The relationship between the site selection of a hilly terrain and the natural ventilation of the Dangdamen building complex,which is a traditional folk house,is revealed by a computational fluid dynamics（CFD）simula...The relationship between the site selection of a hilly terrain and the natural ventilation of the Dangdamen building complex,which is a traditional folk house,is revealed by a computational fluid dynamics（CFD）simulation.The wind press and speed distributions around the building in four cases with different weather conditions and topographies are simulated.The simulation results show that a hill can reduce the absolute values of the wind pressure at the windward and leeward sides of the building.The encouraging effect of the patio on the natural ventilation in a terrain with a hill is greater than that without a hill.The same situation occurs when comparing the patio effects between summer and winter.The wind speed around the building can be reduced by the hill as it is an obstacle and the degrees of the influence of the hill in summer and in winter are quite different because of different wind directions.The analysis results show that this kind of site selection,with the hill to the north,is a suitable way to settle the conflict of the natural ventilation requirements in summer and in winter under subtropical climate conditions,especially in houses with patios.展开更多
With northern pig house as study objective,the 3-D numerical simulation of natural ventilation airflow field of five pig houses with different window area was done by using Fluent software,and the comparative analysis...With northern pig house as study objective,the 3-D numerical simulation of natural ventilation airflow field of five pig houses with different window area was done by using Fluent software,and the comparative analysis was carried out on simulation result and measured result.The results showed that the effect of ventilation was decided by the reasonable area ratio of window and earth and the ratio of length and width of window.According to this real pig house in experiment,there are the best uniformity of ventilation and the least area of having no ventilation by 1：10 of the area ratio of the window and earth in the pig houses,the smaller air retention zone by the smaller ratio of length and width of window,the better effect of ventilation;the results of simulation agree well with the results of measured,the max relative error and the average error was 11.1% and 7.7%,so the software of Fluent was proved effective in the numerical simulation of natural ventilation in the pig houses and the optimal design of pig houses＇ structure.展开更多
Natural ventilation is driven by either buoyancy forces or wind pressure forces or their combinations that inherit stochastic variation into ventilation rates. Since the ventilation rate is a nonlinear function of mul...Natural ventilation is driven by either buoyancy forces or wind pressure forces or their combinations that inherit stochastic variation into ventilation rates. Since the ventilation rate is a nonlinear function of multiple variable factors including wind speed, wind direction, internal heat source and building structural thermal mass, the conventional methods for quantifying ventilation rate simply using dominant wind direction and average wind speed may not accurately describe the characteristic performance of natural ventilation. From a new point of view, the natural ventilation performance of a single room building under fluctuating wind speed condition using the Monte-Carlo simulation approach was investigated by incorporating building facade thermal mass effect. Given a same hourly turbulence intensity distribution, the wind speeds with 1 rain frequency fluctuations were generated using a stochastic model, the modified GARCH model. Comparisons of natural ventilation profiles, effective ventilation rates, and air conditioning electricity use for a three-month period show statistically significant differences （for 80% confidence interval） between the new calculations and the traditional methods based on hourly average wind speed.展开更多
According to the investigations of window opening percentage (WOP) of Shanghai in 2011, the WOP varies significantly from season to season and thus affects the air flow rate of natural ventilation rooms. A three-dimen...According to the investigations of window opening percentage (WOP) of Shanghai in 2011, the WOP varies significantly from season to season and thus affects the air flow rate of natural ventilation rooms. A three-dimensional computional fluid dynamic(CFD) model was applied to simulating the flow fields in a street canyon under different wind speed and WOP. The numerical simulations show that WOP has a significant influence on the static pressure distribution of the downwind building. Therefore, a correction factor k can be used for calculating the flow rate of wind-driven natural ventilation. The results show that k ranges from 0.43 to 0.49 when WOP is 4.44%; when WOP increases to 9.78%, the correction factor k lies in 0.32 and 0.36.展开更多
The natural ventilation widely used in greenhouses has advantages of saving energy and reducing expense. In order to provide information for climate control of greenhouse, a model was developed to predict the variatio...The natural ventilation widely used in greenhouses has advantages of saving energy and reducing expense. In order to provide information for climate control of greenhouse, a model was developed to predict the variation of air temperature in the naturally ventilated greenhouse equipped with insect-proof screen. Roof ventilation and combined roof and sidewall ventilation were considered in the model. This model was validated against the results of experiments conducted in the greenhouse when the wind was parallel to the gutters. The model parameters were determined by the least squares method. In the used model, effects of wind speed and window opening height on the air temperature variation were analyzed. Comparison between two types of ventilation showed that there existed a necessary ventilation rate which results in air temperature decrease in natural ventilation under special climatic conditions. In our experiments when wind speed was less than 3.2 ms?1, wind had a more gradual effect on greenhouse temperature for roof ventilation, compared with combined roof and sidewall ventilation, which had greater air temperature decrease than roof ventilation only.展开更多
Based on the current indoor natural ventilation and lighting in the space of traditional residential buildings,this paper starts from the passive-design optimization of the spatial natural ventilation and lighting,and...Based on the current indoor natural ventilation and lighting in the space of traditional residential buildings,this paper starts from the passive-design optimization of the spatial natural ventilation and lighting,and makes quantitative evaluation on the quality of current interior natural ventilation and lighting for two typical residential buildings by three indexes,including wind speed,static wind area ratio and satisfaction ratio about minimum lighting coefficient. Based on that, this paper conducts the passive design optimization, and establishes the quantitative association and reevaluation among the passive reformation design, natural ventilation,and lighting environmental quality,proposing the general strategy for the existing residential buildings to respond to the passive reformation design of the natural ventilation and lighting. The special reconstruction of core functionary space of integration of "the living room + dining room + partial space"is researched,and the redesign for the optimization and replacement of both indoor and outdoor enclosure parts is explored,which is expected to provide practical exploration on the strategies for passive construction of spatial natural environmental quality within a large number of highly-energy-consumed residential buildings in China,as well as the green design of residential buildings.展开更多
Natural ventilation effects in high and large space buildings of tropical areas greatlya ffect the air conditioning energy consumption.Aiming at nearly zero energy building design,thisp aper mainly contributes to prov...Natural ventilation effects in high and large space buildings of tropical areas greatlya ffect the air conditioning energy consumption.Aiming at nearly zero energy building design,thisp aper mainly contributes to provide theoretical basis and reference for thermal comfortable air conditioning system design of high and large space buildings.Taking a theatre in Hainan as study object,a newly composite enhanced natural ventilation system is proposed by integrating theu nderground tunnel-based earth to air heat exchange system and the solar chimney.Ventilationq uantity,air velocity and air temperature field,human vertical temperature gradient differenceu nder24simulation working conditions are considered and analyzed by using ANSYS Fluent.Fort he underground tunnel,results show that Group Two with double underground tunnels and side airs upply location shows its advantages in cooling effects and air supply uniformity.Then for the solar chimney,results show that the solar radiation intensity contributes to larger difference int ransmission power and leads to different cooling effects.On the whole,the system under workingc ondition No.7with120m long,side air supply,double underground tunnel and20m high,1mw ide,0.6°absorber plate angle solar chimney shows its priority in better comprehensive performance.展开更多
To establish the model of indoor air pollution forecast for decoration. Methods The model was based on the balance model for diffusing mass. Results The data between testing concentration and estimating concentration ...To establish the model of indoor air pollution forecast for decoration. Methods The model was based on the balance model for diffusing mass. Results The data between testing concentration and estimating concentration were compared. The maximal error was less than 30% and average error was 14.6%. Conclusion The model can easily predict whether the pollution for decoration exceeds the standard and how long the room is decorated.展开更多
Due to the urban and town development, it is common to see historical buildings and new buildings intermingled with one and another inside historical regions in Taiwan. With the increase of new buildings, natural vent...Due to the urban and town development, it is common to see historical buildings and new buildings intermingled with one and another inside historical regions in Taiwan. With the increase of new buildings, natural ventilation becomes harder, which leads to the impact on the preservation of historical building and the reduction of thermal comfort for residents. Besides, problems of new buildings＇ construction and design affect the developments of cities and towns in historical district, which has existed for hundreds of years. The Wugoushui Settlement is located in Pingtung County, the southernmost part of Taiwan, and its hot season of a year is pretty long and belongs to warm and humid tropical climate. In 2008, the Pingtung County Government officially registered and announced Wugoushui as traditional settlement and meanwhile, provided the maintenance and preservation for buildings in this region on government subsidies. This paper is based on one-year-long field experiments of Wugoushui Settlement. Residents in Wugoushui Settlement continue constructing new buildings near by the traditional buildings. With the fact that constructions of new buildings result in huge impact on the circumstances of natural ventilation and thermal comfort, which have been for hundreds of years, the simple weather station is set up to collect the data of local microclimate. In addition, four representative traditional architectures were selected to be measured their indoor and outdoor temperature, humidity, wind speed, wind direction and thermal radiation both in winter （December to February） and in summer （May to September）. The measurement time of each building is one week and every data record is kept every minute. Besides, residents were asked to fill out the comfort survey. Based on these data, the distributions of indoor and outdoor thermal environment as well as the thermal comfort of living space under the condition of the natural ventilation are assessed. Finally, focused on the indoor living space of historical districts in southern Taiwan, there are two main suggestions given in the essay： first, a provisional comfort zone in summer is planned and proposed; second, the preliminary suggestions for the design and norms of new buildings in historical district are provided.展开更多
With a sustained period of economic growth, rapidly growing populations and with more diversified economies Africa need sustainable development; hence the greater need for massive investments in energy. Sub-Saharan co...With a sustained period of economic growth, rapidly growing populations and with more diversified economies Africa need sustainable development; hence the greater need for massive investments in energy. Sub-Saharan countries such as Djibouti have the potential and ability to harness their natural ventilation as a passive cooling system for designing new houses. The rapid expansion of the Djibouti city is affecting negatively the environment and the safety and comfort of its inhabitants. Proper atmospheric urban planning and management are key to making cities environmentally friendly and sustainable. Based on energy consumption, climate conditions in Djibouti and numerical analysis using Computational Fluid Dynamics （CFD）, it is apparent that the natural ventilation creates a thermally comfortable indoor environment in buildings during the cool season of the year. Measured wind data from two measurement systems are presented and discussed. Statistical analyses, wind rose, Weibull distribution were carried out to understand the natural ventilation characteristic, which is used for evolving the basic criteria for economic viability of building in the semi-arid climate of Djibouti. The study found that it is possible to benefit from natural ventilation in buildings during the cool season of the year.展开更多
The main aim of this paper was to study the influence of ventilation during a typical experimental day, in the internal air temperature as well as in internal surface temperatures under the conditions of the outer env...The main aim of this paper was to study the influence of ventilation during a typical experimental day, in the internal air temperature as well as in internal surface temperatures under the conditions of the outer environment, using an experimental method which allows a comparison of the thermal performance between four cell tests： a prototype called control （no vegetation） and three with different combinations of vegetation （roofs and facades） installed in a region of tropical climate. The experiments were developed in four test cells with dimensions 2.0 m × 2.50 m × 2.7 m. Measurements of internal surface temperatures and internal air temperatures were collected with the use of specific equipment, a data logger （CR1000, Campbell Scientific Inc.）, connected with two multiplexers 32 channels （416AM Campbell Scientific Inc.）. Data were recorded over a year and a typical heat day was selected, which was September 24, 2015. The results show that ventilation affects the internal temperature of the air, so that this gets even surpass the external temperature. Regarding surface temperatures, increased temperature, except those which are provided with vegetation, namely, the surfaces which have green walls and green roofs file the lower temperatures. Therefore, we can confirm the ability of vegetation to maintain more pleasant internal conditions compared to the test cells built with conventional materials, thus it can reduce cooling load efficiency.展开更多
Natural ventilation is an efficient design strategy for the passive cooling of buildings, especially in tropical countries such as Brazil. Among the ventilation strategies, sheds can be highlighted. These structures c...Natural ventilation is an efficient design strategy for the passive cooling of buildings, especially in tropical countries such as Brazil. Among the ventilation strategies, sheds can be highlighted. These structures consist of roof openings that work as air captors or extractors depending on their location in relation to the prevailing wind directions. The hospitals of the Sarah Network, designed by the Brazilian architect Joao Filgueiras Lima, Lele, are worldwide known for using these elements to improve natural ventilation. This paper analyses the natural ventilation performance of sheds for air collecting and extracting in two Sarah hospitals located in the cities of Salvador and Rio de Janeiro. In each building, the sheds were analyzed for air extracting and collecting. The analyses were carried out by reduced physical models in an atmospheric boundary layer wind tunnel. The wind velocity was measured at external and internal points of the buildings, using hot-wire anemometers. The results show that the wards in Rio de Janeiro hospital are 17% more ventilated than the ones in the Salvador hospital. However, this difference occurs not only because of the collecting sheds but also because of set of openings and the configuration of the covering in hospitals in Rio de Janeiro.展开更多
By taking a modern residence in Meishan area as an example,15 measuring points have been set,and the wind speed of the parlor on the first and second floor and that of many bedding rooms have been measured every other...By taking a modern residence in Meishan area as an example,15 measuring points have been set,and the wind speed of the parlor on the first and second floor and that of many bedding rooms have been measured every other hour from 7:00 to 22:00.Based on the measuring data and indoor architectural pattern,indoor ventilation has been analyzed.The results show that good natural ventilation could be created in modern rural residence by making use of plane layout,orientation and openings'organization,so that indoor air can be distributed evenly,helping to reduce temperature and remove humidness;indoor wind speed of the openings of architectures is the largest;and architectural orientation and opening's position can guide air flow and help to improve natural ventilation obviously.展开更多
Windcatchers are used in building design as natural ventilation devices,providing fresh air supply and thermal comfort under suitable outdoor conditions.However,their performance is often constrained by environmental ...Windcatchers are used in building design as natural ventilation devices,providing fresh air supply and thermal comfort under suitable outdoor conditions.However,their performance is often constrained by environmental factors such as outdoor temperature,wind speed and direction.While passive or low-energy heating,cooling,and heat recovery devices have been integrated into conventional windcatcher designs,the impact of changing wind directions,which can render the windcatcher ineffective,is often not considered.Addressing this gap,this research builds upon a novel dual-channel windcatcher system.This system employs a rotary wind scoop to ensure a consistent fresh air supply and stale air exhaust,irrespective of wind direction and facilitates the integration of passive/low-energy technologies.Using a validated numerical computational fluid dynamics(CFD)model,the design of the proposed system was enhanced by incorporating technologies such as an anti-short-circuit device and wing walls,and modifications such as a larger wind scoop area and a redesigned wind cowl to increase the pressure differential between the inlet and outlet and reduce system friction.The modified windcatcher achieved a 28%improvement in ventilation rate and outperformed a conventional four-sided windcatcher of the same size by up to 58%.Furthermore,full-scale simulations of the building and windcatcher at varying heights were conducted under atmospheric boundary layer wind flow to provide a realistic assessment of the windcatcher’s performance.This research contributes to the development of more efficient windcatcher systems for further passive technology integrations,enhancing their viability as sustainable ventilation solutions.展开更多
The severity and mortality rates associated with respiratory infectious diseases are notably elevated among older adults compared to younger populations.Nursing homes,which accommodate a considerable number of elderly...The severity and mortality rates associated with respiratory infectious diseases are notably elevated among older adults compared to younger populations.Nursing homes,which accommodate a considerable number of elderly individuals,are particularly vulnerable to disease outbreaks.This study proposes a method to assess the spatial infection risk of airborne transmission of respiratory diseases by coupling building layout and infiltrations.Field investigations were conducted to summarize nursing homes layout plan and occupants’activity characteristics.Meteorological parameters were used to obtain the wind pressure on building surfaces through computational fluid dynamics.The building ventilation network was further developed to quantify the pathogen exposure and infection risk of occupants.Results indicated that high infectious aerosol exposure appeared in the rooms with more occupants and low ventilation rates.In nursing homes,activity rooms were the highest infectious aerosol exposure area,accounting for 38.5%–47.9% of total exposure in a standard floor,followed by bedrooms,dining halls,and offices.Self-transmission dominated pathogen aerosol transmission,with self-transmission rates exceeding 70%in most rooms.Enhancing natural ventilation was validated as effective to reduce the risk of infection from infectious aerosol exposure.The proposed infection risk assessment is beneficial for the nursing home design in order to reduce the airborne transmission of respiratory diseases.展开更多
This paper investigated the smoke exhaustion characteristics and critical shaft height in a slope tunnel with naturally ventilated shafts based on reduced-scale tunnel experiments.The effects of longitudinal fire loca...This paper investigated the smoke exhaustion characteristics and critical shaft height in a slope tunnel with naturally ventilated shafts based on reduced-scale tunnel experiments.The effects of longitudinal fire location,shaft setting,heat release rate(HRR) and tunnel slope on smoke exhaustion were studied.Experimental results show that the slope has great effect on smoke exhaustion.Moreover,the critical shaft height for complete smoke exhaustion of slope tunnels was studied theoretically and experimentally.The research indicates that the critical shaft height exhibits no dependency on the HRR.Notably,with the increasing of shaft length,the critical shaft height firstly decreases and then remains stable until it finally decreases to zero.Simultaneously,the critical shaft height increases with the increase of the slope and the distance between the shaft and the fire source.In addition,a theoretical model for predicting the critical shaft height was established and verified.The research results can provide some reference for the design of natural ventilation smoke exhaustion with shafts in slope tunnels.展开更多
The objective of this study is to investigate numerically the characteristics of train-induced unsteady airflow in a subway tunnel with natural ventilation ducts.A three-dimensional numerical model using the dynamic l...The objective of this study is to investigate numerically the characteristics of train-induced unsteady airflow in a subway tunnel with natural ventilation ducts.A three-dimensional numerical model using the dynamic layering method for the moving boundary of a train is first developed,and then it is validated against the model tunnel experimental data.With the tunnel and subway train geometries in the numerical model exactly the same as those in the model tunnel experimental test,but with the ventilation ducts being connected to the tunnel ceiling and a barrier placed at the tunnel outlet,the three-dimensional train-induced unsteady tunnel flows are numerically simulated.The computed distributions of the pressure and the air velocity in the tunnel as well as the time series of the mass flow rate at the ventilation ducts reveal the impact of the train motion on the exhaust and suction of the air through ventilation ducts and the effects of a barrier placed at the tunnel outlet on the duct ventilation performance.As the train approaches a ventilation duct,the air is pushed out of the tunnel through the duct.As the train passes the ventilation duct,the exhaust flow in the duct is changed rapidly to the suction flow.After the train passes the duct,the suction mass flow rate at the duct decreases with time since the air pressure at the opening of the duct is gradually recovered with time.A drastic change in the mass flow rate at a ventilation duct while a train passes the corresponding ventilation duct,causes a change in the exhaust mass flow rate at other ventilation ducts.Also,when a barrier is placed at the tunnel outlet,the air volume discharge rate at each ventilation duct is greatly increased,i.e.,the barrier placed at the tunnel outlet can improve remarkably the ventilation performance through each duct.展开更多
The solar greenhouse is a typical greenhouse type in northern China.It provides a favorable environment for the growth of various plants and extends cultivation periods for almost a whole year to achieve a high yield....The solar greenhouse is a typical greenhouse type in northern China.It provides a favorable environment for the growth of various plants and extends cultivation periods for almost a whole year to achieve a high yield.However,indoor environmental control is primarily based on growers'experience,and the objective test data required for the complex climate control and management of greenhouses are lacking.The present study used three greenhouses in northwest China as research objects:one greenhouse with mature plants(GH-M),one greenhouse with young plants(GH-Y)and one greenhouse without plants(GH-E).Field tests were performed to investigate microclimate characteristics,such as indoor air temperature,relative humidity,and solar radiation under natural ventilation.The results showed that the maximum temperature difference reached approximately 8.2℃in the vertical direction,and semiempirical equations for the normalized temperature distribution were obtained.The soil temperature remained constant at a certain depth(0.4 m).The distribution of the relative humidity and solar radiation was analyzed.The current study is helpful for growers to develop better greenhouse climate control strategies for management practices.展开更多
Large space circular coal storage dome(LSCCSD)offers an environmental and dependable alternative to open stockpiles,and it has been consequently widely applied in China.However,due to the lack of scientific guidelines...Large space circular coal storage dome(LSCCSD)offers an environmental and dependable alternative to open stockpiles,and it has been consequently widely applied in China.However,due to the lack of scientific guidelines,its natural ventilation performance is lower than expected.Natural ventilation potential strongly depends on the roof geometry and opening mode,which have not yet been investigated for LSCCSD.This paper presents a detailed evaluation of the impact of dome geometry(rise span ratio),opening height,and opening modes on the ventilation performance of LSCCSD.The evaluation is based on computational fluid dynamics(CFD)methods and is validated by available wind tunnel testing.We employed three evaluation indicators,which are wind pressure coefficient,effective ventilation rate,and wind speed ratio.The results demonstrate that the rise span ratio has a significant effect on the wind pressure difference and the effective ventilation rate increases by approximately 9%–42%with a single-annular opening.When double-annular openings are set in a strong positive pressure zone,the effective ventilation rate increases by 100%and the average wind speed ratio increases by 50%.When it is compared with single one with similar opening height,the effective ventilation rate increases by 25%.The optimum natural ventilation performance for LSCCSD is achieved at a rise span ratio of 0.37.In addition,the lateral middle opening is kept higher than the ridge top of the coal pile.The proposed evaluation approach and design parameters provided instructive information in the building design and ventilation control for LSCCSDs.展开更多
This study explores architectural design by examining air, fluid mechanics, and the natural ventilation of buildings. In this context, this research introduces a new way of dealing with the process of architectural sy...This study explores architectural design by examining air, fluid mechanics, and the natural ventilation of buildings. In this context, this research introduces a new way of dealing with the process of architectural synthesis. The proposed way can be used either to create new architectural projects or to rethink existing ones. This study is supported by previous investigation into the natural ventilation of buildings via computational and laboratory simulation （Stavddou, 2011; Stavridou and Prinos, 2013）. The investigation into the natural ventilation of buildings provides information and data that affect architectural design through various parameters. The parameters of architectural synthesis that are influenced and discussed in this paper are the following： （i） inspiration and analogical transfer, （ii） initial conception of the main idea using computationat fluid dynamics （digital design）, （iii） development of the main idea through an investigatory process toward building form optimization, and （iv） form configuration, shape investigation, and other morphogenetic prospects. This study illustrates the effect of natural ventitation research on architectural design and thus produces a new approach to the architectural design process. This approach leads to an innovative kind of architecture called ＂breathing architecture.＂展开更多
基金The National Key Technology R&D Program of China during the11th Five-Year Plan Period(No.2006BAJ04A13,2006BAJ04B04,2006BAJ02A08,2006BAJ02A05,2006BAJ04A05)the Excellent Youth Teachers Program of Ministry of Education of China(No.2007-209).
文摘The relationship between the site selection of a hilly terrain and the natural ventilation of the Dangdamen building complex,which is a traditional folk house,is revealed by a computational fluid dynamics（CFD）simulation.The wind press and speed distributions around the building in four cases with different weather conditions and topographies are simulated.The simulation results show that a hill can reduce the absolute values of the wind pressure at the windward and leeward sides of the building.The encouraging effect of the patio on the natural ventilation in a terrain with a hill is greater than that without a hill.The same situation occurs when comparing the patio effects between summer and winter.The wind speed around the building can be reduced by the hill as it is an obstacle and the degrees of the influence of the hill in summer and in winter are quite different because of different wind directions.The analysis results show that this kind of site selection,with the hill to the north,is a suitable way to settle the conflict of the natural ventilation requirements in summer and in winter under subtropical climate conditions,especially in houses with patios.
基金Supported by the Development Program of the Science and Technol-ogy Department of Jilin Province (20060205)Key Modern Produc-tion Technology of Safe and Quality Hog in Jilin Province~~
文摘With northern pig house as study objective,the 3-D numerical simulation of natural ventilation airflow field of five pig houses with different window area was done by using Fluent software,and the comparative analysis was carried out on simulation result and measured result.The results showed that the effect of ventilation was decided by the reasonable area ratio of window and earth and the ratio of length and width of window.According to this real pig house in experiment,there are the best uniformity of ventilation and the least area of having no ventilation by 1：10 of the area ratio of the window and earth in the pig houses,the smaller air retention zone by the smaller ratio of length and width of window,the better effect of ventilation;the results of simulation agree well with the results of measured,the max relative error and the average error was 11.1% and 7.7%,so the software of Fluent was proved effective in the numerical simulation of natural ventilation in the pig houses and the optimal design of pig houses＇ structure.
文摘Natural ventilation is driven by either buoyancy forces or wind pressure forces or their combinations that inherit stochastic variation into ventilation rates. Since the ventilation rate is a nonlinear function of multiple variable factors including wind speed, wind direction, internal heat source and building structural thermal mass, the conventional methods for quantifying ventilation rate simply using dominant wind direction and average wind speed may not accurately describe the characteristic performance of natural ventilation. From a new point of view, the natural ventilation performance of a single room building under fluctuating wind speed condition using the Monte-Carlo simulation approach was investigated by incorporating building facade thermal mass effect. Given a same hourly turbulence intensity distribution, the wind speeds with 1 rain frequency fluctuations were generated using a stochastic model, the modified GARCH model. Comparisons of natural ventilation profiles, effective ventilation rates, and air conditioning electricity use for a three-month period show statistically significant differences （for 80% confidence interval） between the new calculations and the traditional methods based on hourly average wind speed.
基金National Natural Science Foundation of China(No. 51278094)
文摘According to the investigations of window opening percentage (WOP) of Shanghai in 2011, the WOP varies significantly from season to season and thus affects the air flow rate of natural ventilation rooms. A three-dimensional computional fluid dynamic(CFD) model was applied to simulating the flow fields in a street canyon under different wind speed and WOP. The numerical simulations show that WOP has a significant influence on the static pressure distribution of the downwind building. Therefore, a correction factor k can be used for calculating the flow rate of wind-driven natural ventilation. The results show that k ranges from 0.43 to 0.49 when WOP is 4.44%; when WOP increases to 9.78%, the correction factor k lies in 0.32 and 0.36.
基金Project (No. 50175101) supported by the National Natural ScienceFoundation of China
文摘The natural ventilation widely used in greenhouses has advantages of saving energy and reducing expense. In order to provide information for climate control of greenhouse, a model was developed to predict the variation of air temperature in the naturally ventilated greenhouse equipped with insect-proof screen. Roof ventilation and combined roof and sidewall ventilation were considered in the model. This model was validated against the results of experiments conducted in the greenhouse when the wind was parallel to the gutters. The model parameters were determined by the least squares method. In the used model, effects of wind speed and window opening height on the air temperature variation were analyzed. Comparison between two types of ventilation showed that there existed a necessary ventilation rate which results in air temperature decrease in natural ventilation under special climatic conditions. In our experiments when wind speed was less than 3.2 ms?1, wind had a more gradual effect on greenhouse temperature for roof ventilation, compared with combined roof and sidewall ventilation, which had greater air temperature decrease than roof ventilation only.
基金Sponsored by the Key Project of National Natural Science Foundation of China (Grant No.51138004)the South China Key Laboratory Fund (Grant No.20121458321)the Architect Design on Energy-saving Residence in Shanghai (Grant No.08-2A-0183-zong)
文摘Based on the current indoor natural ventilation and lighting in the space of traditional residential buildings,this paper starts from the passive-design optimization of the spatial natural ventilation and lighting,and makes quantitative evaluation on the quality of current interior natural ventilation and lighting for two typical residential buildings by three indexes,including wind speed,static wind area ratio and satisfaction ratio about minimum lighting coefficient. Based on that, this paper conducts the passive design optimization, and establishes the quantitative association and reevaluation among the passive reformation design, natural ventilation,and lighting environmental quality,proposing the general strategy for the existing residential buildings to respond to the passive reformation design of the natural ventilation and lighting. The special reconstruction of core functionary space of integration of "the living room + dining room + partial space"is researched,and the redesign for the optimization and replacement of both indoor and outdoor enclosure parts is explored,which is expected to provide practical exploration on the strategies for passive construction of spatial natural environmental quality within a large number of highly-energy-consumed residential buildings in China,as well as the green design of residential buildings.
基金Sponsored by the National Natural Science Foundation of Guangdong Province(Grant No.2020A1515011092)the Open Projects Fund of KeyL aboratory of Ecology and Energy-saving Study of Dense Habitat(Tongji University),Ministry of Education(Grant No.2020030105)。
文摘Natural ventilation effects in high and large space buildings of tropical areas greatlya ffect the air conditioning energy consumption.Aiming at nearly zero energy building design,thisp aper mainly contributes to provide theoretical basis and reference for thermal comfortable air conditioning system design of high and large space buildings.Taking a theatre in Hainan as study object,a newly composite enhanced natural ventilation system is proposed by integrating theu nderground tunnel-based earth to air heat exchange system and the solar chimney.Ventilationq uantity,air velocity and air temperature field,human vertical temperature gradient differenceu nder24simulation working conditions are considered and analyzed by using ANSYS Fluent.Fort he underground tunnel,results show that Group Two with double underground tunnels and side airs upply location shows its advantages in cooling effects and air supply uniformity.Then for the solar chimney,results show that the solar radiation intensity contributes to larger difference int ransmission power and leads to different cooling effects.On the whole,the system under workingc ondition No.7with120m long,side air supply,double underground tunnel and20m high,1mw ide,0.6°absorber plate angle solar chimney shows its priority in better comprehensive performance.
基金This study was support by Tenth-five Program of China (2001BA70B02)
文摘To establish the model of indoor air pollution forecast for decoration. Methods The model was based on the balance model for diffusing mass. Results The data between testing concentration and estimating concentration were compared. The maximal error was less than 30% and average error was 14.6%. Conclusion The model can easily predict whether the pollution for decoration exceeds the standard and how long the room is decorated.
文摘Due to the urban and town development, it is common to see historical buildings and new buildings intermingled with one and another inside historical regions in Taiwan. With the increase of new buildings, natural ventilation becomes harder, which leads to the impact on the preservation of historical building and the reduction of thermal comfort for residents. Besides, problems of new buildings＇ construction and design affect the developments of cities and towns in historical district, which has existed for hundreds of years. The Wugoushui Settlement is located in Pingtung County, the southernmost part of Taiwan, and its hot season of a year is pretty long and belongs to warm and humid tropical climate. In 2008, the Pingtung County Government officially registered and announced Wugoushui as traditional settlement and meanwhile, provided the maintenance and preservation for buildings in this region on government subsidies. This paper is based on one-year-long field experiments of Wugoushui Settlement. Residents in Wugoushui Settlement continue constructing new buildings near by the traditional buildings. With the fact that constructions of new buildings result in huge impact on the circumstances of natural ventilation and thermal comfort, which have been for hundreds of years, the simple weather station is set up to collect the data of local microclimate. In addition, four representative traditional architectures were selected to be measured their indoor and outdoor temperature, humidity, wind speed, wind direction and thermal radiation both in winter （December to February） and in summer （May to September）. The measurement time of each building is one week and every data record is kept every minute. Besides, residents were asked to fill out the comfort survey. Based on these data, the distributions of indoor and outdoor thermal environment as well as the thermal comfort of living space under the condition of the natural ventilation are assessed. Finally, focused on the indoor living space of historical districts in southern Taiwan, there are two main suggestions given in the essay： first, a provisional comfort zone in summer is planned and proposed; second, the preliminary suggestions for the design and norms of new buildings in historical district are provided.
文摘With a sustained period of economic growth, rapidly growing populations and with more diversified economies Africa need sustainable development; hence the greater need for massive investments in energy. Sub-Saharan countries such as Djibouti have the potential and ability to harness their natural ventilation as a passive cooling system for designing new houses. The rapid expansion of the Djibouti city is affecting negatively the environment and the safety and comfort of its inhabitants. Proper atmospheric urban planning and management are key to making cities environmentally friendly and sustainable. Based on energy consumption, climate conditions in Djibouti and numerical analysis using Computational Fluid Dynamics （CFD）, it is apparent that the natural ventilation creates a thermally comfortable indoor environment in buildings during the cool season of the year. Measured wind data from two measurement systems are presented and discussed. Statistical analyses, wind rose, Weibull distribution were carried out to understand the natural ventilation characteristic, which is used for evolving the basic criteria for economic viability of building in the semi-arid climate of Djibouti. The study found that it is possible to benefit from natural ventilation in buildings during the cool season of the year.
文摘The main aim of this paper was to study the influence of ventilation during a typical experimental day, in the internal air temperature as well as in internal surface temperatures under the conditions of the outer environment, using an experimental method which allows a comparison of the thermal performance between four cell tests： a prototype called control （no vegetation） and three with different combinations of vegetation （roofs and facades） installed in a region of tropical climate. The experiments were developed in four test cells with dimensions 2.0 m × 2.50 m × 2.7 m. Measurements of internal surface temperatures and internal air temperatures were collected with the use of specific equipment, a data logger （CR1000, Campbell Scientific Inc.）, connected with two multiplexers 32 channels （416AM Campbell Scientific Inc.）. Data were recorded over a year and a typical heat day was selected, which was September 24, 2015. The results show that ventilation affects the internal temperature of the air, so that this gets even surpass the external temperature. Regarding surface temperatures, increased temperature, except those which are provided with vegetation, namely, the surfaces which have green walls and green roofs file the lower temperatures. Therefore, we can confirm the ability of vegetation to maintain more pleasant internal conditions compared to the test cells built with conventional materials, thus it can reduce cooling load efficiency.
文摘Natural ventilation is an efficient design strategy for the passive cooling of buildings, especially in tropical countries such as Brazil. Among the ventilation strategies, sheds can be highlighted. These structures consist of roof openings that work as air captors or extractors depending on their location in relation to the prevailing wind directions. The hospitals of the Sarah Network, designed by the Brazilian architect Joao Filgueiras Lima, Lele, are worldwide known for using these elements to improve natural ventilation. This paper analyses the natural ventilation performance of sheds for air collecting and extracting in two Sarah hospitals located in the cities of Salvador and Rio de Janeiro. In each building, the sheds were analyzed for air extracting and collecting. The analyses were carried out by reduced physical models in an atmospheric boundary layer wind tunnel. The wind velocity was measured at external and internal points of the buildings, using hot-wire anemometers. The results show that the wards in Rio de Janeiro hospital are 17% more ventilated than the ones in the Salvador hospital. However, this difference occurs not only because of the collecting sheds but also because of set of openings and the configuration of the covering in hospitals in Rio de Janeiro.
基金Supported by Fund of State Key Laboratory of Subtropical Building Science(2010KB15)Fund of Education Department of Guangdong Province(1184510150)
文摘By taking a modern residence in Meishan area as an example,15 measuring points have been set,and the wind speed of the parlor on the first and second floor and that of many bedding rooms have been measured every other hour from 7:00 to 22:00.Based on the measuring data and indoor architectural pattern,indoor ventilation has been analyzed.The results show that good natural ventilation could be created in modern rural residence by making use of plane layout,orientation and openings'organization,so that indoor air can be distributed evenly,helping to reduce temperature and remove humidness;indoor wind speed of the openings of architectures is the largest;and architectural orientation and opening's position can guide air flow and help to improve natural ventilation obviously.
文摘Windcatchers are used in building design as natural ventilation devices,providing fresh air supply and thermal comfort under suitable outdoor conditions.However,their performance is often constrained by environmental factors such as outdoor temperature,wind speed and direction.While passive or low-energy heating,cooling,and heat recovery devices have been integrated into conventional windcatcher designs,the impact of changing wind directions,which can render the windcatcher ineffective,is often not considered.Addressing this gap,this research builds upon a novel dual-channel windcatcher system.This system employs a rotary wind scoop to ensure a consistent fresh air supply and stale air exhaust,irrespective of wind direction and facilitates the integration of passive/low-energy technologies.Using a validated numerical computational fluid dynamics(CFD)model,the design of the proposed system was enhanced by incorporating technologies such as an anti-short-circuit device and wing walls,and modifications such as a larger wind scoop area and a redesigned wind cowl to increase the pressure differential between the inlet and outlet and reduce system friction.The modified windcatcher achieved a 28%improvement in ventilation rate and outperformed a conventional four-sided windcatcher of the same size by up to 58%.Furthermore,full-scale simulations of the building and windcatcher at varying heights were conducted under atmospheric boundary layer wind flow to provide a realistic assessment of the windcatcher’s performance.This research contributes to the development of more efficient windcatcher systems for further passive technology integrations,enhancing their viability as sustainable ventilation solutions.
基金supported by the National Key R&D Program of China(2023YFC3806502)the National Natural Science Foundation of China(No.52078296)Shenzhen Science and Technology Program(No.ZDSYS20210623101534001,No.JCYJ20210324093204011,No.20220810112113001).
文摘The severity and mortality rates associated with respiratory infectious diseases are notably elevated among older adults compared to younger populations.Nursing homes,which accommodate a considerable number of elderly individuals,are particularly vulnerable to disease outbreaks.This study proposes a method to assess the spatial infection risk of airborne transmission of respiratory diseases by coupling building layout and infiltrations.Field investigations were conducted to summarize nursing homes layout plan and occupants’activity characteristics.Meteorological parameters were used to obtain the wind pressure on building surfaces through computational fluid dynamics.The building ventilation network was further developed to quantify the pathogen exposure and infection risk of occupants.Results indicated that high infectious aerosol exposure appeared in the rooms with more occupants and low ventilation rates.In nursing homes,activity rooms were the highest infectious aerosol exposure area,accounting for 38.5%–47.9% of total exposure in a standard floor,followed by bedrooms,dining halls,and offices.Self-transmission dominated pathogen aerosol transmission,with self-transmission rates exceeding 70%in most rooms.Enhancing natural ventilation was validated as effective to reduce the risk of infection from infectious aerosol exposure.The proposed infection risk assessment is beneficial for the nursing home design in order to reduce the airborne transmission of respiratory diseases.
基金financially supported by National Natural Science Foundation of China (Grant No.52038009)。
文摘This paper investigated the smoke exhaustion characteristics and critical shaft height in a slope tunnel with naturally ventilated shafts based on reduced-scale tunnel experiments.The effects of longitudinal fire location,shaft setting,heat release rate(HRR) and tunnel slope on smoke exhaustion were studied.Experimental results show that the slope has great effect on smoke exhaustion.Moreover,the critical shaft height for complete smoke exhaustion of slope tunnels was studied theoretically and experimentally.The research indicates that the critical shaft height exhibits no dependency on the HRR.Notably,with the increasing of shaft length,the critical shaft height firstly decreases and then remains stable until it finally decreases to zero.Simultaneously,the critical shaft height increases with the increase of the slope and the distance between the shaft and the fire source.In addition,a theoretical model for predicting the critical shaft height was established and verified.The research results can provide some reference for the design of natural ventilation smoke exhaustion with shafts in slope tunnels.
基金supported by the Basic Science Research Program through the National Research Foundation of Korea (NRF) funded by the Ministry of Education, Science and Technology (Grant No. 2009-0063383)the Seoul R and BD program (Grant No. CS070160)the Leading Academic Discipline Project of Shanghai Municipal Education Commission (Grant No. J50502)
文摘The objective of this study is to investigate numerically the characteristics of train-induced unsteady airflow in a subway tunnel with natural ventilation ducts.A three-dimensional numerical model using the dynamic layering method for the moving boundary of a train is first developed,and then it is validated against the model tunnel experimental data.With the tunnel and subway train geometries in the numerical model exactly the same as those in the model tunnel experimental test,but with the ventilation ducts being connected to the tunnel ceiling and a barrier placed at the tunnel outlet,the three-dimensional train-induced unsteady tunnel flows are numerically simulated.The computed distributions of the pressure and the air velocity in the tunnel as well as the time series of the mass flow rate at the ventilation ducts reveal the impact of the train motion on the exhaust and suction of the air through ventilation ducts and the effects of a barrier placed at the tunnel outlet on the duct ventilation performance.As the train approaches a ventilation duct,the air is pushed out of the tunnel through the duct.As the train passes the ventilation duct,the exhaust flow in the duct is changed rapidly to the suction flow.After the train passes the duct,the suction mass flow rate at the duct decreases with time since the air pressure at the opening of the duct is gradually recovered with time.A drastic change in the mass flow rate at a ventilation duct while a train passes the corresponding ventilation duct,causes a change in the exhaust mass flow rate at other ventilation ducts.Also,when a barrier is placed at the tunnel outlet,the air volume discharge rate at each ventilation duct is greatly increased,i.e.,the barrier placed at the tunnel outlet can improve remarkably the ventilation performance through each duct.
基金This paper was supported by the National Natural Science Foundation of China(No.50778145,No.51478377).
文摘The solar greenhouse is a typical greenhouse type in northern China.It provides a favorable environment for the growth of various plants and extends cultivation periods for almost a whole year to achieve a high yield.However,indoor environmental control is primarily based on growers'experience,and the objective test data required for the complex climate control and management of greenhouses are lacking.The present study used three greenhouses in northwest China as research objects:one greenhouse with mature plants(GH-M),one greenhouse with young plants(GH-Y)and one greenhouse without plants(GH-E).Field tests were performed to investigate microclimate characteristics,such as indoor air temperature,relative humidity,and solar radiation under natural ventilation.The results showed that the maximum temperature difference reached approximately 8.2℃in the vertical direction,and semiempirical equations for the normalized temperature distribution were obtained.The soil temperature remained constant at a certain depth(0.4 m).The distribution of the relative humidity and solar radiation was analyzed.The current study is helpful for growers to develop better greenhouse climate control strategies for management practices.
文摘Large space circular coal storage dome(LSCCSD)offers an environmental and dependable alternative to open stockpiles,and it has been consequently widely applied in China.However,due to the lack of scientific guidelines,its natural ventilation performance is lower than expected.Natural ventilation potential strongly depends on the roof geometry and opening mode,which have not yet been investigated for LSCCSD.This paper presents a detailed evaluation of the impact of dome geometry(rise span ratio),opening height,and opening modes on the ventilation performance of LSCCSD.The evaluation is based on computational fluid dynamics(CFD)methods and is validated by available wind tunnel testing.We employed three evaluation indicators,which are wind pressure coefficient,effective ventilation rate,and wind speed ratio.The results demonstrate that the rise span ratio has a significant effect on the wind pressure difference and the effective ventilation rate increases by approximately 9%–42%with a single-annular opening.When double-annular openings are set in a strong positive pressure zone,the effective ventilation rate increases by 100%and the average wind speed ratio increases by 50%.When it is compared with single one with similar opening height,the effective ventilation rate increases by 25%.The optimum natural ventilation performance for LSCCSD is achieved at a rise span ratio of 0.37.In addition,the lateral middle opening is kept higher than the ridge top of the coal pile.The proposed evaluation approach and design parameters provided instructive information in the building design and ventilation control for LSCCSDs.
文摘This study explores architectural design by examining air, fluid mechanics, and the natural ventilation of buildings. In this context, this research introduces a new way of dealing with the process of architectural synthesis. The proposed way can be used either to create new architectural projects or to rethink existing ones. This study is supported by previous investigation into the natural ventilation of buildings via computational and laboratory simulation （Stavddou, 2011; Stavridou and Prinos, 2013）. The investigation into the natural ventilation of buildings provides information and data that affect architectural design through various parameters. The parameters of architectural synthesis that are influenced and discussed in this paper are the following： （i） inspiration and analogical transfer, （ii） initial conception of the main idea using computationat fluid dynamics （digital design）, （iii） development of the main idea through an investigatory process toward building form optimization, and （iv） form configuration, shape investigation, and other morphogenetic prospects. This study illustrates the effect of natural ventitation research on architectural design and thus produces a new approach to the architectural design process. This approach leads to an innovative kind of architecture called ＂breathing architecture.＂
