Wall-mounted swirling ventilation is a new type of system in mechanized excavation faces with a dust sup-pression performance that is closely related to the blowing-to-suction flow ratio.Physical and simulation models...Wall-mounted swirling ventilation is a new type of system in mechanized excavation faces with a dust sup-pression performance that is closely related to the blowing-to-suction flow ratio.Physical and simulation models were developed according to the No.C103 mechanized excavation face in the Nahe Coal Mine of the Baise Mining Bureau,Guangxi Province to optimize the blowing-to-suction flow ratio for wall-mounted swirling ventilation.Both the k-εturbulence model and the discrete phase model were utilized to simulate airflow field structures and dust concentration distribution patterns at various blowing-to-suction flow ratios.The results suggest that higher blowing-to-suction flow ratios increase the airflow field disturbance around the working face and weaken the intensity of the axial air curtain.On the other hand,both the intensity of the radial air curtain and the dust suppression effect are enhanced.At a blowing-to-suction flow ratio of 0.8,the wall-mounted swirling ventilation system achieved the most favorable dust suppression performance.Both the total dust and respirable dust had their lowest concentrations with maximum efficiencies of reducing both types at 90.33%and 87.16%,respectively.展开更多
The transmission of coronavirus disease 2019(COVID-19)has presented challenges for the control of the indoor environment of isolation wards.Scientific air distribution design and operation management are crucial to en...The transmission of coronavirus disease 2019(COVID-19)has presented challenges for the control of the indoor environment of isolation wards.Scientific air distribution design and operation management are crucial to ensure the environmental safety of medical staff.This paper proposes the application of adaptive wall-based attachment ventilation and evaluates this air supply mode based on contaminants dispersion,removal efficiency,thermal comfort,and operating expense.Adaptive wall-based attachment ventilation provides a direct supply of fresh air to the occupied zone.In comparison with a ceiling air supply or upper sidewall air supply,adaptive wall-based attachment ventilation results in a 15%–47%lower average concentration of contaminants,for a continual release of contaminants at the same air changes per hour(ACH;10 h^(-1)).The contaminant removal efficiency of complete mixing ventilation cannot exceed 1.For adaptive wall-based attachment ventilation,the contaminant removal efficiency is an exponential function of the ACH.Compared with the ceiling air supply mode or upper sidewall air supply mode,adaptive wall-based attachment ventilation achieves a similar thermal comfort level(predicted mean vote(PMV)of0.1–0.4;draught rate of 2.5%–6.7%)and a similar performance in removing contaminants,but has a lower ACH and uses less energy.展开更多
In practical engineering,inclined building walls are often presented due to their functional and aesthetic needs.A reasonable air distribution design is essential for creating a satisfactory indoor environment in such...In practical engineering,inclined building walls are often presented due to their functional and aesthetic needs.A reasonable air distribution design is essential for creating a satisfactory indoor environment in such buildings.In the present study,inclined walls with a variable inclination angle β were used as the research object to explore a novel air supply mode.Visualization experiments and numerical simulations were conducted to investigate the induced airflow,such as the airflow pattern,the airflow characteristics(maximum jet velocity decay and jet spreading rate)and the ventilation effect(vertical air temperature difference,draft rate,air diffusion performance index).The results show that the"air lake"phenomena occurred over the floor,which resembles the displacement ventilation to some extent.The proposed air supply mode has a good ventilation effect and could be applied to building spaces with inclined walls.The current study can be used as a reference for ventilation design in buildings with inclined walls.展开更多
With the emergence of urban sentry boxes and capsule hotels,the development of tiny spaces with the concept of a reasonable minimum occupied space has attracted widespread attention from society.The ventilation mode t...With the emergence of urban sentry boxes and capsule hotels,the development of tiny spaces with the concept of a reasonable minimum occupied space has attracted widespread attention from society.The ventilation mode that fits with the limited geometric characteristics of tiny spaces is worth exploring.Combined with the respective ventilation requirements of two types of tiny spaces,i.e.,sentry box space and tiny sleeping space,this paper proposes two attached ventilation modes.A full-scale experiment cabin was established,and the simulation method was optimized through experimental data.The airflow pattern and distribution performance of the two attached ventilation modes in two types of tiny spaces were studied by the CFD method.The results showed that the airflow attached to the vertical wall could form an air curtain at the opening windows of the sentry box space,but there is a phenomenon of air leakage.The installation of the deflector can improve the integrity of the air curtain,and the best installation angle of the deflector is 60 degrees.The double side-attached ventilation mode in the tiny sleeping space can not only relieve the draught of the occupants(DR<15%),but also firstly deliver fresh air to the occupied zone(expiratory zone MAA<92 s).The research conclusions will add new ideas to the diversity of ventilation modes in tiny spaces.展开更多
Sentry buildings have windows that are often open to facilitate communication between personnel.It also provides the possibility for the intrusion of pollutants such as vehicle exhaust emissions.To prevent the intrusi...Sentry buildings have windows that are often open to facilitate communication between personnel.It also provides the possibility for the intrusion of pollutants such as vehicle exhaust emissions.To prevent the intrusion of outdoor pollutants and create an excellent indoor environment,internal circulation with double-attached ventilation(IC-DAV)and external circulation with double-attached ventilation(EC-DAV)are proposed for such buildings,and the isolation effect of two attached ventilation modes on pollutants is compared with that of natural ventilation.A computational fluid dynamics(CFD)method was used to simulate the transportation process and indoor distribution of outdoor pollutants intruding into sentry buildings from the regular openings under different outdoor wind directions,wind velocities,and states of the doors and ventilation modes.The results indicate that the leeward airflow of the three wind directions caused the largest pollutants to invade the room.The amount of pollutants intrusion increased with increasing wind velocity.When the leeward airflow and the windward airflow blow through the building,opening the door increased the amount of pollutants intruding into the room by 3.34 times and 8.85 times,respectively,compared with closing the door.However,the IC-DAV can isolate 81.7% of the pollutants while the EC-DAV can isolate 99.92% of the pollutants as compared with natural ventilation.Applying double attached ventilation mode in buildings can effectively prevent the intrusion of outdoor pollutants into the room,reduce the harm of outdoor pollutants to the health of indoor personnel,and provide a new idea for buildings to improve the indoor air quality.展开更多
Based on the structural characteristics of existing buildings and the disadvantages of current mixed ventilation mode in the application to large space buildings,an original column attachment ventilation(CAV)has been ...Based on the structural characteristics of existing buildings and the disadvantages of current mixed ventilation mode in the application to large space buildings,an original column attachment ventilation(CAV)has been proposed.In this study,the experiment utilized a room space with four columns uniformly distributed in the space to visualize the movement of attached airflow along the cylinder surface and the floor,the numerical technique was employed to study the effects of the column layout(i.e.,uniform,centralized,dispersed,and crossed distribution)on the air distribution of CAV mode in a standard four-column full scale model of a shopping mall.Seven indices,including airflow pattern,air diffusion performance index(ADPI),air temperature distribution,heat removal effectiveness,draught rate(DR),predicted mean vote(PMV),and carbon dioxide(CO2)concentration,were used to assess the ventilation performance.In the CAV mode with a uniform column layout scheme,the experimental results indicated that the air supply flows downward along the wall surface,forming a secondary attachment with the ground and spreading along the floor in a fan radiation flow mode.Further,an“air lake”-like speed and temperature distribution similar to displacement ventilation(DV)was formed in the occupied zone.In all simulation cases,it was found that the average air velocity was less than 0.25 m/s in occupied zone,the effectiveness for heat removal was more significant than 1.0,DR value was less than 20%,the PMV level can also satisfy most people.The average CO2 concentration was around 470 ppm in the occupied breathing zone.These results indicated that the CAV mode could be an efficient air distribution method.They demonstrated the technical feasibility of applying the CAV in the space under different column layout schemes.展开更多
基金support for this work was provided by the National Natural Science Foundation of China(No.51574123)the Scientific Research Project of Hunan Province Office of Education(No.18A185),which are gratefully acknowledged.
文摘Wall-mounted swirling ventilation is a new type of system in mechanized excavation faces with a dust sup-pression performance that is closely related to the blowing-to-suction flow ratio.Physical and simulation models were developed according to the No.C103 mechanized excavation face in the Nahe Coal Mine of the Baise Mining Bureau,Guangxi Province to optimize the blowing-to-suction flow ratio for wall-mounted swirling ventilation.Both the k-εturbulence model and the discrete phase model were utilized to simulate airflow field structures and dust concentration distribution patterns at various blowing-to-suction flow ratios.The results suggest that higher blowing-to-suction flow ratios increase the airflow field disturbance around the working face and weaken the intensity of the axial air curtain.On the other hand,both the intensity of the radial air curtain and the dust suppression effect are enhanced.At a blowing-to-suction flow ratio of 0.8,the wall-mounted swirling ventilation system achieved the most favorable dust suppression performance.Both the total dust and respirable dust had their lowest concentrations with maximum efficiencies of reducing both types at 90.33%and 87.16%,respectively.
基金supported by the Ministry of Science and Technology of China,the Chinese Academy of Engineering,a project on the risk prevention and control of the relationship between the spread of COVID-19 and the environment(2020YFC0842500 and 2020-ZD-15)the National Key Research and Development(R&D)Program of China(2017YFC0702800).
文摘The transmission of coronavirus disease 2019(COVID-19)has presented challenges for the control of the indoor environment of isolation wards.Scientific air distribution design and operation management are crucial to ensure the environmental safety of medical staff.This paper proposes the application of adaptive wall-based attachment ventilation and evaluates this air supply mode based on contaminants dispersion,removal efficiency,thermal comfort,and operating expense.Adaptive wall-based attachment ventilation provides a direct supply of fresh air to the occupied zone.In comparison with a ceiling air supply or upper sidewall air supply,adaptive wall-based attachment ventilation results in a 15%–47%lower average concentration of contaminants,for a continual release of contaminants at the same air changes per hour(ACH;10 h^(-1)).The contaminant removal efficiency of complete mixing ventilation cannot exceed 1.For adaptive wall-based attachment ventilation,the contaminant removal efficiency is an exponential function of the ACH.Compared with the ceiling air supply mode or upper sidewall air supply mode,adaptive wall-based attachment ventilation achieves a similar thermal comfort level(predicted mean vote(PMV)of0.1–0.4;draught rate of 2.5%–6.7%)and a similar performance in removing contaminants,but has a lower ACH and uses less energy.
基金supported by the National Natural Science Foundation of China(No.50778145,No.51478377).
文摘In practical engineering,inclined building walls are often presented due to their functional and aesthetic needs.A reasonable air distribution design is essential for creating a satisfactory indoor environment in such buildings.In the present study,inclined walls with a variable inclination angle β were used as the research object to explore a novel air supply mode.Visualization experiments and numerical simulations were conducted to investigate the induced airflow,such as the airflow pattern,the airflow characteristics(maximum jet velocity decay and jet spreading rate)and the ventilation effect(vertical air temperature difference,draft rate,air diffusion performance index).The results show that the"air lake"phenomena occurred over the floor,which resembles the displacement ventilation to some extent.The proposed air supply mode has a good ventilation effect and could be applied to building spaces with inclined walls.The current study can be used as a reference for ventilation design in buildings with inclined walls.
基金This study was jointly funded by the National Natural Science Foundation of China(No.51408477)the Opening Fund of Key Laboratory of Plateau Green Building and Ecological Community in Qinghai Province(No.KLKF-2020-005)the Natural Science Foundation of Education Department of Shaanxi Province(No.21JK0712).
文摘With the emergence of urban sentry boxes and capsule hotels,the development of tiny spaces with the concept of a reasonable minimum occupied space has attracted widespread attention from society.The ventilation mode that fits with the limited geometric characteristics of tiny spaces is worth exploring.Combined with the respective ventilation requirements of two types of tiny spaces,i.e.,sentry box space and tiny sleeping space,this paper proposes two attached ventilation modes.A full-scale experiment cabin was established,and the simulation method was optimized through experimental data.The airflow pattern and distribution performance of the two attached ventilation modes in two types of tiny spaces were studied by the CFD method.The results showed that the airflow attached to the vertical wall could form an air curtain at the opening windows of the sentry box space,but there is a phenomenon of air leakage.The installation of the deflector can improve the integrity of the air curtain,and the best installation angle of the deflector is 60 degrees.The double side-attached ventilation mode in the tiny sleeping space can not only relieve the draught of the occupants(DR<15%),but also firstly deliver fresh air to the occupied zone(expiratory zone MAA<92 s).The research conclusions will add new ideas to the diversity of ventilation modes in tiny spaces.
基金jointly funded by the National Key Research and Development Program of China(No.2016YFC0700500)the Natural Science Foundation of Shaanxi Province(No.2021JM-361)the Opening Fund of Qinghai Provincial Key Laboratory of Plateau Green Building and Eco-community(No.KLKF-2020-005).
文摘Sentry buildings have windows that are often open to facilitate communication between personnel.It also provides the possibility for the intrusion of pollutants such as vehicle exhaust emissions.To prevent the intrusion of outdoor pollutants and create an excellent indoor environment,internal circulation with double-attached ventilation(IC-DAV)and external circulation with double-attached ventilation(EC-DAV)are proposed for such buildings,and the isolation effect of two attached ventilation modes on pollutants is compared with that of natural ventilation.A computational fluid dynamics(CFD)method was used to simulate the transportation process and indoor distribution of outdoor pollutants intruding into sentry buildings from the regular openings under different outdoor wind directions,wind velocities,and states of the doors and ventilation modes.The results indicate that the leeward airflow of the three wind directions caused the largest pollutants to invade the room.The amount of pollutants intrusion increased with increasing wind velocity.When the leeward airflow and the windward airflow blow through the building,opening the door increased the amount of pollutants intruding into the room by 3.34 times and 8.85 times,respectively,compared with closing the door.However,the IC-DAV can isolate 81.7% of the pollutants while the EC-DAV can isolate 99.92% of the pollutants as compared with natural ventilation.Applying double attached ventilation mode in buildings can effectively prevent the intrusion of outdoor pollutants into the room,reduce the harm of outdoor pollutants to the health of indoor personnel,and provide a new idea for buildings to improve the indoor air quality.
基金This study was jointly funded by the National Natural Science Foundation of China(No.51408477)the Innovative Talent Promotion Plan of Shaanxi Province(No.2018KJXX-087)and the Youth Talent Support Project of Xi’an Association for Science and Technology.
文摘Based on the structural characteristics of existing buildings and the disadvantages of current mixed ventilation mode in the application to large space buildings,an original column attachment ventilation(CAV)has been proposed.In this study,the experiment utilized a room space with four columns uniformly distributed in the space to visualize the movement of attached airflow along the cylinder surface and the floor,the numerical technique was employed to study the effects of the column layout(i.e.,uniform,centralized,dispersed,and crossed distribution)on the air distribution of CAV mode in a standard four-column full scale model of a shopping mall.Seven indices,including airflow pattern,air diffusion performance index(ADPI),air temperature distribution,heat removal effectiveness,draught rate(DR),predicted mean vote(PMV),and carbon dioxide(CO2)concentration,were used to assess the ventilation performance.In the CAV mode with a uniform column layout scheme,the experimental results indicated that the air supply flows downward along the wall surface,forming a secondary attachment with the ground and spreading along the floor in a fan radiation flow mode.Further,an“air lake”-like speed and temperature distribution similar to displacement ventilation(DV)was formed in the occupied zone.In all simulation cases,it was found that the average air velocity was less than 0.25 m/s in occupied zone,the effectiveness for heat removal was more significant than 1.0,DR value was less than 20%,the PMV level can also satisfy most people.The average CO2 concentration was around 470 ppm in the occupied breathing zone.These results indicated that the CAV mode could be an efficient air distribution method.They demonstrated the technical feasibility of applying the CAV in the space under different column layout schemes.