Investigation of the effects of geometrical parameters on heat transfer from buried finned pipes

Heat transfer from finned pipes buried in the soil has been investigated using experimental, analytical and numerical techniques. The experimental setup consists of a ground source heat pump system and two separate ground heat exchangers. Constant surface temperature approach based on Carslaw and Jaeger’s theory study was used for calculating the heat transfer from the pipes analytically. The problem was modeled and solved using a CFD program numerically. Effects of the fin number, fin length and simulation time on the heat transfer rate have been investigated and compared with bare tube. A modified analytical formula was also proposed for finned pipes in this study.     

Effect on Particle Size to Emitted X-Ray Intensity in Pellet Cement Sample Analyzed with WDXRF Spectrometer

Abstract

The particle size and heterogeneity effects on the analyte line were investigated for the analysis of powdered samples by X-ray fluorescence technique. In the analysis of samples utilizing the powder method, these effects caused serious errors with variations in particle size for the emitted intensity. The fluorescence intensities of some elements in pellet samples of cement (the range of particle sizes, < 32 µm, 32–38 µm, 38–45 µm, 45–63 µm, 45–75 µm, 75–106 µm, and 106–150 µm and, at press pressure 3.50 and 1.41 × 10⁷ kg/m²), are measured using a wavelength dispersive X-ray fluorescence (WDXRF) spectrometer for 14 pellets prepared according to the powder method. The results show that the K _α X-ray fluorescence intensities from samples can effect about 17% maximum differences in normalized intensities within selected particle sizes. These experimental results were interpreted by comparing with the other experimental results in the literature.     

Laser cutting of 7050 Al alloy reinforced with Al2O3 and B4C composites

In the present study, laser cutting of 7050 aluminum alloy sheets reinforced with Al₂O₃ and B₄C particles are carried out. The cut geometry is examined using scanning electron microscope and the optical microscope. The lump parameter analysis technique is used to formulate and determine the kerf width size. The predictions for kerf width are compared with experimental data. The percentage kerf width size variation along the cut edges is determined and the influence of the laser power level and duty cycle of the laser pulses on the percentage kerf width size variation is examined. It is found that 7050 aluminum alloy reinforced with 20% Al₂O₃ composite results in relatively large kerf width size as compared to its counter parts that corresponding to 7050 aluminum alloy reinforced with 20% B₄C composite. The kerf width size predicted agreed with the experimental data for both composites.     

Migration behavior of landfill leachate contaminants through alternative composite liners

Four identical pilot-scale landfill reactors with different alternative composite liners were simultaneously operated for a period of about 540 days to investigate and to simulate the migration behaviors of phenolic compounds (phenol, 2-CP, 2-MP, 3-MP, 4-MP, 2-NP, 4-NP, 2,4-DNP, 2,4-DCP, 2,6-DCP, 2,4,5-TCP, 2,4,6-TCP, 2,3,4,6-TeCP, PCP) and heavy metals (Pb, Cu, Zn, Cr, Cd, Ni) from landfill leachate to the groundwater. Alternative landfill liners of four reactors consist of R1: Compacted clay liner (10 cm + 10 cm, k = 10⁻⁸ m/sn), R2: Geomembrane (2 mm HDPE) + compacted clay liner (10 cm + 10 cm, k = 10⁻⁸ m/sn), R3: Geomembrane (2 mm HDPE) + compacted clay liner (10 cm, k = 10⁻⁸ m/sn) + bentonite liner (2 cm) + compacted clay liner (10 cm, k = 10⁻⁸ m/sn), and R4: Geomembrane (2 mm HDPE) + compacted clay liner (10 cm, k = 10⁻⁸ m/sn) + zeolite liner (2 cm) + compacted clay liner (10 cm, k = 10⁻⁸ m/sn). Wastes representing Istanbul municipal solid wastes were disposed in the reactors. To represent bioreactor landfills, reactors were operated by leachate recirculation. To monitor and control anaerobic degradation in the reactors, variations of conventional parameters (pH, alkalinity, chloride, conductivity, COD, TOC, TKN, ammonia and alcaly metals) were also investigated in landfill leachate samples. The results of this study showed that about 35-50% of migration of organic contaminants (phenolic compounds) and 55-100% of migration of inorganic contaminants (heavy metals) to the model groundwater could be effectively reduced with the use of bentonite and zeolite materials in landfill liner systems. Although leachate contaminants can reach to the groundwater in trace concentrations, findings of this study concluded that the release of these compounds from landfill leachate to the groundwater may potentially be of an important environmental concern based on the experimental findings.     

Productivity and costs in the course of timber transportation with the Koller K300 cable system in Turkey

This study was carried out on very steep and difficult terrain. Whole trees were logged uphill to the forest road by a Koller K300 cable crane. Investigations were carried out by time studies for which the repetition time measurement method was selected. Through time studies, the productivity and cost of the Koller cable system were evaluated.     

Transmutation-incineration potential of transuraniums discharged from PWR-UO2 spent fuel in modified PROMETHEUS fusion reactor

This study presents the potential of the burning and/or transmutation (B/T) of transuraniums (TRUs), discharged from the pressured water reactor PWR-UO₂ spent fuel, in the modified PROMETHEUS-H fusion reactor. Two different design shapes (Models A and B) were considered. The transmutation zone (TZ), which contains the mixture of TRU nuclides (10%), was located in the modified blankets. The volume fraction of Pu in the mixture is raised from 0 to 40% stepped by 10% to determine its effect on the B/T. The fuel spheres were cladded with SiC (5%) and cooled with high-pressured helium gas (85%) for nuclear heat transfer. The calculations were performed for an operation period (OP) of up to 10 years by 75% plant factor (η) under a neutron wall load (P) of 4.7 MW/m². The results bring out that: (1) the Model B transmutes the TRUs more rapidly than the Model A; (2) the effective half-lives decrease about 20 and 40% with the increase of Pu fraction in the cases of Models A and B, respectively; (3) the M values are quite high with respect to the M value of the original PROMETHEUS fusion reactor; (4) the blankets can produce substantial electricity in situ.     

Mechanical and microstructural single-crystal Bauschinger effects: Observation of reversible plasticity in copper during bending

We study the Bauschinger effect on a bent and straightened micro-sized single-crystal copper beam (width: 8.64 μm; thickness: 7.05 μm) over three consecutive cycles. The reverse yield strengths (straightening step) are much smaller than those in forward loading (bending step). An upper bound estimate shows a load drop of 73% (1st cycle), 76% (2nd cycle) and 83% (3rd cycle) relative to the forward yield stress. Electron backscatter diffraction reveals a dramatic reduction in the bending-induced misorientation gradients upon load reversal (straightening), documenting an unexpected form of microstructure reversibility. The observed Bauschinger softening is interpreted in terms of two effects. The first consists of internal backstresses that support load reversal. They are created by polarized dislocation arrays that are accumulated during forward bending. The second effect is the reduced requirement to activate dislocation sources during reverse loading as the dislocations that were stored during bending did not participate much in cross-hardening and, hence, serve as mobile dislocations upon reverse loading. After straightening the misorientation gradients are largely removed but the non-polarized dislocations remain. We therefore introduce a revised terminology, namely the “mechanical Bauschinger effect” and the “microstructural Bauschinger effect”. The former term describes a yield stress drop and the latter one the degree of microstructure reversibility upon load path changes.     

Morphology-tailored synthesis of tungsten trioxide (hydrate) thin films and their photocatalytic properties

Tungsten trioxide hydrate (3WO(3)·H(2)O) films with different morphologies were directly grown on fluorine doped tin oxide (FTO) substrate via a facile crystal-seed-assisted hydrothermal method. Scanning electron microscopy (SEM) analysis showed that 3WO(3)·H(2)O thin films composed of platelike, wedgelike, and sheetlike nanostructures could be selectively synthesized by adding Na(2)SO(4), (NH(4))(2)SO(4), and CH(3)COONH(4) as capping agents, respectively. X-ray diffraction (XRD) studies indicated that these films were of orthorhombic structure. The as-prepared thin films after dehydration showed obvious photocatalytic activities. The best film grown using CH(3)COONH(4) as a capping agent generated anodic photocurrents of 1.16 mA/cm(2) for oxidization of methanol and 0.5 mA/cm(2) for water splitting with the highest photoconversion efficiency of about 0.3% under simulated solar illumination.