Browsing by Author "Family, Roxana"

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Analysis of perlite and pumice based building insulation materials
(Elsevier, 2016-06) Çelik, S.; Family, Roxana; Mengüç, Mustafa Pınar; Mechanical Engineering; MENGÜÇ, Mustafa Pınar; Family, Roxana
Insulation panels composed of perlite, pumice, and cement were fabricated. Perlite and pumice were used to achieve high thermal resistance, and low density. Experimentation was conducted for determining R-values of perlite-pumice-cement (PPC) panels at different moisture content values. Dry and moist sample panels were tested with and without soil and moss at the top where the one with the soil and plant coupling represents a green roof. Reverse heat leak method was used in determination of the R-values of the samples. Verification of theory was achieved via experimentation with an acceptable error range. Thermal diffusivity values of the developed samples were measured using flash method.
Open Access
Analysis of sustainable materials for radiative cooling potential of building surfaces
(MDPI AG, 2018) Family, Roxana; Mengüç, Mustafa Pınar; Mechanical Engineering; MENGÜÇ, Mustafa Pınar; Family, Roxana
The main goal of this paper is to explore the radiative cooling and solar heating potential of several materials for the built environment, based on their spectrally-selective properties. A material for solar heating, should have high spectral emissivity/absorptivity in the solar radiation band (within the wavelength range of 0.2-2 m), and low emissivity/absorptivity at longer wavelengths. Radiative cooling applications require high spectral emissivity/absorptivity, within the atmospheric window band (8-13 m), and a low emissivity/absorptivity in other bands. UV-Vis spectrophotometer and FTIR spectroscopy, are used to measure, the spectral absorption/emission spectra of six different types of materials. To evaluate the radiative cooling potential of the samples, the power of cooling is calculated. Heat transfer through most materials is not just a surface phenomenon, but it also needs a volumetric analysis. Therefore, a coupled radiation and conduction heat transfer analysis is used. Results are discussed for the selection of the best materials, for different applications on building surfaces.
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Coupled heat transfer analysis and experiments to evaluate the radiative cooling potential of concrete and green roofs for buildings
(Springer Nature, 2020-08) Family, Roxana; Çelik, S.; Mengüç, Mustafa Pınar; Mechanical Engineering; MENGÜÇ, Mustafa Pınar; Family, Roxana
Improving building energy efficiency is one of the most important challenges towards the mitigation of climate change concerns. Buildings use significant amount of energy for cooling loads. Development of new night-time and day-time radiative cooling modalities by roofs is essential for reducing the energy consumption during the summer months. If a surface is desired to be kept cool while exposed to the sun, it should have (i) the maximum reflection of solar energy at visible wavelength range, and (ii) the maximum radiative emission from the surface at atmospheric radiation bands (8-13 mu m wavelength range). In this study, reinforced concrete panels and three different types of plant-covered roof layers were investigated for their potential use for passive cooling applications, including moss, cactus and green leaves. Fourier transform infrared spectroscopy (FTIR) measurements were conducted to determine the absorbance of different samples at infrared wavelengths. In addition, reverse heat leak method was used to determine the effective conductivity values (R-values). The power of cooling parameter of each sample was determined first, and after that a coupled radiation and conduction heat transfer analysis was carried out to evaluate their insulation potential. It was demonstrated that moss is a better candidate to be used as a radiative cooling material, and it is a better insulator than the other tested materials.
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Materials for radiative cooling: a review
(Elsevier, 2017) Family, Roxana; Mengüç, Mustafa Pınar; Mechanical Engineering; Bikas, D.; Theodosiou, T.; Katerina, T.; MENGÜÇ, Mustafa Pınar; Family, Roxana
Buildings use more than one-third of the total energy consumed in counties within the Mediterranean climate zones like in Turkey. During the summer months, the absorption of solar energy by the buildings increases the required cooling load significantly. One unconventional solution to this problem is the radiative cooling of the building surfaces and façades. If a surface benefits from daytime radiative cooling, its equilibrium temperature will be lower. This can be achieved only if 88% of solar radiation within the visible and near-infrared spectrum is reflected. For this purpose, paints and coatings may have an obvious advantage because of their low cost, simplicity and ease of application;however, strong solar reflectors may significantly mutate the color. On the other hand, the use of spectrally selective surfaces isof great value in practical applications such as collection of solar energy and spacecraft temperature control. In addition, the development of novel nano-patterning techniques and new designer materials for various applications are likely to surface. These developments may help to develop a wider data base for spectral and directional radiative properties of different materials. This review is to provide an overview of mainstream and such as cermets, paints and coatings, and metal oxides that can be used for radiative cooling of buildings. Also, a summary is provided for the theories, fabrication methods, usual design and possible future research opportunities to optimize these materials for spectral selectivity for specific applications.
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Radiative cooling by spectrally selective materials for building
(2018-01-03) Family, Roxana; Mengüç, Mustafa Pınar; Mengüç, Mustafa Pınar; Mengüç, Mustafa Pınar; Bundur, Zeynep Başaran; Çelik, S.; Şendur, K.; Başol, Altuğ Melik; Department of Mechanical Engineering; Family, Roxana
Buildings utilize more than one-third of the total energy consumed in counties within the Mediterranean climate zones like in Turkey. Particularly during the summer months, the absorption of solar energy by the buildings increases the required cooling load profoundly. In warmer zones, and in Mediterranean countries, air conditioning applications are becoming more common with every passing year, with their sizable negative impact on energy use. A possible solution to this problem is the radiative cooling of the building surfaces and roofs. This requires tailoring of the radiative properties of surfaces to decrease or increase their natural ability to absorb, emit, or reflect radiant energy. It is favorable to have the utmost emission from the surface with the highest reflection of solar energy and that is for situations where a surface is to be kept cool while exposed to the sun. Note that the Earth’s atmosphere is relatively transparent between the wavelength of 8-13 m; therefore, buildings emitting this is called as “transparency window” for electromagnetic waves. This window allows the radiation emitted by the earth to escape to space with no absorption within the atmosphere. This spectral energy loss, versus the radiation absorbed by the Earth is the reason for the atmospheric radiation cooling. If a building surface emits mostly in this window, than the building can be cooled effectively as well. For daytime radiative cooling which was the goal of this study, coating or painting an object with a strong solar reflector can be considered but significantly mutate its color, which may not be desired. By manufacturing a surface that had an absorptivity large in the spectral region of short wavelengths about the peak solar energy, but small in the spectral region of longer wavelengths where the peak surface emission would occur, it might be possible to absorb almost as a blackbody while emitting very little energy that such surfaces are called “Spectrally selective”. Spectrally selective surfaces can also be useful where it is required to cool an object exposed to incident radiation from any high-temperature source. These situations are objects subjected to the sun, such as the roof of a building. In this study, for the first time sustainable and economically viable materials for radiative cooling in the buildings and the roofs were developed. In the first stage a large group of materials mostly sustainable materials were selected and the morphology and optical properties of them (by optical microscope, UV-Visible, and FTIR) were obtained. For the next stage six sustainable materials were chosen. To evaluate the radiative cooling potential of the samples, the power of cooling was calculated and the results were compared with the selective and broadband emitters. Furthermore, the power of the cooling for the summer and winter time, in daytime and night time cases were also calculated and compared with each other. Heat transfer through most materials is not just a surface phenomenon, but it also needs a volumetric analysis. Therefore, a coupled radiation and conduction heat transfer analysis was solved for all six selected samples. Results are discussed for the selection of the best materials, for different applications on building surfaces. Meanwhile, coupled conduction and radiation was solved for two cases of one layer (concrete roof) and three layers (concrete with soil and the moss on the surface of it) and at last the results were compared with each other.