Study on optimum design method for pleasant outdoor thermal environment using genetic algorithms (GA) and coupled simulation of convection,radiation and conduction

Extensive research has recently been conducted into improving outdoor thermal environments in summer. In this paper, (1) an optimum design method is developed with genetic algorithms (GAs) and coupled simulation of convection, radiation, and conduction for comfortable outdoor thermal environments, and (2) in order to examine the validity of the proposed optimum design system, an apartment block space in an urban area is set up as an analysis target and the optimum arrangement of buildings and trees in two cases are analyzed for pleasant outdoor thermal environment design. For the optimum arrangement of trees, two different cases within the target area are examined to clarify the effect of different target areas (all open space or walkways) on optimization. For the optimum arrangement of buildings, in order to clarify the effect of the different positions of apartment blocks and building coverage ratio, three cases with different positions or building shapes in the target domain are examined. As a result, the optimum arrangements of the buildings are derived using GA and simulations for the three cases, and the validity of the optimum design method is confirmed.     

Wind comfort in a public urban space—Case study within Dublin Docklands

Open public spaces provide venues for cultural, recreational events and promote informal social contact between citizens. Successful outdoor spaces promote comfort and invite people to stay outdoors. Provision of thermal comfort outdoors present a challenge, as an extended range of environmental conditions must be dealt with. The present study examines whether climatic characteristics in Dublin facilitate exercising long-term outdoor activities during summer, and investigates the extent to which urban planning and the resulting urban morphology of the built environment influences microclimates created, from the viewpoint of wind environment. Microclimates at Grand Canal Square have been simulated by ENVI-met. Wind velocity has been expressed in relation to that of the ‘‘background’’ climate in order to verify if the site has a wind protecting character or to the contrary, it enhances airflow. The results show for the dominant wind directions (W, SW, S) that 60% higher wind velocity than at Dublin Airport can occur around buildingcornersandatrestrictedflowsections—preventing any kind of long-term outdoor activity during a ‘‘typical’’ day. S and SW winds cause 15%-20% acceleration at the W waterfront area. Windy urban environment can call forth a limited frequentation of urban space.     

Comfort in urban spaces: defining the boundaries of outdoor thermal comfort for the tropical urban environments

With rapid urbanisation, often without climate responsive guidelines, cities in the Tropics are progressively falling short of sustaining outdoor life. While at the building level such inadvertent climatic modifications have lead to a remarkable demand on the urban energy resources. The rationale for developing a thermally desirable outdoor ambience in such a context has implications that go beyond the requisites of urban design and well into the design of buildings. In order to re-establish and sustain life outdoors it is important that we try to make urban spaces comfortable as far as the ambient climate permits. In order to ascertain conditions of comfort for outdoor spaces we need to define comfort for outdoors. This paper presents findings on outdoor comfort based on field investigations conducted in Dhaka, a city in the wet-Tropics. Findings from a survey conducted on a large number of randomly selected people from urban spaces are presented. The findings include factors affecting comfort outdoors for Dhaka and a comfort regime based on environmental parameters for urban outdoors is presented. Interestingly, comfortable ambient climate leads to comfortable indoor environment particularly with regard to free running buildings. With regard to mechanically controlled indoor environments a comfortable outdoor produces lesser strain on energy environment relationship. By defining conditions of comfort for outdoor environments an important step towards achieving sustainability of our urban environments can be made.     

带天井高层住宅建筑热环境试验和分析

为研究带天井的高层住宅建筑的热环境现状以及更好地利用天井的自然通风来改善建筑内的热环境,采用实测和问卷调查相结合的方法,对长沙市的一栋带天井的高层住宅建筑进行了热性能试验和分析。在不同的夏日天气状况下,该建筑物居住区房间的平均温度和走廊的平均温度都比室外平均温度低,天井的自然通风在夏季对其周围空间具有良好的降温效果。     

Indoor thermal environment and energy saving for urban residential buildings in China

The purpose of this survey is to investigate the actual conditions of the residential indoor thermal environment in urban areas in China for evaluating thermal comfort and predicting the energy conservation feasibility for space heating and cooling.The apartment homes under investigation were located in the urban areas of nine major cities. The questionnaire survey revealed building characteristics, the types of space heating and cooling system in use, aspects of life style, during winter and summer seasons, and so on. The measurement showed that winter indoor temperatures in Harbin, Urumqi, Beijing and Xi’an remain at a relatively stable level near 20 °C due to the central heating system installed. However in the other cities lacking central heating systems, indoor temperatures fluctuated as a function of the change of outdoor temperature. On the other hand, summer indoor evening temperatures in Shanghai, Changsha, Chongqing and Hong Kong were higher than the comfort zone of ASHRAE. Therefore it is expected that energy use for space heating and cooling in the southern China will increase in the near future because of occupants’ requirement for comfortable indoor environment. Based on the results yielded by this study, in Beijing the calculation of space heating and cooling loads indicated that the energy used to heat indoor spaces can be halved by installing thermal insulation and properly sealing the building.     

湿热地区室外动态热环境中二节点模型的验证及修正

快速城镇化和全球变暖使城市室外环境的热不舒适加剧,热安全风险提高。为了解湿热地区室外动态热环境中人体生理量的变化规律,为快速评价室外热环境提供依据,开展了室外人体热反应观测实验。基于实测数据,对二节点模型进行了模拟精度分析和吻合度检验,研究得到了人体在室外受风速、MRT和自身调节的作用下,皮肤温度和体核温度呈现不同的变化规律及二节点模型修正方法。在室外动态热环境中应用二节点模型,需从皮肤、体核调定温度、人体标准模型、肌体启动体温调节的环境温度值及人体与室外环境的对流换热系数4个方面对人体二节点模型进行修正,相关参数和调节过程应写成可赋值的变量或数学表达式,修正后的二节点模型对室外人体热反应预测具有通用性和适用性。     

Characteristics of indoor and outdoor airborne fungi at suburban and urban homes in two seasons

Literature has suggested association between damp environments, microbial exposure, and higher prevalence of respiratory symptoms and diseases. The study began by evaluating the airborne fungal concentrations at urban and suburban areas of a typical metropolitan city in southern Taiwan for the estimation of related health risks. A group of representative homes, based on the housing characteristics questionnaires completed earlier, were selected from two parts of the city; urban and suburban. Burkard sampler (BURKARD, Rickmansworth, England) was used to collect airborne fungi onto agar plates with malt-extract. After incubation and identification, concentrations of airborne fungi were calculated as CFU/m3. The geometric mean (GM) concentration for indoors was 8946 (4372-18,306) CFU/m3 in winter and 4381 (1605-11,956) in summer. For outdoors, it was 11,464 (5767-22,788) CFU/m3 in winter and 4689 (1895-11,603) in summer. In summer, the total fungal concentration, both indoors and outdoors of suburban homes, were significantly higher than those of urban homes. The dominant fungi contributing to such a difference were indoor Cladosporium spp. and outdoor Penicillium spp. (P < 0.01). The indoor/outdoor ratio (I/O) was similar in two areas except for Penicillium spp. in winter and Aspergillus spp. in summer; both higher in the suburban area. Significantly higher levels of airborne fungi were observed in this region than those seen in northern Taiwan or other parts of the world. Future investigations are needed to further examine the effects of these exposures on the related health problems.     

Measurement of thermal environment in Kyoto city and its prediction by CFD simulation

In the summer of 2002, measurements were simultaneously performed to investigate the characteristics of heat flow in urban areas at three locations in Kyoto city: (1) a commercial urban area mixed with low-rise traditional residential buildings that represents the urban area of Kyoto; (2) a university campus area with lots of green zones; and (3) a plaza covered with a concrete slab which was used as a reference point of measurement. Heat flux of boundary layer over the three locations and the surface temperatures of building walls and streets were measured to investigate the urban thermal environment. For the analysis, a new simulation code was developed by combining unsteady state heat conduction of building walls and grounds, radiation heat exchange between them, and airflow by computational fluid dynamics (CFD). By using this code, the thermal environment of the urban areas such as air temperature, humidity, wind velocity, and boundary layer heat flux was predicted and compared with the measured results. It was found that this model could predict the real thermal environment of the urban area. Using this code, the effect of additional green on roofs and grounds can be investigated in order to mitigate urban heat island and to improve urban thermal environment at the street level.     

Seasonal effects of urban street shading on long-term outdoor thermal comfort

As shading, an important factor in urban environments, affects thermal environments and long-term thermal comfort, this study conducted several field experiments to analyze the outdoor thermal conditions on urban streets in central Taiwan. The RayMan model was utilized for predicting long-term thermal comfort using meteorological data for a 10-year period. Analytical results indicate that slightly shaded areas typically have highly frequent hot conditions during summer, particularly at noon. However, highly shaded locations generally have a low physiologically equivalent temperature (PET) during winter. Correlation analysis reveals that thermal comfort is best when a location is shaded during spring, summer, and autumn. During winter, low-shade conditions may contribute to the increase in solar radiation; thus, thermal comfort is improved when a location has little shade in winter. We suggest that a certain shading level is best for urban streets, and trees or shade devices should be used to improve the original thermal environment.     

Evaluation of effects of windows installed with near-infrared rays retro-reflective film on thermal environment in outdoor spaces using CFD analysis coupled with radiant computation

Recently, windows with low-e double-glazing or heat-shading films often have been installed to the exterior surfaces of buildings to reduce the cooling load of the buildings. These windows specularly reflect solar radiation into pedestrian spaces. It has been pointed out that the increase in the incident solar radiation reflected at the windows degrades the thermal comfort levels of pedestrians. The installation of near-infrared rays retro-reflective film to window surfaces may both reduce the cooling load of the building and reduce the impacts on the thermal environment in outdoor spaces. Hence, it is expected that the installation of this film will counteract this problem and have positive effects. To assess the feasibility of installing retro-reflective materials to the exterior surfaces of the building walls and ground forming part of a city block, for improving the thermal environment in outdoor spaces, computational methods could serve as a powerful tool for analyzing the radiant environment in urban and building spaces. In this paper, a computational method is outlined for considering the directional reflections from the exterior surfaces of building walls and windows. The method is used to estimate the effects on the outdoor thermal comfort of pedestrians in the summer season.     

湿热地区步行商业街夏季室外热环境实测分析

我国湿热地区夏季空气温度和湿度相对较高,太阳辐射强烈,人们在此种气候条件下的室外步行商业街区活动可能会造成身体不适,甚至是中暑。因此,高品质的室外热环境既对于步行商业街区在吸引人流方面扮演了重要角色,同时也为城市公共空间提供活力。通过对南宁市典型步行商业街区夏季室外热环境变量进行测试,从而得出热环境与周围材质和建筑类型有关,遮阳形式是决定人在步行通道空间中是否感到舒适的重要因素。     

天津原租界街区夏季室外热舒适研究

人口的增长和城市区域的逐渐扩大,导致城市夏季室外热环境逐渐变差。天津原九国租界多为天津的重要旅游景点,每年客流量大,其夏季热环境问题不容忽视。主要目的是探讨天津5个不同典型的原租界街区的热环境差异及其设计因子与夏季室外热舒适之间的关系。通过实地测量的方式,搜集5个原租界街区的热环境相关参数,并计算生理等效温度（PET）以对街区热舒适环境进行评价。通过分析发现,相比于气象站,植被覆盖率大的原英国租界街区的平均PET增值最小,仅1.20 ℃;植物覆盖率小的原奥匈帝国租界街区的平均PET增值最大,为8.50 ℃。此外,本研究从街区设计的规划指标、空间形态和细节设计三方面,量化分析设计因子与PET的关系。结果表明,绿化率、街道百分比、天空视域因子（SVF）和街巷高宽比会对PET产生不同程度的影响,同时街道朝向、植物种类及其形状、建筑遮阳构建和喷泉等因素也会影响原租界街区的夏季室外热环境。     

Personal exposures to volatile organic compounds among outdoor and indoor workers in two Mexican cities

There are limited data on exposures to ambient air toxics experienced by inhabitants of urban areas in developing countries that have high levels of outdoor air pollution. In particular, little is known about exposures experienced by individuals working outdoors - typically as part of the informal sector of the economy - as compared to workers in office-type environments that approach the indoor air quality conditions of the more developed countries. The objective of this study is to explore these differences in personal exposures using a convenience sample of 68 outdoor and indoor workers living in Mexico City (higher outdoor air pollution) and Puebla (lower outdoor air pollution), Mexico. Occupational and non-occupational exposures to airborne volatile organic compounds (VOCs) were monitored during a 2 day period, monitoring 2 consecutives occupational and non-occupational periods, using organic vapor monitors (OVMs). Socio-demographic and personal time-location-activity information were collected by means of questionnaires and activity logs. Outdoor workers experienced significantly higher exposures to most VOCs compared to indoor workers in each of these cities. The outdoor workers in Mexico City had the highest exposures both during- and off-work, with maximum occupational exposures for toluene, MTBE, n-pentane, and d-limonene exceeding 1 mg/m(3). The inter-city pattern of exposures between the outdoor workers is consistent with the higher outdoor air pollution levels in Mexico City, and is above exposures reported for urban areas of the more developed countries. Results from this study suggest that elevated outdoor air pollution concentrations have a larger impact on outdoor workers' personal exposures compared to the contribution from indoor pollution sources. This contrasts with the more dominant role of indoor air VOC contributions to personal exposures typically reported for urban populations of the more developed countries.     

对热舒适、空气感觉质量及能耗的模拟研究

室内空调设计温度和新风量对热舒适，室内空气质量及能耗量有重要影响，然而对它们之间相互关系进行研究的文献却较少。通过计算机模拟空调系统在7种室内设计温度和7种新风量条件下的运行情况，得到不同的设计条件组合对热舒适、人体感觉空气质量及建筑能耗量的影响。基于这项分析，提出了此办公建筑合理的室内设计温度和新风量取值。     

湿热地区老年人夏季室外热舒适阈值研究

旨在探索湿热地区老年人夏季室外热舒适阈值。以课题示范工程、样本量集中的广州市老人院为研究案例,结合现场实测与问卷调研,获得各气象要素（空气温度、相对湿度、黑球温度、风速）的逐时数据及老年人室外热舒适状况;借助Rayman模型,计算生理等效温度PET,运用SPSS进行回归分析建立老年人室外热舒适评价模型;并评析不同类型测点空间的热环境情况与特点。结论如下：（1）湿热地区夏季老年人室外热环境中性PET值为25.60℃;台湾、香港、广州等湿热气候地区,老年人与混合年龄层中性PET值接近,人群中性PET值具有一定普适性;（2）老年人热感觉中性范围为23.79℃~27.41℃,较混合年龄层窄;老年人室外环境热舒适PET范围为22.70℃~32.53℃,老年人对偏凉感觉（PET=23.10℃）更感舒适;老年人达到90%可接受率的PET范围是22.62℃~31.15℃;（3）老年人夏季热敏感度为3.62PET（℃）/TSV,夏季老年人对室外热环境敏感度明显高于混合年龄层,因此室外热环境设计对老年人具有更大影响;（4）在适当遮荫条件（植物或建筑）下,老年人在夏季依然乐于接受室外阳光辐射;但需综合运用遮阳、通风、降温等设计策略才能满足老年人对热环境的舒适需求。以期为湿热地区室外环境适老设计提供研究方法和设计目标的参考。     

Chemical characterization of indoor and outdoor fine particulate matter in an occupied apartment in Rome,Italy

The daily concentration and chemical composition of PM_2.5 was determined in indoor and outdoor 24‐h samples simultaneously collected for a total of 5 weeks during a winter and a summer period in an apartment sited in Rome, Italy. The use of a specifically developed very quiet sampler (<35 dB) allowed the execution of the study while the family living in the apartment led its normal life. The indoor concentration of PM_2.5 showed a small seasonal variation, while outdoor values were much higher during the winter study. Outdoor sources were found to contribute significantly to indoor PM concentration especially during the summer, when the apartment was naturally ventilated by opening the windows. During the winter the infiltration of outdoor PM components was lower and mostly regulated by the particle dimensions. Organics displayed In/Out ratios higher than unity during both periods; their indoor production increased significantly during the weekends, where the family stayed mostly at home. PM components were grouped into macrosources (soil, sea, secondary inorganics, traffic, organics). During the summer the main contributions to outdoor PM_2.5 came from soil (30%), secondary inorganics (29%) and organics (22%). Organics dominated both indoor PM_2.5 during the summer (60%) and outdoor and indoor PM_2.5 during the winter (51% and 66%, respectively).     

Study on mitigation measures for outdoor thermal environment on present urban blocks in Tokyo using coupled simulation

The heat island phenomenon and degradation of the urban thermal environmental have become serious problems in Japan. In order to improve the outdoor thermal environment, it is necessary to understand quantitatively the effects of various measures. In this paper, the authors have performed coupled simulations of convection, radiation and conduction to evaluate the outdoor thermal environment over different urban blocks – ōtemachi as representative of a high-rise area and Kyobashi as a mid-rise area in Tokyo, Japan – to compare the effects of measures such as the heat release point and means of air-conditioning, greening, high surface albedo, and traffic volume. The results showed that the effectiveness of moderation countermeasures differed according to the configuration of the urban blocks.     

计算机模拟辅助云阳县热环境规划

运用计算机模拟云阳地区的热环境,并结合实测数据,对云阳新城的现有热环境进行分析,并从热环境的角度对云阳的城市规划提出了辅助性的建议;同时证明使用计算机模拟能够为城市的热环境分析提供一个较为准确而便利的手段。     

A simple technique to classify urban locations with respect to human thermal comfort: Proposing the HXG scale

An attempt is made to present a new scale to study urban microclimates and outdoor thermal comfort using simple in-situ measurement data. For this purpose, six urban locations with distinct physical characteristics are selected in a metropolitan city, Chennai. At each location, three streets with diverse orientations (North–south; East–west and Northeast–southwest) are identified and their microclimatic conditions are monitored during the summer months of April, May and June. The variations in microclimate are studied using ANOVA single factor test and later, correlated with the site’s physical characteristics. The assessment of microclimate and outdoor thermal comfort is done using Physiological equivalent temperature (PET).     

基于计算流体力学数值模拟的城市绿地温湿效应及室外热舒适评价研究进展

近年来随着计算机与各学科领域交叉研究的发展,计算流体力学数值模拟方法在城市环境的微气候研究方面得到较多应用,为研究绿地在有限面积内更有效地实现其降温效应提供了新的思路。回顾计算流体力学(CFD)数值模拟方法在不同尺度的城市绿地温湿效应及室外热舒适度评价研究中的应用,在此基础上,总结目前存在的问题及不足,对未来该领域的研究方向提出3点展望,以期为未来城市绿地微气候研究提供参考:1)多平台与尺度扩展研究;2)微气候特征指标的综合交叉分析;3)高适配度模拟模型的及时更新。