URBAN FACADE GEOMETRY ON OUTDOOR COMFORT CONDITIONS: A REVIEW

Author(s):  
Elahe Mirabi ◽  
Nasrollahi Nazanin

<p>Designing urban facades is considered as a major factor influencing issues<br />such as natural ventilation of buildings and urban areas, radiations in the<br />urban canyon for designing low-energy buildings, cooling demand for<br />buildings in urban area, and thermal comfort in urban streets. However, so<br />far, most studies on urban topics have been focused on flat facades<br />without details of urban layouts. Hence, the effect of urban facades with<br />details such as the balcony and corbelling on thermal comfort conditions<br />and air flow behavior are discussed in this literature review. <strong>Aim</strong>: This<br />study was carried out to investigate the effective factors of urban facades,<br />including the effects of building configuration, geometry and urban<br />canyon’s orientation. <strong>Methodology and Results</strong>: According to the results,<br />the air flow behavior is affected by a wide range of factors such as wind<br />conditions, urban geometry and wind direction. Urban façade geometry<br />can change outdoor air flow pattern, thermal comfort and solar access.<br /><strong>Conclusion, significance and impact study</strong>: In particular, the geometry of<br />the facade, such as indentation and protrusion, has a significant effect on<br />the air flow and thermal behavior in urban facades and can enhance<br />outdoor comfort conditions. Also, Alternation in façade geometry can<br />affect pedestrians' comfort and buildings energy demands.</p>

Author(s):  
Mauro Cepeda ◽  
Santiago Morales F. ◽  
Viviana Cabrera

When high thermal comfort and energy efficiency are provided in an academic environment many beneficial effects on student’s comfort, performance, productivity, and health are shown. The research provides a parametric airflow evaluation of a skylight in a ground floor of new educational building assuming a variation of 4 stages with eight scenarios for the admissions office. By means of the bioclimatic analysis, Predicted Mean Vote (PMV) and Predicted Percentage of Dissatisfied (PPD) indices, the best internal airflow performance for the study area applying natural ventilation is achieved with the air flow optimization. A minimum area of 1.79 m has been established for extraction and movement of the internal flow, both with the natural extraction louvers system measuring 12 inches by 60 inches and the 18 inches by 60 inches, they work properly. However, the 18 inches by 60 inches system has better effectiveness as it has fewer louver units to be placed, is more homogeneous, avoids turbulence and provides better air extraction. In addition, by having fewer louver units distributed along the length of the skylight, it will allow the operation to be more controlled during the operation of the building. The use of 8 louvers of those proportions, with an individual effective area of 0.23 m and a total of 1.84 m was recommended in accordance with the results obtained.


2011 ◽  
Vol 361-363 ◽  
pp. 1056-1060 ◽  
Author(s):  
Bao Lin ◽  
Xue Ting Wang ◽  
Xiao Hu

Because of the relatively narrow space and high density distribution of the passengers, the bus interior environment deteriorates in summer. Natural ventilating introduces a fresh natural freeze, provides the bus interior with appropriate distribution of air supply temperature and velocity field. Making good use of natural ventilation is an operating strategy ideal for improving passengers’ satisfaction, which is considered as an environmental friendly and cost effective approach. Based on CFD numerical simulation, with a whole-domain approach, this paper predicts air flow and thermal comfort in naturally ventilated bus. The outside and inside airflow is modelled simultaneously and within the same computational domain. The thermal environment in different parts of the bus interior is compared. Different vehicle velocities and conditions of windows are taken into account, analysis are made regarding to the effect of both of them on the interior thermal comfort. The result shows, air disturbance at the bus rear parts are intenser than the other parts with better thermal satisfaction; the quality of air flow in different parts makes the temperature difference in bus achieve as high as 3°C; the use of roof openings distributes the temperature more evenly.


2016 ◽  
Vol 824 ◽  
pp. 278-287 ◽  
Author(s):  
Flóra Szkordilisz ◽  
Márton Kiss

According to the EPBD (2010) whilst improving the thermal performance of buildings good or at least tolerable thermal comfort conditions must be provided. But better thermal insulation and more airtight buildings increase the risk of summer overheating which makes mechanical cooling inevitable. This idea has been verified by the tendency of the last decade, when people were willing to install and use more frequently air conditioning devices during the summer heatwaves – increasing their energy consumption and electricity bills at the same time. We cannot neglect the importance of studies triggering an efficient way to minimise the cooling load of residential buildings by obstructing solar radiation. The usage of plants in front of transparent surfaces of the façade can avoid indoor overheating. Deciduous plants obstruct buildings’ solar access so that the microclimate around the building is improved too. The use of Green Infrastructure in different levels of planning processes, which would provide sustainable solutions for urban management, is also prescribed in the EU Biodiversity Strategy 2020. Of course in order to investigate the actual effect of trees on indoor thermal comfort we should take into consideration a list of other factors: such as orientation the type and thermal properties of the windows / transparent structures used, and the thermal transmittance values and heat storage capacity of the building. If we have taken into consideration the mentioned factors during simulation we can prove the effectiveness of vegetation for each case. Simulations are made on the base of transparency measurements carried out during the summer of 2014. The shading efficiency of trees is a species-specific attribute because of the varying crown structure and leaf density. Our analyses aimed at the quantification of the transmissivity of characteristic individuals of three frequently planted species (Celtis occidentalis, Sophora japonica, Tilia cordata). The measured data were the amount of transmitted shortwave radiation, compared with a measurement point under unobstructed sunlight. In preliminary studies we have shown that depending on species – a tree in front of the façade can decrease the solar gain on internal horizontal surface up to ~18-30 per cents. As the tree obstructs the solar access of the wall and that of transparent surfaces, a difference in indoor comfort is to be observed too.


2020 ◽  
Vol 17 (1) ◽  
pp. 78-86 ◽  
Author(s):  
Maher Dhahri ◽  
Hana Aouinet

Purpose The purpose of this study is to investigate air flow, temperature distribution and thermal confort in natural ventilation induced by solar chimney for different operating. Design/methodology/approach Numerical simulation is performed using a commercial computational fluid dynamics (CFD) package ANSYS CFX software to understand the effects of air temperature, air velocity and solar heat flux on the performance of the solar chimney and thermal comfort. The comfort level was evaluated using the air diffusion performance index (ADPI) according to ASHRAE (55-210). The flow was investigated at inclination angles 45° solar heat flux 550-750 W/m2 and in a solar chimney of 1.4 m length, 0.6 m width and 0.20 m air gab. Findings The numerical results from the present simulation were first validated with experimental data, which was used for the thermal comfort indexes calculation. The obtained results of the analysis showed that the used numerical technique could accurately predict air flow and temperature distribution in natural ventilated building using solar chimney; the air temperature, air velocity and solar heat flux have a significant impact on thermal comfort; the temperature of 19°C with velocity of 0.15 m.s−1 gives the best effective draft temperature (EDT) satisfy ASHRAE (55-210) criteria that V = 0.35 m.s−1 and EDT range between −1.7 and 1.1. Originality/value In the present paper, air flow, temperature distribution and thermal comfort inside a room equipped with inclined solar chimney were numerically investigated and analyzed. The commercial CFD package (CFX 15) is used. Calculations are carried out in an empty room without any human or mechanical activity and the numerical results are compared with measurement points.


2021 ◽  
Vol 21 (2) ◽  
pp. 67-87
Author(s):  
Marilia Ramalho Fontenelle ◽  
Leopoldo Eurico Gonçalves Bastos ◽  
Sylvie Lorente

Abstract Recent studies underline that simple and non-invasive retrofit solutions can recover natural ventilation potential in existing buildings under temperate climate. Nonetheless, the efficiency of these solutions in dense urban contexts under hot and humid climate remains unclear. This paper aims to evaluate the thermal comfort gains caused by natural ventilation when retrofitting an office building in downtown Rio de Janeiro. Computational Fluid Dynamics (CFD) and thermal simulations are carried out on Ansys CFX and Design builder to assess indoor air flow before and after retrofit. The diagnosis of the current scenario indicates that the surrounding buildings block a significant part of the wind flow, and occupants experience only a few hours of thermal comfort during the year, especially on lower floors. To increase indoor air flow, the fixed upper windows were transformed into pivot windows and kept open permanently. This measure increases the annual hours of thermal comfort by 0.5-35%, depending on the floor and the adaptive comfort model. These findings suggest that natural ventilation itself may not be sufficient to ensure occupants' comfort throughout the year under the investigated context.


2020 ◽  
Vol 12 (23) ◽  
pp. 9845
Author(s):  
Hsin-Hung Lin ◽  
Jui-Hung Cheng

Natural disasters, such as earthquakes, windstorms, and tsunamis, can occur all over the world, and disasters caused by human factors, such as civil wars, are also a source of major disturbance. The temporary rehousing of the population is a major problem when disasters occur. The installation of the combination house is time consuming, and tents cannot be used in the event of strong rain and wind; therefore, the container house is the most effective way of solving the rehousing problem. Natural ventilation is the main factor affecting the indoor air quality, thermal comfort, and health inside a container house, and solar radiation heat can also affect temperature changes inside. The air flow field inside a dwelling is very complex, and its flow mode is affected by inlet wind speed, inlet temperature, solar radiation heat, and the size of doors and windows, etc. In this paper, the influence of natural ventilation on the ventilation inside container houses is analyzed. Assuming that there is complex fluid motion in the activity space of the container house, it is not easy to use conventional methods to predict the flow rate. Based on the correlation analysis motion between the corresponding internal flow rates, the calculation and application method of flow is simplified from the results of the wind speed coefficient obtained previously. In addition, an analysis of flow characteristics in the container house is made; simulation analysis in the container house is made by carrying out the numerical analysis of several factors, including velocity field and temperature field. The variation state of the temperature of the environment and a numerical variation of the three-dimensional space are obtained by numerical calculation; the standard k-ε turbulence model is adopted to describe the turbulence phenomena of the fluid, and the mathematical model matched by B-spline surface is used for data analysis through the surface algorithm in order to deal with complex simulation data. The research results show that, regarding the influence of natural ventilation on container houses, the ideal relative position of openings includes the combination of asymmetric windows, followed by the central positioning of the door. The four-opening configurations, where better natural ventilation performance can be achieved, are located at different diagonal positions. The average flow velocity vector form, velocity amplitude, radiation temperature distribution, and the effect of the air volume coefficient of temperature change are analyzed. The research results show that the design of container houses can meet the requirements of air flow, such as the energy consumed by the thermal comfort space. Measurements taken over time and algorithms can also check the residents’ indoor natural ventilation and provide health care by the use of various sensors.


Author(s):  
Patrick H. Oosthuizen ◽  
Marilyn Lightstone

Energy simulation (ES) computer programs have been and still are widely used in the design and analysis of building energy systems. However, most ES programs assume that the air in the indoor building space is well mixed. As a result such programs cannot accurately predict building energy consumption for buildings with non-uniform air temperature distributions in the indoor space. They also cannot predict variations in thermal comfort levels in different parts of the building. Computational Fluid Dynamics (CFD), as a result, has become quite widely used in the design and evaluation of buildings energy systems in recent years. CFD can be used, for example, to predict the thermal comfort, natural lighting, natural ventilation, spread of smoke and contaminants in the building, and indoor air quality in a building. As a result it is proving to be an extremely valuable tool in the design of buildings and building systems. This, together with the fact that today’s commercial CFD software packages are relatively easy to use, has led to this quite widespread adoption of CFD methods in building energy analysis. Energy usage in buildings can be decreased by, for example, the use of daylighting (use of solar illumination in place of artificial lighting), by the use of natural ventilation, and by solar heating. CFD analysis provides a means of relatively accurately studying the effect of building design on the effectiveness of daylighting, natural ventilation, and solar heating. Another example of the use of CFD is in the study of the effect of various window blind arrangements on the building performance. In order for a CFD package to be used effectively in building energy analysis it should allow the use of a wide range of turbulence models, it should allow the incident solar radiation on the building to be found and used in the calculation of the indoor flow and temperature fields, it should allow the radiant heat exchange in the building to be incorporated into the calculation, and it should allow the effects of the thermal masses of the walls, floors, etc. to be easily incorporated into the calculation when they are deemed to be important. In this paper, the use of CFD methods in building energy analysis will be discussed as will some applications of CFD in building design. The use of CFD methods in developing design guidelines for particular types of buildings will also be briefly discussed.


Author(s):  
D. Dursun ◽  
M. Yavaş

<p><strong>Abstract.</strong> In this study, it is aimed to understand the relation between micro-climate and urban planning in the case of a cold-climate city, Erzurum. The effects of different urban patterns on micro-climate are analyzed in the context of this study. As a methodology, ENVI-met is used for processing micro-climate simulation of selected urban areas by using measured and obtained climate data such as air temperature, relative humidity, average reflected temperature, surface temperatures, sky view factor, wind velocity and direction. In order to check the accuracy of the simulation for the case study area, obtained data (from meteorology station) is simulated with ENVI-met and results were compared with measured data in the area. Also, land uses and field searches based on the observation of existing situation of urban environment were included into analysis. The findings show that irregular building plot sizes and building heights are mostly existing in historical areas and those urban forms increase thermal comfort under cold climate conditions. The results of simulations provided that same heights of the buildings, regular separation of buildings and regular plot sizes have led to severe urban micro-climates. In contrast, it is observed that variety of those urban physical environment features supported comfortable micro-climate conditions. Urban geometry and climate variables are two of the most important factors shaping outdoor spaces thermal comfort feeling.</p>


EDIS ◽  
2017 ◽  
Vol 2017 (6) ◽  
Author(s):  
Claudia Paez ◽  
Jason A. Smith

Biscogniauxia canker or dieback (formerly called Hypoxylon canker or dieback) is a common contributor to poor health and decay in a wide range of tree species (Balbalian & Henn 2014). This disease is caused by several species of fungi in the genus Biscogniauxia (formerly Hypoxylon). B. atropunctata or B. mediterranea are usually the species found on Quercus spp. and other hosts in Florida, affecting trees growing in many different habitats, such as forests, parks, green spaces and urban areas (McBride & Appel, 2009).  Typically, species of Biscogniauxia are opportunistic pathogens that do not affect healthy and vigorous trees; some species are more virulent than others. However, once they infect trees under stress (water stress, root disease, soil compaction, construction damage etc.) they can quickly colonize the host. Once a tree is infected and fruiting structures of the fungus are evident, the tree is not likely to survive especially if the infection is in the tree's trunk (Anderson et al., 1995).


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