surface Method (RSM) with numerical simulations as well as visualization experiment to get better performance of the device. Parametric optimization was conducted for the three influencing variables, i.e., the air supply volume, opening rate of orifice plate, and width of wall-attached jet. Analysis of variance (ANOVA) indicates that all the three factors are significant. Moreover, the optimal combination can be obtained within the admissible range of the three factors through response optimization. A regression equation is developed to predict the effect of the novel air supply device for any input values of the three influencing variables.
Boundary conditions for CFD simulations.
The tiny spaces of sentry boxes in cities, such as mobile security guards, highway toll booths, etc., are mostly located beside roads with harsh outdoor environments. Due to office demands, work windows often need to be kept or frequently opened. The intrusion of outdoor pollutants through the windows leads to the deterioration of the indoor air quality, and threatens the health of employees. This paper takes the gaseous pollutant NO 2 as the representative and discusses the effective ventilation design scheme for improving the air quality in the sentry box with openings using two attached ventilation modes as the carrier. Taking the vertical wall-attached ventilation as an example, the formation of the air curtain at the window hole and its barrier performance to outdoor pollutants were studied. The conclusion is that when the air supply velocity is sufficient to form a complete air curtain at the window hole, it can effectively block the pollutants. The horizontal wall-attached ventilation shows that clean air is delivered to the space with openings, and the indoor air quality can also be well improved due to the dilution effect, but the effect of positive pressure control is not obvious due to the large opening. The conclusions can provide guidance for the ventilation design of sentry boxes with openings.
The variation law of UTCI with time
In order to improve the human thermal comfort of the ecological community, aiming at the characteristics of low humidity and large wind and sand in northwest areas such as Lanzhou, the method was proposed to improve the human thermal comfort by water evaporation from porous pavement. Firstly, the outdoor environmental model of the ecological community was established and the environmental parameters of a community are simulated by using the model in Lanzhou. The simulation results are compared with the experimental results, and the relative error is less than 15%. Secondly, the change law of outdoor thermal and humid environment is simulated and analysed when porous pavement and ordinary pavement are used in ecological community, respectively. The results show that the humid environment of the community has changed significantly and the maximum change is about 7% after considering the water evaporation from porous pavement. Meanwhile, the amount of single water sprayed onto the porous pavement should meet the water evaporation requirement of 1.67h under the climatic conditions at that time. The above research results provide theoretical guidance for improving the outdoor thermal comfort of residential buildings in dry region.
Reported fire incidences in ORRA for schools in Oslo by place of origin, 2012-2021.
Cause of fire for all educational buildings in Norway, between 2000-2021. N=1608. Source: BRIS.
The situation at arrival, fire statistics of all educational buildings between 2000-2021. N=1608. Source: BRIS.
Annual costs of school fires for Oslo (excluding the cost of school 22 in 2017) and according to the database BRASK (all educational buildings).
Overview of the fire incidents in Oslo schools and related costs (including 300k NOK deductibles for the municipality), from the insurance company. *Indicates that the ventilation system is not connected to the fire alarm system.
School fires are causes of concern in many countries. Although most of these fires are minor in terms of heat release rate, the amount of smoke produced can be substantial and cause significant damage beyond the room of origin. Currently, Norwegian schools have a wide spread of different ventilation strategies and systems, and building owners struggle with how to test, maintain and keep them fire safe. A systematic survey of fire incidences and ventilation strategies in schools for three municipalities in Norway was done to gain better insights into fire safety in schools. The results indicated that the place of origin is often in locker rooms/toilets, kitchen, or outdoors, and the fires were usually deliberately set. For non-arson fires, electrical failure was the most common cause. The majority of the fire incidences were small but would often result in smoke damage and spread of soot in the building, leading to high restoration costs for the local municipality. A lack of documentation of the fire safety and the function of the ventilation system was also identified, indicating a need for improved routines and systems for registering fire incidences and documentation of the technical systems.
Average cumulative exposure levels with and without human walking.
Summary of cumulative exposure levels under different temperature levels.
Summary of the average range scale and time scale robustness values under different ventilation systems (18 °C, 23 °C and 28 °C).
Ventilation system’s effectiveness can be affected by walking-induced disturbances. A series of experiments were performed in a chamber in this study (6.0 m × 5.9 m × 2.5 m) to measure the walking-induced temperature/flow/pollution field fluctuation characteristics. A method for quantifying the robustness of a ventilation system in the control of walking-induced fluctuations was used in this study. The experimental results showed that the cumulative particle exposure levels under walking modes W1, W2 and W3 were 2.04 ± 0.27, 1.72 ± 0.26 and 0.87 ± 0.12 times the exposure levels without human walking. The four ventilation systems all performed well in indoor temperature disturbance control; however, different walking modes and ventilation systems would result in different walking-induced disturbances of the flow and pollutant fields. For the flow field, the highest range scale robustness value was achieved by the side supply and side return (SS) system. For the pollutant field, the range scale robustness value of the SS system was still the highest, 18.7% larger than the lowest value. With the increase in temperature from 18 °C to 28 °C , the range and time scale robustness of the different ventilation systems decreased by 7.7–18.4% and 1.3–15.7%, respectively.
Formaldehyde is one of the main indoor pollutants, and living in an environment with formaldehyde for a long time can cause serious damage to the human body. In this paper, non-woven fabrics and new reduced graphene oxide air filter materials were used to perform static adsorption tests on formaldehyde volatilized from glue. The results show that the new reduced graphene oxide air filter material has good formaldehyde adsorption performance, and the adsorption saturation of this material is as long as 4 hours, which is twice that of F6 non-woven fabric. Within 4 hours, the formaldehyde removal efficiency of the new reduced graphene oxide air filter material and F6 non-woven fabric were 15.4% and 2.9%, respectively, and the formaldehyde adsorption was 0.81·10 ⁻³ mg and 4.32·10 ⁻³ mg, respectively, and the removal efficiency was improved5.9 times. This paper provides reference and reference value for the adsorption performance of new composite air filter materials on harmful gas pollutants.
The residential natural ventilation rates have a significant impact on indoor thermal comfort and air quality and building energy consumption. The characteristics of the indoor-outdoor temperature difference and wind pressure change over time, as well as the occupants' window opening behavior and the use of HVAC systems, resulting in the residential air change rate being dynamic with time. Many previous studies of residential ventilation measured the steady-state air change rates, which does not reflect the actual dynamic characteristics. In this study, a field measurement was conducted in a bedroom of one natural ventilation residential building in Beijing with continuously monitoring the CO 2 concentration, indoor air temperature, and outdoor meteorological parameters for one year. Using the CO 2 released by occupants as a tracer gas, the extended Kalman filter based on the Transient Mass Balance Equation (TMBE) was adopted to calculate the dynamic air change rate. This method can effectively filter the CO 2 concentration measurement noise. The trend of air change rate with each influencing factor was analyzed. This study is expected to lay the foundation for future studies of dynamic air change rates in residential buildings.
presents the measured temperature distribution at A, B positions and shaft for the traditional and new NV systems with the surrounding temperature at around 21.5 ℃ in the experiments. It should be noted that the temperature data over 0.8 m height in New-B & shaft are the temperature distribution in the shaft. shows that the temperatures are very close at the bottom for the two NV systems, which means that the new NV system can maintain the temperature of the occupied space as low as the traditional NV system. For example, the temperature differences between two NV systems are 1.1℃ and 0.5 ℃ at the bottom of A and B positions. To further investigate the ventilation performance of two NV systems, Fig. 4 presents the measured mass flow rate and calculated heat transfer by ventilation. It was found that compared with the traditional NV system, the mass flow rate and the heat removed by ventilation in the new NV system increase 22% and 21% respectively. These results that the new NV system can better utilize the buoyancy force and ventilation to remove heat. However, it can be found that the temperature near the segmentation slab in the new NV system is clearly higher than the temperature at the same height in the traditional NV system. This difference may be caused by the heat transfer through the wall and airflow pattern, which requires further investigation in future.
Measured mass flow rates and calculated heat transfer by ventilation in the experiments.
Smoke layer height at A and B positions in (a) traditional design and (b) new design.
Natural ventilation (NV) is an effective energy-saving strategy to remove the excessive heat in high-rise atria. The traditional NV system in high-rise atria has inlet openings at the bottom and outlet openings at the top. However, this traditional system may bring fire safety concerns due to the rapid spread of smoke during an atrium fire. To remove the fire safety concern, a new NV system was proposed in this study. This new system applies a segmentation slab to divide the high-rise atrium into upper and lower parts, which can limit the smoke movement. A ventilation shaft is installed to maintain the NV rate and extract smoke. To investigate the energy and smoke control performance of the new and traditional NV systems, a 1:20 small-scale experimental model and CFD numerical model were built. The results indicate that the new NV system with the shaft and segmentation can remove more heat than the traditional NV system. Furthermore, the new NV system can simplify the mechanical smoke exhaust system and improve the smoke control performance, e.g., requires a lower volumetric flow rate and maintains a thinner smoke layer.
Indoor occupants' distribution scenarios are in a dynamic change randomly. Moreover, in many occasions with fixed seats, people in areas where cold air blows directly have a poor thermal experience. Therefore, to meet the differentiated environmental demands, novel ventilation strategies to satisfy the changing environmental requirements needs to be explored. In this study, a multi-vent module-based adaptive ventilation (MAV) system with a multi-vent dynamic ventilation module as a core is proposed to increase the adjustability of air distribution and better adapt to variable demands. MAV has three control characteristics of zoning division, completion of the inlets and outlets conversion, and the use of dynamic airflow adjustment. Simulations are conducted based on a typical multifunctional classroom with four common scenarios. The performance of MAV and MV under different scenarios is compared by considering airflow pattern, SVE4, PMV and DR. The results reveal: this ventilation module can effectively realize the zoning division control. MAV can create a more comfortable thermal environment when compared with MV. Various vents schemes realized by the function of the reversing device create different airflow patterns and thermal environments, which can be matched to diverse indoor scenarios. When the indoor scenario changes, the local uncomfortable state can be improved by switching the device to change the vents schemes. In order to deeply adjust thermal discomfort caused by the airflow pattern of downwards under the multi-vents air supply, it is reasonable to introduce dynamic airflow in MAV to improve the draught comfort. This ventilation strategy might be expected as a promising air terminal system that provide flexibility and adaptability for real applications.
While the multi-point access to urban underground roads solve traffic congestion, the pollutants (CO, NOx, etc.) emitted during tunnel travel also pose environmental and health risks to the tunnel drivers and passengers as well as the residents near the tunnel openings. To this end, this study focuses on the environmental safety of urban underground roads with multiple points of entry and exit as the focus of research, based on the law of conservation of mass, fluid dynamics and ventilation engineering theory and simulation of experimental research methods, combined with motor traffic and pollutant (CO, NOx, etc.) emission characteristics, proposed NO concentration prediction model, combined with the urban underground road air flow and ventilation system operating characteristics, the longitudinal distribution law of pollutant concentration along the tunnel is calculated through case analysis, the intelligent control strategy of the ventilation system is proposed. The results show that when the traffic flow reaches 2000veh·h ⁻¹ , two fans need to be started, and the power consumption is 50% less than that of the whole fan. It is expected to provide a reference basis for the design and efficient low-carbon operation of ventilation system design for urban underground roads with complex structures.
Comparison of air temperature after oil heating within 2 min.
Particle mass concentration in each scenario in kitchen and adjacent room in y=1.5 m.
Boundary conditions for grid sensitivity.
Three scenarios in the simulation.
Kitchen is an important place in Chinese residential building. However, unfavourable thermal environment and unsatisfied air quality occur during cooking. Studies on kitchen environment are experimentally investigated with enough make-up airflow. But mostly normal kitchens are merely installed with a exhaust hood and have not installed air supply system. This work carried out numerical simulation to investigate kitchen indoor environment under natural air make-ups. Air inflow under window fully open, insufficient air inflow from window crack and well-controlled constant inflow volume from window opening are included. Results show that there was a uniform temperature distribution in occupant’s working zone under window open condition. Vertical temperature differences were 4.0 °C under insufficient air make-up. In breathing zone, temperature difference was 6.0 °C and 4.7 °C under uncontrolled and well-controlled airflow, respectively. Mean particle concentration could be largely reduced under controlled and well-organized enough make-up air in kitchen.
Top-cited authors
Sri Rum Giyarsih
  • Universitas Gadjah Mada
Ikhwan Amri
  • Universitas Gadjah Mada
Dmitriy Rudoy
  • Don State Technical University
Elena Pozdeeva
  • Peter the Great St.Petersburg Polytechnic University
Lidiya Ivanovna Evseeva
  • Peter the Great St.Petersburg Polytechnic University