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Steam
Kinds of Steam Terms modified by Steam Selected AbstractsPhase-rotation in in-vivo localized spectroscopyCONCEPTS IN MAGNETIC RESONANCE, Issue 3 2007Saadallah Ramadan Abstract Phase-rotation is an alternative method to phase-cycling in acquisition of magnetic resonance spectroscopic data. However, there has only been two papers describing its implementation in point resolved spectroscopy (PRESS) and stimulated echo acquisition mode (STEAM) to date. This article aims to introduce and explain the principles of phase-rotation, describe the implementations that were carried out so far in the current literature, compare phase-rotation and phase-cycling experimentally, and introduce the application of phase-rotation in double-quantum filtered (DQF) spectroscopy. © 2007 Wiley Periodicals, Inc. Concepts Magn Reson Part A 30A: 147,153, 2007 [source] PEELABILITY AND YIELD OF PROCESSING TOMATOES BY STEAM OR LYEJOURNAL OF FOOD PROCESSING AND PRESERVATION, Issue 1 2006ELISABETH GARCIA ABSTRACT Approximately 25% of the processed tomatoes grown in California are made into value-added foods such as whole peeled and diced tomatoes. Peel removal is the first step in this process, and it must be optimized for both quality and yield. The effect of peeling conditions on tomato cultivars Halley 3155 and Heinz 8892 (H 8892) was evaluated. Considerable texture loss results from peeling; however, firmness was greater for cv. Halley 3155 than for cv. H 8892 regardless of peeling conditions utilized. Peeling under low steam pressures (12 psig) was insufficient to adequately peel either cultivar. While high pressure steam (18 psig) was more efficient at peel removal, increasing vacuum level from 20 in. to 24 in. did not improve peelability of either cultivar. Because cultivar affected peelability and yield, specific tomato cultivars should be evaluated and directed to either paste or whole peeled and diced tomatoes as appropriate. [source] Radial single-shot STEAM MRIMAGNETIC RESONANCE IN MEDICINE, Issue 4 2008Kai Tobias Block Abstract Rapid MR imaging using the stimulated echo acquisition mode (STEAM) technique yields single-shot images without any sensitivity to resonance offset effects. However, the absence of susceptibility-induced signal voids or geometric distortions is at the expense of a somewhat lower signal-to-noise ratio than EPI. As a consequence, the achievable spatial resolution is limited when using conventional Fourier encoding. To overcome the problem, this study combined single-shot STEAM MRI with radial encoding. This approach exploits the efficient undersampling properties of radial trajectories with use of a previously developed iterative image reconstruction method that compensates for the incomplete data by incorporating a priori knowledge. Experimental results for a phantom and human brain in vivo demonstrate that radial single-shot STEAM MRI may exceed the resolution obtainable by a comparable Cartesian acquisition by a factor of four. Magn Reson Med 59:686,691, 2008. © 2008 Wiley-Liss, Inc. [source] MRI of muscular fatMAGNETIC RESONANCE IN MEDICINE, Issue 4 2002Fritz Schick Abstract An MRI technique with high selectivity and sensitivity to the signal components in the chemical shift range of methylene and methyl protons of fatty acids has been developed for noninvasive assessment of muscular fat in vivo. A spoiled gradient-echo sequence with spatial-spectral excitation by six equidistant pulses with 2°-(,9°)-17°-(,17°)-9°-(,2°) and a multi-echo train (TE = 16, 36, 56, 76, 96, and 116 ms) allowed a series of images to be recorded with a receiver bandwidth of 78 Hz per pixel. SIs from phantoms with lipid contents between 0.1% and 100% were compared to those from pure water. Thirty healthy volunteers underwent fat-selective imaging of their lower leg, and parallel localized proton spectroscopy of the tibialis anterior and the soleus muscle by a single-voxel stimulated echo acquisition mode (STEAM) technique (TR = 2 s, TE = 10 ms, TM = 15 ms). Results show a high correlation (r = 0.91) between fat imaging and the spectroscopic approach in the soleus muscle, considering the percentage total fat content of musculature. The correlation coefficient was clearly lower (r = 0.55) in the tibialis anterior muscle due to signal contaminations from adjacent subcutaneous fat in the images, inhomogeneous fat distribution, and generally lower lipid content in this muscle. Applications of the new imaging technique showed marked intra- and interindividual variability in the spatial distribution of lipids in the musculature of the lower leg. No significant correlation of the muscular fat with the thickness of the subcutaneous fat layer was found. In addition, the body mass index does not appear to determine muscular fat content, except in very obese cases. Magn Reson Med 47:720,727, 2002. © 2002 Wiley-Liss, Inc. [source] Noninvasive quantification of human brain ascorbate concentration using 1H NMR spectroscopy at 7,TNMR IN BIOMEDICINE, Issue 3 2010Melissa Terpstra Abstract Ascorbate (Asc, vitamin C) was quantified in the human brain noninvasively using two different 1H NMR spectroscopy methods: short-echo time STEAM and MEGA-PRESS homonuclear editing. Taking advantage of increased sensitivity and chemical shift dispersion at 7,T, Asc was quantified with increased reliability relative to our previous study accomplished at 4,T. Asc concentration quantified from short-echo time spectra measured from the occipital lobe of eight healthy subjects ([Asc],=,1.1,±,0.3,µmol/g, mean,±,SD) was in excellent agreement with Asc concentration quantified from the same volume of interest using homonuclear editing ([Asc],=,1.2,±,0.2,µmol/g). This agreement indicates that at 7,T, Asc can be reliably quantified in the human brain simultaneously with 15 other metabolites. Additional advantages of the short-echo time approach were: shorter measurement time than homonuclear editing and minimal effect of T2 relaxation on Asc quantification. High magnetic field was also beneficial for Asc quantification with MEGA-PRESS because increased chemical shift dispersion enabled editing with full efficiency, which resulted in a supra-linear gain in signal-to-noise ratio relative to 4,T. Copyright © 2009 John Wiley & Sons, Ltd. [source] Steam, hot air, and small change: Matthew Boulton and the reform of Britain's coinageECONOMIC HISTORY REVIEW, Issue 3 2003George Selgin This article challenges the claim that Great Britain solved its ,big problem of small change' (the problem of keeping decent low-denomination coins in circulation) by embracing Matthew Boulton's steam-based coining technology. Evidence from Great Britain's commercial token episode (1787,97) shows that a successful small change system depended, not on the motive power employed in coining, but on the quality and consistency of coin engravings and on having means for systematically withdrawing worn coins. The Tower Mint failed to solve Great Britain's small change problem, not because its equipment was old-fashioned, but because its policies and constitution were flawed. [source] EFFECTS of SHUCKING METHOD ON OPENING, MEAT YIELD and SELECTED QUALITY PARAMETERS of WEST AFRICAN CLAM, GALATEA PARADOXA (BORN)JOURNAL OF FOOD PROCESSING AND PRESERVATION, Issue 5 2000E.O. EKANEM Samples (n= 100) of freshly harvested clams (Galatea paradoxa Born) from the Cross River, Nigeria, were subjected after 24 h depurations to heat treatment (steam and water at 60, 70, 80, 90, 100C) for 1,6 min to evaluate the effects of level of heat treatment on opening, meat yield, sensory properties, proximate composition, pH and electrical conductivity (EC). Observations were also made on the effects of some chemical shucking aids (NaOH, NaHCO3, Na2CO3, NaCl) in 60C water on these parameters. Results showed that boiling water was most effective in opening the clams, with 100% shucking achieved in 1 min. Steam was least effective, requiring 6 min for 100% opening. Temperature significantly and strongly influenced meat yield (p<0.05;r=-0.92). pH (p<0.01; r=0.97), EC (p<0.05; r =0.65) and sensory properties (p<0.05). In general, shucking aids reduced opening time, significantly p<0.05) raised meat pH and EC, and with the exception of NaCl, insignificantly (P>0.05) improved yield. NaHCO3, and Na2CO3, which cut time for 100% opening from 5 min to 2 min were most effective. There were slight but significant (P <0.05) drops in meat moisture, crude protein and ash contents with increase in temperature (T). the model equations, pH = 4.69 + 0.021 T and % yield = 39.95,0.172 T were found to reliably predict meat pH and yield, with insignificant differences (P>0.05) between predicted and experimental values. [source] Acetic Acid, Ethanol and Steam Effects on the Growth of Botrytis cinerea in vitro and Combination of Steam and Modified Atmosphere Packaging to Control Decay in KiwifruitJOURNAL OF PHYTOPATHOLOGY, Issue 2 2009Anastasia L. Lagopodi Abstract The effects of acetic acid fumigation, ethanol fumigation, and steam heat treatment on growth of Botrytis cinerea in vitro were investigated. The effect of steam heat treatments in combination with modified atmosphere packaging (MAP) on Botrytis decay development on ,Hayward' kiwifruit was also studied. The fungus was grown in Petri dishes on potato dextrose agar. Ethanol fumigation with 100 ,l/l for 3 or 6 min, or 200 ,l/l for 6 min enhanced the growth of B. cinerea. The effect of acetic acid on growth of B. cinerea was time and dosage-dependent. Fumigation with 1 ,l/l for 6 min, 2 ,l/l for 3 min, and 4 ,l/l for 3 min promoted radial growth of the fungus when compared to the growth of the untreated control. Fumigation with 2 ,l/l for 6 min delayed the growth of the fungus for the first 6 days, while fumigation with 6 ,l/l for 3 min delayed the growth of the fungus after the sixth day. Fumigation with 4 or 6 ,l/l acetic acid for 6 min, and 8 ,l/l acetic acid for 3 or 6 min resulted in complete inhibition of fungal growth. Steam heat treatment at 45°C for 6 min, and at 48, 51, and 54°C for 3 or 6 min completely inhibited fungal growth in vitro. Furthermore, steam treatments at 47, 50, and 53°C for 3 or 6 min completely inhibited decay at the stem end of kiwifruit kept at 10°C in MAP for 12 days. However, none of the steam treatments inhibited decay in wounds on the surface of the fruit kept in MAP. [source] USS Annapolis:The Wardroom and The Crews MessNAVAL ENGINEERS JOURNAL, Issue 1 2003Cdr. E.D. Maissian USNR (Ret.) BACKGROUND USS Annapolis (PG-10) was the first of four gunboats (Vicksburg, Newport, Princeton) built during the transition period of the maritime world, that is -sail to steam, wood to steel. The Annapolis' original barkentine rig was of the composite type, typical for the day , steel keel and frames, steel shell plating from main deck to waterline, and wood planking with copper sheathing to the keel. Copper being resistant to barnacles, this method was used, in as much as dry docks were a scarcity in those days. Rear Admiral Phillip Hichborn, chief constructor of the Bureau of Construction and Repair, designed the hull. Rear Admiral George Wallace Melville, chief of the Bureau of Steam Engineering, designed her power plant. He was one of few survivors of the Jeannette expedition through the Bering Straits to the North Pole. Her power plant was a triple expansion reciprocating steam engine, better known as an "Up-n-Downer". Steam was supplied by two watertube boilers at 180 psi. These gunboats were pioneers in the use of watertube boilers. [source] Rail, Steam, and Speed: The "Rocket" and the Birth of Steam Locomotion , By Christopher McGowanTHE HISTORIAN, Issue 4 2008Marsh Wilkinson Jones No abstract is available for this article. [source] Influence of xylan on the enzymatic hydrolysis of steam-pretreated corn stover and hybrid poplarBIOTECHNOLOGY PROGRESS, Issue 2 2009Renata Bura Abstract The focus of this study was to alter the xylan content of corn stover and poplar using SO2 -catalyzed steam pretreatment to determine the effect on subsequent hydrolysis by commercial cellulase preparations supplemented with or without xylanases. Steam pretreated solids with xylan contents ranging from ,1 to 19% (w/w) were produced. Higher xylan contents and improved hemicellulose recoveries were obtained with solids pretreated at lower severities or without SO2 -addition prior to pretreatment. The pretreated solids with low xylan content (<4% (w/w)) were characterized by fast and complete cellulose to glucose conversion when utilizing cellulases. Commercial cellulases required xylanase supplementation for effective hydrolysis of pretreated substrates containing higher amounts of xylan. It was apparent that the xylan content influenced both the enzyme requirements for hydrolysis and the recovery of sugars during the pretreatment process. © 2009 American Institute of Chemical Engineers Biotechnol. Prog., 2009 [source] Original article: Apparent thermal diffusivity estimation for the heat transfer modelling of pork loin under air/steam cooking treatmentsINTERNATIONAL JOURNAL OF FOOD SCIENCE & TECHNOLOGY, Issue 9 2010Massimiliano Rinaldi Summary Apparent thermal diffusivity linear functions vs. product temperature were estimated for pork cooked under two different treatments (forced convection, FC and forced convection/steam combined, FC/S) at 100, 110, 120 and 140 °C by means of experimental time,temperature data and a developed finite-difference algorithm. Slope and intercept of each function were employed to calculate apparent thermal diffusivity at 40, 55 and 70 °C. Generally, FC/S treatments gave significantly higher apparent thermal diffusivities in comparison with FC conditions. Apparent thermal diffusivities were used to develop a model for cooking time and final core temperature prediction on the basis of oven setting. The model was validated by means of additional cooking tests performed at different temperatures of those employed for model development. Root mean square error values lower than 3.8 °C were obtained comparing predicted and experimental temperature profiles. Percentage errors lower than 3.1% and 3.5% were, respectively, obtained for cooking times and final core temperatures. [source] Energetic, exergetic and thermoeconomic analysis of Bilkent combined cycle cogeneration plantINTERNATIONAL JOURNAL OF ENERGY RESEARCH, Issue 11 2006C. Ozgur Colpan Abstract This paper is a case study of thermodynamics and economics related analyses applied to an existing gas/steam combined cycle cogeneration plant. Basic thermodynamic properties of the plant are determined by energy analysis utilizing main operation conditions. Exergy destructions within the plant and exergy losses to environment are investigated to determine thermodynamic inefficiencies and to assist for guiding future improvements in the plant. Cost balances and auxiliary equations are applied to several subsystems in the plant, hence, cost formation in the plant is observed. Additionally, cost rate of each product of the plant is calculated. Copyright © 2005 John Wiley & Sons, Ltd. [source] Java applet on computation of thermodynamic properties of steam and R134a refrigerantCOMPUTER APPLICATIONS IN ENGINEERING EDUCATION, Issue 4 2003F. L. Tan Abstract This paper describes the application of Java programming on the computation of thermodynamic properties of steam and the HFC-134a, 1,1,1,2-tetrafluoroethane (R134a) refrigerant through the Java applets. The Java applets can compute thermodynamic properties of steam and R134a refrigerant, such as specific volume, internal energy, enthalpy, and entropy in the phases of saturated mixture, compressed liquid, and superheated vapor. The calculated values are accurate compared to the standard reference properties tables for steam and refrigerant. © 2004 Wiley Periodicals, Inc. Comput Appl Eng Educ 11: 211,225, 2003; Published online in Wiley InterScience (www.interscience.wiley.com); DOI 10.1002/cae.10049 [source] Regional industrial recycling network in energy supply,the case of Joensuu city, FinlandCORPORATE SOCIAL RESPONSIBILITY AND ENVIRONMENTAL MANAGEMENT, Issue 3 2002Jouni Korhonen Industrial recycling networks offer an example of the practical application of some of the industrial ecology (IE) principles. In the industrial ecosystem and eco-industrial park approaches the material cycles and energy cascades in a natural ecosystem serve as the metaphoric vision for a local/regional industrial system in which waste material and waste (residual) energy are utilized through cooperation between the actors in the system. In this paper, a local/regional recycling network scenario is presented with the energy supply system of the city of Joensuu in Finland. The conditions of success include the co-production of heat and electricity (heat and power, CHP), waste energy utilization for industrial steam and renewable flow use as fuel. Some difficulties in the industrial ecosystem-type development of the system are discussed. Methodological suggestions for industrial ecosystem and eco-industrial park case studies are considered and the experience from this Finnish case is discussed in terms of wider application of IE in local/regional economic energy systems. For future research on the theme, it is suggested that regional industrial ecology may benefit from regional economics theory and, vice versa, regional economics theory may find a new area of application in regional industrial ecology. Copyright © 2002 John Wiley & Sons, Ltd. and ERP Environment. [source] Steam, hot air, and small change: Matthew Boulton and the reform of Britain's coinageECONOMIC HISTORY REVIEW, Issue 3 2003George Selgin This article challenges the claim that Great Britain solved its ,big problem of small change' (the problem of keeping decent low-denomination coins in circulation) by embracing Matthew Boulton's steam-based coining technology. Evidence from Great Britain's commercial token episode (1787,97) shows that a successful small change system depended, not on the motive power employed in coining, but on the quality and consistency of coin engravings and on having means for systematically withdrawing worn coins. The Tower Mint failed to solve Great Britain's small change problem, not because its equipment was old-fashioned, but because its policies and constitution were flawed. [source] Proposal and evaluation of a gas engine and gas turbine hybrid cogeneration system in which cascaded heat is highly utilizedELECTRICAL ENGINEERING IN JAPAN, Issue 3 2009Pyong Sik Pak Abstract A high-efficiency cogeneration system (CGS) is proposed for utilizing high-temperature exhaust gas (HTEG) from a gas engine (GE). In the proposed system, for making use of heat energy of HTEG, H2O turbine (HTb) is incorporated and steam produced by utilizing HTEG is used as working fluid of HTb. HTb exhaust gas is also utilized for increasing power output and for satisfying heat demand in the proposed system. Both of the thermodynamic characteristics of the proposed system and a gas engine CGS (GE-CGS) constructed by using the original GE are estimated. Energy saving characteristics and CO2 reduction effects of the proposed CGS and the GE-CGS are also investigated. It was estimated that the net generated power of the proposed CGS has been increased 25.5% and net power generation efficiency 6.7%, compared with the original GE-CGS. It was also shown that the proposed CGS could save 27.0% of energy consumption and reduce 1137 t-CO2/y, 1.41 times larger than those of GE-CGS, when a case study was set and investigated. Improvements of performance by increasing turbine inlet temperature were also investigated. © 2008 Wiley Periodicals, Inc. Electr Eng Jpn, 166(3): 37, 45, 2009; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/eej.20708 [source] Thermal modeling and simulation of an integrated solid oxide fuel cell and charcoal gasification systemENVIRONMENTAL PROGRESS & SUSTAINABLE ENERGY, Issue 3 2009C. Ozgur Colpan Abstract In this study we propose a novel integrated charcoal gasification and solid oxide fuel cell (SOFC) system, which is intended to produce electricity and heat simultaneously. This system mainly consists of an updraft gasifier using air and steam as the gasification agents, a planar and direct internal reforming SOFC and a low temperature gas cleanup system. The performance of this system is assessed through numerical modeling using a pre-developed and validated heat transfer model of the SOFC and thermodynamic models for the rest of the components. These models are used to simulate the performance of the cell and system for a case study. In addition, a parametric study is conducted to assess the effect of Reynolds number at the fuel channel inlet of the SOFC on the cell performance, e.g., fuel utilization and power density, and the system performance, e.g., electrical efficiency, exergetic efficiency, and power to heat ratio. The number of stacks is also calculated for different Reynolds numbers to discuss the economical feasibility of the integrated system. The results show that the electrical efficiency, exergetic efficiency and power to heat ratio of this system are 33.31%, 45.72%, and 1.004, respectively, for the base case. The parametric study points out that taking the Reynolds number low yields higher electrical and exergetic efficiencies for the system, but it also increases the cost of the system. © 2009 American Institute of Chemical Engineers Environ Prog, 2009 [source] Optimization of a single-effect evaporation system to effectively utilize thermal energyENVIRONMENTAL PROGRESS & SUSTAINABLE ENERGY, Issue 2 2009Raafat Alnaizy Abstract Wastewater treatment facilities at Emirates Gold in Dubai seek to improve the steam economy of the existing single-effect with recirculation and vapor-compression evaporation process. Maximizing steam economy is important as it impacts treatment costs. There are two main approaches for improving steam economy in evaporators. One is to use a multiple-effect evaporator; the other is to use a mechanical vapor recompression. Multiple-effect evaporators were rejected because of higher capital and power cost. One of the suggestions that were made towards improving the steam economy was to recover heat from the steam condensate. A modified process flow diagram was proposed and investigated. The modified process was simulated using SuperPro Designer and Hysys with complete material and energy balance computation. The modified process increased the total water evaporation capacity and gained 40% better steam economy of the process. Another advantage was an increase in the amount of water reused, which is both economical and environmentally friendly. © 2008 American Institute of Chemical Engineers Environ Prog, 2009 [source] Optimization of industrial-scale deodorization of high-oleic sunflower oil via response surface methodologyEUROPEAN JOURNAL OF LIPID SCIENCE AND TECHNOLOGY, Issue 3 2008Vito Martin Abstract Optimization of industrial-scale deodorization of high-oleic sunflower oil (HOSO) via response surface methodology is presented in this study. The results of an experimental program conducted on an industrial-scale deodorizer were analyzed statistically. Predictive models were derived for each of the oil quality indicators (QI) in dependence on the studied variable deodorization process parameters. The deodorization behavior of some minor components was analyzed on a pilot-scale deodorizer. For comparison, a similar experimental program was also performed on the laboratory-scale. The results of this study demonstrate that optimization of the deodorization process requires a suitable compromise between often mutually opposing demands dictated by different oil QI. The production of HOSO with top-quality organoleptic and nutritional values (high tocopherol and phytosterol contents and low free and trans fatty acid contents) and high oxidative stability demands deodorization temperatures in the range between 220 and 235,°C and a total sparge steam above 2.0% (wt/wt in oil). The response surface methodology provides the tools needed to identify the optimum deodorization process conditions. However, the laboratory-scale experiments, while showing similar response characteristics of QI in dependence on the process parameters and thus helpful as a guide, are of limited value in the optimization of an industrial-scale operation. [source] Flow Behavior of Sandwich Structures for Cooling Thermally Highly Loaded Steam Turbine Components,ADVANCED ENGINEERING MATERIALS, Issue 5 2009Paul Beiss To increase steam temperature and pressure in the steam turbine, a new cooling structure (see picture) was developed comprising a woven wire mesh interlayer between two plane sheets. Cooling steam is fed into the interlayer, where it can flow without severe losses. To characterize the mechanical high temperature behavior of the structure, the flow behavior under static loading was investigated and simulated by the finite element method (FEM). [source] Extraction of rosemary essential oil by steam distillation and hydrodistillationFLAVOUR AND FRAGRANCE JOURNAL, Issue 6 2003C. Boutekedjiret Abstract Rosemary oil was extracted by both steam and hydrodistillations then analysed by gas chromatography and gas chromatography,mass spectrometry. The effect of time of extraction enabled us to follow the evolution of the yield and oil composition obtained by both processes. Copyright © 2003 John Wiley & Sons, Ltd. [source] Abiotic,biotic controls on the origin and development of spicular sinter: in situ growth experiments, Champagne Pool, Waiotapu, New ZealandGEOBIOLOGY, Issue 2 2005K. M. HANDLEY Abiotic,biotic mechanisms of microstromatolitic spicular sinter (geyseritic) initiation and development were elucidated by in situ growth experiments at Champagne Pool (75 °C, pH 5.5). Siliceous sinter formed subaerially on glass slides placed along the margin of the hot spring. Environment,silica,microbe interactions were revealed by periodic collections of incremental sinter growth that formed under a range of environmental conditions including quiescence vs. wave turbulence, and wind,evaporation vs. steam,condensation. Sinter surfaces were intermittently colonized by voluminous networks of filamentous micro-organisms, with submicron diameters, that provided an extensive surface area for silica deposition. The subaerial distribution of sinter and its textures reflected micron- to centimetre-scale differences in environmental conditions, particularly relating to the balance between wave-supplied dissolved silica and its precipitation, forced by cooling and evaporation. A continuum of sinter textures formed, representing rates of silica precipitation that either out-paced biofilm growth or regulated the structural development of biofilms, and hence also the nature of microbially templated sinter. Massive laminae of porous, filamentous-network sinter and/or fenestrae (up to 10's of microns in thickness and diameter) formed at relatively low rates of silica deposition (approximately 0.2 mg slide,1 day,1). At high rates (>1.9 mg slide,1 day,1), densely packed, granular or nonporous sinter formed, with filament networks disappearing into the siliceous matrix and becoming imperceptible under scanning electron microscopy (SEM). Furthermore, spicules were nucleated by filamentous microcolonies, where their discrete conical morphologies were preserved by accretion of thin sinter laminae. Microstromatolitic spicular growth ensued at fluctuating low to high rates of silica precipitation. Greater apical sinter build-up, and hence upward polarity, resulted from focused microbial recolonization and progressively greater subaerial exposure at microspicule tips. The biogenic origin of spicular sinter at Champagne Pool clearly demonstrates that micron-scale biofilms, displaying self-organization patterns common to both biofilms and microbial mats, can be an essential factor in shaping characteristic centimetre-scale sinter macrostructures. These findings suggest that a biogenic origin for geyserites elsewhere should also be considered. Moreover, results corroborate the supposition that microbially generated surface roughness may be significant for stromatolite morphogenesis in cryptic Precambrian carbonates. [source] Research on Marangoni condensation heat transfer for water and ethanol mixture vaporHEAT TRANSFER - ASIAN RESEARCH (FORMERLY HEAT TRANSFER-JAPANESE RESEARCH), Issue 8 2004He Yang-peng Abstract A brass block was constructed as a test block to study the Marangoni condensation in this paper. The maximal temperature difference of the block surface on which pure steam condensed was 11°C when the block was cooled by the normal temperature water. Regulations and modes of Marangoni condensation for mixture vapor with different mass fractions were studied when the speed of vapor was 0.3 m/s. As both temperature gradients and concentration gradients exist on the condensing surface, the experimental results indicate that the maximal heat transfer coefficient of mixture vapor can be 2.8 times that of pure steam when the Marangoni condensation of mixture vapor appears. The heat transfer coefficient of mixture vapor increases with the decrease of surface subcooling, and it appears a steep increase when the surface subcooling is small enough; the heat transfer flux has a maximum value as the surface subcooling rises; and the different modes of condensation are confirmed when the different ethanol concentration and different surface subcooling exist. © 2004 Wiley Periodicals, Inc. Heat Trans Asian Res, 33(8): 505,514, 2004; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/htj.20035 [source] Direct Synthesis of Highly Stable Mesoporous Molecular Sieves Containing Zeolite Building Units,ADVANCED FUNCTIONAL MATERIALS, Issue 2 2005A. Sakthivel Abstract A novel, one-step synthesis of a highly stable mesoporous molecular sieve (MMS-H), which has a structure analogous to MCM-48 but which contains zeolite building units, is reported. A variety of experimental techniques,X-ray diffraction (XRD), N2 adsorption/desorption, transmission electron microscopy (TEM), Fourier-transform infrared (FTIR) spectroscopy, hyperpolarized 129Xe,NMR, and solid-state 27Al and 31P,magic-angle spinning (MAS) NMR spectroscopies,have been used to characterize the framework structure, porosity, and acidity of this novel mesoporous/microporous composite material, which is also found to possess superior thermal, hydrothermal, steam, and mechanical stabilities. [source] Geothermal-based hydrogen production using thermochemical and hybrid cycles: A review and analysisINTERNATIONAL JOURNAL OF ENERGY RESEARCH, Issue 9 2010M. Tolga Balta Abstract Geothermal-based hydrogen production, which basically uses geothermal energy for hydrogen production, appears to be an environmentally conscious and sustainable option for the countries with abundant geothermal energy resources. In this study, four potential methods are identified and proposed for geothermal-based hydrogen production, namely: (i) direct production of hydrogen from the geothermal steam, (ii) through conventional water electrolysis using the electricity generated through geothermal power plant, (iii) by using both geothermal heat and electricity for high temperature steam electrolysis and/or hybrid processes, and (iv) by using the heat available from geothermal resource in thermochemical processes. Nowadays, most researches are focused on high-temperature electrolysis and thermochemical processes. Here we essentially discuss some potential low-temperature thermochemical and hybrid cycles for geothermal-based hydrogen production, due to their wider practicality, and examine them as a sustainable option for hydrogen production using geothermal heat. We also assess their thermodynamic performance through energy and exergy efficiencies. The results show that these cycles have good potential and attractive overall system efficiencies over 50% based on a complete reaction approach. The copper-chlorine cycle is identified as a highly promising cycle for geothermal-hydrogen production. Copyright © 2009 John Wiley & Sons, Ltd. [source] Effect of supplementary firing options on cycle performance and CO2 emissions of an IGCC power generation systemINTERNATIONAL JOURNAL OF ENERGY RESEARCH, Issue 7 2009N. V. Gnanapragasam Abstract Supplementary firing is adopted in combined-cycle power plants to reheat low-temperature gas turbine exhaust before entering into the heat recovery steam generator. In an effort to identify suitable supplementary firing options in an integrated gasification combined-cycle (IGCC) power plant configuration, so as to use coal effectively, the performance is compared for three different supplementary firing options. The comparison identifies the better of the supplementary firing options based on higher efficiency and work output per unit mass of coal and lower CO2 emissions. The three supplementary firing options with the corresponding fuel used for the supplementary firing are: (i) partial gasification with char, (ii) full gasification with coal and (iii) full gasification with syngas. The performance of the IGCC system with these three options is compared with an option of the IGCC system without supplementary firing. Each supplementary firing option also involves pre-heating of the air entering the gas turbine combustion chamber in the gas cycle and reheating of the low-pressure steam in the steam cycle. The effects on coal consumption and CO2 emissions are analysed by varying the operating conditions such as pressure ratio, gas turbine inlet temperature, air pre-heat and supplementary firing temperature. The results indicate that more work output is produced per unit mass of coal when there is no supplementary firing. Among the supplementary firing options, the full gasification with syngas option produces the highest work output per unit mass of coal, and the partial gasification with char option emits the lowest amount of CO2 per unit mass of coal. Based on the analysis, the most advantageous option for low specific coal consumption and CO2 emissions is the supplementary firing case having full gasification with syngas as the fuel. Copyright © 2008 John Wiley & Sons, Ltd. [source] A closed-loop proposal for hydrogen generation using steel waste and a prototype solar concentratorINTERNATIONAL JOURNAL OF ENERGY RESEARCH, Issue 5 2009Abdul-Majeed Azad Abstract An economically viable and environmental-friendly method of generating PEM grade hydrogen has been proposed and is by the reaction of certain metals with steam, appropriately called ,metal,steam reforming',MSR. The drawbacks of conventional processes (hydrogen and carbothermic reduction schemes) are overcome by resorting to solution-based reduction schemes and are made economically feasible using iron oxides from steel industry's mill-scale waste. A novel aqueous-based room temperature technique using sodium borohydride (NaBH4) as the reducing agent has been developed that produces highly active nanoscale iron particles (,40,nm). By using hydrazine as an inexpensive and, compared with NaBH4, more stable reductant, body centered cubic iron particles with ,5,nm edges were obtained via solvothermal process under mild conditions from acid digested mill-scale waste. The nanoscale zerovalent iron (nZVI) powder showed improved kinetics and greater propensity for hydrogen generation than the coarser microscale iron. The rate constants for the MSR were obtained for all the reduction schemes employed in this work and are given by khydrogen=0.0158,min,1kcarbon=0.0248,min,1ksodiumborohydride=0.0521,min,1 and khydrazine=0.1454,min,1, assuming first order kinetics. Another innovative effort converted the magnetite waste directly into nZVI under solvothermal conditions, thus obviating the sluggish and time-consuming acid dissolution step. This particular aspect has significant ramification in terms of time and cost of making the iron precursor. To initiate and sustain the somewhat endothermic MSR process, a solar concentrator consisting of a convex polyacrylic bowl with reflective aluminum coating was fabricated and evaluated. This unique combination of mill-scale waste as iron source, hydrazine as reductant, mild process conditions and solar energy as the MSR actuator obviates several drawbacks plaguing the grand scheme of producing and delivering pure and humidified H2 to a PEMFC stack. Copyright © 2008 John Wiley & Sons, Ltd. [source] Cost numerical optimization of the triple-pressure steam-reheat gas-reheat gas-recuperated combined power cycle that uses steam for cooling the first GTINTERNATIONAL JOURNAL OF ENERGY RESEARCH, Issue 15 2008A. M. Bassily Abstract Optimization is an important method for improving the efficiency and power of the combined cycle. In this paper, the triple-pressure steam-reheat gas-reheat gas-recuperated combined cycle that uses steam for cooling the first gas turbine (the regular steam-cooled cycle) was optimized relative to its operating parameters. The optimized cycle generates more power and consumes more fuel than the regular steam-cooled cycle. An objective function of the net additional revenue (the saving of the optimization process) was defined in terms of the revenue of the additional generated power and the costs of replacing the heat recovery steam generator (HRSG) and the costs of the additional operation and maintenance, installation, and fuel. Constraints were set on many operating parameters such as air compression ratio, the minimum temperature difference for pinch points (,Tppm), the dryness fraction at steam turbine outlet, and stack temperature. The net additional revenue and cycle efficiency were optimized at 11 different maximum values of turbine inlet temperature (TIT) using two different methods: the direct search and the variable metric. The optima were found at the boundaries of many constraints such as the maximum values of air compression ratio, turbine outlet temperature (TOT), and the minimum value of stack temperature. The performance of the optimized cycles was compared with that for the regular steam-cooled cycle. The results indicate that the optimized cycles are 1.7,1.8 percentage points higher in efficiency and 4.4,7.1% higher in total specific work than the regular steam-cooled cycle when all cycles are compared at the same values of TIT and ,Tppm. Optimizing the net additional revenue could result in an annual saving of 21 million U.S. dollars for a 439,MW power plant. Increasing the maximum TOT to 1000°C and replacing the stainless steel recuperator heat exchanger of the optimized cycle with a super-alloys-recuperated heat exchanger could result in an additional efficiency increase of 1.1 percentage point and a specific work increase of 4.8,7.1%. The optimized cycles were about 3.3 percentage points higher in efficiency than the most efficient commercially available H-system combined cycle when compared at the same value of TIT. Copyright © 2008 John Wiley & Sons, Ltd. [source] Transient thermal modelling of heat recovery steam generators in combined cycle power plantsINTERNATIONAL JOURNAL OF ENERGY RESEARCH, Issue 11 2007Sepehr Sanaye Abstract Heat recovery steam generator (HRSG) is a major component of a combined cycle power plant (CCPP). This equipment is particularly subject to severe thermal stress especially during cold start-up period. Hence, it is important to predict the operational parameters of HRSGs such as temperature of steam, water, hot gas and tube metal of heating elements as well as pressure change in drums during transient and steady-state operation. These parameters may be used for estimating thermal and mechanical stresses which are important in HRSG design and operation. In this paper, the results of a developed thermal model for predicting the working conditions of HRSG elements during transient and steady-state operations are reported. The model is capable of analysing arbitrary number of pressure levels and any number of elements such as superheater, evaporator, economizer, deaerator, desuperheater, reheater, as well as duct burners. To assess the correct performance of the developed model two kinds of data verification were performed. In the first kind of data verification, the program output was compared with the measured data collected from a cold start-up of an HRSG at Tehran CCPP. The variations of gas, water/steam and metal temperatures at various sections of HRSG, and pressure in drums were among the studied parameters. Mean differences of about 3.8% for temperature and about 9.2% for pressure were observed in this data comparison. In the second kind of data verification, the steady-state numerical output of the model was checked with the output of the well-known commercial software. An average difference of about 1.5% was found between the two latter groups of data. Copyright © 2007 John Wiley & Sons, Ltd. [source] | |||||||||||||||||||||||||||||||||||||||||||