Current Issue : July - September Volume : 2016 Issue Number : 3 Articles : 6 Articles
A considerable difference between experimental and theoretical results has been observed in the studies of segmented\nthermoelectric generators (STEGs). Because of simplicity, the approximate methods are widely used for design and optimization\nof the STEGs. This study is focused on employment of exact method for design and optimization of STEGs and comparison of\nexact and approximate results. Thus, using new highly efficient thermoelectric materials, four STEGs are proposed to operate in\nthe temperature range of 300 to 1300 kelvins. The proposed STEGs are optimally designed to achieve maximum efficiency. Design\nand performance characteristics of the optimized generators including maximum conversion efficiency and length of elements\nare calculated through both exact and approximate methods. The comparison indicates that the approximate method can cause a\ndifference up to 20% in calculation of some design characteristics despite its appropriate results in efficiency calculation.The results\nalso show that the maximum theoretical efficiency of 23.08% is achievable using the new proposed STEGs. Compatibility factor\nof the selected materials for the proposed STEGs is also calculated using both exact and approximate methods. The comparison\nindicates a negligible difference in calculation of compatibility factor, despite the considerable difference in calculation of reduced\nefficiency (temperature independence efficiency)....
Outstanding performance of natural camel hair has attracted much attention on the effective use of such specialty fiber to apparel\ntextiles. In this paper, sodium bisulfide (SB) and lithium bromide (LB) solutions were used to process the camel guard hair before\nits slenderization. It is found that camel guard hair processed by SB solution shows the highest breaking elongation (âË?¼140%) due\nto the breakage of disulfide bonds (reflected by Raman spectra). LB ions result in the disruption of hair crystalline phase with\nslight benefit to the slenderization (determined by X-ray diffraction and differential scanning calorimetry). IR spectra indicate that\nhydrogen bonds of camel guard hair act as fixation switch in the programmed tensile test. It is discovered that guard hair reveals the\nbest water-induced shape memory with 90% of stretching shape recovery, whereas the value remained to be 70% and 60% for hair\nprocessed by LB and SB solutions after breaking partial crystalline phase and disulfide cross-links separately (polymer net-points).\nThe poorer shape memory of processed guard hair benefits its slenderization for more stable fixation of stretched length....
The use of biomass due to the reduction in greenhouse gas emissions and environmental impacts has attracted many researchers�\nattention in the recent years. Access to an energy conversion system which is able to have the optimum performance for applying\nvaluable low heating value fuels has been considered by many practitioners and scholars. This paper focuses on the accurate\nmodeling of biomass gasification process and the optimal design of a multigeneration system (heating, cooling, electrical power,\nand hydrogen as energy carrier) to take the advantage of this clean energy. In the process of gasification modeling, a thermodynamic\nequilibrium model based on Gibbs energy minimization is used. Also, in the present study, a detailed parametric analysis of\nmultigeneration system for undersigning the behavior of objective functions with changing design parameters and obtaining the\noptimal design parameters of the system is done as well. The results show that with exergy efficiency as an objective function this\nparameter can increase from19.6% in base case to 21.89% in the optimized case. Also, for the total cost rate of system as an objective\nfunction it can decrease from 154.4 $/h to 145.1 $/h....
The influence of the bottom shape on the flow field distribution and particle suspension in a DTB crystallizer was investigated by\nComputational Fluid Dynamics (CFD) coupled with Two-Fluid Model (Eulerian model). Volume fractions of three sections were\nmonitored on time, and effect on particle suspension could be obtained by analyzing the variation tendency of volume fraction.\nThe results showed that the protruding part of a ...
The catalysts Ni/Al2O3 and CaO modified Ni/Al2O3 were prepared by impregnation method and applied for methanation of\nCO2.The catalysts were characterized by N2 adsorption/desorption, temperature-programmed reduction of H2 (H2-TPR), X-ray\ndiffraction (XRD), and temperature-programmed desorption of CO2 and H2 (CO2-TPD and H2-TPD) techniques, respectively.\nTPR and XRD results indicated that CaO can effectively restrain the growth of NiO nanoparticles, improve the dispersion of NiO,\nand weaken the interaction between NiO and Al2O3. CO2-TPD and H2-TPD results suggested that CaO can change the environment\nsurrounding of CO2 and H2 adsorption and thus the reactants on the Ni atoms can be activated more easily.The modified Ni/Al2O3\nshowed better catalytic activity than pure Ni/Al2O3. Ni/CaO-Al2O3 showed high CO2 conversion especially at low temperatures\ncompared to Ni/Al2O3, and the selectivity to CH4 was very close to 1. The high CO2 conversion over Ni/CaO-Al2O3 was mainly\ncaused by the surface coverage by CO2-derived species on CaO-Al2O3 surface....
The coalescence of droplets in oil can be implemented rapidly by high-voltage pulse electric field, which is an effective\ndemulsification dehydration technological method. At present, it is widely believed that the main reason of pulse electric field\npromoting droplets coalescence is the dipole coalescence and oscillation coalescence in pulse electric field, and the optimal\ncoalescence pulse electric field parameters exist. Around the above content, the dynamics of high-voltage pulse electric field\npromoting the coalescence of emulsified droplets is studied by researchers domestically and abroad. By review, the progress of\nhigh-voltage pulse electric field demulsification technology can get a better understanding, which has an effect of throwing a sprat\nto catch a whale on promoting the industrial application....
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