Ground water level influence on thermal response test in Adana,Turkey

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.     

Temperature dependence of the electrical and interface states of the Sn/Rhodamine-101/p-Si Schottky structures

In this paper, the current–voltage (I–V) characteristics of Sn/Rhodamine-101/p-Si/Al contacts have been measured at temperatures ranging from 80 to 400 K at 30 K intervals. The nonpolymeric organic compound Rhodamine-101 (Rh101) film on a p-type Si substrate has been formed by means of the evaporation process and the Sn/Rhodamine-101/Si contacts have been fabricated. The current–voltage characteristics of the diode show rectifying behaviour consistent with a potential barrier formed at the interface. The obtained I–V barrier heights (Φ_b) were in the range of 0.208–0.940 eV with ideality factors (n) of 14.37–2.72. The high values of ideality factor (n) may be ascribed to decrease the exponentially increase rate in current due to space-charge injection into Rh101 thin film at higher voltage. Temperature dependence of the energy distribution of interface states density profile was determined from the forward bias I–V characteristics. It is shown that organic semiconductor layer (Rhodamine-101) controls electrical charge transport properties of Sn/p-Si Schottky structure by excluding effects.     

Application of artificial neural networks for prediction of natural convection from a heated horizontal cylinder

A generalized neural network analysis for natural convection heat transfer from a horizontal cylinder is developed in this paper. Cylinder diameter, cylinder surface temperature and ambient temperature are selected as the input parameters, while the Nusselt number as the output. A three-layer network is used for predicting the Nusselt number. The number of the neurons in the hidden layer was determined by a trial and error process together with cross-validation of the experimental data evaluating the performance of the network and standard sensitivity analysis. The trained network gives the best values over the correlations with less than 2.5% mean relative error. The experimental data of the average Nusselt number over the horizontal cylinders having different diameters of 4.8 mm–9.45 mm are from Atay?lmaz and Teke [1]. The results from the trained network were compared with the proposed correlation for the average Nusselt number over the cylinder and it is shown that the results are in satisfactory agreement. The Nusselt numbers obtained from the experimental study were seen to be consistent by ± 20% with the well known correlations for natural convection heat transfer from horizontal cylinder developed by Morgan [2], Fand and Brucker [3], and Churchill and Chu [4]. Moreover it is seen that that results from the trained network show absolute agreement with the experimental data in ± 5% deviation band better than the correlations given by Morgan [2], Fand and Brucker [3], and Churchill and Chu [4].     

Performance evaluation of different carbide inserts in turning of newly developed Al-12Si-0.1Sr alloy

An Al-12Si-0.1Sr alloy ingot was manufactured using a permanent mold casting technique. The microstructure and mechanical properties of this alloy were researched. Effects of different cutting conditions (cutting speed-V: 200 m/min, 300 m/min, and 400 m/min and feed rate-f: 0.05 mm/rev, 0.1 mm/rev, and 0.15 mm/rev) on the cutting force (F) and surface roughness (R_a) during machining using uncoated and physical vapor deposition- titanium aluminum nitride coated carbide inserts were also revealed. Microstructure of the alloys consists of α phase, intermetallic δ and Al₄Sr phases, thin spherical eutectic, and irregular coarse-shaped primary silicon particles. Cutting force and surface roughness decreased with the increased cutting speed during turning with uncoated, and titanium aluminum nitride coated inserts while they increased feed rate. A built-up edge and built-up layer were formed in both cutting inserts. The built-up edge and built-up layer decreased with increasing cutting speed and increased feed rate. The cutting force, surface roughness, built-up edge, and built-up layer were lower in uncoated inserts compared to the titanium aluminum nitride coated inserts.     

Machinability of AA 2024 aluminum alloy by fiber laser engraving process

The main objective of the present study is to investigate the machinability of AA 2024-T351 aluminum alloy by laser beam-assisted engraving process. The surface in a defined area was machined with the engraving process parameters of scan speed, frequency, and pulse width. While surface roughness measurements were performed to characterize the texture of the processed surface with laser engraving parameters, machining depth measurements were carried out to determine the material removal capacity. In addition, a mathematical relation was built for engraving depth and surface roughness using the response surface methodology. An increase in scan speed and pulse width led to a decrease in engraving depth and surface roughness. Unlike the scan speed and pulse width, any increase in frequency led to increased surface roughness and decreased engraving depth. After processing with lower pulse width and scan speed, a chaotic topography was formed on the surface. The effects of process parameters on engraving depth and surface roughness were analyzed statistically using factorial analysis. Except for the frequency, all parameters for surface roughness were statistically significant, whereas all parameters for engraving depth were statistically significant.     

Nano polyurethane based surface modification on the anti-felting functionalization of wool fabrics

Nano polyurethane (Nano PU) was used for the fabrication of multilayer nanocomposite film deposition on wool fabrics by electrostatic self-assembly to improve the anti-felting properties. Oppositely charged cationic poly (diallyldimethylammonium chloride) (PDDA) and anionic Nano PU were alternately deposited on the surface of wool fabrics. 8, 12 and 16 multilayer films of PDDA/Nano PU were deposited on the wool fabric surfaces using a padder. Attenuated Total Reflectance Fourier Transform Infrared Spectroscopy (FTIR-ATR) and Scanning Electron Microscopy (SEM-EDX) were used to verify the presence of deposit nanolayers. Breaking strength, whiteness and yellowness value analysis was performed on the fabrics before and after the treatment with Nano PU by the electrostatic self-assembly method. The build-up of the multilayer films and the level of colour strength (K/S) achieved are discussed after the acid dyeing process. To examine the anti-felting properties of the multilayered fabrics, the fabric shrinkage after washing was determined.     

Energy and exergy efficiencies in Turkish transportation sector, 1988–2004

This study aims at examining energy and exergy efficiencies in Turkish transportation sector. Unlike the previous studies, historical data is used to investigate the development of efficiencies of 17 years period from 1988 to 2004. The energy consumption values in tons-of-oil equivalent for eight transport modes of four transportation subsectors of the Turkish transportation sector, including hard coal, lignite, oil, and electricity for railways, oil for seaways and airways, and oil and natural gas for highways, are used. The weighted mean energy and exergy efficiencies are calculated for each mode of transport by multiplying weighting factors with efficiency values of that mode. They are then summed up to calculate the weighted mean overall efficiencies for a particular year. Although the energy and exergy efficiencies in Turkish transport sector are slightly improved from 1988 to 2004, the historical pattern is cyclic. The energy efficieny is found to range from 22.16% (2002) to 22.62% (1998 and 2004) with a mean of 22.42±0.14% and exergy efficiency to range from 22.39% (2002) to 22.85% (1998 and 2004) with a mean of 22.65±0.15%. Overall energy and exergy efficiencies of the transport sector consist mostly of energy and exergy efficiencies of the highways subsector in percentages varying from 81.5% in 2004 to 91.7% in 2002. The rest of them are consisted of other subsectors such as railways, seaways, and airways. The overall efficiency patterns are basically controlled by the fuel consumption in airways in spite of this subsector's consisting only a small fraction of total. The major reasons for this are that airways efficiencies and the rate of change in fuel consumption in airways are greater than those of the others. This study shows that airway transportation should be increased to improve the energy and exergy efficiencies of the Turkish transport sectors. However, it should also be noted that no innovations and other advances in transport technologies are included in the calculations. The future studies including such details will certainly help energy analysts and policy makers more than our study.