For applications like the calibration of measuring instruments or the verification of measuring techniques, the production of sprays with predetermined, discrete polydisperse drop size spectra may be ...desired. Such sprays can only be achieved by means of drop production techniques which allow drops with a controllable size to be produced, e.g., the Rayleigh-type jet disintegration. Drop or spray generators working on the basis of this technique may be equipped with multihole nozzles for producing such discrete polydisperse sprays. The subject of the present paper is to provide the theoretical basis for the design of such a multihole nozzle according to a required drop size spectrum and liquid flow rate. Using the calculated design parameters, a multihole nozzle was manufactured and its performance verified experimentally. It was found that the design procedure developed works very well and the produced spray drop size spectra meet the requirements.
The temporal instability behavior of non-Newtonian liquid jets moving in an inviscid gaseous environment is investigated theoretically for axisymmetrical disturbances. The corresponding dispersion ...relation between the wave growth rate and the wave number is derived. The linearized stability analysis shows that a jet of a viscoelastic fluid exhibits a larger growth rate of axisymmetric disturbances than a jet of a Newtonian fluid with the same Ohnesorge number, indicating that non-Newtonian liquid jets are more unstable than their Newtonian counterparts. This is a well-known effect for small perturbations of the jet surface. For non-Newtonian liquid jets the instability behavior is influenced by the interaction of the liquid viscosity and elasticity effects, in which the liquid viscosity tends to dampen the instability, whereas the elasticity results in an enhancement of instability for small perturbations. The validity of the theoretical results for the growth rate spectra and breakup lengths of viscoelastic liquid jets is tested against experimental results from the literature. The comparisons confirm that the linearized theory fails to describe the nonlinear phenomena involved in viscoelastic jet breakup correctly, but it yields good results for the growth rate of disturbances in a regime of low jet Weber numbers and small deformations. The limits of validity of linear theories for viscoelastic jet instability are quantified, taking also into account the onset of non-axisymmetric deformations due to bending.
Simultaneous measurements of diameter, velocity, and concentration of particles are carried out in a flow with two disperse phases in a liquid. For high-accuracy particle recognition by different ...light-scattering mechanisms, an extended phase-Doppler anemometer utilizing the sign of the signal phase shift is used. The possibility of distinguishing between two disperse phases is verified with water as the continuous phase, and air bubbles and glass particles as the disperse phases, in a specially developed three-phase flow channel. The technique is demonstrated for three-phase flows with different loadings of bubbles and glass beads. (Author)
The present work deals with the evaporation of acoustically levitated droplets. It was shown before by the authors that droplets of pure liquids in acoustic levitators evaporate mostly due to the ...convective effect of the acoustic streaming arising near the free droplet surface. In the present work acoustically levitated droplets of binary liquid mixtures are considered. The theoretical model of acoustically driven droplet evaporation, as developed in an earlier publication of the authors, is extended for these liquids, and experimental investigations on the evaporation of droplets consisting of the liquids are conducted. Results from theory and experiment are compared and discussed.
Here, we present experimental data and a theoretical model for the dynamics of detachment of hexadecane drops from a solid substrate (glass plate) in aqueous solutions of anionic surfactant and salt, ...at various temperatures. The influence of the experimental conditions on the motion of the three-phase contact line is investigated. We found indications that water molecules can propagate by lateral diffusion in a thin layer on the surface of the solid plate. The driving force of the detachment process, viz., the imbalance of the interfacial tensions at the contact line, is engendered by the water penetration, while the line friction force compensates this imbalance and determines the stationary speed. Excellent agreement between theory and experiment is achieved. The present study specifies the parameters that can be used to quantitatively characterize the rate of drop detachment, determines the values of these parameters at various experimental conditions, and indicates tools for control of the investigated spontaneous process.
Die Beschichtung von optischen Fasern und Metalldrähten geschieht durch konvektive Trocknung eines Auftrags einer Polymerlösung auf dem jeweiligen kreiszylindrischen Substrat. Die erreichbare ...Qualität wird maßgeblich durch die Morphologie der Beschichtung und somit durch die Konzentrationsverteilung der Lösungskomponenten bestimmt. Die vorliegende Arbeit behandelt den Stofftransport in der schrumpfenden flüssigen Schicht während der Trocknung und zeigt die Berechnung radialer Profile der Gemisch‐Massenanteile bei gegebenem Verhältnis der Schrumpfungsrate des Beschichtungsquerschnitts zum flüssigseitigen Diffusionskoeffizienten für variierende Zeiten.
In verschiedenen Branchen der Industrie werden beschichtete optische Fasern und Drähte eingesetzt. Die Beschichtungen werden durch Auftrag flüssiger Lösungen polymerer Substanzen und Verdunstung des Lösungsmittels hergestellt. Die vorliegende Arbeit behandelt den Stofftransport in der schrumpfenden, flüssigen Schicht während der Trocknung.
The study investigates the effectiveness of aerosol treatment on gas exchange and pulmonary inflammatory reaction using perfluorocarbons with different molecular structure and vapor pressure.
...Experimental, prospective, randomized, controlled study.
Experimental laboratory at a university hospital.
Twenty anesthetized neonatal piglets assigned to four groups.
After establishment of lung injury by bronchoalveolar lavage, piglets either received aerosolized FC77 (n = 5), perfluorooctylbromide (n = 5), or FC43 (n = 5, 10 mL x kg(-1) x hr(-1) for 2 hrs) or intermittent mandatory ventilation (control, n = 5). Thereafter, animals were supported for another 6 hrs.
Pao2 significantly improved in the perfluorocarbon groups compared with control (p < .01). Final Pao2 (mean +/- SEM) was FC77, 406 +/- 27 mm Hg; perfluorooctylbromide, 332 +/- 32 mm Hg; FC43, 406 +/- 19 mm Hg; control, 68 +/- 8 mm Hg. Paco2 and mean pulmonary arterial pressure were lower in all perfluorocarbon groups compared with control. The ratio of terminal dynamic compliance to total compliance was significantly higher in the FC77 than in the FC43, perfluorooctylbromide, and control groups. Relative gene expression of interleukin-1beta, interleukin-8, P-selectin, E-selectin, and intercellular adhesion molecule-1 in lung tissue was determined by TaqMan real time polymerase chain reaction normalized to hypoxanthineguanine-phosphoribosyl-transferase and was shown to be reduced by all perfluorocarbons.
Aerosol treatment with all the perfluorocarbons investigated improved gas exchange and reduced pulmonary inflammatory reaction independently from molecular structure and vapor pressure of the perfluorocarbons. Although differences in vapor pressure and molecular structure may account for varying optimal dosing strategies, several different perfluorocarbons were shown to be principally suitable for aerosol treatment.
