This paper analyzes the applications of four air terminal device（ATD）models（i.e.,the basic model,the box model,the N-point momentum model,the jet main region specification model）in computational fluid dynamics（CF...This paper analyzes the applications of four air terminal device（ATD）models（i.e.,the basic model,the box model,the N-point momentum model,the jet main region specification model）in computational fluid dynamics（CFD）simulation and their performance in case study.A full-scale experiment is performed in an environment chamber,and the measured air velocity and temperature fields are compared with the simulation results by using four ATD models.The velocity and temperature fields are measured by an omni-directional thermo-anemometer system.It demonstrates that the basic model and the box model are not applicable to complicated air terminal devices.At the occupant area,the relative errors between simulated and measured air velocities are less than 20% based on the N-point momentum model and the jet main region specification model.Around the ATD zone,the relative error between the numerical and measured air velocity based on the jet main region specification model is less than 15%.The jet main region specification model is proved to be an applicable approach and a more accurate way to study the airflow pattern around the ATD with complicated geometry.展开更多
The research focuses on the effect of air movement through building constructions. Although the typical air movement inside building constructions is quite small （velocity is of order -10-5 m/s）, this research shows...The research focuses on the effect of air movement through building constructions. Although the typical air movement inside building constructions is quite small （velocity is of order -10-5 m/s）, this research shows the impact on the heat and moisture characteristics. The paper presents a case study on the modeling and simulation of 2D heat and moisture transport with and without air movement for a building construction using a state-of-art multiphysics FEM software tool. Most other heat and moisture related models don＇t include airflow or use a steady airflow through the construction during the simulation period. However, in this model, the wind induced pressure is dynamic and thus also the airflow through the construction is dynamic. For this particular case study, the results indicate that at the intemal surface, the vapor pressure is almost not influenced by both the 2D effect and the wind speed. The temperatures at the inner surface are mostly influenced by the 2D effect. Only at wind pressure differences above 30 Pa, the airflow has a significant effect. At the extemal surface, the temperatttres are not influenced by both the 2D effect and the wind speed. However, the vapor pressure seems to be quite dependent on the wind induced pressure. Overall it is concluded that air movement through building materials seems to have a significant impact on the heat and moisture characteristics. In order to verify this statement and validate the models, new in-depth experiments including air flow through materials are recommended.展开更多
Air traffic controllers are the important parts of air traffic management system who are responsible for the safety and efficiency of the system.They make traffic management decisions based on information acquired fro...Air traffic controllers are the important parts of air traffic management system who are responsible for the safety and efficiency of the system.They make traffic management decisions based on information acquired from various sources.The understanding of their information seeking behaviors is still limited.We aim to identify controllers′ behavior through the examination of the correlations between controllers′eye movements and air traffic.Sixteen air traffic controllers were invited to participate real-time simulation experiments,during which the data of their eye ball movements and air traffic were recorded.Tweny-three air traffic complexity metrics and six eye movements metrics were calculated to examine their relationships.Two correlational methods,Pearson′s correlation and Spearman′s correlation,were tested between every eye-traffic pair of metrics.The results indicate that controllers′two kinds of information-seeking behaviors can be identified from their eye movements:Targets tracking,and confliction recognition.The study on controllers′ eye movements may contribute to the understanding of information-seeking mechanisms leading to the development of more intelligent automations in the future.展开更多
In plant factories,the plant microclimate is affected by the control system,plant physiological activities and aerodynamic characteristics of leaves,which often leads to poor ventilation uniformity,suboptimal environm...In plant factories,the plant microclimate is affected by the control system,plant physiological activities and aerodynamic characteristics of leaves,which often leads to poor ventilation uniformity,suboptimal environmental conditions and inefficient air conditioning.In this study,interlayer cool airflow(ILCA)was used to introduce room air into plants’internal canopy through vent holes in cultivation boards and air layer between cultivation boards and nutrient solution surface(interlayer).By using optimal operating parameters at a room temperature of 28℃,the ILCA system achieved similar cooling effects in the absence of a conventional air conditioning system and achieved an energy saving of 50.8% while bringing about positive microclimate change in the interlayer and nutrient solution.This resulted in significantly reduced root growth by 41.7% without a negative influence on lettuce crop yield.Future development in this precise microclimate control method is predicted to replace the conventional cooling(air conditioning)systems for crop production in plant factories.展开更多
During the past few decades, both positive and negative aspects of indoor air movement on human comfort perception have been studied. However, most research has focused on collecting empirical evidence to support the ...During the past few decades, both positive and negative aspects of indoor air movement on human comfort perception have been studied. However, most research has focused on collecting empirical evidence to support the potential application of airflows in practice. In this context, numerous studies have encouraged the use of moving air to promote comfort in warm environments, especially with regard to the application of dynamic airflows. Through these studies, the effects of different airflow parameters(such as air velocity, turbulence intensity, and fluctuation frequency) on human comfort perception have gradually been identified and even quantified. This article aims to summarize the progress in the literature concerning dynamic characteristics and comfort assessment of airflows in four main sections: demand for indoor airflows, parameters of indoor airflows, comfort assessment of indoor airflows, and dynamic airflows and their application.This paper will hopefully aid the understanding of human perception of indoor airflows and guide future research.展开更多
Arc resistance is an important parameter for characterizing long arcs in air, and its laboratory testing is of importance for accurate arc modeling of electromagnetic transient caused by short circuit fault. Therefore...Arc resistance is an important parameter for characterizing long arcs in air, and its laboratory testing is of importance for accurate arc modeling of electromagnetic transient caused by short circuit fault. Therefore, we constructed an experimental system to study the cha- racteristics of long AC arc in air. Driven by currents of 10 kA or 40 kA (root mean square value), the system produces arcs with different initial lengths of 1 m, 2 m and 4 m, and the movement of the arcs are captured by a high-speed camera. After performing experiments using the system, we carried out analysis and comparisons of the arc resistance of arcs with different lengths and different currents, as well as a study of the relationship between the macro-morphology and the resistance of the arcs. Conclusions were drawn from the experimental re- sults: the arc voltage had obvious saturation characteristics; the arc resistance increased with the increase of arc length and the decrease of current; the arcs bended or extended significantly in time and the peak arc voltage within a single cycle increased correspondingly; the arcs had voltage and current in the same phase. In the end, a formula of arc resistance based on the experiment results is derived.展开更多
Air sparging is a remedial method for groundwater. The remedial region is similar to the air flow region in the saturated zone. If soil particles are transported during air sparging, the porosity distributions in the ...Air sparging is a remedial method for groundwater. The remedial region is similar to the air flow region in the saturated zone. If soil particles are transported during air sparging, the porosity distributions in the saturated zone change, which may alter the flow path of the air. To understand better the particle movement, this study performed a sandbox test to estimate the soil porosity change during air sparging. A clear fracture was formed and the phenomenon of particle movement was observed when the air injection was started. The moved sand filled the porous around the fracture and the reparked sand filled the fracture, reducing the porosity around the fracture. The results obtained from the photographs of the sandbox, the current measurements and the direct sand sample measurements were close to each other and are credible. Therefore, air injection during air sparging causes sand particle movement of sand, altering the characteristic of the sand matrix and the air distribution.展开更多
文摘This paper analyzes the applications of four air terminal device（ATD）models（i.e.,the basic model,the box model,the N-point momentum model,the jet main region specification model）in computational fluid dynamics（CFD）simulation and their performance in case study.A full-scale experiment is performed in an environment chamber,and the measured air velocity and temperature fields are compared with the simulation results by using four ATD models.The velocity and temperature fields are measured by an omni-directional thermo-anemometer system.It demonstrates that the basic model and the box model are not applicable to complicated air terminal devices.At the occupant area,the relative errors between simulated and measured air velocities are less than 20% based on the N-point momentum model and the jet main region specification model.Around the ATD zone,the relative error between the numerical and measured air velocity based on the jet main region specification model is less than 15%.The jet main region specification model is proved to be an applicable approach and a more accurate way to study the airflow pattern around the ATD with complicated geometry.
文摘The research focuses on the effect of air movement through building constructions. Although the typical air movement inside building constructions is quite small （velocity is of order -10-5 m/s）, this research shows the impact on the heat and moisture characteristics. The paper presents a case study on the modeling and simulation of 2D heat and moisture transport with and without air movement for a building construction using a state-of-art multiphysics FEM software tool. Most other heat and moisture related models don＇t include airflow or use a steady airflow through the construction during the simulation period. However, in this model, the wind induced pressure is dynamic and thus also the airflow through the construction is dynamic. For this particular case study, the results indicate that at the intemal surface, the vapor pressure is almost not influenced by both the 2D effect and the wind speed. The temperatures at the inner surface are mostly influenced by the 2D effect. Only at wind pressure differences above 30 Pa, the airflow has a significant effect. At the extemal surface, the temperatttres are not influenced by both the 2D effect and the wind speed. However, the vapor pressure seems to be quite dependent on the wind induced pressure. Overall it is concluded that air movement through building materials seems to have a significant impact on the heat and moisture characteristics. In order to verify this statement and validate the models, new in-depth experiments including air flow through materials are recommended.
基金supported by the National Natural Science Foundation of China (No.61304190)the Fundamental Research Funds for the Central Universities (No.NJ20150030)the Natural Science Foundation of Jiangsu Province of China (No.BK20130818)
文摘Air traffic controllers are the important parts of air traffic management system who are responsible for the safety and efficiency of the system.They make traffic management decisions based on information acquired from various sources.The understanding of their information seeking behaviors is still limited.We aim to identify controllers′ behavior through the examination of the correlations between controllers′eye movements and air traffic.Sixteen air traffic controllers were invited to participate real-time simulation experiments,during which the data of their eye ball movements and air traffic were recorded.Tweny-three air traffic complexity metrics and six eye movements metrics were calculated to examine their relationships.Two correlational methods,Pearson′s correlation and Spearman′s correlation,were tested between every eye-traffic pair of metrics.The results indicate that controllers′two kinds of information-seeking behaviors can be identified from their eye movements:Targets tracking,and confliction recognition.The study on controllers′ eye movements may contribute to the understanding of information-seeking mechanisms leading to the development of more intelligent automations in the future.
基金This work was supported by the National Natural Science Foundation of China(31701969)the Key Projects of Ningxia Key R&D Program Fund,China(2018BBF02012)the Science and Technology Program of Shaanxi Province,China(2017ZDXM-NY-057).
文摘In plant factories,the plant microclimate is affected by the control system,plant physiological activities and aerodynamic characteristics of leaves,which often leads to poor ventilation uniformity,suboptimal environmental conditions and inefficient air conditioning.In this study,interlayer cool airflow(ILCA)was used to introduce room air into plants’internal canopy through vent holes in cultivation boards and air layer between cultivation boards and nutrient solution surface(interlayer).By using optimal operating parameters at a room temperature of 28℃,the ILCA system achieved similar cooling effects in the absence of a conventional air conditioning system and achieved an energy saving of 50.8% while bringing about positive microclimate change in the interlayer and nutrient solution.This resulted in significantly reduced root growth by 41.7% without a negative influence on lettuce crop yield.Future development in this precise microclimate control method is predicted to replace the conventional cooling(air conditioning)systems for crop production in plant factories.
文摘During the past few decades, both positive and negative aspects of indoor air movement on human comfort perception have been studied. However, most research has focused on collecting empirical evidence to support the potential application of airflows in practice. In this context, numerous studies have encouraged the use of moving air to promote comfort in warm environments, especially with regard to the application of dynamic airflows. Through these studies, the effects of different airflow parameters(such as air velocity, turbulence intensity, and fluctuation frequency) on human comfort perception have gradually been identified and even quantified. This article aims to summarize the progress in the literature concerning dynamic characteristics and comfort assessment of airflows in four main sections: demand for indoor airflows, parameters of indoor airflows, comfort assessment of indoor airflows, and dynamic airflows and their application.This paper will hopefully aid the understanding of human perception of indoor airflows and guide future research.
基金Project supported by National Natural Science Foundation of China（50907036）, National Basic Research Program of China （973 Program ） （2011CB209403）.
文摘Arc resistance is an important parameter for characterizing long arcs in air, and its laboratory testing is of importance for accurate arc modeling of electromagnetic transient caused by short circuit fault. Therefore, we constructed an experimental system to study the cha- racteristics of long AC arc in air. Driven by currents of 10 kA or 40 kA (root mean square value), the system produces arcs with different initial lengths of 1 m, 2 m and 4 m, and the movement of the arcs are captured by a high-speed camera. After performing experiments using the system, we carried out analysis and comparisons of the arc resistance of arcs with different lengths and different currents, as well as a study of the relationship between the macro-morphology and the resistance of the arcs. Conclusions were drawn from the experimental re- sults: the arc voltage had obvious saturation characteristics; the arc resistance increased with the increase of arc length and the decrease of current; the arcs bended or extended significantly in time and the peak arc voltage within a single cycle increased correspondingly; the arcs had voltage and current in the same phase. In the end, a formula of arc resistance based on the experiment results is derived.
文摘Air sparging is a remedial method for groundwater. The remedial region is similar to the air flow region in the saturated zone. If soil particles are transported during air sparging, the porosity distributions in the saturated zone change, which may alter the flow path of the air. To understand better the particle movement, this study performed a sandbox test to estimate the soil porosity change during air sparging. A clear fracture was formed and the phenomenon of particle movement was observed when the air injection was started. The moved sand filled the porous around the fracture and the reparked sand filled the fracture, reducing the porosity around the fracture. The results obtained from the photographs of the sandbox, the current measurements and the direct sand sample measurements were close to each other and are credible. Therefore, air injection during air sparging causes sand particle movement of sand, altering the characteristic of the sand matrix and the air distribution.
