A novel approach to enhance outdoor air quality: Pedestrian ventilation system

Higher population density has altered the cities' old landscape with dense areas consisting of high-rise buildings. As a result, detrimental phenomena appeared inside modern cities that threatened the inhabitant's health and comfort. Among these phenomena, the Urban Heat Island (UHI) is known as the most harmful side effect of the urbanization which affects the Outdoor Air Quality (OAQ).     

The effects of outdoor air supply rate in an office on perceived air quality, sick building syndrome (SBS) symptoms and productivity

Perceived air quality, Sick Building Syndrome (SBS) symptoms and productivity were studied in a normally furnished office space (108 m3) ventilated with an outdoor airflow of 3, 10 or 30 L/s per person, corresponding to an air change rate of 0.6, 2 or 6 h-1. The temperature of 22 degrees C, the relative humidity of 40% and all other environmental parameters remained unchanged. Five groups of six female subjects were each exposed to the three ventilation rates, one group and one ventilation rate at a time. Each exposure lasted 4.6 h and took place in the afternoon. Subjects were unaware of the intervention and remained thermally neutral by adjusting their clothing. They assessed perceived air quality and SBS symptoms at intervals, and performed simulated normal office work. Increasing ventilation decreased the percentage of subjects dissatisfied with the air quality (P < 0.002) and the intensity of odour (P < 0.02), and increased the perceived freshness of air (P < 0.05). It also decreased the sensation of dryness of mouth and throat (P < 0.0006), eased difficulty in thinking clearly (P < 0.001) and made subjects feel generally better (P < 0.0001). The performance of four simulated office tasks improved monotonically with increasing ventilation rates, and the effect reached formal significance in the case of text-typing (P < 0.03). For each two-fold increase in ventilation rate, performance improved on average by 1.7%. This study shows the benefits for health, comfort and productivity of ventilation at rates well above the minimum levels prescribed in existing standards and guidelines. It confirms the results of a previous study in the same office when the indoor air quality was improved by decreasing the pollution load while the ventilation remained unchanged.     

Impact of building regulations on the perceived outdoor thermal comfort in the mixed-use neighbourhood of Chennai

The population in urban areas is increasing rapidly around the world in most of the cities.In India,this growth has forced the local governments to review the planning norms regularly with the main focus of making an affordable urban living.This resulted in increasing the built density without evaluating the effect of such developments on human thermal com-fort.Outdoor microclimate is one of the significant factors that determine the quality of out-door spaces.This study investigates the potential impact of the built geometry guided by the newly published development control rules of Chennai,India on the various parameters that influence microclimate.The existing and future scenario has been modelled for three locations in a typical mixed-use neighborhood of Chennai.Further,air temperature and relative humid-ity were measured in three locations on a typical summer month of May 2018.The recorded data was used for validating the simulated model and calibrating the model settings.Most of the studies on outdoor thermal comfort compare a base case scenario and project future scenarios.This paper is a more realistic comparison of outdoor thermal comfort between the actual resultant built environment guided by the new Tamil Nadu Combined Development and Building Rules,2019 for selected locations and the existing built geometry which is the outcome of revised development control rules of 2013.The study found a significant reduction of 18℃in mean radiant temperature(Tmrt)and a reduction of 12℃in Physiological Equiv-alent Temperature(PET)between the 2013 and the predicted built geometry as per 2019 build-ing rules.Further the duration of extreme heat stress in the Physiological Equivalent Temperature(PET)scale show a reduction of 3 h during the day time.The study will assist ur-ban planners and designers to include outdoor thermal comfort also as an important factor while developing building rules.     

Impact of building regulations on the perceived outdoor thermal comfort in the mixed-use neighbourhood of Chennai

The population in urban areas is increasing rapidly around the world in most of the cities. In India, this growth has forced the local governments to review the planning norms regularly with the main focus of making an affordable urban living. This resulted in increasing the built density without evaluating the effect of such developments on human thermal comfort. Outdoor microclimate is one of the significant factors that determine the quality of outdoor spaces. This study investigates the potential impact of the built geometry guided by the newly published development control rules of Chennai, India on the various parameters that influence microclimate. The existing and future scenario has been modelled for three locations in a typical mixed-use neighborhood of Chennai. Further, air temperature and relative humidity were measured in three locations on a typical summer month of May 2018. The recorded data was used for validating the simulated model and calibrating the model settings. Most of the studies on outdoor thermal comfort compare a base case scenario and project future scenarios. This paper is a more realistic comparison of outdoor thermal comfort between the actual resultant built environment guided by the new Tamil Nadu Combined Development and Building Rules, 2019 for selected locations and the existing built geometry which is the outcome of revised development control rules of 2013. The study found a significant reduction of 18 C in mean radiant temperature (Tmrt) and a reduction of 12 C in Physiological Equivalent Temperature (PET) between the 2013 and the predicted built geometry as per 2019 building rules. Further the duration of extreme heat stress in the Physiological Equivalent Temperature (PET) scale show a reduction of 3 h during the day time. The study will assist urban planners and designers to include outdoor thermal comfort also as an important factor while developing building rules.     

A review of ventilation and the quality of ventilation air

Ventilation is pivotal in terms of securing optimum indoor air quality. In addition, it also has a major impact on energy use in buildings. It is important, therefore, that the role and impact of ventilation is fully understood and that ventilation is employed efficiently. The purpose of this paper is to review these aspects with particular reference to recent research and developments. Key aspects are concerned with identifying the role of ventilation and reviewing this role in the context of the other measures that must be taken to secure a healthy indoor environment. References are particularly made to the development of standards and recent related research. Although good progress is being made, areas that still need to be addressed include maintaining good outdoor air quality and preventing contaminated outdoor air from entering buildings. The outcome of recent research must also be disseminated in practical ways to policy makers, building occupiers and practitioners. Good indoor climate can be achieved, not so much by introducing expensive concepts, but by developing a rationale approach to identifying needs and applying the necessary tools to deal with each need.     

某建筑中庭气流组织的数值模拟

利用Fluent软件分别对冬、夏季工况下的球形喷口侧送风方案、条形风口侧送风方案和冬季工况下的条形风口侧送风+地板辐射供暖方案的气流组织进行了模拟,并对模拟结果进行了评价分析。结果表明条形风口侧送风+地板辐射供暖方案具有更好的舒适效果。     

Numerical simulations of wind-driven rain on building envelopes based on Eulerian multiphase model

A numerical simulation approach for evaluation of wind-driven rain (WDR) on building envelopes is presented based on Eulerian multiphase model. Unlike existing methods, which are generally on the basis of Lagrange frame to deal with raindrop motions by trajectory-tracking techniques, the present approach considers both wind and rain motions and their interactions under Euler frame. By virtue of the Eulerian multiphase model, the present method could significantly reduce the complexity in evaluations of WDR parameters, simplify the boundary condition treatments and is more efficient to predict transient states of WDR, spatial distributions of rain intensity, impacting rain loads on building surfaces, etc. A numerical example shows that the simulation results by the present method agree well with available experimental and numerical data, verifying the accuracy and reliability of the WDR simulation approach based on the Eulerian multiphase model. It is also demonstrated through the validation example that the present method is an effective tool for numerical evaluations of WDR on building envelopes.     

基于改进遗传算法的建筑室内空气品质评价

在分析室内空气品质的关键影响因素的基础上,提出采用改进的GA遗传算法应用于室内空气品质评价测试,给出了改进遗传算法室内空气品质综合评价的基本原理,对江门市室内空气实测数据进行了综合评价对比,验证了所提出评价法的有效性。     

Numerical investigation on the ingress of particulate matter from ambient air into the inlet of a building air handling unit

The transportation of ambient particulate matter (PM) from outdoor air into the inlet of a mechanical building ventilation system is poorly understood. No studies have examined the effect commonly used commercial air handling unit (AHU) inlet designs have upon the migration of PM from the ambient environment into the building ventilation system, and implications of this on energy consumption and indoor air quality (IAQ). Through the numerical analysis of commercial AHU inlets, the differences in concentration of PM in ambient air and that within AHUs were determined, more commonly referred to as Aspiration Efficiency (AE %). A 20–50% difference in particle concentrations between ambient air and the in-AHU concentration was observed between forward and rear-facing AHUs relative to ambient wind direction and speed, and at the maximum ventilation flow rate. Furthermore, a decrease in the ventilation flow rates resulted in a significant reduction in PM concentrations entering the rear-facing AHU. Increasing the Stoke number led to lower AE as a continuous decrease was observed for both rear-facing inlets. The findings of this paper show that AHU inlet design has significant implications on IAQ and building energy consumption, and scope exists to design these inlets to impact both aspects positively.     

室外环境对露天幕墙检测的影响

当幕墙检测装置处于露天时,复杂多变的室外环境、恶劣的天气对检测结果和安全方面会造成一定的影响。本文主要对这些影响因素进行分析,并提出相应的对策。     

基于变频空调器的舒适性指标与室内空气质量智能控制研究

以衡量热舒适性的PMV和反映室内空气质量的CO2浓度为控制输入参数,建立了相应的控制策略,分别对变频空调器压缩机、蒸发器风机、新风阀(机)和台式小风扇进行控制以同时满足0相似文献   

Relationship between outdoor and indoor air quality in eight French schools

In the frame of the French national research program PRIMEQUAL (inter-ministry program for better air quality in urban environments), measurements of outdoor and indoor pollution have been carried out in eight schools in La Rochelle (France) and its suburbs. The buildings were naturally ventilated by opening the windows, or mechanically ventilated, and showed various air permeabilities. Ozone, nitrogen oxides (NO and NO(2)), and airborne particle (particle counts within 15 size intervals ranging from 0.3 to 15 mum) concentrations were continuously monitored indoors and outdoors for two 2-week periods. The indoor humidity, temperature, CO(2) concentration (an indicator of occupancy), window openings and building permeability were also measured. The temporal profiles of indoor and outdoor concentrations show ozone and nitrogen oxides behave differently: NO and NO(2) indoor/outdoor concentration ratios (I/O) were found to vary in a range from 0.5 to 1, and from 0.88 to 1, respectively, but no correlation with building permeability was observed. On the contrary, I/O ratios of ozone vary in a range from 0 to 0.45 and seem to be strongly influenced by the building air-tightness: the more airtight the building envelope, the lower the ratio. Occupancy, through re-suspension of previously deposited particles and possible particle generation, strongly influences the indoor concentration level of airborne particles. However, this influence decreases with particle size, reflecting the way deposition velocities vary as a function of size. The influence of particle size on deposition and penetration across the building envelope is also discussed by analyzing the I/O ratios measured when the buildings were unoccupied, by comparing the indoor concentrations measured when the buildings were occupied and when they were not (O/U ratios), and by referring to previously published studies focussing on this topic. Except one case, I/O were found to vary in the range from 0.03 to 1.79. All O/U are greater than one and increase up to 100 with particle size. PRACTICAL IMPLICATIONS: Assessing children's total exposure requires the knowledge of outdoor and indoor air contaminant concentrations. The study presented here provides data on compared outdoor and indoor concentration levels in school buildings, as well as information on the parameters influencing the relationship between outdoor and indoor air quality. It may be used as a basis for estimating indoor concentrations from outdoor concentrations data, or as a first step in designing buildings sheltering children against atmospheric pollution.     

空调房间3种侧送风方式下室内气流组织的数值模拟与分析

采用雷诺时均的Navier-Stokes方程与标准κ-ε双方程模型,对常用的3种侧送风方式下的办公建筑进行数值模拟,对室内空气的速度场、温度场以及空气龄进行分析,认为送回风同侧的通风方式优于送回风对侧的通风方式,可获得较高的室内空气品质。     

Impact of varying area of polluting surface materials on perceived air quality

A laboratory study was performed to investigate the impact of the concentration of pollutants in the air on emissions from building materials. Building materials were placed in ventilated test chambers. The experimental set-up allowed the concentration of pollution in the exhaust air to be changed either by diluting exhaust air with clean air (changing the dilution factor) or by varying the area of the material inside the chamber when keeping the ventilation rate constant (changing the area factor). Four different building materials and three combinations of two or three building materials were studied in ventilated small-scale test chambers. Each individual material and three of their combinations were examined at four different dilution factors and four different area factors. An untrained panel of 23 subjects assessed the air quality from the chambers. The results show that a certain increase in dilution improves the perceived air quality more than a similar decrease in area. The reason for this may be that the emission rate of odorous pollutants increases when the concentration in the chamber decreases. The results demonstrate that, in some cases the effect of increased ventilation on the air quality may be less than expected from a simple dilution model.     

冬季三种通风方式下室内环境的数值模拟

采用雷诺平均的Navier-Stokes方程与RNG的k-ε涡粘性湍流模型,模拟了内设障碍物的冬季房间模型常用的3种不同通风方案下室内空气的速度场,温度场以及污染物的浓度分布。通过分析认为同侧下送上回的通风方式可使室内较好地保持热量,因此可有效地节约能源。对侧下送上回通风可使工作区得到较高的空气品质,较高的热舒适性和较高的通风效率。     

The effects of outdoor air supply rate on work performance during 8-h work period

The purpose of this study is to evaluate the effect of ventilation rate on work performance and perceived air quality through short-term laboratory experiments. The experiment was designed to simulate office work, and a laboratory space was modified using new finish materials to become a typical office space. High levels of volatile organic compounds (VOCs) were found in the exposure chamber, most probably originating from the new finishing materials that were present. Twenty-four subjects were divided into six groups that were randomly exposed to the three ventilation rates, 5, 10, and 20 l/s per person. The subjects performed work tasks three separate times for each ventilation rate over an 8-h exposure period. The work performance of the subjects logarithmically improved with increased ventilation rates, which was similar to the previous research findings. Statistical significance was found for addition task, text-typing task, and memorization task. Increased work performance in this experiment was slightly lower than the results of previous short-term laboratory experiments, yet remained higher than results of previous long-term field experiments. However, it was difficult to directly compare the results of this experiment with those of previous experiments, because of the higher concentration of VOC present in the office rooms and the learning effect associated with the repeated tasks. PRACTICAL IMPLICATIONS: The results of this experiment show that ventilation had positive impacts on perceived air quality and work performance for the subjects tested. Work performance logarithmically increased by approximately 2.5-5% as ventilation rates were increased from 5 to 20 l/s per person. The positive effect of ventilation rate on work performance was shown to be limited at the low ventilation rate. The positive effects on work performance were at lower ventilation rates. The learning effect in repeated work performance tasks could increase the uncertainty of the work performance analysis in 8-h exposure period.     

Persistent allergic rhinitis and indoor air quality perception--an experimental approach

In order to compare patterns of indoor air perception, including perceptions of temperature, air movement, indoor air quality (IAQ), mental concentration, and comfort, 33 subjects either with persistent allergic rhinitis or controls were exposed to different temperatures and constant relative humidity in an experimental office environment. Results were obtained by means of a self-administered visual analogue scale, analyzed using mean score comparisons and principal component analysis. At 14 degrees C, the rhinitis group reported higher scores for sensations of air dryness than controls. At 18 degrees C, in the rhinitis group, there was a correlation between dry, stagnant air, and difficult mental concentration. This group also correlated heat, dry air, and poor IAQ, in contrast to the control group, which correlated comfort, easy mental concentration, and freshness. At 22 degrees C, the rhinitis group correlated heat, dryness, stagnant air, and overall discomfort. This group also correlated non-dry air, freshness, and comfort, whereas the control group correlated heat, humidity, good indoor air, freshness, and comfort. This study suggests that the rhinitis group perceives indoor temperatures of 14 degrees C as dryer than controls do, and that at 18 and 22 degrees C this group positively correlates different adverse perceptions of IAQ. By means of a self-administered questionnaire in an experimental condition, the present study compares subjective patterns of indoor air perception from individuals with respiratory allergy (allergic rhinitis) to control individuals. It reports different patterns of perception of indoor air quality (IAQ) between the two groups, suggesting that allergic individuals could have different IAQ perception.     

新回风比例对室内生物污染分布影响的数值分析

采用数值计算方法 ,对带有回风的空调系统中类似SARS病毒颗粒的生物颗粒浓度的分布规律进行了模拟分析。提出了一种计算带有回风的空调系统中污染物浓度的方法 ,基于这种方法 ,比较了不同新风比下的室内生物颗粒浓度和安全距离。结果表明 ,新风比对整个空间的生物颗粒污染物的分布有重要影响。但是 ,全新风时和回风较少时并不存在质的差异 ,两种情况下的污染物平均浓度和安全距离都差别不大。     

室内空气品质研究的探讨

针对室内空气品质是人们生活和工作最重要的环境因素之一,并通过目前国内外室内空气品质的定义和评价,分析了几种可能影响室内空气品质的因素,并探讨了空气质量的控制问题,从而充分改善室内空气品质。