Current Issue : January - March Volume : 2013 Issue Number : 1 Articles : 8 Articles
Experimental research on the pyrolysis and gasification of randomly packed straw pellets was conducted with an emphasis on the\r\nreactive properties of the shrinking porous structure of the pellets. The apparent kinetics of such pyrolysis was approximated by\r\nthe random pore, grain, and volumetric models. The best approximation results were obtained with the grain and random pore\r\nmodels. The self-organized oscillations of the pellet conversion rate during pyrolysis were observed. Two complementary explanations\r\nof the phenomenon are proposed....
Natural flow rate and sweet peppers productivity in tropical greenhouse are improved by CFD simulation is the main objective\r\nof this research work. Most of the greenhouse types today are in the arch shape. To develop an improved greenhouse structure\r\nfor the region, the arch type was built and used as the control model. Mae Sar Mai agriculture research station under the royal\r\nproject foundation was selected as the field test site. Temperature sensors with data logger were installed to monitor variation of\r\ntemperature inside the greenhouse. The measured temperature data were used as the boundary conditions for the CFD analysis. A\r\nnew greenhouse model with two-step roof shape was designed and the air flow behavior was simulated by using CFD. Regarding\r\nCFD results the air flow rate of the new model is about 39% higher than that of old model. The maximum temperature of the\r\nnew model is lower than that of the old one. The sweet paper growths in both greenhouse models were measured and compared.\r\nResults show that the new model obtains 4?C lower maximum temperature in day time, 97% in number and 90% in weight higher\r\nthe first grade pepper productivity than the old one....
The authors investigate the far-field noise emissions of a datum fan blade fitted with tip end-plate geometries, originally designed to\r\ncontrol the leakage vortex swirl level. The end-plate geometries influence the tip-leakage flow, vortex formation, and swirl level. In\r\ndoing so, the end-plate geometries influence the sound-power levels. After an evaluation of fan rotors� aerodynamic performance,\r\nthe study compares the rotors� far-field noise signature characterised in terms of sound-power and pressure-level spectra to enable\r\nand assess the end-plate acoustic pay-off. The investigation attempts to establish a cause-and-effect relationship between the tipflow\r\ndynamics and the radiated sound fields, exploring the diverse directivity patterns. The authors found a tonal reduction,\r\ndue to the enhanced blade-tip end-plates and clarified the relevance of the tip features influencing the radial distribution of the\r\nnoise sources using coherence analysis. The modified multiple-vortex breakdown end-plate design was effective in reducing the\r\nbroadband noise, giving an improvement in the frequency range of the turbulent noise....
The hardness and wear behavior properties of two C 18000 copper alloys with variations in Ni, Si, and Cr concentrations, both\r\nwithin the range of C18000 chemical analysis standard, were studied after the alloy samples had been prepared by melting and\r\ncasting in sand molds and then heat-treated in solution using two-stage aging for different heating time periods. The results\r\nobtained from sample sets of the aforementioned two alloys, C0 and C1, show that the alloy C1, with slightly higher Si and Ni\r\nand lower Cr concentrations than the alloy C0, produced significantly higher hardness values and wear resistance than the alloy\r\nC0. Optical and electron microscopy microstructure studies of representative samples revealed a copper matrix containing nickel\r\nand silicon in solution and precipitates of chromium and nickel silicides. By studying the wear surfaces and debris of the former\r\nsamples with electron microscopy, different types of wear mechanisms including adhesive, abrasive, oxidation, and repeated-cycle\r\ndeformation were found. The wear behavior was expressed as mass weight loss, which correspondingly shows a typical inverse\r\nrelationship with the hardness values for both the C0 and C1 alloy groups....
Low-head microhydro systems for energy production are becoming accepted because of oil crises and new advances in their\r\ndesign and efficiencies. As this is still a new area for development and experimentation, it is important to test and validate\r\nthe optimal conditions and the hydrodynamic behaviour of such systems under different conditions. The aim of this paper is\r\nto present a turbine design validation practise, which researchers and equipment manufactures can use for the hydrodynamic\r\nbehaviour analysis of new low-head turbines prior to production and application. Laboratory experimental tests and advanced\r\nCFD numerical analysis are described for the flow behaviour analysis of a new prototype microtubular propeller. Laboratory\r\nexperimental results are presented and used for the evaluation of the turbine performance curves. Comparisons between\r\nexperimental and CFD results are also presented. Finally, an assessment of the hydrodynamic behaviour is made for a scaled\r\nmodel application, using the theory of turbomachine similarity....
This paper deals with the different microstructure evaluation of steel casing at different temp. Means at normal and higher temp. (150 Degree c) as well as in corrosion atmosphere also. Artificial corrosion environment was produced with the help of different acids like sulphuric acid and hydro chloric acid of different concentration....
In the present investigation, a numerical study of the flow and heat transfer analysis of viscoelastic\r\nsecond grade fluid due to heated, continuous stretching of a vertical sheet has been carried out. The\r\nstretching velocity is assumed to vary linearly with the distance measured from the leading edge. The\r\nsurface heat flux is assumed to be varied in power of distance measured from the leading edge. The\r\ngoverning differential equations are transformed by introducing proper non-similarity variables and\r\nsolved numerically using two different methods, namely, the local non-similarity method with second\r\nlevel of truncation and the implicit finite difference method for values of ? (=Grx/Rex\r\n2) ranging from 0 to\r\n10. The comparisons of the results obtained by the aforementioned methods are found in excellent\r\nagreement. Effects of the viscoelastic parameter, ? (Deborah number) on the skin-friction and the heat\r\ntransfer coefficients have been shown graphically for the fluid with Prandtl number equal to 0.7, 7.03\r\nand 15.0....
Among the available alternative sources of energy in Bangladesh bio-oil is recognized to be a promising alternative energy source.\r\nBio-oil can be extracted by pyrolysis as well as expelling or solvent extraction method. In these days bio-oil is merely used in vehicles\r\nand power plants after some up gradation .However, it is not used for domestic purposes like cooking and lighting due to its high\r\ndensity and viscosity. This paper outlines the design of a gravity stove to use high dense and viscous bio-oil for cooking purpose.\r\nFor this, Pongamia pinnata (karanj) oil extracted by solvent extraction method is used as fuel fed under gravity force. Efficiency of\r\ngravity stove with high dense and viscous bio-oil (karanj) is 11.81% which of kerosene stove is 17.80% also the discharge of karanj\r\noil through gravity stove is sufficient for continuous burning. Thus, bio-oil can be effective replacement of kerosene for domestic\r\npurposes....
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