Heat transfer reduction at the separation point on a spinning sphere in mixed convection

The unsteady laminar thermal boundary‐layer flow over an impulsively started translating and spinning isothermal body of revolution in the case of mixed convection is investigated. Velocity components and temperature are obtained as series of functions in powers of time. The general results are applied to a spinning sphere and the development of the surface heat flux evaluated at the separation point as it advances upstream is determined. The surface heat flux evaluated at the separation point as it moves forward decreases due to the increasing magnitude and influence of the centrifugal force and it is augmented by the opposing flow and reduced by the aiding flow. Reduction of the surface heat flux at the separation point is as low as 50 per cent as compared to the heat flux at the front stagnation point. Copyright © 2002 John Wiley & Sons, Ltd.     

DETERMINATION OF THE GERMANIUM CONTENT OF LIGNITE BY ATOMIC ABSORPTION SPECTROMETRY USING A SOLID SAMPLE AND A GRAPHITE FURNACE ATOMISER

The germanium content of lignite is directly determined using a solid lignite sample. A standard solution of Ge was added to powdered coal samples which were then dried. A simple metallic bar with a cavity in it was used to introduce the sample into the furnace. Optimum temperature programming was determined to obtain Ge signals as free as possible from matrix interferences. Under optimum conditions 1 ng of Ge could be determined in a solid sample. The sensitivity of Ge as (Absorbancs/g Ge) was about 500 times greater in solid sample analysis then in liquid sample analysis.     

Supercritical-gas extraction of two lignites

Supercritical-gas extracts of two lignites have been obtained; the yields were similar to those reported for mature coals. The extracts have been fractionated and many of the compounds they contain have been identified by gas chromatography/mass spectrometry. The formation and yields of these compounds are discussed in terms of the structure of the parent fuels and the mechanism of extraction.     

基于GIS的土耳其国际保护区G(o)ksu河水质的调查与建模

Goksu Delta is an important wetland where the G(o)ksu River reaches to sea in the eastern of the town Tasucu-lce1. The delta is classified as a Wetland of Intemational Impor-tance according to the Ramsar Convention on Wetlands of International Importance. The amount of fertilizers used in this area was 7200 tons in 2006. These pollutants affect the surface and groundwater quality negatively. The intensively used fertilizers and pesticides contain not only N-and P compounds but also some heavy metals. The contents of all pol-lutants in surface waters were determined for four different seasons between 2006 and 2008 and with these data a Geographic Information System(GIS)has been constructed by using Map Info. From the photometric heavy metal analysis, it is inferred that the excess concen-tration of Fe, Ni, Mn, Mo and Cu at some locations is the cause of undesirable quality for drinking purposes. The source of excess concentration of various heavy metals is the agri-cultural activities and fertilizers. It is determined that in all periods between 2006 and 2008 the heavy metals and other pollutants in the fertilizers and pesticides transported easily to river water with irrigation return flow. The organic pollutants, including COD, BOD, NH3 and NO3 followed the sharply increasing trends from Silifke city to Mediterranean Sea. The water quality of G(o)ksu River is modeled and determined that the waste water discharge of 10,700 m3/day from Silifke city does not create a serious problem because of the high amount of flow rate of G(o)ksu River.     

Preparation of polyurethane/hectorite,polyurethane/montmorillonite,and polyurethane/laponite nanocomposites without organic modifiers

Polyurethane (PU) nanocomposites were prepared from hectorite (HEC) and laponite without adding any organic modifier. PU‐montmorillonite nanocomposites were prepared for comparison. The structure of the composites were investigated by transmission electron microscopy, X‐ray diffraction spectroscopy, and Fourier transform infrared spectroscopy. Thermal gravimetric analysis and dynamic mechanic analysis were used for determination of the thermal and viscoelastic behaviors, respectively. Tensile tests were conducted for characterization of the mechanical properties. The results showed a 113.5% increase in the tensile strength of PU containing 7 wt % HEC compared to that of neat PU. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

DETERMINATION OF THE GERMANIUM CONTENT OF LIGNITE BY ATOMIC ABSORPTION SPECTROMETRY USING A SOLID SAMPLE AND A GRAPHITE FURNACE ATOMISER

ABSTRACT

The germanium content of lignite is directly determined using a solid lignite sample. A standard solution of Ge was added to powdered coal samples which were then dried. A simple metallic bar with a cavity in it was used to introduce the sample into the furnace. Optimum temperature programming was determined to obtain Ge signals as free as possible from matrix interferences. Under optimum conditions 1 ng of Ge could be determined in a solid sample. The sensitivity of Ge as (Absorbancs/g Ge) was about 500 times greater in solid sample analysis then in liquid sample analysis.     

Investigation of dissolution mechanism of six Turkish coals in tetralin with microwave energy

Rates of formation of oil, asphaltenes, and preasphaltenes during liquefaction of six Turkish coals in tetralin with microwave heating have been experimentally determined. Five reaction mechanisms have been proposed and tested to estimate the rates of formation of products. Proposed mechanisms are based on assumptions that the reactions are irreversible and pseudo-first order with respect to the reacting species. Pseudo-first order rate constants for each of the indicated mechanistic steps have been calculated by multivariable non-linear regression analysis. The best fit between experimental data and models suggested was obtained from model 3 (this model suggests that oils, asphaltenes and preasphaltenes formed directly from coal) with Tunçbilek and Zonguldak, from model 4 (this model assumes oils to be produced directly from preasphaltenes in addition to being formed from coal according to model 3) with Mu la–Yata an and Soma–Merkez, and from model 5 (this model describes conversion of coal to solvent fractionation products incorporating both series and parallel reactions) with Bolu–Göynük and Beypazarı coals. The results indicated that the reaction mechanism of coal liquefaction depends on the coal type.     

The initial boundary-layer flow past a translating and spinning rotational symmetric body

The boundary-layer flow on an impulsively started translating and spinning rotational symmetric body is considered. The stream function and the swirl component of the velocity are expanded in series in powers of time. Leading and first order solutions are obtained analytically and the second order solutions are determined numerically. The results are applied to a translating and spinning sphere and the rotation is found to reduce the friction drag and facilitate flow separation.     

RELATION BETWEEN SWELLING OF LIGNITES AND THE CHARACTERISTICS OF SWELLING AGENTS

Relation between swelling ratio of lignites and lignite and solvent characteristics was developed using a third level factorial design with three variables; percent carbon content, particle size of the lignite and electron donor number of the solvent. The results indicate that particle size of the lignite does not affect the swelling ratio. While swelling ratio of the lignites decreases slightly with increasing carbon content of the lignites electron donor number of the solvent has a noticeable effect on the swelling ratio.