Plain Liquid Research Articles

Modelling of the atomization of a plain liquid fuel jet in crossflow at gas turbine conditions

The penetration and atomization of a plain jet of kerosene fuel in air crossflow were modelled and compared with the experiment at test conditions relevant to lean premixed prevaporized combustion in gas turbines. Tests were conducted at an air velocity of 100 and 75 m/s and an air pressure of 6 and 9 bar at ambient temperature. The fuel nozzle diameter was 0.45 mm and the liquid-to-air momentum flux ratio was between 2 and 18. Measurement techniques employed include time-resolved shadowgraphs, Mie-scattering laser light sheets, and Phase-Doppler-Anemometry. Hence qualitative information on jet disintegration as well as quantitative data regarding jet penetration, fuel placement and dropsize distribution were obtained. The numerical model predicts the jet penetration by treating the liquid fuel jet conceptually as a cylinder deflected by the airflow. Fracture of the liquid column is modelled by a characteristic time criterion. Shear breakup of the liquid column and its fragments is modelled as liquid boundary layer stripping. The engineering model has been implemented as an extension into a 3d CFD-code with Lagrangian particle tracking. Within its application limits, the model fills the gap of lacking droplet initial conditions in numerical spray simulation, while at the same time requiring low computational effort.

Effectiveness of Handwashing with Electrolyzed Water and Its Comparison with Several Types of Handwashing Methods against Bacteria on Hands after Nursing Procedures.

To examine the antibacterial effectiveness of handwashing with electrolyzed water (EW) when everyday nursing procedures are performed, the cleansing effectiveness of washing for 10s or 30s with EW, washing with 7.5O (w/v) povidone-iodineliquid (PI-washing), washing with medicated liquid soap (mls-washing), and washing with non-antiseptic, plain liquid soap (Is-washing) was compared. When the bacterial counts from hands after nursing procedures were 103cfu/hand or greater, it was suggested that washing for 10s or 30s with EW could be expected to have the same level of washing effectiveness asthat for mis-washing or Iswashing. Compared to PI-washing, however, the survival ratios were higher. When the bacterial counts from hands were less than 103cfu/hand after nursing procedures, washing for 10s or 30s with EW was more effective than Is-washing. Furthermore, EW could keep the bacterial counts from hands as low as those after PI-washing. Based on the above results, washing with EW was as effective as mls-washing, and though slightly less effective than PI-washing, it was considered that the same level of effectiveness seen with PI-washing could be expected for relatively lightly contaminated hands after daily nursing procedures.

Effectiveness of hand-cleansing agents for removing Acinetobacter baumannii strain from contaminated hands

Background: The effectiveness of hand-cleansing agents (plain liquid soap, 70% ethyl alcohol, 10% povidone-iodine, and 4% chlorhexidine gluconate) for removing a hospital strain of Acinetobacter baumannii from artificially contaminated hands of 5 volunteers was studied. Methods: The experiments were performed by using a Latin square statistical design, with two 5 × 4 randomized blocks, and the results were estimated by ANOVA. In the first and second blocks, the fingertips of the volunteers were contaminated with approximately 10 3 colony-forming units (light contamination hand) and 10 6 colony-forming units (heavy contamination hand), respectively. Results: In the first block, all products tested were effective, almost completely removing the microbial population of A baumannii artificially applied to the hands. In the second block, the use of hand-cleansing agents resulted in 91.36% (4% chlorhexidine), 92.33% (liquid soap), 98.49% (10% povidone-iodine), and 98.93% (70% ethyl alcohol) reduction in counts of A baumannii cells applied to the fingertips. The ethyl alcohol and povidone-iodine had significantly higher removal rates than plain soap and chlorhexidine ( P < .05). Conclusions: These results suggest that 70% ethyl alcohol and 10% povidone-iodine may be the most effective hand-cleansing agents for removing A baumannii strain from heavily contaminated hands (10 6 colony-forming units/fingertip). (AJIC Am J Infect Control 1999;27:327-31)

Viscoelastic Behavior of Polymer Surface during Wetting and Dewetting Processes

The contact angle of water was measured with the Wilhelmy plate method on apolar polymers: soft ethylene-propylene copolymer (EP), rigid polypropylene (PP), and their blends PP/EP (80 wt % PP) and EP/PP (20 wt % PP). Upon liquid displacement, the contact angles of the soft materials, EP and EP/PP, depended on viscoelastic energy dissipation due to solid deformation. This was observed in different situations: wetting and dewetting, liquid displacement due to the relative motion of the plain liquid with respect to the solid, and meniscus relaxation when that motion was stopped. The wetting hysteresis of polymer blends may be understood by considering viscoelastic energy dissipation and the static contact angles. The former depends on the elastic modulus while the latter is determined by the more hydrophobic phase and the less hydrophobic phase, for advancing and receding contact angles, respectively.

Radial Symmetry for an Electrostatic, a Capillarity and some Fully Nonlinear Overdetermined Problems on Exterior Domains

We consider two physically motivated problems: (1) Suppose the surface of a body in \mathbb R^2 or \mathbb R^3 is charged with a constant density. If the induced single-layer potential is constant inside the body, does it have to be a ball? (2) Suppose a straight solid cylinder of unknown cross-section is dipped into a large plain liquid reservoir. If the liquid rises to the same height on the cylinder wall, does the cylinder necessarily have circular cross-section? Both questions are answered with yes, and both problems are shown to be of the type \mathrm {div} (g(|\triangledown u |)\triangledown u) + f(u, | \triangledown u|) = 0 \ \mathrm {in} \ \Omega, \ \ u = \mathrm {const}, \frac{\partial u}{\partial v} = \mathrm {const} \ \mathrm {on} \ \partial \Omega, \ u = 0 \ \mathrm {at} \ \infty where \partial_u f ≤ 0 and \Omega = \mathbb R^N \ \bar{G} is the connected exterior of the smooth bounded domain G . The overdetermined nature of this possibly degenerate boundary value problem forces \Omega to be radial. This is shown by a variant of the Alexandroff-Serrin method of moving hyperplanes, as recently developed for exterior domains by the author in [19]. The results extend to Monge-Ampere equations.

Mass-transfer coefficients and equilibrium solubilities for fluid-supercritical-solvent systems by online near-IR spectroscopy

Mass-transfer coefficients and equilibrium solubilities for the systems α-tocopherol-carbon dioxide, isophytol-carbon dioxide, and dihydroisophytol-carbon dioxide were determined in the temperature range from 327 to 353 K and pressures up to 35 MPa. A rectangular, plain liquid film was used as mass-transfer surface. Reynolds numbers were varied between 100 and 3000 (laminar and transition flow region). Liquid concentrations in the supercritical solvent could be measured online by means of a fiber-optical near-IR spectrometer. The resulting mass-transfer coefficients could not be described by known Sherwood number correlations. Especially, the dependence on Schmidt numbers was completely unusual. Introducing a diffusion-hindering term into the usual dimensionless equation resulted in a correct correlation of the measured values for the investigated systems.

Shelf Life of Plain Liquid Yogurt Manufactured in Saudi Arabia

The shelf life of plain liquid yogurt under local conditions of manufacture and handling has been investigated. Initial coliform counts of <1 cfu/ml in the product remained constant throughout 14 d of storage at 7, 10 or 15°C. With initial counts of mold and yeast not exceeding 1 cfu/ml, growth of these microorganisms was nominal (22 cfu/ml) after 14 d of storage at 7°C. At 10 and 15°C storage, however mold and yeast increased substantially from initial levels not exceeding 1 cfu/ml to 2 × 103 cfu/ml and 3 × 103 cfu/ml after 5 and 10 d of storage respectively. The high initial quality of the product, with ⩽10 cfu/ml coliform, ⩽10 cfu/ml mold and yeast and a hedonic score of 8 (like very much), was maintained for 5 d at 7°C storage. After 5 d of storage at 7°C, the mold and yeast count and organoleptic property of the product became unacceptable. The organoleptic quality deteriorated irrespective of the microbial contamination of the product. Quality assessment of the product before expiration (4 d) and under prevailing commercial conditions of manufacture, handling and storage revealed acceptable sensory and microbial quality. The possible causes of product sensory deterioration irrespective of growth of mold and yeast are discussed.