Efficiency Values (efficiency + value)

Distribution by Scientific Domains


Selected Abstracts


Performance improvements for olive oil refining plants

INTERNATIONAL JOURNAL OF ENERGY RESEARCH, Issue 6 2010
Elif Bozoglan
Abstract The main objective of this study, which is conducted for the first time to the best of the authors' knowledge, is to identify improvements in olive oil refinery plants' performance. In the analyses, the actual operational data are used for performance assessment purposes. The refinery plant investigated is located in Izmir Turkey and has an oil capacity of 6250,kg,h,1. It basically incorporates steam generators, several tanks, heat exchangers, a distillation column, flash tanks and several pumps. The values for exergy efficiency and exergy destruction of operating components are determined based on a reference (dead state) temperature of 25°C. An Engineering Equation Solver (EES) software program is utilized to do the analyses of the plant. The exergy transports between the components and the consumptions in each of the components of the whole plant are determined for the average parameters obtained from the actual data. The exergy loss and flow diagram (the so-called Grassmann diagram) are also presented for the entire plant studied to give quantitative information regarding the proportion of the exergy input that is dissipated in the various plant components. Among the observed components in the plant, the most efficient equipment is found to be the shell- and tube-type heat exchanger with an exergy efficiency value of 85%. The overall exergetic efficiency performance of the plant (the so-called functional exergy efficiency) is obtained to be about 12%, while the exergy efficiency value on the exergetic fuel,product basis is calculated to be about 65%. Copyright © 2009 John Wiley & Sons, Ltd. [source]


Gas-phase basicities for ions from bradykinin and its des-arginine analogues

JOURNAL OF MASS SPECTROMETRY (INCORP BIOLOGICAL MASS SPECTROMETRY), Issue 8 2001
Nigel P. Ewing
Abstract Apparent gas-phase basicities (GBapps) for [M + H]+ of bradykinin, des-Arg1 -bradykinin and des-Arg9 -bradykinin have been assigned by deprotonation reactions of [M + 2H]2+ in a Fourier transform ion cyclotron resonance mass spectrometer. With a GBapp of 225.8 ± 4.2 kcal mol,1, bradykinin [M + H]+ is the most basic of the ions studied. Ions from des-Arg1 -bradykinin and des-Arg9 -bradykinin have GBapp values of 222.8 ± 4.3 kcal mol,1 and 214.9 ± 2.3 kcal mol,1, respectively. One purpose of this work was to determine a suitable reaction efficiency ,break point' for assigning GBapp values to peptide ions using the bracketing method. An efficiency value of 0.1 (i.e. approximately 10% of all collisions resulting in a deprotonation reaction) was used to assign GBapps. Support for this criterion is provided by the fact that our GBapp values for des-Arg1 -bradykinin and des-Arg9 -bradykinin are identical, within experimental error, to literature values obtained using a modified kinetic method. However, the GBapps for bradykinin ions from the two studies differ by 10.3 kcal mol,1. The reason for this is not clear, but may involve conformation differences produced by experimental conditions. The results may be influenced by salt-bridge conformers and/or by conformational changes caused by the use of a proton-bound heterodimer in the kinetic method. Factors affecting the basicities of these peptide ions are also discussed, and molecular modeling is used to provide information on protonation sites and conformations. The presence of two highly basic arginine residues on bradykinin results in its high GBapp, while the basicity of des-Arg1 -bradykinin ions is increased by the presence of two proline residues at the N-terminus. The proline residue in the second position folds the peptide chain in a manner that increases intramolecular hydrogen bonding to the protonated N-terminal amino group of the proline at the first position. Copyright © 2001 John Wiley & Sons, Ltd. [source]


Synthesis and applications of low-bandgap conjugated polymers containing phenothiazine donor and various benzodiazole acceptors for polymer solar cells

JOURNAL OF POLYMER SCIENCE (IN TWO SECTIONS), Issue 21 2010
Harihara Padhy
Abstract A series of soluble donor-acceptor conjugated polymers comprising of phenothiazine donor and various benzodiazole acceptors (i.e., benzothiadiazole, benzoselenodiazole, and benzoxadiazole) sandwiched between hexyl-thiophene linkers were designed, synthesized, and used for the fabrication of polymer solar cells (PSC). The effects of the benzodiazole acceptors on the thermal, optical, electrochemical, and photovoltaic properties of these low-bandgap (LBG) polymers were investigated. These LBG polymers possessed large molecular weight (Mn) in the range of 3.85,5.13 × 104 with high thermal decomposition temperatures, which demonstrated broad absorption in the region of 300,750 nm with optical bandgaps of 1.80,1.93 eV. Both the HOMO energy level (,5.38 to ,5.47 eV) and LUMO energy level (,3.47 to ,3.60 eV) of the LBG polymers were within the desirable range of ideal energy level. Under 100 mW/cm2 of AM 1.5 white-light illumination, bulk heterojunction PSC devices containing an active layer of electron donor polymers mixed with electron acceptor [6,6]-phenyl-C61 -butyric acid methyl ester (PC61BM) or [6,6]-phenyl-C71 -butyric acid methyl ester (PC71BM) in different weight ratios were investigated. The best performance of the PSC device was obtained by using polymer PP6DHTBT as an electron donor and PC71BM as an acceptor in the weight ratio of 1:4, and a power conversion efficiency value of 1.20%, an open-circuit voltage (Voc) value of 0.75 V, a short-circuit current (Jsc) value of 4.60 mA/cm2, and a fill factor (FF) value of 35.0% were achieved. © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2010 [source]


Soil and plant diet exposure routes and toxicokinetics of lindane in a terrestrial isopod

ENVIRONMENTAL TOXICOLOGY & CHEMISTRY, Issue 10 2000
José Paulo Sousa
Abstract In most studies dealing with effects of toxic substances in saprotrophic isopods, animals are exposed to the test substance through contaminated food. Because these animals can be in a close contact with the soil surface, the substrate, as an exposure pathway, should not be neglected. Here the authors analyze the toxicokinetic behavior of lindane (,-hexachlorocyclohexane [,-HCH]) in the isopod species Porcellionides pruinosus, comparing two exposure routes: food and two soil types (artificial Organisation for Economic Cooperation and Development [OECD] soil and a natural agricultural soil). In the feeding experiment, a strong decrease of ,-HCH concentration over time was observed on the food material, with the animals showing a broader range in chemical assimilation efficiency values (averaging 17.7% and ranging from 10 to 40%). The ,-HCH bioaccumulation results indicate that when animals incubated under both soil types reached a steady state, they displayed much higher body burdens (1,359.60 pg/animal on OECD soil and 1,085.30 pg/animal on natural soil) than those exposed to contaminated food (43.75 pg/animal). Kinetic models also revealed much lower assimilation and elimination rates in the food experiment (20.66 pg/d and 0.10 pg/d) than in both soil experiments (238.60 pg/d and 350.54 pg/d for the assimilation rate and 0.19 pg/d and 0.32 pg/d for the elimination rate). Differences in results between exposure routes are discussed according to equilibrium-partitioning theory and the enhanced relevance of the substrate exposure route is analyzed under future prospects on chemical toxicity testing using isopods. [source]


Dynamic energy and exergy analyses of an industrial cogeneration system

INTERNATIONAL JOURNAL OF ENERGY RESEARCH, Issue 4 2010
Yilmaz Yoru
Abstract The study deals with the energetic and exergetic analyses of a cogeneration (combined heat and power, CHP) system installed in a ceramic factory, located in Izmir, Turkey. This system has three gas turbines with a total capacity of 13,MW, six spray dryers and two heat exchangers. In the analysis, actual operational data over one-month period are utilized. The so-called CogeNNexT code is written in C++ and developed to analyze energetic and exergetic data from a database. This code is also used to analyze turbines, spray dryers and heat exchangers in this factory. Specifications of some parts of system components have been collected from the factory. Based on the 720,h data pattern (including 43,200 data), the mean energetic and exergetic efficiency values of the cogeneration system are found to be 82.3 and 34.7%, respectively. Copyright © 2009 John Wiley & Sons, Ltd. [source]


Exergetic analysis of an aircraft turbofan engine

INTERNATIONAL JOURNAL OF ENERGY RESEARCH, Issue 14 2007
Enis T. Turgut
Abstract The main objective of the present study is to perform an exergy analysis of a turbofan kerosene-fired engine with afterburner (AB) at sea level and an altitude of 11 000 m. The main components of this engine include a fan, a compressor, a combustion chamber, a turbine, an AB and an exhaust. Exergy destructions in each of the engine components are determined, while exergy efficiency values for both altitudes are calculated. The AB unit is found to have the highest exergy destruction with 48.1% of the whole engine at the sea level, followed by the exhaust, the combustion chamber and the turbine amounting to 29.7, 17.2 and 2.5%, respectively. The corresponding exergy efficiency values for the four components on the product/fuel basis are obtained to be 59.9, 65.6, 66.7 and 88.5%, while those for the whole engine at the sea level and an altitude of 11 000 m are calculated to be 66.1 and 54.2%. Copyright © 2007 John Wiley & Sons, Ltd. [source]


Exergetic performance assessment of a ground-source heat pump drying system

INTERNATIONAL JOURNAL OF ENERGY RESEARCH, Issue 8 2007
Ebru Hancioglu Kuzgunkaya
Abstract In evaluating the efficiency of heat pump (HP) systems, the most commonly used measure is the energy (or first law) efficiency, which is modified to a coefficient of performance (COP) for HP systems. However, for indicating the possibilities for thermodynamic improvement, energy analysis is inadequate and exergy analysis is needed. This study presents an exergetic assessment of a ground-source (or geothermal) HP (GSHP) drying system. This system was designed, constructed and tested in the Solar Energy Institute of Ege University, Izmir, Turkey. The exergy destructions in each of the components of the overall system are determined for average values of experimentally measured parameters. Exergy efficiencies of the system components are determined to assess their performances and to elucidate potentials for improvement. COP values for the GSHP unit and overall GSHP drying system are found to range between 1.63,2.88 and 1.45,2.65, respectively, while corresponding exergy efficiency values on a product/fuel basis are found to be 21.1 and 15.5% at a dead state temperature of 27°C, respectively. Specific moisture extraction rate (SMER) on the system basis is obtained to be 0.122 kg kW,1 h,1. For drying systems, the so-called specific moisture exergetic rate (SMExR), which is defined as the ratio of the moisture removed in kg to the exergy input in kW h, is also proposed by the authors. The SMExR of the whole GSHP drying system is found to be 5.11 kg kW,1 h,1. Copyright © 2006 John Wiley & Sons, Ltd. [source]


Turkey's sectoral energy and exergy analysis between 1999 and 2000

INTERNATIONAL JOURNAL OF ENERGY RESEARCH, Issue 13 2004
Zafer Utlu
Abstract This study analyses sectoral energy and exergy utilization in Turkey between 1999 and 2000. Total energy and exergy utilization efficiencies are calculated to be 43.24 and 24.04% in 1999, and 44.91 and 24.78% in 2000, respectively. In order to calculate these efficiency values, Turkey is subgrouped into four main sectors, namely utility, industrial, transportation and commercial-residential. The energy efficiency values are found to be 23.88, 30.10, 68.97 and 57.76% in 1999, and 23.71, 30.11, 68.81 and 57.05% in 2000 for transportation, utility, industrial and commercial-residential sectors, respectively. Besides this, the exergy efficiency values are obtained to be 23.80, 30.28, 35.97 and 8.12% in 1999, and 23.65, 30.47, 35.51 and 8.02% in 2000 for the same order of sectors. The present study has clearly shown the necessity of the planned studies towards increasing exergy efficiencies in the sectors studied. Copyright © 2004 John Wiley & Sons, Ltd. [source]


The perspectives of energy production from coal-fired power plants in an enlarged EU

INTERNATIONAL JOURNAL OF ENERGY RESEARCH, Issue 9 2004
P. Grammelis
Abstract The aim of this paper is to present the current status of the coal-fired power sector in an enlarged EU (EU-15 plus EU member candidate states) in relation with the main topics of the European Strategy for the energy production and supply. It is estimated that 731 thermoelectric units, larger than 100 MWe, are operating nowadays, and their total installed capacity equals to 200.7 GWe. Coal contribution to the total electricity generation with reference to other fuel sources, is by far more intensive in the non-EU part (EU member candidate states), compared to the EU member states. It is expected that even after the enlargement, the European Union will strongly being related to coal. Enlargement will bring additional factors into play in order to meet the requirements of rising consumption, growing demand for conventional fuels and increasing dependence on imports. Besides the technology, boiler size, efficiency, age and environmental performance will determine the necessities of the coal-fired power sector in each country. Depending on the case, lifetime extension measures in operating coal-fired power plants or clean coal technologies can play an important role towards the energy sector restructuring. Low efficiency values in the non-EU coal-fired units and heavily aged power plants in EU countries will certainly affect decisions in favour of upgrading or reconstruction. The overall increase of efficiency, the reduction of harmful emissions from generating processes and the co-combustion of coal with biomass and wastes for generating purposes indicate that coal can be cleaner and more efficient. Additionally, plenty of rehabilitation projects based on CCT applications, have already been carried out or are under progress in the EU energy sector. The proclamations of the countries' energy policies in the coming decades, includes integrated renovation concepts of the coal-fired power sector. Further to the natural gas penetration in the electricity generation and CO2 sequestration and underground storage, the implementation of CCT projects will strongly contribute to the reduction of CO2 emissions in the European Union, according to the targets set in the Kyoto protocol. In consequence, clean coal technologies can open up new markets not only in the EU member candidate states, but also in other parts of the world. Copyright © 2004 John Wiley & Sons, Ltd. [source]


CLIMATE CHHANGE SENSITIVITY ASSESSMENT ON UPPER MISSISSIPPI RIVER BASIN STREAMFLOWS USING SWAT,

JOURNAL OF THE AMERICAN WATER RESOURCES ASSOCIATION, Issue 4 2006
Manoj Jha
ABSTRACT: The Soil and Water Assessment Tool (SWAT) model was used to assess the effects of potential future climate change on the hydrology of the Upper Mississippi River Basin (UMRB). Calibration and validation of SWAT were performed using monthly stream flows for 1968,1987 and 1988,1997, respectively. The R2 and Nash-Sutcliffe simulation efficiency values computed for the monthly comparisons were 0.74 and 0.69 for the calibration period and 0.82 and 0.81 for the validation period. The effects of nine 30-year (1968 to 1997) sensitivity runs and six climate change scenarios were then analyzed, relative to a scenario baseline. A doubling of atmospheric CO2 to 660 ppmv (while holding other climate variables constant) resulted in a 36 percent increase in average annual streamflow while average annual flow changes of ,49, ,26, 28, and 58 percent were predicted for precipitation change scenarios of ,20, ,10, 10, and 20 percent, respectively. Mean annual streamflow changes of 51,10, 2, ,6, 38, and 27 percent were predicted by SWAT in response to climate change projections generated from the CISRO-RegCM2, CCC, CCSR, CISRO-Mk2, GFDL, and HadCMS general circulation model scenarios. High seasonal variability was also predicted within individual climate change scenarios and large variability was indicated between scenarios within specific months. Overall, the climate change scenarios reveal a large degree of uncertainty in current climate change forecasts for the region. The results also indicate that the simulated UMRB hydrology is very sensitive to current forecasted future climate changes. [source]


Quantitative FRET Analysis With the E0GFP-mCherry Fluorescent Protein Pair

PHOTOCHEMISTRY & PHOTOBIOLOGY, Issue 1 2009
Lorenzo Albertazzi
Fluorescence resonance energy transfer (FRET) between fluorescent proteins (FPs) is a powerful tool to investigate protein,protein interaction and even protein modifications in living cells. Here, we analyze the E0GFP-mCherry pair and show that it can yield a reproducible quantitative determination of the energy transfer efficiency both in vivo and in vitro. The photophysics of the two proteins is reported and shows good spectral overlap (Förster radius R0 = 51 Ĺ), low crosstalk between acceptor and donor channels, and independence of the emission spectra from pH and halide ion concentration. Acceptor photobleaching (APB) and one- and two-photon fluorescence lifetime imaging microscopy (FLIM) are used to quantitatively determine FRET efficiency values. A FRET standard is introduced based on a tandem construct comprising donor and acceptor together with a 20 amino acid long cleavable peptidic linker. Reference values are obtained via enzymatic cleavage of the linker and are used as benchmarks for APB and FLIM data. E0GFP-mCherry shows ideal properties for FLIM detection of FRET and yields high accuracy both in vitro and in vivo. Furthermore, the recently introduced phasor approach to FLIM is shown to yield straightforward and accurate two-photon FRET efficiency data even in suboptimal experimental conditions. The consistence of these results with the reference method (both in vitro and in vivo) reveals that this new pair can be used for very effective quantitative FRET imaging. [source]


Prediction variance and G-criterion location for split-plot designs

QUALITY AND RELIABILITY ENGINEERING INTERNATIONAL, Issue 4 2009
Wayne R. Wesley
Abstract Prediction variance properties for completely randomized designs (CRD) are fairly well covered in the response surface literature for both spherical and cuboidal designs. This paper evaluates the impact of changes in the variance ratio on the prediction properties of second-order split-plot designs (SPD). It is shown that the variance ratio not only influences the value of the G-criterion but also its location, in contrast with the G-criterion tendencies in CRD. An analytical method, rather than a heuristic optimization algorithm, is used to compute the prediction variance properties, which include the maximum, minimum and integrated variances for second-order SPD. The analytical equations are functions of the design parameters, radius and variance ratio. As a result, the exact values for these quantities are reported along with the location of the maximum prediction variance used in the G-criterion. The two design spaces of the whole plot and the subplot are studied and as a result, relative efficiency values for these distinct spaces are suggested. Copyright © 2008 John Wiley & Sons, Ltd. [source]


Is the efficiency of mammalian (mouse) skeletal muscle temperature dependent?

THE JOURNAL OF PHYSIOLOGY, Issue 19 2010
C. J. Barclay
Myosin crossbridges in muscle convert chemical energy into mechanical energy. Reported values for crossbridge efficiency in human muscles are high compared to values measured in vitro using muscles of other mammalian species. Most in vitro muscle experiments have been performed at temperatures lower than mammalian physiological temperature, raising the possibility that human efficiency values are higher than those of isolated preparations because efficiency is temperature dependent. The aim of this study was to determine the effect of temperature on the efficiency of isolated mammalian (mouse) muscle. Measurements were made of the power output and heat production of bundles of muscle fibres from the fast-twitch extensor digitorum longus (EDL) and slow-twitch soleus muscles during isovelocity shortening. Mechanical efficiency was defined as the ratio of power output to rate of enthalpy output, where rate of enthalpy output was the sum of the power output and rate of heat output. Experiments were performed at 20, 25 and 30°C. Maximum efficiency of EDL muscles was independent of temperature; the highest value was 0.31 ± 0.01 (n= 5) at 30°C. Maximum efficiency of soleus preparations was slightly but significantly higher at 25 and 30°C than at 20°C; the maximum mean value was 0.48 ± 0.02 (n= 7) at 25°C. It was concluded that maximum mechanical efficiency of isolated mouse muscle was little affected by temperature between 20 and 30°C and that it is unlikely that differences in temperature account for the relatively high efficiency of human muscle in vivo compared to isolated mammalian muscles. [source]


Application of mixtures of tartaric acid derivatives in resolution via supercritical fluid extraction

CHIRALITY, Issue 6 2007
Ildikó Kmecz
Abstract Racemic N -methylamphetamine (rac -MA) was resolved with 2R,3R -tartaric acid (TA) and its derivatives (O,O,-dibenzoyl-(2R,3R)-tartaric acid monohydrate (DBTA) and O,O,-di- p -toluoyl-(2R,3R)-tartaric acid (DPTTA)), individually and using them in different combinations. After partial diastereomeric salt formation, the free enantiomers were extracted by supercritical fluid extraction using carbon dioxide as solvent. DBTA and DPTTA are efficient resolving agents for rac -MA, the best chiral separation being obtained at a molar ratio of 0.25 resolving agent to racemic compound for both resolving agents (eeE = 82.5% and eeE = 57.9%, respectively). Compared with the two other acids, TA is practically unsuitable for enantiomer separation (eeE < 5%). Applying a mixture of one individually active and one ineffective acid in half the equivalent molar ratio, when the acids are in 1:1 ratio in the mixture, the resolution efficiency values obtained exceeded those obtained by using the components individually. Decreasing the molar ratio of resolving agent mixture to 0.25, at which the individual resolving agents give the best chiral separation, the obtained resolution efficiency values did not differ significantly from those expected. The outcome of the resolution process depended only on the amount of the individually active resolving agents in the mixture. Chirality, 2007. © 2007 Wiley-Liss, Inc. [source]