Search

One of the contemporary approaches to reduce the damage to cementitious composite resulting from the freeze–thaw effect is the incorporation of phase-change materials (PCM). In this study, the composites were produced adding n-tetradecane, which is a microencapsulated organic PCM, at rates of 0, 2, 4, 6 and 8% of the cement weight. In two different simulations representing the climate conditions of the two distinct regions in Türkiye, its effect on restricting the temperature amplitudes that the composite experienced was determined. It was determined that the PCM, with a working range similar to the temperature range applied to the composite in simulation, was successful in reducing the temperature amplitudes, and the rate and type of the PCM should be chosen with care according to the climate conditions likely to be experienced by the composite when in use. In addition to PCM's thermal properties, its effects on the mechanical properties and consistency results were investigated. [ABSTRACT FROM AUTHOR]

Thermal springs are very difficult environments for organisms due to the high temperature, and physicochemical parameters. Cyanobacteria, which are photosynthetic prokaryotes, are best adapted to these environments. Kütahya is an important thermal area in Turkey. The aim of the study was to determine the cyanobacterial flora with a morphologic and ecologic approach in the 11 thermal. The physicochemical properties of the thermal springs in Kütahya province were measured. The thermal springs are alkaline (pH>6) with an average temperature of 52°C. As a result, 54 cyanobacteria taxa were identified. Oscillatoriales were the predominant order in terms of taxa diversity (24 taxa) and biomass size. Statistical analyses were conducted to reveal the physicochemical properties of the thermal springs and the distribution of cyanobacteria in detail. According to these analyses, the thermal springs were classified into two main groups with a Piper. As a result of the RDA analysis under CANOCO 5.0, the total variation was 55.45455, and the first two axes explained a total of 57.43% of the variance. There was a significant difference (P<0.001) in the comparison of the physicochemical parameters including pH, EC, TDS, and temperature values of the thermal springs in the Kruskal Wallis tests. [ABSTRACT FROM AUTHOR]

Knowledge of heat flow density on the Earth's surface and subsurface temperature distribution is essential for the interpretation of several processes in the crust such as for the evaluation of the geothermal potential of a region. With this study, we investigate the conductive heat flow distribution in western Anatolia to understand the thermal state and its relationship to regional tectonics in the region. The new heat flow data are collected and combined with previously published data to obtain the new heat flow map of western Anatolia. Analysis of data sets after appropriate corrections yields a better picture of the regional distribution of heat flow within the region. Generally, high values are observed around the grabens of Menderes Massif due to the intense tectonic activity. We also present the 2D steady-state thermal model of Gediz. The modeled temperatures are validated by temperature measurements from two deep wells. Numerical simulation results show that the dominant heat transfer mechanism in Gediz graben can be explained by conduction. Temperature distribution in the deep subsurface of the graben is controlled by both thickness distribution and thermal properties of the different stratigraphic sections. Thermal conductivity contrast between different stratigraphic sections causes anomalously elevated heat flow values at the edges of the graben. The comprehensive results of this study will bring a new perspective to geothermal studies in particular Enhanced Geothermal Systems (EGS) resource estimations in Gediz graben. [ABSTRACT FROM AUTHOR]

Apricot kernel is one of the most abundant types of agro‐waste in the eastern Anatolia regions of Turkey. In this study, apricot kernel shells (AKShs) were chemically modified using levulinic acid (LA) for the first time, and their potential for developing biobased composites was evaluated. Phenol novolac epoxy resin was used as matrix owing to its high thermal and superior adhesion properties. Shell treatments to improve interfacial bonding were carried out using alkali, acetic acid, and LA. These treatments were aimed at improving the mechanical properties, wettability, and bonding of the composites. Moreover, these treatments could prevent the deterioration of the fiber/matrix interface (hydrophilic and hydrophobic effect) and mitigate damage to the fiber during production, which is one of the main reasons for the reduced strength of the composites. The thermal characteristics, crystallinity index, chemical composition, and surface morphology of the untreated and chemically modified AKShs and composites were studied by thermogravimetric analysis, differential scanning calorimetry, X‐ray diffraction, Fourier transform infrared spectroscopy, and scanning electron microscopy, respectively. In addition, the composites were analyzed in detail using mechanical tests and contact angle measurements. The chemical treatment using LA resulted in composites with superior mechanical behavior. [ABSTRACT FROM AUTHOR]

In this study, the adsorption of methane (CH) on zeolite from Sivas-Yavu region of Turkey and on forms treated with 1 M heavy metal nitrate solutions (AgYZ, Cu YZ and FeYZ) and 1, 3 and 5 M HCl solutions (HYZ, 3HYZ and 5HYZ) was investigated. Adsorption isotherms of methane by zeolite minerals were obtained using volumetric apparatus at 0 and 25 °C up to 100 kPa. Natural and modified samples were characterized by X-ray fluorescence, X-ray diffraction (XRD), thermogravimetric/differential thermal analysis and nitrogen adsorption methods. Quantitative XRD analysis showed that the major components of the natural zeolite were clinoptilolite and mordenite, together with minor amounts of quartz, feldspar and clay mineral. Among all the modified forms, Fe-form of zeolite sample exhibited the highest adsorption capacity for CH at both temperatures. The adsorption capacity of CH on FeYZ increased from 0.597 to 0.796 mmol g as the temperature decreased from 25 to 0 °C. In addition, uptake of CH on the adsorbents decreased with increasing acid concentrations. [ABSTRACT FROM AUTHOR]

Snow temperature is a major component of many physical processes in a snowpack. The temperature and the change in temperature across a layer have a dominant effect on physical properties of snow grains as well as its hardness, strength, and failure resistance. In this study, temperature and snow cover thickness were measured during the snow season of 2007-2008 in 11 elevation classes and in three different sampling locations, one in an open area and two under different forest canopy covers for each class along Kartalkaya road, Bolu. Each sampling site was visited 44 times to collect data including snow depth, snow surface temperature, ground temperature, and temperature within snowpack at 20-cm intervals. Seven different models are developed to determine snowpack temperature variations under forest canopy covers and in an open area with different leaf area index values. All models were performed using a multilayer perceptron (MP) method for the Bolu-Kartalkaya area, Turkey. MP approach constitutes a standard form of neural network modeling and can modify two-layer linear perceptron methods using three and more layers. The ability of MP is to handle complex nonlinear interactions, which ease the natural process of modeling. This method can overcome complex computations using neuron networks, and they can easily nonlinearly link input and output variables. The predictive errors are determined on the basis of mean absolute error and mean square error criteria. The Nash-Sutcliffe sufficiency score showing compliance between observed and predicted values is also calculated. According to the mean absolute error, the mean square error, and the Nash-Sutcliffe sufficiency score criteria, the predictive errors are within reasonable error intervals, justifying the use of the developed MP models for engineering applications. Copyright © 2012 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

Abstract: The design of an earth to air heat exchanger (EAHE) requires knowledge of its total thermal resistance (R Tot ) for heating and cooling applications. In this research, a 47m long horizontal, 56cm nominal diameter U-bend buried galvanized was studied experimental EAHE used for the determination and evaluation of thermal properties of heat exchanger. This system was designed and installed in the Solar Energy Institute, Ege University, Izmir, Turkey. Based on the experimental results, generalized relationships were developed for predicting of thermal resistance of the heat exchanger. Average total heat exchanger thermal resistance was estimated to be 0.021K-m/W as a constant value under steady state condition. [Copyright &y& Elsevier]

Thermal and structural properties of three clays (sepiolite and two kaolinites) from Turkey were studied by thermal analysis (TG-DTA), X-ray diffraction (XRD), X-ray fluorescence (XRF), Fourier transform infrared (FT-IR), and surface area measurement techniques The adsorption of sulfur dioxide (SO) gas by these clays was also investigated. SO adsorption values of K1, K2, and S clay samples were measured at 20 °C and pressures up to 106 kPa. Sepiolite sample (S) primarily consists of pure sepiolite, only dolomite present as accompanying mineral. Both kaolinite samples, K1 and K2, mainly contain kaolinite as the major clay mineral and quartz as impurity. In K2 sample, muscovite phase is also present. Simultaneous TG-DTA curves of all clay samples were obtained at three different heating rates 10, 15, and 20 °C min over the temperature range 30-1200 °C. It was found that the retention value of SO by S clay (2.744 mmol/g) was higher than those of K1 (0.144 mmol/g) and K2 (0.164 mmol/g) samples. [ABSTRACT FROM AUTHOR]

For optimum design of borehole thermal energy storage (BTES) and ground sources heat pump (GSHP) applications, determination of underground thermal properties is required. The design and economic feasibility (number and depth of boreholes) of these systems need thermal conductivity of geological structure, λ (W m-1 K-1), and thermal resistance of ground heat exchanger, R (K W-1 m). Thermal properties measured in laboratory experiments do not coincide with data of in situ conditions. Therefore, in situ thermal response test equipment has been developed and used in Canada, England, Germany, Norway, U.K., U.S.A. and Sweden to ensure precise designing of BTES systems. This paper describes the results and evaluations of the Adana continual thermal response test measurements. Copyright © 2007 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

This paper presents a study performed on the radiological character of the Çatalağzi Thermal Power Plant (ÇTPP/ÇATES), on the west Black Sea coast of Turkey. Natural radioactivity distribution of the terrestrial radionuclides 238U, 232Th, and 40K of surface soil samples around the ÇTPP was analyzed. The average radioactivity concentrations for 232Th, 238U, and 40K for soil samples were 39.7, 30.5, and 378.7 Bq kg-1, respectively. 238U and 40K concentrations are lower than the world average values, 35 Bq kg-1 and 400 Bq kg-1, respectively, and the 232Th concentration is higher than the world average value, 30 Bq kg-1. [ABSTRACT FROM AUTHOR]

In this paper, the effect of various system parameters on horizontal ground source compression refrigeration machine (CRM) performance is studied experimentally in Bursa, Turkey. A ground heat exchanger (GHE) system connected to CRM in a test room in the air conditioning and refrigeration laboratory of Uludag University has been designed and constructed. This system was tested for space cooling in August and September 2004 and performance tests were performed during this period. Overall, system mainly consists of the GHE (GHE–water circuit) and CRM (CRM–refrigerant circuit). Refrigerant is R134a. Hourly variations of inlet and outlet water temperatures, extracted heat from test room, rejected heat to ground, compression ratio, total power consumption, and coefficient of performance (COP) values for both whole system and only CRM are obtained. Thermal properties of soil are also estimated by using experimental data and theory. Cooling load of test room and rejected heat to ground, and all COP values are also presented. Finally, heat rejection rate to ground with respect to leaving water temperature from GHE is given. The COP of the overall system changes between 2 and 2.5, also CRM COP values are in the range of 3 and 3.86. Copyright © 2007 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

A cylindrical shaped box type solar cooker was constructed and its thermal performance was tested under the prevailing weather conditions in Karabuk, Turkey. Experiments were conducted on a single glazed cooker with a plane reflector and one cooking pot during August 2004. The international test procedure was applied to the solar cooker and the stagnation temperature, and the sensible water heating tests were performed to predict the heating characteristic curves. The results obtained from the tests were used to calculate the two figures of merit, overall thermal efficiency, specific and characteristic boiling times as well as the cooking power. The first figure of merit obtained was greater than value suggested in the international standard test procedure. The second figure of merit was found to increase almost linearly with the quantity of water. These figures of merit are then used to predict the characteristic heating curves. Good agreement exists between the predicted heating curves and the experimental results. The solar cooker with 1 m2 aperture area is able to boil 1 kg water in 13·6 min with 30·5% daily thermal efficiency. [ABSTRACT FROM AUTHOR]

Thermal stratification in a mantled hot water storage tank is analysed numerically for different water inlet velocities. The aim is to obtain higher thermal stratification and supply hot water for usage as long as possible. Twelve different water inlet velocities to the hot water storage tank are considered. The numerical method is validated by comparing its results against experimental and numerical results from the literature. It turned out that the results obtained from the numerical analysis have shown very good agreements with the results from previous works. As a result, the water temperature in the tank increases with the increase of the water inlet velocities to the mantle but this increment is not proportional. After a period of operation of 7.2 h, which corresponds to the average sunshine duration in Turkey, temperature increments of 6.5 and 35K have been estimated for the hot water inlet velocities of 0.01 and 0.3 m s-1, respectively, at a radial distance of 0.1 m and a height of 1 m inside the storage tank. [ABSTRACT FROM AUTHOR]

Combustion characteristics of coking, semicoking, and noncoking Turkish bituminous coal samples from Zonguldak basin were investigated applying differential thermal analysis (DTA) and differential thermogravimetry (DTG) techniques. Results were compared with that of the coke from Zonguldak bituminous coal, a Turkish lignite sample from Soma, and a Siberian bituminous coal sample. The thermal data from both techniques showed some differences depending on the proximate analyses of the samples. Noncombustible components of the volatile matter led to important changes in thermal behavior. The data from both methods were evaluated jointly, and some thermal properties were interpreted considering these methods in a complementary combination. [ABSTRACT FROM AUTHOR]