Compounds with higher molar masses and that are polar will have the highest boiling points. The first compound, 2-methylpropane, contains only C—H bonds, which are not very polar because C and H have similar electronegativities. It should therefore have a very small but nonzero dipole moment and a very low boiling point.
As a result, the C—O bond dipoles partially reinforce one another and generate a significant dipole moment that should give a moderately high boiling point. The C—O bond dipole therefore corresponds to the molecular dipole, which should result in both a rather large dipole moment and a high boiling point.
Thus far we have considered only interactions between polar molecules, but other factors must be considered to explain why many nonpolar molecules, such as bromine, benzene, and hexane, are liquids at room temperature, and others, such as iodine and naphthalene, are solids. What kind of attractive forces can exist between nonpolar molecules or atoms?
This question was answered by Fritz London — , a German physicist who later worked in the United States. In , London proposed that temporary fluctuations in the electron distributions within atoms and nonpolar molecules could result in the formation of short-lived instantaneous dipole moments , which produce attractive forces called London dispersion forces between otherwise nonpolar substances.
Consider a pair of adjacent He atoms, for example. On average, the two electrons in each He atom are uniformly distributed around the nucleus. Because the electrons are in constant motion, however, their distribution in one atom is likely to be asymmetrical at any given instant, resulting in an instantaneous dipole moment.
The net effect is that the first atom causes the temporary formation of a dipole, called an induced dipole , in the second.
Interactions between these temporary dipoles cause atoms to be attracted to one another. These attractive interactions are weak and fall off rapidly with increasing distance.
Doubling the distance therefore decreases the attractive energy by 2 6 , or fold. Instantaneous dipole—induced dipole interactions between nonpolar molecules can produce intermolecular attractions just as they produce interatomic attractions in monatomic substances like Xe. The reason for this trend is that the strength of London dispersion forces is related to the ease with which the electron distribution in a given atom can be perturbed.
In small atoms such as He, the two 1 s electrons are held close to the nucleus in a very small volume, and electron—electron repulsions are strong enough to prevent significant asymmetry in their distribution.
In larger atoms such as Xe, however, the outer electrons are much less strongly attracted to the nucleus because of filled intervening shells. As a result, it is relatively easy to temporarily deform the electron distribution to generate an instantaneous or induced dipole.
The ease of deformation of the electron distribution in an atom or molecule is called its polarizability. Because the electron distribution is more easily perturbed in large, heavy species than in small, light species, we say that heavier substances tend to be much more polarizable than lighter ones. The polarizability of a substance also determines how it interacts with ions and species that possess permanent dipoles. The strengths of London dispersion forces also depend significantly on molecular shape because shape determines how much of one molecule can interact with its neighboring molecules at any given time.
Neopentane is almost spherical, with a small surface area for intermolecular interactions, whereas n -pentane has an extended conformation that enables it to come into close contact with other n -pentane molecules. As a result, the boiling point of neopentane 9. All molecules, whether polar or nonpolar, are attracted to one another by London dispersion forces in addition to any other attractive forces that may be present. In general, however, dipole—dipole interactions in small polar molecules are significantly stronger than London dispersion forces, so the former predominate.
Arrange n -butane, propane, 2-methylpropane [isobutene, CH 3 2 CHCH 3 ], and n -pentane in order of increasing boiling points. Determine the intermolecular forces in the compounds and then arrange the compounds according to the strength of those forces. The substance with the weakest forces will have the lowest boiling point. The four compounds are alkanes and nonpolar, so London dispersion forces are the only important intermolecular forces.
These forces are generally stronger with increasing molecular mass, so propane should have the lowest boiling point and n -pentane should have the highest, with the two butane isomers falling in between. Of the two butane isomers, 2-methylpropane is more compact, and n -butane has the more extended shape. Consequently, we expect intermolecular interactions for n -butane to be stronger due to its larger surface area, resulting in a higher boiling point. Molecules with hydrogen atoms bonded to electronegative atoms such as O, N, and F and to a much lesser extent Cl and S tend to exhibit unusually strong intermolecular interactions.
Methane and its heavier congeners in group 14 form a series whose boiling points increase smoothly with increasing molar mass. This is the expected trend in nonpolar molecules, for which London dispersion forces are the exclusive intermolecular forces. Why do strong intermolecular forces produce such anomalously high boiling points and other unusual properties, such as high enthalpies of vaporization and high melting points? Issue 6, From the journal: Green Chemistry. You have access to this article.
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Submitted 07 Oct Accepted 05 Jan First published 05 Jan Download Citation. Water co-deposited with up to mbar methane or mbar isobutane at K onto a Pt substrate yielded pure crystalline ice, i.
Exposing metastable, less than 2 molecular layers thick, water films to mbar methane does not alter their morphology, suggesting that the presence of the Pt surface is not a strong driver for hydrate formation.
Similar desorption temperatures were observed for desorption from amorphous solid water. Volatile organic compound adsorption in a gas-solid fluidized bed. Fluidization finds many process applications in the areas of catalytic reactions, drying, coating, combustion, gasification and microbial culturing.
This work aims to compare the dynamic adsorption characteristics and adsorption rates in a bubbling fluidized bed and a fixed bed at the same gas flow-rate, gas residence time and bed height.
Adsorption with ppm methanol and ppm isobutane by the ZSM-5 zeolite of different particle size in the two beds enabled the differentiation of the adsorption characteristics and rates due to bed type, intraparticle mass transfer and adsorbate-adsorbent interaction. Adsorption of isobutane by the more commonly used activated carbon provided the comparison of adsorption between the two adsorbent types.
With the same gas residence time of 0. Intraparticle mass transfer and adsorbent-adsorbate interaction played significant roles in affecting the rate of adsorption, with intraparticle mass transfer being more dominant. The bubbling bed was observed to have a steeper decline in adsorption rate with respect to increasing outlet concentration compared to the fixed bed.
The adsorption capacities of zeolite for the adsorbates studied were comparatively similar in both beds; fluidizing, and using smaller particles in the bubbling bed did not increase the adsorption capacity of the ZSM-5 zeolite. The adsorption capacity of activated carbon for isobutane was much higher than the ZSM-5 zeolite for isobutane , although at a lower adsorption rate.
Fourier transform infra-red FTIR spectroscopy was used as an analytical tool for the quantification of gas concentration. Calibration was done using a series of standards prepared by in situ dilution with nitrogen gas, based on the ideal gas law and relating partial pressure to gas.
Isotopic study on mechanism for skeletal isomerization of n-butane over solid acids. Reaction mechanism for skeletal isomerization of n-butane over typical strong solid acids were investigated by using 1,4- 13 C 2 -n-butane. On the other hand, at K over Cs2. This result demonstrates that an intramolecular monomolecular rearrangement became significant at K over Cs2. The contribution of monomolecular pathway was higher on Cs2.
We presumed that the contribution of mechanism is related to the acidic property and the dehydrogenation ability of the catalyst. In this study we have employed periodic DFT calculations combined with microkinetic simulations to investigate the complex reaction mechanism of isobutane—propene alkylation catalyzed by zeolitic solid acids.
Our calculations reveal that hydride transfer from isobutane to a carbenium ion occurs via a concerted C—C bond formation between a tert-butyl fragment and an additional olefin, or via deprotonation of the tert-butyl fragment to generate isobutene. Theoretical analysis of a combined power and ejector refrigeration cycle using zeotropic mixture.
The performances of different mixture compositions are compared. An exergy analysis is conducted for the cycle. The parametric analysis of generator temperature, condenser temperature and evaporator temperature for all the mixtures shows that, all these three thermodynamic parameters have a strong effect on the cycle performance. Single photon detection in the SQS mode. Results are presented concerning the detection of single UV photons in self quenching streamer detectors by photoionization of one of the gas mixture components, in this case TEA tri ethyl-amine , whose molecules have low photoionization potential and large absorption cross section.
As a UV light source, a gas scintillation counter filled with krypton was used, whose emission light spectrum, centered at approximately nm, overlaps well the photoionization spectrum of TEA.
Catalytic conversion of light alkanes. Final report, January 1, October 31, During the course of the first three years of the Cooperative Agreement Phase I-III , we uncovered a family of metal perhaloporphyrin complexes which had unprecedented activity for the selective air-oxidation of fight alkanes to alcohols. Isobutane was so reactive that the proof-of concept stage of a process for producing tert-butyl alcohol from isobutane was begun Phase V.
As of this writing, however, the program has been terminated during the later stages of Phases V and VI so that further work is not anticipated. We made excellent progress during in generating a class of less costly new materials which have the potential for high catalytic activity. New routes were developed for replacing costly perfluorophenyl groups in the meso-position of metalloporphyrin catalysts with far less expensive and lower molecular weight perfluoromethyl groups.
Modeling and analysis of advanced binary cycles. A computer model Cycle Analysis Simulation Tool, CAST and a methodology have been developed to perform value analysis for small, low- to moderate-temperature binary geothermal power plants. The value analysis method allows for incremental changes in the levelized electricity cost LEC to be determined between a baseline plant and a modified plant. Thermodynamic cycle analyses and component sizing are carried out in the model followed by economic analysis which provides LEC results.
The emphasis of the present work is on evaluating the effect of mixed working fluids instead of pure fluids on the LEC of a geothermal binary plant that uses a simple Organic Rankine Cycle. A variety of isobutane and propane based mixtures, in addition to pure fluids, were used as working fluids. Supercritical cycles were found to have the lowest cost at all resources. The focus of this study is to analyse if an efficiency increase by using zeotropic mixtures as working fluid overcompensates additional requirements regarding the major power plant components.
The optimization approach is compared to systems with pure media. Based on process simulations, heat exchange equipment is designed and cost estimations are performed. The uncertainties regarding fluid properties of zeotropic mixtures, mainly affect the heat exchange surface. However, the influence on the determined economic parameter is marginal.
In general, zeotropic mixtures are a promising approach to improve the economics of geothermal ORC systems. Additionally, the use of mixtures increases the spectrum of potential working fluids, which is important in context of present and future legal requirements considering fluorinated refrigerants. Estimation of lower flammability limits of C-H compounds in air at atmospheric pressure, evaluation of temperature dependence and diluent effect.
A set of C-H compounds was divided into a correlation set and a prediction set of 60 compounds each. The absolute average relative error for the total set was 7. However, it was shown that by considering different sources of experimental data the values were reduced to 6.
The method showed consistency with Le Chatelier's law for binary mixtures of C-H compounds. When nitrogen was added, the absolute average relative errors were 2. When carbon dioxide was added, the absolute relative errors were 1.
The SLD drift chamber requires a 'slow' drifting gas and low diffusion to allow wave form digitization. CO 2 provides this but requires an admixture of a quencher to provide more gain. Results and discussions are presented. Forensic medical evaluation of deaths resulting from inhalation of cigarette lighter refill fuel in Turkey.
Lighter gas abuse-related death is still an important health problem in Turkey. In this study, 25, case files and final reports submitted to the Institute of Forensic Medicine of the First Specialization Board between January and December were evaluated retrospectively. In 56 of these cases, lighter gas inhalation n-butane, propane, isobutane was recorded as the cause of death.
All subjects were male with a mean age of According to eyewitness and crime scene investigation reports, in 48 It was determined that The importance of lighter gas inhalation-related deaths in Turkey has been increasing. Strict measures against the abuse of these very dangerous substances should be undertaken by the mutual efforts of medical specialists and legislators.
High temperature heat pumps for industrial cooling; Hoejtemperatur varmepumper til industriel koeling. This report deals with theoretical analysis of various types of integration of heat pumps in the industry, as well as a demonstration plant that serves the project's practical execution.
The report describes the system integration between heat pumps and existing industrial cooling systems. It can be seen through the project that the combination of heat pump with existing cooling installations may produce favorable situations where the efficiency of the heat pump is extremely high while at the same time electricity and water consumption for the cooling system is reduced. In the demonstration project, the report shows that the heat pump alone has a COP of 4.
In this study we have employed periodic DFT calculations combined with microkinetic simulations to investigate the complex reaction mechanism of. Selective hydrogen atom abstraction by hydrogen atoms in photolysis and radiolysis of alkane mixtures at K. Selective hydrogen atom abstraction reaction by H atoms, has been found in Isobutane , 2,2,3,3-tetramethylbutane TMB , cyclopropane matrices besides neopentane matrix.
The selective hydrogen atom abstraction reaction in neopentane- isobutane mixture is affected by the difference of kinetic energies of H atoms. The reaction occurs more favorably with decreasing the kinetic energy of H atoms.
The rate constants of these reactions in neopentane matrix are quite different from these of thermal H atom reaction, but similar to those of hot H atom reaction. Importance of the selective hydrogen atom abstraction reaction by H atoms is pointed out in the radical formation in the radiolysis of pure TMB at 77 K [pt.
X-ray scattering on liquid-gas interfaces; Roentgenstreuung an Fluessigkeits-Gas Grenzflaechen. In the framework of this thesis two different theme-fields were studied with dhe methods of the elastic, surface sensitive X-ray scattering.
In the first part of the thesis the liquid-gas interfaces water-propane and glycerol- isobutane were studied concerning the structure formation on these interfaces.
The system water-propane served for the study of the gas hydrate formation on the water-gas interface. Studies on this interface could give no hints on the formation of propane hydrates or propane-hydrate fragments. However the adsorption of molecularly thin propane films on the water surface was observed. The adsorption behaviour of gases on liquid surfaces was studied by further experiments on the glycerol- isobutane interface.
In the second part of the thesis the surfaces of aqueous salt solutions and water were studied. The lateralstructure of these liquid-gas interfaces was studied by the method of the diffuse X-ray scattering. Electron thermalization distances and free-ion yields in dielectric fluids: Effect of electron scavengers. Free-ion yields were measured in isobutane and in solutions containing sulfur hexafluoride, at densities from the liquid at K to the supercritical fluid.
The SF 6 captured the electrons while they were still at epithermal energies, and terminated their flight away from their sibling ions. Plastic tube hadron calorimeter: study of operation properties and particle separation. The DELPHI hadron calorimeter prototype plastic tubes were tested to show a long-term stability of the prototype operating with the gas mixture carbon dioxide isobutane.
The operating properties of the prototype are investigated and presented as well as the results on particles separation. The alkylation of isobutane with 2-butene is carried out using a zeolitic catalyst in a well stirred slurry reactor. Whereas application of fixed bed technology using a solid acid alkylation catalyst has in the led to catalysts lifetimes in the range of minutes, in this work we report catalyst.
Phage inactivation by triplet acetone. The exposure of lambda phage to triplet acetone is studied. The triplet acetone is obtained from aerobic oxidation of isobutanal catalysed by peroxidase. A decrease of lambda phage ability to infect Escherichia coli is reported, perhaps, partially due to the possible production of lesions in the phage genome.
Ruan, L. Calderon de la Barca; Reed, R. Each detector has 12 strips, read-out at both ends, which are each 3. There was good uniformity in the performance across the different strips. Trigger scans along and across the strip direction were also performed. Experimental investigation of hydrocarbon mixtures to replace HFCa in an automotive air conditioning system. This paper presents an experimental study on the application of hydrocarbon mixtures to replace HFCa in automotive air conditioners.
The hydrocarbons investigated are propane R , butane R and isobutane Ra. The measured data are obtained from an automotive air conditioning test facility utilizing HFCa as the refrigerant.
The air conditioner, with a capacity of 3. The experiments are conducted at the same surrounding conditions. The temperature and pressure of the refrigerant at every major position in the refrigerant loop, the temperature, flow rate and humidity of air, torque and engine speed are recorded and analyzed.
The parameters investigated are the refrigeration capacity, the compressor power and the coefficient of performance COP. Condensation heat transfer coefficients of flammable refrigerants on various enhanced tubes. C on a fpm low fin and turbo-C tubes. Flammable refrigerants' data obtained on enhanced tubes showed a typical trend that external condensation HTCs decrease with increasing wall subcooling.
Beatty and Katz' correlation predicted the HTCs of the flammable refrigerants obtained on a low fin tube within a mean deviation of 7. Turbo-C tube showed the best performance due to its 3 dimensional surface geometry for fast removal of condensate. The main products were iso-butane , propane, and pentane. Raft River binary-cycle geothermal pilot power plant final report. The design and performance of a 5-MW e binary-cycle pilot power plant that used a moderate-temperature hydrothermal resource, with isobutane as a working fluid, are examined.
Operating problems experienced and solutions found are discussed and recommendations are made for improvements to future power plant designs.
The plant and individual systems are analyzed for design specification versus actual performance figures. Determination of the Townsend primary ionization coefficient using a parallel plate avalanche counter. The results for methane agreed well with the values obtained by Heylen. Ambient HO measurements by low-pressure laser-excited fluorescence with chemical modulation, and supporting ozone and water-vapor data, are presented for periods in May and August The observed peak daytime ambient HO concentrations are in the range 2.
Direct measurements of the interference at fixed O3 give the dependence on ambient H2O and on the modulating reagent isobutane. Production of HO by the reaction of isobutane with O 1D accounts for the negative interference. Quenching of HO fluorescence by the modulating reagent contributes a smaller positive term to the interference; kinetic measurements of the quenching rate coefficient are reported.
The experimental interference results are compared with a detailed kinetic model of HO production, excitation, relaxation, and detection; reasonable agreement is found. Positive ion scavenging by olefins in trans-decalin: TRMC and product analysis studies. The rate constants for scavenging of the mobile positive ion in trans-decalin have been measured using the time-resolved microwave conductivity TRMC pulse radiolysis technique for a series of olefins and cyclopropane.
The results are explained in terms of the formation of a complex between the solvent radical cation and isobutene which can dissociate, within a timescale of approx.
Cyclopropane is unreactive, i. Bennet, J. A study of gas mixtures for use in the streamer tube is discussed. Method of detection of transition radiation by wire chambers operating in self-quenching streamer mode. A method for detecting X-ray transition radiation against the background of the signal from relativistic charged particles is suggested that is based on the use of peculiarities of the development of self-queenching streamer mode.
The effect of separation of signals from the relativistic particle and from soft X-ray, is obtained. Liu, Chong; van Santen, Rutger A. Particular emphasis was given to addressing the selectivity of the alkylate formation versus alkene formation, which requires a high rate o The leak microstructure.
It is possible to observe primary avalanches with a size of more than 2. Single electrons emitted by a heated This work aims to investigate the energy performances of small-scale Organic Rankine Cycles ORCs for the exploitation of high temperature geothermal sources in volcanic areas. For this purpose, a thermodynamic model has been developed, and a parametric analysis has been performed that considers subcritical and transcritical configurations, and different organic fluids isobutane , isopentane, and Rca.
The investigation illustrates the significant effect of the temperature at the entrance Control of electrothermal heating during regeneration of activated carbon fiber cloth. Electrothermal swing adsorption ESA of organic gases generated by industrial processes can reduce atmospheric emissions and allow for reuse of recovered product. Desorption energy efficiency can be improved through control of adsorbent heating, allowing for cost-effective separation and concentration of these gases for reuse.
ESA experiments with an air stream containing ppm v isobutane and activated carbon fiber cloth ACFC were performed to evaluate regeneration energy consumption.
ACFC was also heated to a ramped set-point, and the average absolute error between the actual and set-point temperatures was small 0. Implementing such control logic improves energy efficiency for separating and concentrating organic gases for post-desorption liquefaction of the organic gas for reuse.
Performance estimation of ejector cycles using heavier hydrocarbon refrigerants. Computer software basing on theoretical model of Huang et al. Investigation was focused on nine hydrocarbons: propane, butane, iso-butane , pentane, iso-pentane, hexane, heptane and octane.
Calculation results show that none of the hydrocarbons enables high efficiency of a cycle in a wide range of temperature. Each hydrocarbon has its own maximal entrainment ratio at its individual temperature of optimum. Temperatures of entrainment ratios optimum increase according to the hydrocarbon heaviness with simultaneous increase of entrainment ratio peak values. Peak values of the COP do not increase according to the hydrocarbons heaviness.
Heptane and octane can be ignored. The data available for the thermodynamic properties of propane, -butane, and isobutane at temperatures above K are outdated and show significant discrepancies with each other. The ambiguity associated with these data could be limiting to the development of any understanding related to the effects of mixing of these substances with other materials such as , ammonia, and non-flammable or lower-flammable HFC refrigerants.
In this study, the p, , T properties of propane, -butane, and isobutane were measured at temperatures ranging from to K and pressures ranging from 50 to MPa. Precise measurements were carried out using a metal-bellows variable volumometer with a thermostatted air bath. The expanded uncertainties in the temperature, pressure, and density measurements were estimated to be 5 mK, 0. The data obtained throughout this study were systematically compared with the calculated values derived from the available equations of state.
These models agree well with the measured data at higher temperatures up to K, demonstrating their suitability for an effective and precise examination of the mixing effects of potential alternative mixtures. Regeneration of zeolite catalysts of isobutane alkylation with butenes.
The industrial adoption of alkylation of isoalkanes with alkenes is held back by the rapid and irreversible deactivation of the zeolite catalysts appropriate to the process. This paper is aimed specifically at the restoration of the catalytic activity and increase in the service life of zeolite alkylation catalysts. The catalyst chosen for the investigation was HLaCaNaX zeolite both unmodified and modified with various multivalence cations.
The thermochemical and oxidative regeneration process as well as the equipment utilized are described.
Both the advantages and the drawbacks of the method are given; explanations for the possibly irreversible losses of the catalytic properties in the regenerated zeolites are also put forward. Simultaneous environmental and economic process synthesis of Isobutane Alkylation. This multidisciplinary study concerns the optimal design of processes with a view to both maximizing profit and minimizing environmental impacts. This can be achieved by a combination of traditional chemical process design methods, measurements of environmental impacts and advanced mathematical optimization techniques.
More to the point, this paper presents a hybrid simulation-multiobjective optimization approach that at once optimizes the production cost and minimizes the associated environm Inter- and intra-annular proton exchange in gaseous benzylbenzenium ions protonated diphenylmethane. Two distinct proton exchange reactions occur in metastable gaseous benzylbenzenium ions, generated by isobutane chemical ionization of diphenylmethane and four deuterium-labelled analogues.
Whereas the proton ring-walk at the benzenium moiety is fast giving rise to a completely random intraannular proton exchange, the interannular proton exchange is surprisingly slow and competes with the elimination of benzene.
Damages induced in lambda phage DNA by enzyme-generated triplet acetone. Exposure of lambda phage to triplet acetone, generated during the aerobic oxidation of isobutanal by peroxidase, leads to genome lesions. The majority of these lesions are detected as DNA single-strand breaks only in alkaline conditions, so true breaks were not observed. The participation of triplet acetone in the generation of such DNA damage is discussed. Author [pt. Feasibility assessment of refinery waste heat-to-power conversion using an organic Rankine cycle.
This study investigates the technical and economic feasibility of converting waste heat from a stream of liquid kerosene which must be cooled down to control the vacuum distillation temperature. The process conditions were determined for a simple kW organic Rankine cycle ORC with a heat extraction loop. The pinch point technique was adopted to determine the optimum evaporation and condensation temperatures and assess the influence of the kerosene temperature at the evaporator exit on net power output.
A financial model was established for the total plant cost. Results show that isobutane , of the pure fluids, yields the best plant efficiency of 6.
Therefore, if the detailed. Metal dissolution kinetics in organic solvents using rotating ring-disc voltammetry. Final report. The effect of a two-phased liquid system - composed of geothermal brine and an organic heat transfer fluid - on the stability of materials used in the energy conversion system was investigated. The principle organic liquids used were isobutane and isopentane. The effects of relative fluid velocity on the corrosion behavior of representative construction materials, austenitic stainless steels, nickel, and copper alloy were determined using an autoclave incorporating a rotating ring-disc electrode.
We unveil a unique kinetic driven separation material for selectively removing linear paraffins from iso-paraffins via a molecular sieving mechanism.
Subsequent carbonization and thermal treatment of CD-MOF-2, the cyclodextrin metal-organic framework, afforded a carbon molecular sieve with a uniform and reduced pore size of ca. A position sensitive parallel plate avalanche counter. A position sensitive parallel plate avalanche counter with a distributed constant delay-line-cathode PSAC is described. The strips formed on the printed board were served as the cathode and the delay line for readout of signals.
The detector PSAC was operated in isobutane gas at the pressure range from 10 to 20 torr. The position resolution is better than 1 mm and the time resolution is about ps, for Cf fission-spectrum source.
Catalytic cracking of slack wax with molten mixtures containing aluminum chloride and bromide. The cracking rate was proportional to the amount of unreacted wax. The difference in cracking activity between this catalyst and a solid acid catalyst is discussed based on the product distribution.
Hardly any reaction took place without HCl, which shows that the presence of HCl is essential for this cracking. The cracking rate increased sharply with an increase in the amount of the catalyst.
The results show that the cracking reaction probably occurs heterogeneously at the interface between the liquid wax and the molten catalyst. Passivation of gas microstrip detectors and stability of long-term operation. Salomon, M. We have studied the long-term operation of gas microstrip detectors which have been passivated with a layer of nickel oxide. In all three cases we found that the detectors are stable after passivation and can operate for a month without changes in gain at rates of MHz.
The total accumulated charge was approximately mC. Impact of molecular structure on the lubricant squeeze-out between curved surfaces with long range elasticity. The branched isobutane forms more disordered structures which permit it to stay liquidlike at smaller surface separations.
During squeezing the solvation forces show oscillations corresponding to the width At low speeds interfacial squeezing velocity in most practical applications is very low when the lubricant layer has molecular thickness, one expects n-butane to be a better boundary lubricant than Nowadays, the substitution of HFCa with low GWP refrigerants is one of the most important challenge for refrigeration and air conditioning.
Crystalline mesoporous zirconia catalysts having stable tetragonal pore wall structure. Sulfate deposition is preferred for the transformation of a mesoporous precursor with amorphous pore walls into a material with crystalline pore walls maintaining the mesoporous characteristics.
III Krenek P. IV Kimura T. Study of ionization losses in He-based gas mixtures. Helium based gas mixtures are particularly interesting since they have a good tracking resolution because of the reduced multiple scattering.
The results show that helium performs well in measuring energy losses for charged particles. The North American natural gas liquids markets are chaotic. In this paper the authors test for deterministic chaos i. They conclude that there is evidence consistent with a chaotic nonlinear generation process in all five natural gas liquids markets. The leak microstructure, preliminary results.
The leak microstructure, a new type of element for position-sensitive proportional gas counter, is introduced. For every single detected ionizing radiation it gives a pair of ''induced'' charges of the same quantity pulses of the same amplitude , of opposite sign, with the same collection time and essentially in time coincidence, that are proportional to the collected primary ionization.
A gas multiplication up to 1. The complete absence of insulating materials in the active volume of this microstructure enables to avoid problems of charging-up and makes its behaviour stable and repeatable.
By using the charge-pair generated, it allows the development of a position-sensitive detecting board with a two-dimensional read-out.
Between the two external surfaces of this board it is possible to insert an intermediate third conducting layer which reduces or practically suppresses the capacitive cross-talk between the X and Y read-out strip systems.
Furthermore, this intermediate layer can give a very fast trigger to coordinate the charge-pair and to govern the data acquisition system. By reading every strip separately it is possible to resolve the multi hit problem in two-dimensions. Performance analysis of a combined organic Rankine cycle and vapor compression cycle for power and refrigeration cogeneration.
A thermodynamic analysis of cogeneration of power and refrigeration activated by low-grade sensible energy is presented in this work. An organic Rankine cycle ORC for power production and a vapor compression cycle VCC for refrigeration using the same working fluid are linked in the analysis, including the limiting case of cold production without net electricity production. We investigate the effects of key parameters on system performance such as net power production, refrigeration, and thermal and exergy efficiencies.
Characteristic indexes proportional to the cost of heat exchangers or of turbines, such as total number of transfer units NTU tot , size parameter SP and isentropic volumetric flow ratio VFR are also examined. Three important system parameters are selected, namely turbine inlet temperature, turbine inlet pressure, and the flow division ratio.
The analysis is conducted for several different working fluids. For a few special cases, isobutane is used for a sensitivity analysis due to its relatively high efficiencies. Our results show that the system has the potential to effectively use low grade thermal sources. System performance depends both on the adopted parameters and working fluid. Isobutane is used for a sensitivity analysis. Full Text Available The thermodynamic performance of a regenerative organic Rankine cycle that utilizes low temperature heat sources to facilitate the selection of proper organic working fluids is simulated.
Thermodynamic models are used to investigate thermodynamic parameters such as output power, and energy efficiency of the ORC Organic Rankine Cycle. In addition, the cost rate of electricity is examined with exergo-economic analysis. Nine working fluids are considered as part of the investigation to assess which yields the highest output power and exergy efficiency, within system constraints. Exergy efficiency and cost rate of electricity are used as objective functions for system optimization, and each fluid is assessed in terms of the optimal operating condition.
The degree of superheat and the pressure ratio are independent variables in the optimization. Ra and iso-butane are found to exhibit the highest energy and exergy efficiencies, while they have output powers in between the systems using other working fluids. The largest exergy destructions occur in the boiler and the expander. The electricity cost rates for the system vary from 0.
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