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61.
Proper design of helium systems with large number of components and involved configurations such as helium liquefiers/refrigerators requires the use of tools like process simulators. The accuracy of the simulation results, to a great extent, depends on the accuracy of property data. For computation of thermodynamic properties of helium, the 32-parameter MBWR equation of state proposed by McCarty and Arp [1] is widely used. However, it is computationally involved, makes the simulation process more time-consuming and sometimes leads to computational difficulties such as numerical oscillations, divergence in solution especially, when the process operates over a wide thermodynamic region and is constituted of many components. Substituting MBWR EOS by simpler equations of state (EOS(s)) at selected thermodynamic planes, where the simpler EOS(s) have the similar accuracy as that of MBWR EOS may enhance ease of computation. In the present paper, the methodology to implement this concept has been elucidated with examples of steady state and dynamic simulation of helium liquefier/refrigerator based on Collins cycle. The above concept can be applied to thermodynamic analysis of other process cycles where computation of fluid property is involved. 相似文献
62.
Biplab Hazra Karuna Sindhu Ghosh Rajdeep Sarkar Supriya Bera 《Materials Science & Technology》2013,29(13):1632-1641
A novel short duration heat treatment schedule is proposed in the present investigation for the Al-17?wt-% Si-5?wt-% Cu alloy (AR alloy). The existing heat treatment uses long duration (4–24?h) holding at solutionising temperature prior to ageing treatment. In the present investigation, the AR alloy is subjected to isothermal holding at 590°C for 15?min followed by warm water quenching prior to the normal ageing schedule. Detailed microstructural investigations involving size and shape of primary as well as eutectic Si particles, porosity measurements along with hardness and tensile property characterisation are carried out to find the effect of isothermal heat treatment. The study reveals considerable improvement in microstructure and mechanical properties after this isothermal heat treatment. 相似文献
63.
This article presents the preparation of well dispersed alumina slurries containing relatively large alumina particles that can withstand accelerated weather conditions. Besides using conventional dispersants such as phosphate esters and menhaden fish oil, dispersants widely used in the surface coatings industries such as Disperbyk 110 and Triton X 100 have also been employed. However, sedimentation tests, sediment density, viscosity and gloss measurements indicate the failure of the anionic dispersants as well as menhaden fish oil to disperse the alumina particles in non-aqueous medium. Instead the binder polyvinyl butyral itself acts as the best dispersant. The well dispersed alumina slurry is stabilized in the presence of a commercially available rheology modifier, Bentone SD2 for a period of 144 h at 60 °C. The rheological behavior of the aged sample was studied under various conditions. Although a rise in viscosity of the suspension was observed when the slurry was exposed to accelerated weather conditions, a lower shear thinning index and higher gloss values indicate a better dispersion state with aging. 相似文献
64.
This paper describes a PC based centralized monitoring of the running condition of a multi-machine system. This kind of monitoring from remote central location is one of the primary requirements in today’s era of automation. The convergence of embedded system like microcontroller/DSP/FPGA, etc., now-a-days, is adding a new dimension to enhance the capability of the PC based data acquisition. In this present approach, conditions of different parameters of each motor have been measured by dedicated microcontroller based hardware. All these units are connected in a network using bus topology. All parameters are communicated to a remote PC through this bus where user friendly state-of-the-art developed software stores it for display and analysis purposes. 相似文献
65.
Abhinandan Rana Madhusudan Bera Durga Sankar Chowdhuri Debdoot Hazari Swapan Kumar Jana Ennio Zangrando Sudipta Dalai 《Journal of Inorganic and Organometallic Polymers and Materials》2012,22(2):360-368
Abstract
A new 3D silver complex [Ag(mela)(H2O)(NO3)]n (1) (mela = melamine or 2,4,6-triaminotriazine) is synthesized and characterized by single crystal X-ray diffraction, IR, and elemental analysis. The structural characterization shows that the compound crystallizes in space group C c, a = 8.181(2), b = 10.269(3) c = 11.347(3) ?, β = 105.88(2)°, Z = 4. Out of several structurally characterized transition metal compounds comprising melamine, the titled complex represents a rare example of μ 3 -melamine coordination mode realized through the heterocycle nitrogen donors. The fluorescent property of complex 1 was investigated and the mechanism was validated by means of a density functional theory (DFT) calculation. 相似文献66.
Rajavel Vijayakumar Murugesan Rajkumar Parthasarathi Sridhar Sethuraman Pitchumani 《Journal of Applied Electrochemistry》2012,42(5):319-324
The effect of the anode and cathode flow field depths on the performance of a single cell Direct methanol fuel cell (DMFC)
of 45 cm2 active area were experimentally investigated. Double serpentine flow fields (DSFFs) with varying channel depth namely, 0.2,
0.4, 0.6, 0.8, and 1 mm but with fixed channel and rib width each of 1 mm on both anode and cathode were designed, fabricated,
and tested. The experimental study involved measurement of pressure drops across anode and cathode flow field plates, polarization,
and carbon dioxide concentration measurements at various current densities. The mass transport at both anode and cathode were
found to increase with increase in pressure drop across the flow field on account of reduced channel depth from 1.0 to 0.4 mm
at all current densities. However, further decrease to a channel depth of 0.2 mm was found to be counter-productive with different
phenomena operating on either side viz., increased CO2 slug length on the anode flow channel and increased methanol crossover on the cathode side. Hence, the maximum performance
for DMFCs was observed for a channel depth of 0.4 mm on anode and cathode flow fields. A decrease in flow field channel depth
at cathode was found to increase the methanol crossover due to convective mass transfer effect. 相似文献
67.
The aim of the present work was to study the rock-fluid interaction in presence of surfactants and thereby their effects on wettability alteration of oil-wet sandstone for its essentiality in enhanced oil recovery. Characterization of sandstone sample and its interaction with crude oil, brine and surfactants were investigated by Fourier Transform Infrared spectroscopy. Scanning electron microscope and X-ray diffraction studies were performed to characterize the sandstone sample. Critical micelle concentrations of sodium dodecyl sulfate, cetyltrimethylammonium bromide, Tergitol 15-S-7, Tergitol 15-S-9, and Tergitol 15-S-12 were determined by interfacial tension measurement method. Wettability alteration of sandstone was studied by contact angle method. 相似文献
68.
Kalisankar Bera Irishi N. N. Namboothiri 《Advanced Synthesis \u0026amp; Catalysis》2013,355(7):1265-1270
α‐Nitro‐γ‐sulfonyl phosphonates with a key tetrasubstituted chiral α‐carbon center have been synthesized for the first time in high yield and enantioselectivity through a quinine‐squaramide‐catalyzed conjugate addition of α‐nitro phosphonates to aryl vinyl sulfones. Representative examples presented here for the transformation of nitrosulfonyl phosphonates to aminosulfonyl phosphonates, alkylation at the α‐position of the sulfonyl group followed by desulfonation and scale‐up of the conjugate addition highlight the practical applications of the methodology. 相似文献
69.
Parthasarathi Bera Michael Rajamathi M. S. Hegde P. Vishnu Kamath 《Bulletin of Materials Science》2000,23(2):141-145
Mass spectrometric analysis of gases evolved during thermal decomposition of divalent metal hydroxides, hydroxysalts and hydrotalcites
show that all these compounds undergo dehydration in the temperature range 30 <T < 220°C followed by decomposition at temperatures above 250°C. The latter step involves simultaneous deanation and dehydroxylation
of the layers. Our observations conclusively prove that alternative mechanisms which envisage CO2 evolution due to deanation at lower temperatures proposed by Kanezaki to be wrong. 相似文献
70.
Journal of Mechanical Science and Technology - The hybrid manipulators are always found to be of great use in industries due to the major shortcoming of serial manipulators (lesser accuracy and... 相似文献