Energy consumed by buildings accounts for approximately one-third of the total energy consumption of the society.Moreover,energy systems employed in buildings emit hazardous pollutants,such as,NOx,PM2.5 and CO2,into t...Energy consumed by buildings accounts for approximately one-third of the total energy consumption of the society.Moreover,energy systems employed in buildings emit hazardous pollutants,such as,NOx,PM2.5 and CO2,into the environment.Consequently,increasing the energy efficiency of buildings constitutes an important problem concerning the field of building-energy and environment conservation.Thermal resistance and capacitance are two important thermophysical properties of building walls significantly impacting their heat-transfer performance.Traditional theories concerning these properties,however,face certain limitations:(1)the concept of thermal resistance is only valid for one-dimensional,steady heat conduction without existence of an internal heat source;(2)thermal resistance and capacitance are relevant,and can,therefore,not be used to analyze heat-transfer and storage performance,respectively,of building walls.Based on the entransy-dissipation-based impedance theory,a new approach towards realization of heat-transfer analysis and optimization has been proposed in this study.The weightiness of thermal resistance and capacitance with regard to heat-transfer performance has been described along with deduction of the corresponding substitutional relation via illustrative examples.The proposed approach has been demonstrated to effectively overcome aforementioned limitations of building energy conservation problems.展开更多
Substantially glazed facades are extensively used in contemporary high-rise buildings to achieve attractive architectural aesthetics.Inherent conflicts exist among architectural aesthetics,building energy consumption,...Substantially glazed facades are extensively used in contemporary high-rise buildings to achieve attractive architectural aesthetics.Inherent conflicts exist among architectural aesthetics,building energy consumption,and solar energy harvesting for glazed facades.In this study,we addressed these conflicts by introducing a new dynamic and vertical photovoltaic integrated building envelope(dvPVBE)that offers extraordinary flexibility with weather-responsive slat angles and blind positions,superior architectural aesthetics,and notable energy-saving potential.Three hierarchical control strategies were proposed for different scenarios of the dvPVBE:power generation priority(PGP),natural daylight priority(NDP),and energy-saving priority(ESP).Moreover,the PGP and ESP strategies were further analyzed in the simulation of a dvPVBE.An office room integrated with a dvPVBE was modeled using EnergyPlus.The influence of the dvPVBE in improving the building energy efficiency and corresponding optimal slat angles was investigated under the PGP and ESP control strategies.The results indicate that the application of dvPVBEs in Beijing can provide up to 131%of the annual energy demand of office rooms and significantly increase the annual net energy output by at least 226%compared with static photovoltaic(PV)blinds.The concept of this novel dvPVBE offers a viable approach by which the thermal load,daylight penetration,and energy generation can be effectively regulated.展开更多
Sandstorm,which injects generous newly emerging microbes into the atmosphere covering cities,adversely affects the air quality in built environments.However,few studies have examined the change of airborne bacteria du...Sandstorm,which injects generous newly emerging microbes into the atmosphere covering cities,adversely affects the air quality in built environments.However,few studies have examined the change of airborne bacteria during severe sandstorm events.In this work,we analyzed the airborne bacteria during one of the strongest sandstorms in East Asia onMarch 15th,2021,which affected large areas of China and Mongolia.The characteristics of the sandstorm were compared with those of the subsequent clean and haze days.The composition of the bacterial community of air samples was investigated using quantitative polymerase chain reaction(qPCR)and high-throughput sequencing technology.During the sandstorm,the particulate matter(PM)concentration and bacterial richnesswere extremely high(PM_(2.5):207μg/m^(3);PM_(10):1630μg/m^(3);5700 amplicon sequence variants/m^(3)).In addition,the sandstorm brought 10 pathogenic bacterial genera to the atmosphere,posing a grave hazard to human health.As the sandstorm subsided,small bioaerosols(0.65–1.1μm)with a similar bacterial community remained suspended in the atmosphere,bringing possible long-lasting health risks.展开更多
Volatile organic compounds(VOCs)emitted by building materials pose severe health risk.It is critical to identify major pollution sources for consequent intervention.An in-situ sampling method is introduced in this stu...Volatile organic compounds(VOCs)emitted by building materials pose severe health risk.It is critical to identify major pollution sources for consequent intervention.An in-situ sampling method is introduced in this study to determine solid-gas interface concentrations of building materials to help realize source apportionment with minimal disturbance and cost.The method is featured as an upended cylindrical chamber with two openings.A sampling flow rate lower than a critical value allows diffusion-controlled environment in the chamber and concentration equilibrium between building surfaces and the air.It is validated by tests under various sampling flow rates(difference of 2%–11%)and in an enclosed chamber(difference of 4.7%–14%).Flow field analysis shows that air speed in the chamber is lower than 0.001 m/s and Reynolds number is smaller than 0.5,confirming the diffusion nature.Results indicate that a chamber with large bottom area and/or low height could have high acceptable sampling flow rate,which would reduce sampling time needed.A field test demonstrated that the method can reasonably help reconstruct pollution field and capture interface concentrations change along with temperature.The proposed in-situ method could facilitate better diagnose indoor air pollution by quantifying source contributions.展开更多
Kunming,a city in southwest China,has a climate that is different from most of the other places in the world because of its unique geographical characteristics.Due to its temperate climate,most of the residential buil...Kunming,a city in southwest China,has a climate that is different from most of the other places in the world because of its unique geographical characteristics.Due to its temperate climate,most of the residential buildings in this region are naturally ventilated.Accordingly,a winter thermal comfort study was conducted in Kunming to reveal the thermal response of residents.Indoor and outdoor environmental parameters were measured,and participants were investigated about their clothing,thermal sensations,thermal preferences,and thermal acceptance using online questionnaires.Data from 162 valid questionnaires were collected in the survey.Although the climate is referred to as“mild”,the survey showed that the indoor temperature during winter was lower than the typical comfort range.Nevertheless,the participants responded that most of them felt neutral and comfortable.The neutral temperature of participants living in Kunming was determined to be 16.96℃.The acceptable thermal sensation vote(TSV)range of the residents is-0.72 to 1.52.The acceptable indoor air temperature range is 15.03℃to 19.55℃,and the optimum indoor air temperature is 17.2℃.According to this study,the existing thermal comfort evaluation models can hardly predict residents’thermal responses in Kunming well.展开更多
Passive house has been constructed in China on a large-scale over the past couple years for its great energy saving potential.However,research indicates that there is a significant discrepancy in energy performance fo...Passive house has been constructed in China on a large-scale over the past couple years for its great energy saving potential.However,research indicates that there is a significant discrepancy in energy performance for heating and cooling between passive houses in different climate zones.Therefore,this research develops a comparative analysis on the energy saving potential of passive houses with the conventional around China.A sensitivity analysis of thermal characteristics of building envelope(insulation of exterior walls and windows,and airtightness)on energy consumption is further carried out to improve the climate adaptability of passive house.Moreover,the variation of energy consumption under different heat gain intensity is also compared,to evaluate the effects of envelope thermal characteristics comprehensively.Results suggest that the decrease of exterior wall insulation leads to the greatest increase in energy consumption,especially in severe cold zone in China.However,the optimal insulation may change with the internal heat gain intensity,for instance,the decrease of insulation(from 0.4 to 1.0 W/(m^(2)·K))could reduce the energy consumption by 4.65 kW·h/(m^(2)·a)when the heat gain increases to 20 W/m^(2)for buildings in Hot Summer and Cold Winter zone in China.展开更多
The measurement of volatile organic compound (VOC) emissions from materials is normally conducted under standard environmental conditions, i.e., (23±1) ℃ temperature, (50±5)% relative humidity, and 0.1 MPa ...The measurement of volatile organic compound (VOC) emissions from materials is normally conducted under standard environmental conditions, i.e., (23±1) ℃ temperature, (50±5)% relative humidity, and 0.1 MPa pressure. In order to define VOC emissions in non-standard environmental conditions, it is necessary to study the impact of key environmental parameters on emissions. This paper evaluates the impact of air pressure on VOC emissions from an aircraft carpet. The correlation between air pressure and VOC diffusion coefficient is derived, and the emission model is applied to studying the VOC emissions under pressure conditions of less than 0.1 MPa.展开更多
For the release of hazardous contaminant indoors, source identification is critical for developing effective response measures. A method which can quickly and accurately identify the position, emission rate, and relea...For the release of hazardous contaminant indoors, source identification is critical for developing effective response measures. A method which can quickly and accurately identify the position, emission rate, and release time of a single constant contaminant source by using real sensors was presented. The method was numerically demonstrated and validated by a case study of contaminant release in a three-dimensional office. The effects of the measurement errors and total sampling period of sensor on the performance of source identification were thoroughly studied. The results indicate that the adverse effects of the measurement errors can be mitigated by extending the total sampling period. For reaching a desirable accuracy of source identification, the total sampling period should exceed a certain threshold, which can be determined by repeatedly running the identification method tmtil the results tend to be stable. The method presented can contribute to develop an onsite source identification system for protecting occupants from indoor releases.展开更多
Volatile organic compounds(VOCs) emitted from three types of carpets used in aircrafts were compared by using headspace and dynamic chamber tests. The headspace samples contained many compounds that were not detected ...Volatile organic compounds(VOCs) emitted from three types of carpets used in aircrafts were compared by using headspace and dynamic chamber tests. The headspace samples contained many compounds that were not detected in the dynamic chamber test; in addition, the dominant VOCs found by these two methods were different. The findings indicate that for highly sorptive materials such as carpets, headspace analysis may give inaccurate indication of actual VOC emissions, and it is necessary to conduct dynamic chamber tests over a certain period of time in order to identify the true emission characteristics. From the dynamic chamber tests, 2-ethyl-1-hexanol was the main VOC emitted from all three carpets. The study also examined the emission characteristics of aircraft carpets. In all experiments, total VOC(TVOC) concentration peaked within a few hours after the start of the experiment and was followed by rapid decay. The emission parameters of TVOC emitted by all three carpets were calculated and the simulated data matched the measured data well.展开更多
Chinese urban residential buildings face serious indoor air quality problems.Air purification systems(e.g.,air purifiers,fresh air systems)that supply fresh air or purify indoor air are widely used in residential buil...Chinese urban residential buildings face serious indoor air quality problems.Air purification systems(e.g.,air purifiers,fresh air systems)that supply fresh air or purify indoor air are widely used in residential buildings to improve indoor air quality.Considering the challenges of energy conservation and emission reduction,it is urgent to guide residents on choosing appropriate air purification systems.The key problem is how to identify the best air purification system with the lowest energy consumption or operating cost.Comparisons of air purification systems have rarely been conducted on the premise that they should deliver air such that the main indoor pollutant concentrations all meet air quality standards.Also ignored in comparisons are the increased filtration resistance caused by dust accumulation on the filter and the cost of filter replacement.In this study,we propose a method to compare residential air purification systems based on energy consumption and total cost,and we provide methods to select air purification systems in China's different climatic regions.We used a standard two-person bedroom as the example,and determined the most suitable(minimum cost or energy consumption)air purification systems for the capital cities of the provinces in Chinese mainland.展开更多
The air infiltration rate of buildings strongly influences indoor environment and energy consumption.In this study,several traditional methods for determining the air infiltration rate were compared,and their accuracy...The air infiltration rate of buildings strongly influences indoor environment and energy consumption.In this study,several traditional methods for determining the air infiltration rate were compared,and their accuracy in different scenarios was examined.Additionally,a method combining computational flow dynamics(CFD)with the Swami and Chandra(S-C)model was developed to predict the influence of the surrounding environment on the air infiltration rate.Two buildings in Dalian,China,were selected:one with a simple surrounding environment and the other with a complex surrounding environment;their air infiltration rates were measured.The test results were used to validate the accuracy of the air infiltration rate solution models in different urban environments.For the building with a simple environment,the difference between the simulation and experimental results was 0.86%–22.52%.For the building with a complex environment,this difference ranged from 17.42%to 159.28%.We found that most traditional models provide accurate results for buildings with simple surrounding and that the simulation results widely vary for buildings with complex surrounding.The results of the method of combining CFD with the S-C model were more accurate,and the relative error between the simulation and test results was 10.61%.The results indicate that the environment around the building should be fully considered when calculating the air infiltration rate.The results of this study can guide the application of methods of determining air infiltration rate.展开更多
The presence of walls’thermal defects can lead to large deviations between predicted and actual values of energy consumption.Infrared images have been used to compare the differences in U-value(heat transfer coeffici...The presence of walls’thermal defects can lead to large deviations between predicted and actual values of energy consumption.Infrared images have been used to compare the differences in U-value(heat transfer coefficient)and heat flow between defect and normal building walls.However,the extent to which different defects affect the U-value of building walls remains to be investigated.This study proposes a method for evaluating the impact of various defects on the U-value of building wall envelopes.Infrared images were acquired for a building in Beijing,China to demonstrate the method.First,the accuracy of the method for measuring heat flow through building walls was validated using the heat flow meter method.Second,the K-means method was applied to classify wall pixel temperatures and to identify defects of building walls.The area and boundary of defects were got.Then,the validated infrared method was used to calculate the U-value for different defects.Finally,the difference in heat transfer coefficients(ΔU_(sd))was used to evaluate the impact of various defects on the building wall.The results indicated that variations in the area and temperature of defects contributed differently to the wall’s U-value.The maximum difference between the U-value of the repaired defect and the unrepaired wall is 0.42 W/(m^(2)·K).The method proposed in this study quantitatively assesses the extent to which defects affect the U-value of a building wall,providing reference data for making decisions regarding wall renovation.展开更多
Particles suspended in air are often non-spherical shapes, giving rise to shape-dependent complex dynamical processes. Suspended non-spherical particles are associated with a wide array of engineering and scientific s...Particles suspended in air are often non-spherical shapes, giving rise to shape-dependent complex dynamical processes. Suspended non-spherical particles are associated with a wide array of engineering and scientific scenarios, embodying both their microscopic and macroscopic dynamical behaviors. A comprehensive understanding of the dynamical behaviors of non-spherical particles in air hinges on the accurate identification and description of particle shape, the development of shape-specific models for the forces and torques acting on these particles, and the subsequent micro- and macroscopic phenomena that emerge as a result. This review surveys the latest advancements in the field of non-spherical particles, spanning from shape identification to the characterization of their dynamical properties. An emphasis is placed on establishing a connection between the micro- and macroscopic dynamical behaviors of non-spherical particles. The shape-induced features encompass periodic rotation and preferential orientation, which result in an oscillating migration path and lead to distinctive macroscopic characteristics. The macroscopic features of non-spherical particles are elucidated based on the preceding analysis of forces, torques, and particle-flow interactions. The future perspectives are also discussed in this review.展开更多
With the rapid global urbanization and increasing climate risks in urban environments,urban planning has emerged as a pivotal component of climate policy[1,2].Urban areas are significant contributors to greenhouse gas...With the rapid global urbanization and increasing climate risks in urban environments,urban planning has emerged as a pivotal component of climate policy[1,2].Urban areas are significant contributors to greenhouse gas emissions and highly vulnerable to climate change exposures.Urban planning crucially contributes to changing the behavior and dynamics of exposure to both indoor and outdoor air pollution.At the 28th United Nations Climate Change Conference(COP28),a declaration on health was adopted globally.展开更多
The underlying uncertainty associated with long-term exposure to indoor pollutants at the population level has prevented point prediction models for indoor PM_(2.5)from providing adequate information for large-scale a...The underlying uncertainty associated with long-term exposure to indoor pollutants at the population level has prevented point prediction models for indoor PM_(2.5)from providing adequate information for large-scale applications.Moreover,physics-based prediction models are constrained by the untraceable input complexity.In this study,we predicted the large-scale spatiotemporal distributions of residential PM_(2.5)concentration using three data-driven models:Gaussian Process Regression(GPR),Quantile Random Forest(QRF),and Bayesian Neural Network(BNN).These three models were selected based on their established representative status within the spectrum of machine learning,ranging from“shallow”to“deep”methodologies.Our findings underscore the superior performance of the BNN model,which achieved an R2 ranging from 0.48 to 0.70 and 95%prediction interval coverage between 85%and 88%across multiple datasets.The comprehensive framework presented herein for model comparison,validation,and attribution can assist future studies in elucidating the complex nonlinear relationships between urban characteristics and indoor air pollutants,thereby providing valuable insights into urban planning,design,and policy development from the perspective of indoor PM_(2.5)pollution mitigation.展开更多
Improving the thermal performance of building envelope is an important way to save building energy consumption. The phase change energy storage building envelope is helpful to effective use of re-newable energy, reduc...Improving the thermal performance of building envelope is an important way to save building energy consumption. The phase change energy storage building envelope is helpful to effective use of re-newable energy, reducing building operational energy consumption, increasing building thermal com-fort, and reducing environment pollution and greenhouse gas emission. This paper presents the con-cept of ideal energy-saving building envelope, which is used to guide the building envelope material selection and thermal performance design. This paper reviews some available researches on phase change building material and phase change energy storage building envelope. At last, this paper pre-sents some current problems needed further research.展开更多
For a future carbon-neutral society,it is a great challenge to coordinate between the demand and supply sides of a power grid with high penetration of renewable energy sources.In this paper,a general power distributio...For a future carbon-neutral society,it is a great challenge to coordinate between the demand and supply sides of a power grid with high penetration of renewable energy sources.In this paper,a general power distribution system of buildings,namely,PEDF(photovoltaics,energy storage,direct current,flexibility),is proposed to provide an effective solution from the demand side.A PEDF system integrates distributed photovoltaics,energy storages(including traditional and virtual energy storage),and a direct current distribution system into a building to provide flexible services for the external power grid.System topology and control strategies at the grid,building,and device levels are introduced and analyzed.We select representative work about key technologies of the PEDF system in recent years,analyze research focuses,and summarize their major challenges&future opportunities.Then,we introduce three real application cases of the PEDF system.On-site measurement results demonstrate its feasibility and advantages.With the rapid growth of renewable power production and electric vehicles,the PEDF system is a potential and promising approach for largescale integration of renewable energy in a carbon-neutral future.展开更多
It is of great importance to improve the energy performance of the air-conditioning system for building energy conversation. Entransy provides a novel perspective to investigate the losses existing in the air-conditio...It is of great importance to improve the energy performance of the air-conditioning system for building energy conversation. Entransy provides a novel perspective to investigate the losses existing in the air-conditioning system. The progress of entransy analysis in the air-conditioning system is comprehensively investigated in the present study. Firstly missions and characteris- tics of the air-conditioning system are analyzed with emphasis on heat or mass transfer process. It is found that reducing the temperature difference, i.e. reducing the entransy dissipation helps to improve the performance. Entransy dissipations and thermal resistances of typical transfer processes in the air-conditioning system are presented. Characteristics of sensible heat transfer process and coupled heat and mass transfer processes are researched in terms of entransy dissipation analysis. Reasons leading to entransy dissipation are also clarified with the help of unmatched coefficient 4. Principles for reducing the entransy dissipation and constructing a high temperature cooling system are summarized on the basis of case studies in typical handling processes. It＇s recommended that reducing mixing process, improving match properties are main approaches to reduce the entransy dissipation. The present analysis is beneficial to casting light on the essence of the air-conditioning system and proposing novel approaches for performance optimization.展开更多
The prevalence and risk factors of sick building syndrome(SBS)symptoms in domestic environments were studied by a questionnaire survey on the home environment.Parents of 5299 3–6 years old children from randomly sele...The prevalence and risk factors of sick building syndrome(SBS)symptoms in domestic environments were studied by a questionnaire survey on the home environment.Parents of 5299 3–6 years old children from randomly selected kindergartens in Chongqing,China returned completed questionnaires between December 2010 and April 2011.The prevalence of parents’SBS symptoms(often(every week)compared with never)were:11.4%for general symptoms,7.1%for mucosal symptoms and 4.4%for skin symptoms.Multiple logistic regressions were applied controlling for gender and asthma/allergic rhinitis/eczema.Living near a main road or highway was a strong risk factor for general symptoms(adjusted odds ratio,aOR=2.16,P<0.001),skin symptoms(aOR=2.69,P<0.001),and mucosal symptoms(aOR=1.63,P<0.01).Redecoration was a risk factor for general symptoms(aOR=2.00,P<0.001),skin symptoms(aOR=1.66,P<0.01),and mucosal symptoms(aOR=1.66,P<0.05).New furniture was a risk factor for general symptoms(aOR=2.16,P<0.001)and skin symptoms(aOR=1.67,P<0.01).Dampness related problems(mould spot,damp stain,water damage and condensation)were all risk factors for SBS symptoms,as was the presence of cockroaches,rats,and mosquitoes/flies and use of incense.Protective factors include cleaning the child’s bedroom every day and frequently exposing bedding to sunshine.In conclusion,adults’SBS symptoms were related to factors of the home environment.展开更多
This paper sets up an analytic model of double surface emission of volatile organic com- pound (VOC) from dry,flat-plate building materials. Based on it,the influence of factors including air change rate,loading facto...This paper sets up an analytic model of double surface emission of volatile organic com- pound (VOC) from dry,flat-plate building materials. Based on it,the influence of factors including air change rate,loading factor of materials in the room,mass diffusion coefficient,partition coefficient,con- vective mass transfer coefficient,thickness of mate- rials,asymmetric convective flow and initial VOC concentration distribution in the building material on emission is discussed. The conditions for simplifying double surface emission into single surface emission are also discussed. The model is helpful to assess the double surface VOC emission from flat-plate building materials used in indoor furniture and space partition.展开更多
基金support for the research,authorship,and/or publication of this article:the Youth Science Research Foundation of China Academy of Building Research(20160118331030053).
文摘Energy consumed by buildings accounts for approximately one-third of the total energy consumption of the society.Moreover,energy systems employed in buildings emit hazardous pollutants,such as,NOx,PM2.5 and CO2,into the environment.Consequently,increasing the energy efficiency of buildings constitutes an important problem concerning the field of building-energy and environment conservation.Thermal resistance and capacitance are two important thermophysical properties of building walls significantly impacting their heat-transfer performance.Traditional theories concerning these properties,however,face certain limitations:(1)the concept of thermal resistance is only valid for one-dimensional,steady heat conduction without existence of an internal heat source;(2)thermal resistance and capacitance are relevant,and can,therefore,not be used to analyze heat-transfer and storage performance,respectively,of building walls.Based on the entransy-dissipation-based impedance theory,a new approach towards realization of heat-transfer analysis and optimization has been proposed in this study.The weightiness of thermal resistance and capacitance with regard to heat-transfer performance has been described along with deduction of the corresponding substitutional relation via illustrative examples.The proposed approach has been demonstrated to effectively overcome aforementioned limitations of building energy conservation problems.
基金supported by the National Natural Science Foundation of China(52078269 and 52325801).
文摘Substantially glazed facades are extensively used in contemporary high-rise buildings to achieve attractive architectural aesthetics.Inherent conflicts exist among architectural aesthetics,building energy consumption,and solar energy harvesting for glazed facades.In this study,we addressed these conflicts by introducing a new dynamic and vertical photovoltaic integrated building envelope(dvPVBE)that offers extraordinary flexibility with weather-responsive slat angles and blind positions,superior architectural aesthetics,and notable energy-saving potential.Three hierarchical control strategies were proposed for different scenarios of the dvPVBE:power generation priority(PGP),natural daylight priority(NDP),and energy-saving priority(ESP).Moreover,the PGP and ESP strategies were further analyzed in the simulation of a dvPVBE.An office room integrated with a dvPVBE was modeled using EnergyPlus.The influence of the dvPVBE in improving the building energy efficiency and corresponding optimal slat angles was investigated under the PGP and ESP control strategies.The results indicate that the application of dvPVBEs in Beijing can provide up to 131%of the annual energy demand of office rooms and significantly increase the annual net energy output by at least 226%compared with static photovoltaic(PV)blinds.The concept of this novel dvPVBE offers a viable approach by which the thermal load,daylight penetration,and energy generation can be effectively regulated.
基金This work was supported by the National Natural Science Foundation of China(No.52078269).
文摘Sandstorm,which injects generous newly emerging microbes into the atmosphere covering cities,adversely affects the air quality in built environments.However,few studies have examined the change of airborne bacteria during severe sandstorm events.In this work,we analyzed the airborne bacteria during one of the strongest sandstorms in East Asia onMarch 15th,2021,which affected large areas of China and Mongolia.The characteristics of the sandstorm were compared with those of the subsequent clean and haze days.The composition of the bacterial community of air samples was investigated using quantitative polymerase chain reaction(qPCR)and high-throughput sequencing technology.During the sandstorm,the particulate matter(PM)concentration and bacterial richnesswere extremely high(PM_(2.5):207μg/m^(3);PM_(10):1630μg/m^(3);5700 amplicon sequence variants/m^(3)).In addition,the sandstorm brought 10 pathogenic bacterial genera to the atmosphere,posing a grave hazard to human health.As the sandstorm subsided,small bioaerosols(0.65–1.1μm)with a similar bacterial community remained suspended in the atmosphere,bringing possible long-lasting health risks.
基金supported by the National Natural Science Foundation of China(Grant No.52408112)。
文摘Volatile organic compounds(VOCs)emitted by building materials pose severe health risk.It is critical to identify major pollution sources for consequent intervention.An in-situ sampling method is introduced in this study to determine solid-gas interface concentrations of building materials to help realize source apportionment with minimal disturbance and cost.The method is featured as an upended cylindrical chamber with two openings.A sampling flow rate lower than a critical value allows diffusion-controlled environment in the chamber and concentration equilibrium between building surfaces and the air.It is validated by tests under various sampling flow rates(difference of 2%–11%)and in an enclosed chamber(difference of 4.7%–14%).Flow field analysis shows that air speed in the chamber is lower than 0.001 m/s and Reynolds number is smaller than 0.5,confirming the diffusion nature.Results indicate that a chamber with large bottom area and/or low height could have high acceptable sampling flow rate,which would reduce sampling time needed.A field test demonstrated that the method can reasonably help reconstruct pollution field and capture interface concentrations change along with temperature.The proposed in-situ method could facilitate better diagnose indoor air pollution by quantifying source contributions.
基金Project(2018YFC0704500)supported by the National Key R&D Program of ChinaProjects(51838007,52130803)supported by the National Natural Science Foundation of China。
文摘Kunming,a city in southwest China,has a climate that is different from most of the other places in the world because of its unique geographical characteristics.Due to its temperate climate,most of the residential buildings in this region are naturally ventilated.Accordingly,a winter thermal comfort study was conducted in Kunming to reveal the thermal response of residents.Indoor and outdoor environmental parameters were measured,and participants were investigated about their clothing,thermal sensations,thermal preferences,and thermal acceptance using online questionnaires.Data from 162 valid questionnaires were collected in the survey.Although the climate is referred to as“mild”,the survey showed that the indoor temperature during winter was lower than the typical comfort range.Nevertheless,the participants responded that most of them felt neutral and comfortable.The neutral temperature of participants living in Kunming was determined to be 16.96℃.The acceptable thermal sensation vote(TSV)range of the residents is-0.72 to 1.52.The acceptable indoor air temperature range is 15.03℃to 19.55℃,and the optimum indoor air temperature is 17.2℃.According to this study,the existing thermal comfort evaluation models can hardly predict residents’thermal responses in Kunming well.
基金Project(51825802)supported by the National Science Foundation for Distinguished Young Scholars of ChinaProject(2018YFE0106100)supported by the National Key R&D Program of China。
文摘Passive house has been constructed in China on a large-scale over the past couple years for its great energy saving potential.However,research indicates that there is a significant discrepancy in energy performance for heating and cooling between passive houses in different climate zones.Therefore,this research develops a comparative analysis on the energy saving potential of passive houses with the conventional around China.A sensitivity analysis of thermal characteristics of building envelope(insulation of exterior walls and windows,and airtightness)on energy consumption is further carried out to improve the climate adaptability of passive house.Moreover,the variation of energy consumption under different heat gain intensity is also compared,to evaluate the effects of envelope thermal characteristics comprehensively.Results suggest that the decrease of exterior wall insulation leads to the greatest increase in energy consumption,especially in severe cold zone in China.However,the optimal insulation may change with the internal heat gain intensity,for instance,the decrease of insulation(from 0.4 to 1.0 W/(m^(2)·K))could reduce the energy consumption by 4.65 kW·h/(m^(2)·a)when the heat gain increases to 20 W/m^(2)for buildings in Hot Summer and Cold Winter zone in China.
基金Project supported by Boeing Commercial Airplanes,USA
文摘The measurement of volatile organic compound (VOC) emissions from materials is normally conducted under standard environmental conditions, i.e., (23±1) ℃ temperature, (50±5)% relative humidity, and 0.1 MPa pressure. In order to define VOC emissions in non-standard environmental conditions, it is necessary to study the impact of key environmental parameters on emissions. This paper evaluates the impact of air pressure on VOC emissions from an aircraft carpet. The correlation between air pressure and VOC diffusion coefficient is derived, and the emission model is applied to studying the VOC emissions under pressure conditions of less than 0.1 MPa.
基金Project(50908128) supported by the National Natural Science Foundation of ChinaProject(51125030) supported by the National Science Foundation for Distinguished Young Scholars in China
文摘For the release of hazardous contaminant indoors, source identification is critical for developing effective response measures. A method which can quickly and accurately identify the position, emission rate, and release time of a single constant contaminant source by using real sensors was presented. The method was numerically demonstrated and validated by a case study of contaminant release in a three-dimensional office. The effects of the measurement errors and total sampling period of sensor on the performance of source identification were thoroughly studied. The results indicate that the adverse effects of the measurement errors can be mitigated by extending the total sampling period. For reaching a desirable accuracy of source identification, the total sampling period should exceed a certain threshold, which can be determined by repeatedly running the identification method tmtil the results tend to be stable. The method presented can contribute to develop an onsite source identification system for protecting occupants from indoor releases.
基金Funded by the National Basic Research Program of China(973 Program) under Grant No.2012CB720100
文摘Volatile organic compounds(VOCs) emitted from three types of carpets used in aircrafts were compared by using headspace and dynamic chamber tests. The headspace samples contained many compounds that were not detected in the dynamic chamber test; in addition, the dominant VOCs found by these two methods were different. The findings indicate that for highly sorptive materials such as carpets, headspace analysis may give inaccurate indication of actual VOC emissions, and it is necessary to conduct dynamic chamber tests over a certain period of time in order to identify the true emission characteristics. From the dynamic chamber tests, 2-ethyl-1-hexanol was the main VOC emitted from all three carpets. The study also examined the emission characteristics of aircraft carpets. In all experiments, total VOC(TVOC) concentration peaked within a few hours after the start of the experiment and was followed by rapid decay. The emission parameters of TVOC emitted by all three carpets were calculated and the simulated data matched the measured data well.
基金supported by the National Natural Science Foundation of China(Grant No.51976106)。
文摘Chinese urban residential buildings face serious indoor air quality problems.Air purification systems(e.g.,air purifiers,fresh air systems)that supply fresh air or purify indoor air are widely used in residential buildings to improve indoor air quality.Considering the challenges of energy conservation and emission reduction,it is urgent to guide residents on choosing appropriate air purification systems.The key problem is how to identify the best air purification system with the lowest energy consumption or operating cost.Comparisons of air purification systems have rarely been conducted on the premise that they should deliver air such that the main indoor pollutant concentrations all meet air quality standards.Also ignored in comparisons are the increased filtration resistance caused by dust accumulation on the filter and the cost of filter replacement.In this study,we propose a method to compare residential air purification systems based on energy consumption and total cost,and we provide methods to select air purification systems in China's different climatic regions.We used a standard two-person bedroom as the example,and determined the most suitable(minimum cost or energy consumption)air purification systems for the capital cities of the provinces in Chinese mainland.
基金the National Natural Science Foundation of China(51838007)the Tsinghua-Toyota Joint Research Institute Inter-disciplinary Program.
文摘The air infiltration rate of buildings strongly influences indoor environment and energy consumption.In this study,several traditional methods for determining the air infiltration rate were compared,and their accuracy in different scenarios was examined.Additionally,a method combining computational flow dynamics(CFD)with the Swami and Chandra(S-C)model was developed to predict the influence of the surrounding environment on the air infiltration rate.Two buildings in Dalian,China,were selected:one with a simple surrounding environment and the other with a complex surrounding environment;their air infiltration rates were measured.The test results were used to validate the accuracy of the air infiltration rate solution models in different urban environments.For the building with a simple environment,the difference between the simulation and experimental results was 0.86%–22.52%.For the building with a complex environment,this difference ranged from 17.42%to 159.28%.We found that most traditional models provide accurate results for buildings with simple surrounding and that the simulation results widely vary for buildings with complex surrounding.The results of the method of combining CFD with the S-C model were more accurate,and the relative error between the simulation and test results was 10.61%.The results indicate that the environment around the building should be fully considered when calculating the air infiltration rate.The results of this study can guide the application of methods of determining air infiltration rate.
基金funded by the China Postdoctoral Science Foundation(2024M751701).
文摘The presence of walls’thermal defects can lead to large deviations between predicted and actual values of energy consumption.Infrared images have been used to compare the differences in U-value(heat transfer coefficient)and heat flow between defect and normal building walls.However,the extent to which different defects affect the U-value of building walls remains to be investigated.This study proposes a method for evaluating the impact of various defects on the U-value of building wall envelopes.Infrared images were acquired for a building in Beijing,China to demonstrate the method.First,the accuracy of the method for measuring heat flow through building walls was validated using the heat flow meter method.Second,the K-means method was applied to classify wall pixel temperatures and to identify defects of building walls.The area and boundary of defects were got.Then,the validated infrared method was used to calculate the U-value for different defects.Finally,the difference in heat transfer coefficients(ΔU_(sd))was used to evaluate the impact of various defects on the building wall.The results indicated that variations in the area and temperature of defects contributed differently to the wall’s U-value.The maximum difference between the U-value of the repaired defect and the unrepaired wall is 0.42 W/(m^(2)·K).The method proposed in this study quantitatively assesses the extent to which defects affect the U-value of a building wall,providing reference data for making decisions regarding wall renovation.
文摘Particles suspended in air are often non-spherical shapes, giving rise to shape-dependent complex dynamical processes. Suspended non-spherical particles are associated with a wide array of engineering and scientific scenarios, embodying both their microscopic and macroscopic dynamical behaviors. A comprehensive understanding of the dynamical behaviors of non-spherical particles in air hinges on the accurate identification and description of particle shape, the development of shape-specific models for the forces and torques acting on these particles, and the subsequent micro- and macroscopic phenomena that emerge as a result. This review surveys the latest advancements in the field of non-spherical particles, spanning from shape identification to the characterization of their dynamical properties. An emphasis is placed on establishing a connection between the micro- and macroscopic dynamical behaviors of non-spherical particles. The shape-induced features encompass periodic rotation and preferential orientation, which result in an oscillating migration path and lead to distinctive macroscopic characteristics. The macroscopic features of non-spherical particles are elucidated based on the preceding analysis of forces, torques, and particle-flow interactions. The future perspectives are also discussed in this review.
基金funded by the Hang Lung Center for Real Estate,Tsinghua University,China.
文摘With the rapid global urbanization and increasing climate risks in urban environments,urban planning has emerged as a pivotal component of climate policy[1,2].Urban areas are significant contributors to greenhouse gas emissions and highly vulnerable to climate change exposures.Urban planning crucially contributes to changing the behavior and dynamics of exposure to both indoor and outdoor air pollution.At the 28th United Nations Climate Change Conference(COP28),a declaration on health was adopted globally.
基金funded by the Hang Lung Center for Real Estate,Tsinghua University,China.
文摘The underlying uncertainty associated with long-term exposure to indoor pollutants at the population level has prevented point prediction models for indoor PM_(2.5)from providing adequate information for large-scale applications.Moreover,physics-based prediction models are constrained by the untraceable input complexity.In this study,we predicted the large-scale spatiotemporal distributions of residential PM_(2.5)concentration using three data-driven models:Gaussian Process Regression(GPR),Quantile Random Forest(QRF),and Bayesian Neural Network(BNN).These three models were selected based on their established representative status within the spectrum of machine learning,ranging from“shallow”to“deep”methodologies.Our findings underscore the superior performance of the BNN model,which achieved an R2 ranging from 0.48 to 0.70 and 95%prediction interval coverage between 85%and 88%across multiple datasets.The comprehensive framework presented herein for model comparison,validation,and attribution can assist future studies in elucidating the complex nonlinear relationships between urban characteristics and indoor air pollutants,thereby providing valuable insights into urban planning,design,and policy development from the perspective of indoor PM_(2.5)pollution mitigation.
基金Supported by National Supporting Program for Science and Technology of China (Grant Nos. 2006BAA04B02 and 2006BAJ02A09)
文摘Improving the thermal performance of building envelope is an important way to save building energy consumption. The phase change energy storage building envelope is helpful to effective use of re-newable energy, reducing building operational energy consumption, increasing building thermal com-fort, and reducing environment pollution and greenhouse gas emission. This paper presents the con-cept of ideal energy-saving building envelope, which is used to guide the building envelope material selection and thermal performance design. This paper reviews some available researches on phase change building material and phase change energy storage building envelope. At last, this paper pre-sents some current problems needed further research.
基金supported in part by the National Natural Science Foundation of China(No.52208112)the major consulting project of the Chinese Academy of Engineering(52021-HYZD-16)+1 种基金the Energy Foundation(No.G-2209-34123),the China Postdoctoral Science Foundation(2021M701935)the Shuimu Tsinghua Scholar Program of Tsinghua University(2021SM001).
文摘For a future carbon-neutral society,it is a great challenge to coordinate between the demand and supply sides of a power grid with high penetration of renewable energy sources.In this paper,a general power distribution system of buildings,namely,PEDF(photovoltaics,energy storage,direct current,flexibility),is proposed to provide an effective solution from the demand side.A PEDF system integrates distributed photovoltaics,energy storages(including traditional and virtual energy storage),and a direct current distribution system into a building to provide flexible services for the external power grid.System topology and control strategies at the grid,building,and device levels are introduced and analyzed.We select representative work about key technologies of the PEDF system in recent years,analyze research focuses,and summarize their major challenges&future opportunities.Then,we introduce three real application cases of the PEDF system.On-site measurement results demonstrate its feasibility and advantages.With the rapid growth of renewable power production and electric vehicles,the PEDF system is a potential and promising approach for largescale integration of renewable energy in a carbon-neutral future.
基金supported by National Natural Science Foundation of China(Grant Nos.51422808&51521005)the National Science&Technology Pillar Program during the 12th Five-year Plan Period(Grant No.2014BAJ02B01)the China Postdoctoral Science Foundation(Grant No.2015M570107)
文摘It is of great importance to improve the energy performance of the air-conditioning system for building energy conversation. Entransy provides a novel perspective to investigate the losses existing in the air-conditioning system. The progress of entransy analysis in the air-conditioning system is comprehensively investigated in the present study. Firstly missions and characteris- tics of the air-conditioning system are analyzed with emphasis on heat or mass transfer process. It is found that reducing the temperature difference, i.e. reducing the entransy dissipation helps to improve the performance. Entransy dissipations and thermal resistances of typical transfer processes in the air-conditioning system are presented. Characteristics of sensible heat transfer process and coupled heat and mass transfer processes are researched in terms of entransy dissipation analysis. Reasons leading to entransy dissipation are also clarified with the help of unmatched coefficient 4. Principles for reducing the entransy dissipation and constructing a high temperature cooling system are summarized on the basis of case studies in typical handling processes. It＇s recommended that reducing mixing process, improving match properties are main approaches to reduce the entransy dissipation. The present analysis is beneficial to casting light on the essence of the air-conditioning system and proposing novel approaches for performance optimization.
基金supported by the Key National Project of Physical Science(50838009)National Technology Support Project(2012BAJ02B06)
文摘The prevalence and risk factors of sick building syndrome(SBS)symptoms in domestic environments were studied by a questionnaire survey on the home environment.Parents of 5299 3–6 years old children from randomly selected kindergartens in Chongqing,China returned completed questionnaires between December 2010 and April 2011.The prevalence of parents’SBS symptoms(often(every week)compared with never)were:11.4%for general symptoms,7.1%for mucosal symptoms and 4.4%for skin symptoms.Multiple logistic regressions were applied controlling for gender and asthma/allergic rhinitis/eczema.Living near a main road or highway was a strong risk factor for general symptoms(adjusted odds ratio,aOR=2.16,P<0.001),skin symptoms(aOR=2.69,P<0.001),and mucosal symptoms(aOR=1.63,P<0.01).Redecoration was a risk factor for general symptoms(aOR=2.00,P<0.001),skin symptoms(aOR=1.66,P<0.01),and mucosal symptoms(aOR=1.66,P<0.05).New furniture was a risk factor for general symptoms(aOR=2.16,P<0.001)and skin symptoms(aOR=1.67,P<0.01).Dampness related problems(mould spot,damp stain,water damage and condensation)were all risk factors for SBS symptoms,as was the presence of cockroaches,rats,and mosquitoes/flies and use of incense.Protective factors include cleaning the child’s bedroom every day and frequently exposing bedding to sunshine.In conclusion,adults’SBS symptoms were related to factors of the home environment.
基金the National Natural Science Foundation of China （Grant No. 50478012）.
文摘This paper sets up an analytic model of double surface emission of volatile organic com- pound (VOC) from dry,flat-plate building materials. Based on it,the influence of factors including air change rate,loading factor of materials in the room,mass diffusion coefficient,partition coefficient,con- vective mass transfer coefficient,thickness of mate- rials,asymmetric convective flow and initial VOC concentration distribution in the building material on emission is discussed. The conditions for simplifying double surface emission into single surface emission are also discussed. The model is helpful to assess the double surface VOC emission from flat-plate building materials used in indoor furniture and space partition.
