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Browsing by Author "Çelik, S."

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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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    Thermal analysis of perlite-reinforced concrete panels at varying moisture contents
    (Begell House Inc., 2020) Çelik, S.; Mengüç, Mustafa Pınar; Mechanical Engineering; MENGÜÇ, Mustafa Pınar
    Research on composite materials to be used in building insulation is presented. Building energy efficiency gained much broader significance following the COP 21 Paris agreement. In light of this outcome, this study focuses on the analysis of a construction material with improved potential building energy performance. A composite material consisting of Portland cement and perlite was developed and tested. R-values of perlite-reinforced panels at different moisture levels were measured by using the reverse heat leak method. Results obtained by this method were verified by testing materials with known properties and compared to theoretical calculations. Verification of theory was achieved within 1.8% error range. 'Thermal diffusivity values of the developed samples were also measured using the flash method. It was observed that addition of perlite to cement increases the thermal insulation capacity while thermal resistance decreases with increasing moisture content in the panels. Thermal diffusivity was found to be increasing up to a critical moisture level beyond which it decreases due to the effect of density of water that dominates the increase in thermal conductivity. These findings are considered to be significant for the construction industries, especially for regions with abundant perlite reserves.