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Öğe An experimental investigation of the effect of thermophysical properties on time lag and decrement factor for building elements(Gazi University, 2020-06-01) Oktay, Hasan; Yumrutaş, Recep; Argunhan, ZekiThe time lag (TL) and decrement factor (DF) are essential for the heat storage capabilities of building elements, which strictly depend on the thermophysical properties of the elements. Many investigations are presented in literature arguing to find the influence of each thermophysical property on TL and DF by keeping the other properties constant. This study aims to investigate the effect of each property on TL and DF, utilizing relationships between the measurement values of the thermophysical properties of wall materials. Therefore, first, 132 new concrete wall samples were produced, and their thermophysical properties were tested. Secondly, TL and DF values for each building element are computed from the solution of the problem by Complex Finite Fourier Transform (CFFT) technique. Finally, a multivariate regression analysis has been performed, and the variations of each thermophysical property versus TL and DF are presented, and also the findings are compared with literature. The results show that each property alone (keeping the other properties constant) is not adequate to identify the thermal inertia and thermal performance of a wall element. Besides, 87.3 % decrease in thermal diffusivity corresponds to 6.03 h increase in the value of TL and 88.8 % decrease in value of DF; respectively, for W1 wall assembly.Öğe Comparison of heat gain values obtained for building structures with real and constant properties(Bitlis Eren Üniversitesi, 2019-12-24) Oktay, Hasan; Yumrutaş, Recep; Argunhan, ZekiThe magnitude of energy consumption due to the heating and cooling of buildings has led to the demand for increasing the thermal performance of building structures. Many investigations are presented in literature arguing to find the effect of each thermophysical property on the thermal characteristics of building components, while the properties have been assumed as independent of each other. In this context, this paper focuses on the effect of each property on heat gain value utilizing relationships between the measurement values of the thermophysical properties of building structures. In the previous study, 102 new wall samples were produced, their thermophysical properties were tested and expressions among these properties are obtained. In this study, the heat gain values through the structures are computed using the solution of the transient heat transfer problem by using both the obtained expressions between the thermophysical properties and assumptions proposed from the literature. Results obtained for varying and constant thermophysical properties have been compared with those values presented in the literature. The results show that the assumptions are not realistic in a significant number of cases. Moreover, if one of the thermophysical properties of a material is known, heat gain values can be calculated easily for the selected wall or roof types.Öğe Duvarlarının termofiziksel özellikleri arasındaki ilişkileri ile bu özelliklerin dinamik ısıl karakterlerine etkilerinin araştırılması(Süleyman Demirel Üniversitesi, 2018-08-15) Oktay, Hasan; Yumrutaş, Recep; Yıldırım, MurtazaBinaların ısıtılması ve soğutulması için tüketilen enerjinin artmasıyla birlikte ısıl performansı yüksek olan inşaat malzemelerinin geliştirilmesine ihtiyaç duyulmuştur. Bu malzemelerin ısıl performansı ise doğrudan termofiziksel özelliklere bağlı olarak değişmektedir. Her ne kadar literatürde her bir termofiziksel özelliğin dinamik ısıl karakterleri olan; faz kayması (TL) ve sönüm oranına (DF) etkisi incelense de, bu özelliklerin birbiri arasındaki ilişkiler göz ardı edilmiştir. Bu çalışmada ise; her bir termofiziksel özelliğin arasındaki ilişki deneysel yöntemler ile elde edilerek, bu özelliklerin DF ve TL üzerindeki etkileri gerçekçi olarak incelenmiştir. Bu yüzden farklı bileşimli 102 beton duvar numunesi üretilerek, termofiziksel özellikleri ASTM ve EN standartlarına göre ölçülmüş ve aralarındaki ilişkiler denklemlerle tanımlanmıştır. Termofiziksel özelliklerin yapıların ısıl karakterlere olan etkisini incelemek amacıyla, analitik çözüm kullanılarak MATLAB tabanlı bir bilgisayar program hazırlanmış ve elde edilen sonuçlar irdelenmiştir. Sonuç olarak, bu yapılan çalışma sayesinde herhangi bir termofiziksel özelliği belli olan bir bina duvar veya tavan malzemelerinin TL ve DF değerleri kolaylıkla bulunabilmektedirÖğe Mechanical and thermophysical properties of lightweight aggregate concretes(Elsevier, 2015-10-15) Oktay, Hasan; Yumrutaş, Recep; Akpolat, AbdullahIn this study, experimental investigation is performed for producing new cement-based with relatively high strength, low density and good thermal properties for energy efficient buildings. Different types of concretes containing silica fume (SF), superplasticizer (SP) and air-entrained admixtures are prepared with a constant water–cement ratio, and normal aggregates replaced by lightweight aggregates (LWAs) including pumice (PA), expanded perlite (EPA) and rubber aggregates (RA) at different volume fractions of 10%, 20%, 30%, 40% and 50%. 102 samples with different materials and compositions are produced, and their characteristics are tested in accordance with ASTM and EN standards. Based on the experimental results, equations are presented to determine the relation between the thermophysical properties of composite samples. The investigation revealed that the addition of PA, EPA and RA reduced the material bulk density and compressive strength, and improved the insulation characteristics of the composite concretes. Furthermore, it was found out that the reductions in thermal conductivity and diffusivity of the produced samples reached to 82% and 74%, respectively.Öğe Comparison of thermal performance of newly produced lightweight wall and roof elements for energy-efficient buildings(Hitit Üniversitesi, 2020-03-01) Oktay, Hasan; Yumrutaş, Recep; Argunhan, ZekiIn this study, both experimental and theoretical investigations are performed to obtain new concrete types with high thermal insulating characteristics for energy-efficient buildings. In this regard, 102 new concrete wall samples were produced using different aggregates at different volume fractions, and their thermophysical properties were tested according to EN and ASTM standards. The experimental research focused on developing new wall or roof types with higher thermal insulation properties in order to reduce the energy consumption of buildings due to heating or cooling. In order to specify the thermal performance of developed lightweight concretes, an analytical solution method is developed by the Complex Finite Fourier Transform CFFT method to estimate heat gain utilizing measured thermophysical properties data of those samples. The results indicated that the reduction in heat gain value was obtained as 83.21 % for the PC100 wall corresponding to conventional concrete. Consequently, the thermal insulation effect of those samples shows excellent potential for development.
