Browsing Department of Mechanical Engineering & the Built Environment by Subjects
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Evaluation of the application of cool materials in urban spaces: A case study in the center of FlorinaIn the last years there is a strong interest for application of bioclimatic techniques and practices in urban neighborhoods and open spaces. This paper presents a bioclimatic study of an open space in an urban area by the use of simulation tools giving emphasis on the replacement of conventional materials with cool materials. Routes linking traditional monuments in the Greek city of Florina are characterized of decreased human thermal comfort conditions during summer time. The employment of computational fluid dynamics has contributed in the understanding of what interventions should be made on urban populated routes in order to meet defined thermal related targets during the warmest day of the year. The proposed replacement of conventional materials by “cool” ones would result in the reduction of the mean surface temperature by 3.52 °C while the mean maximum air temperature would be reduced by 1.39 °C during noon of the warmest day.
Studying the effect of “cool” coatings in street urban canyons and its potential as a heat island mitigation techniqueSurface temperature measurements carried out during summer period, at canyons’ facades, pavements and street inside a deep urban canyon, in the center of Athens. At the same time experimental data of air temperature were collected through extensive monitoring in the center of the urban canyon. CFD simulations performed in order to calculate surface temperature in buildings’ facades and at street level as well as air temperature inside the canyon. On the first part of this study comparison carried out between the measured and calculated values for a) surface temperature for the initial coating and b) the air temperature in the center of a deep street urban canyon. The calculated data have been thoroughly analyzed and used as well for the CFD model validation. The second task of this work was the calculation of the surface and air temperature, inside the deep urban canyon, by using a “cool” coating and the possible mitigation of the heat island effect in the specific urban area. The use of “cool” coatings, providing high reflectivity of solar radiation on the materials used on pavements and walls inside a canyon, estimated able to decrease surface temperature up to 7–8 °C at ground level. The decrease on walls’ surface temperature estimated close to 2–3 °C. Ambient air temperature inside the urban street canyon may decrease up to 1 °C. The reduction of absorbed solar radiation may lead to the energy consumption and thermal comfort conditions in cities and fight the increased heat island effect.
Use of cool materials and other bioclimatic interventions in outdoor places in order to mitigate the urban heat island in a medium size city in GreeceThe materials that are used in outdoor spaces are of prime importance as they modulate the air temperature of the lowest layers of the urban canopy layer, they are central to the energy balance of the surface and they form the energy exchanges that affect the comfort conditions of city people. Paved surfaces contribute to sunlight's heating of the air near the surface. Their ability to absorb, store and emit radiant energy has a substantial affect on urban microclimate. The thermal behaviour of typical construction materials in an urban center of North Greece, at Serres, was investigated. The thermal fluctuation during the day and the surface temperature differences between different materials in a selected area inside the urban centre of the city was monitored. The replacement of conventional materials with cool materials was evaluated to have significant benefits. CFD simulations showed that materials replacement, accompanied by other mitigation techniques in the area, result at reduction of the mean surface temperature in the streets of the area of 6.5 °C. The results of the measurements and the CFD simulations are presented in the paper.