The mechanism of the appearance of luminescence and electrification in liquid flows through narrow channels

The mechanism of the effects observed in hydrodynamic unit throttles was studied. These effects included luminescence in the visible range localized in a microscopic toroidal volume and electric pulses when a dielectric liquid flew through a narrow passage orifice. Equations for charging and conduction currents were obtained. The stationary electric charge, potential, and field strength on the internal surface of a passage orifice were calculated. It was shown theoretically that the appearance of luminescence most probably occurred in electrical breakdowns in cavitation bubbles in the initial flow section inside the passage orifice. Electric charge formed not only during hydrodynamic cavitation but also in a laminar throttle in the absence of cavitation in the liquid; the electrokinetic mechanism applied to this phenomenon too. It was shown experimentally that electric charges appeared not only in plastic but also in metallic throttles. The suggested mechanism of light emission and electric charge appearance was in agreement with the experimental results.     

Optimization and improvement of PM2.5 thermophoretic deposition efficiency in turbulent gas flowing over tube surfaces

PM2.5 thermophoretic deposition efficiency in turbulent gas flowing over tube surfaces is analyzed using the new concept of potential capacity and potential capacity variation. According to Romay's model, a thermophoretic deposition efficiency model in turbulent gas flowing over tube surfaces is built up based on the potential capacity. Through computing and analyzing thermophoretic deposition efficiency, PM2.5 thermophoretic deposition efficiency in turbulent gas flowing over tube surfaces in direct ratio to the potential capacity variation and in inverse ratio to the temperature ratio of tube wall to entrance gas-particle mixture. And the imprecise notion of thermophoretic deposition efficiency direct ratio to the temperature difference between tube wall and entrance gas-particle mixture is reviewed. There are credible foundations to be provided for improving and researching thermophoretic deposition efficiency in theory and experiment.     

Nonequilibrium bubbles in a flowing langmuir monolayer

We investigate the nonequilibrium behavior of two-dimensional gas bubbles in Langmuir monolayers. A cavitation bubble is induced in liquid expanded phase by locally heating a Langmuir monolayer with an IR-laser. At low IR-laser power the cavitation bubble is immersed in quiescent liquid expanded monolayer. At higher IR-laser power thermo capillary flow around the laser-induced cavitation bubble sets in. The thermo capillary flow is caused by a temperature dependence of the gas/liquid line tension. The slope of the line tension with temperature is determined by measuring the thermo capillary flow velocity. Thermodynamically stable satellite bubbles are generated by increasing the surface area of the monolayer. Those satellite bubbles collide with the cavitation bubble. Upon collision the satellite bubbles either coalesce with the cavitation bubble or slide past the cavitation bubble. Moreover we show that the satellite bubbles can also be produced by the emission from the laser-induced cavitation bubbles.     

Shock tube study of OH reactions with linear hydrocarbons near 1100 K

Reactions of the hydroxyl radical with several linear hydrocarbon species occurring in combustion chemistry have been considered at temperatures near 1100 K and 1 atmosphere in shock tube experiments. The OH density was monitored using 310 nm UV absorption of the A²Σ⁺ (SINGLEBOND) X ²Π transition. Rate coefficients for the reaction of OH with ethane (8.37 × 10⁻¹² cm³ molecule⁻¹ s^{− 1}; 970 K), hexane (2.18 × 10⁻¹¹; 962 K), heptane (3.34 × 10⁻¹¹, 1186 K), octane (4.42 × 10⁻¹¹; 1078 K), nonane (4.55 × 10⁻¹¹; 1097 K), and decane (5.64 × 10⁻¹¹; 1109 K) have been determined. These values are compared with previous experimental results and transition state theory calculations. © 1996 John Wiley & Sons, Inc.     

Orientation of a dispersion of kaolinite flowing in a jet

Orientational alignment in a dilute dispersion of kaolinite particles has been investigated in a flow pattern that combines both shear and elongational stress, namely flow at a jet created by a 2 mm diameter nozzle inserted in a 6 mm diameter pipe. Spatially-resolved X-ray diffraction with synchrotron radiation permits detailed maps of the alignment to be deduced and compared with fluid mechanics calculations of the flow. The angular distribution of diffracted intensity from a given position in the pipe provides information about the orientation distribution of the particles. This is quantified and presented in terms of order parameters. The cone-shaped nozzle provides a jet of liquid giving a high degree of alignment of the particles that is uniform along lines across the conical section and constant in the small straight-sided region at the exit of the nozzle. The vortex motion that arises from the flow with a modest Reynolds number could be determined as well as the tendency for some particles to align with their large faces perpendicular to the overall flow direction at the flat surface of the nozzle outlet.     

Luminescence and electrification in a flow of dielectric liquids through narrow channels

Blue-violet luminescence was observed in a mineral oil, which appeared under hydrodynamic cavitation conditions in a channel orifice 1 mm in diameter in a transparent throttling device at inlet pressures higher than 2 MPa. The appearance of electric pulses when a dielectric liquid flew through a thin channel orifice was observed much earlier than luminescence arose. A device for continuously scanning electric potential along a flow without disturbing it was developed. According to the oscillograms obtained, the electric signal was high-frequency, could not be synchronized, and its separate peaks reached 1000 mV. Light emission flux decreased as the temperature of the liquid increased to 30–35°C and inlet pressure grew. The appearance of luminescence and its intensity depended on the sharpness of the entrance edge of the throttle. Studies of hydrodynamic luminescence revealed hysteresis of light emission. A mechanism of localized light emission based on an important role played by electrokinetic phenomena was suggested.     

Convective performance and particle effect analysis on aqua-antifreeze based oxomagnesium nanofluids while flowing through a micro-fin tube with twisted tapes

Journal of Thermal Analysis and Calorimetry - The heat transfer and entropy generation analysis upon the single-phase flow of antifreeze and water (50:50) mixture with solution combustion-derived...     

The anodic behaviour of zinc in flowing electrolyte systems

The current-time behaviour has been calculated for successive two dimensional nucleation under potentiostatic conditions. Using numerical integration the contributions due to the first 50 layers have been found and the steady state behaviour has been estimated.     

Description of a flowing cascade arc plasma

The plasma in a cascaded arc in argon with flow is studied both experimentally and theoretically. The plasma pressure has been measured as a function of axial position in the are channel with a Baratron pressure transducer. The electron density and the electron temperature have been determined as a function of axial position using H_β-Stark broadening and line-continuum emissivity ratio, respectively. Comparison of the gas pressure measurements with an equilibrium model suggests that the /low is laminar. A one-dimensional nonequilibrium model based on the electron- and heavy-particle number balances and the heavy-particle energy balance is presented. The measured axial profiles of the electron density agree well with the model predictions, especially in the most upstream part of the arc channel. The plasma is strongly ionizing. Temperature equilibration takes about 20 mm of arc length, depending on the argon flow.     

Strain-induced reversal of charge transfer in contact electrification

We have contact! Material strain can have a dominating effect on contact electrification. When a deflated (relaxed) balloon is rubbed against teflon, the teflon surface charges positively, but when the same balloon is inflated (strained), the teflon surface charges negatively. This result illustrates that material strain can control contact electrification and alter the driving force of some (yet unknown) charge-transfer species.     

The electronic spectra of unsaturated hydrocarbons a VESCF-CI treatment

A modified Pariser-Parr method, which allows for the inductive effect of alkyl groups by a VESCF method, has been applied to the calculation of the electronic spectra of a number of hydrocarbons. All singly- and doubly-excited configurations are included in the configuration interaction treatment, except for large molecules for which the configuration interaction matrices are truncated to an order of 110. The red shifts which result from methylation of the polyenes are well calculated. For azulene, the shift to either the red or the blue, depending on the location of the substituent, is also well calculated. The largest deviation between the calculated and experimental transition energies for all of the compounds studied was 1.1 eV, while the standard deviation of all observed transitions for planar compounds was 0.24 eV. The ionization potentials and the singlet-triplet transitions of these compounds were also studied.

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Zusammenfassung Die Spektren einer Reihe von Kohlenwasserstoffen wurden nach einer modifizierten Pariser-Parr-Methode, bei der der induktive Effekt von Alkylgruppen mittels eines VESCF-Verfahrens berücksichtigt wird, berechnet, wobei alle ein- und zweifach angeregten Konfigurationen eingeschlossen wurden außer bei sehr großen Molekülen, wo deren Zahl auf 110 begrenzt wurde. Dabei ergeben sich in schöner Weise die Rotverschiebungen, die bei Methylierung von Polyenen beobachtet werden, desgleichen die Rot- und Violettverschiebungen je nach Ort des Substituenten bei Azulen. Die größten Abweichungen zwischen berechneten und beobachteten Übergangsenergien ist 1,1 eV, die Standardabweichung bei planaren Verbindungen 0,24 eV. Ferner wurden Ionisationspotentiale sowie Sigulett-Triplett-Übergänge der behandelten Verbindungen untersucht.

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Résumé Une méthode Pariser-Parr modifieé, qui tient compte de l'effet inductif des groupes alkyles dans le cadre VESCF, a été employeé pour calculer les spectres électroniques de quelques hydrocarbures. Toutes les configurations mono- et di-excitées sont comprises dans le traitement d'interaction de configurations, excepté pour les grosses molécules; pour ces dernières, l'ordre des matrices d'interaction de configuration a été réduit à 110. Les déplacements versle rouge, après methylation de polyènes, sont bien calculés. Pour l'azulène, les déplacements vers le rouge ou le bleu, suivant le lieu de substitution, sont également bien calculés. La plus grande déviation entre les énergies de transition calculée et expérimentale était de 1.1 eV pour tous les produits étudiés, alors que la déviation standard de toutes les transitions observeés était de 0,24 eV dans les composés planaires. Le potential d'ionisation et les transitions singulet-triplet ont aussi été étudiés.

     

Diffusion of a trace gas into a flowing carrier

Numerical Methods were used to solve the differential equation for diffusion of a trace gas into a flowing carrier gas having a parabolic velocity profile in a cylindrical tube. Steady state solutions are given in the form of contour diagrams of constant trace gas concentration.     

The flowing mercury electrode in polarography. part I

A polarisable electrode of constant surface area is described in which the surface layer of a column of mercury is continuously renewed from an internal mercury supply. Reproducible diffusion currents are obtainable which do not exhibit maxima. Wave heights are proportional to the concentration of reducible ion. The mercury consumption is similar to that of the dropping mercury electrode. The electrode and cell are constructed throughout in polyethylene.     

The continuous removal of oxygen from flowing solutions

An apparatus for continuous removal of oxygen or other dissolved gases from liquid samples is described; it is useful in continuous analyses. The gas diffuses through a semipermeable membrane into a space with a lower partial pressure of the particular gas. The separation unit consists of two concentric tubes and is practical and efficient. The mathematical model for transport under conditions of stationary gas diffusion with laminar flow of the liquid in the tube did not correspond satisfactorily to the experimental relationship, probably because of turbulence in the flow.     

Numerical investigation of entropy production in SWCNT/H2O nanofluid flowing through inwardly corrugated tube in turbulent flow regime

Journal of Thermal Analysis and Calorimetry - This work numerically investigates the entropy production rate in single-walled carbon nanotubes (SWCNTs)/H2O nanofluid flowing through an inwardly...     

Sliding-friction electrification of polymers and charge decay

Linear low-density polyethylene (LLDPE) and polypropylene (PP) were charged by sliding under a cylindrical aluminium contact. The surface charge accumulation on the polymer films was time dependent, and a function of the sliding velocity, metal contact force, and film type. The surface potential increased linearly with velocity in the range 0.33–0.75 m/s, and showed a square-root dependence on the contact force up to 6.5 N. Thermally stimulated charge decay (TSCD) studies showed longer charge lifetimes in samples friction-charged on one side than in corona-charged samples. Friction charging creates deeper near-surface traps than are normally present in the polymers. Charge stability is further imporved by simultaneously friction charging both surfaces of the films, increasing the half-value charge decay temperature (T_1/2) by 27°C and 37°C over that in corona-charged samples (i.e., to 98°C and 120°C for LLDPE and PP, respectively). These monopolarity electrets should prove useful in charge storage devices.     

The amidoalkylation of aromatic hydrocarbons

The Nyberg procedure (the use of trifluoroacetic acid in chloroform) for the efficient amidoalkylation of aromatic hydrocarbons is limited to substrates more nucleophilic than benzene. The reaction involves protonation of the electrophile, cleavage to a carbonium ion and alkylation of the nucleophile by the carbonium ion. Either the cleavage step or the alkylation step may be rate-determining. The present work identifies some cases where a carbonium ion is formed but fails to alkylate the nucleophile (with benzene and nitro-substituted benzenes as nucleophiles) and other cases where the reaction conditions are not sufficient to permit cleavage of the protonated electrophile (the reactions of N-phthalimidomethylamides).