Lubomira Broniarz-Press

DRAG REDUCTION EFFECT IN PIPE SYSTEMS AND LIQUID FALLING FILM FLOW

In this paper the most important literature data on polymer and surfaceactive additives effect on flow drag reduction and heat transfer effect in pipeline systems, as well as on liquid film flow characteristics, are presented. Previous published reviews by Gyr and Bewersdorff [1995], Choi [2000] and Graham [2004] were concerned with drag reduction effects in polymer solutions, and drag reduction effects in surfactant solutions were reviewed by Zakin et al. [1998]. The authors of the present review paper limited themselves to review important issues related to drag reduction effect and heat transfer in turbulent flows without phase change. Special attention was directed to elaborate the similarities and differences of drag reduction in high-molecular polymers and surfactants solutions, which relate to the flow phenomena and the associated heat transfer in straight tubes, coils and in falling films. It has been underlined that despite the large amount of research, which includes applications of modern measurement techniques to study turbulence phenomena and the Theological characteristics, the details of the drag reduction and heat transfer mechanisms are still not well understood. In the experimental studies performed in the last years with mixed drag reducers systems (polymer/surfactant, surfactant/surfactant), it has been shown that the presence of other surfactants or polymer in drag reducing surfactant systems causes an increase of the system stability and of the temperature range in which the additives are most effective. Perhaps the zwitterionic surfactants with special additives have the potential to become very useful in the future. It has been shown that another important issue for future research is finding drag reducing systems for long-distance transport of non-polar fluids, taking into account changeable environment temperature conditions.

The effect of shear and extensional viscosity on atomization in medical inhaler.

The paper contains the results of experimental studies of water, aqueous solutions of glycerol and aqueous solutions of glycerol-polyethylene oxide (PEO) atomization process in a medical inhaler obtained by the use of the digital microphotography method. The effect of the shear and extensional viscosity on the drop size, drop size histogram and mean drop diameter has been analyzed. The obtained results have shown that the drop size increases with the increase in shear and extensional viscosity of liquid atomized. Extensional viscosity has a greater impact on the spraying process. It has been shown that the change in liquid viscosity leads to significant changes in drop size distribution. The correlation for Sauter mean diameter as function of the shear and extensional viscosity was proposed.

The effect of shear and extensional viscosities on atomization of Newtonian and non-Newtonian fluids in ultrasonic inhaler.

The paper contains results of the experimental study on atomization process of aqueous solutions of glycerol and aqueous solutions of glycerol-polyacrylamide (Rokrysol WF1) in an ultrasonic inhaler. In experiments the different concentration aqueous solutions of glycerol and glycerol-polyacrylamide have been tested. The results have been obtained by the use of laser diffraction technique. The differences between characteristics of ultrasonic atomization for test liquids have been observed. The analysis of drop size histograms shows that the different sizes of drops have been formed during atomization process. The present study confirmed the previous reports which suggested that the drops size changes with the increase in viscosity of solution changes in spray characteristics were also observed. It has been shown that the shear and extensional viscosities affect the process of atomization.

Rheology and Structure of Emulsions and Suspensions

This article contains the results of experimental investigation of the rheological characteristics and structures of emulsions and suspensions. The emulsions had the oil volume fraction in the range from 0.1 to 0.4. The suspensions with nanoparticles are represented by suspensions of silica with concentrations from 1 to 4%. Paprika and coffee suspensions with concentrations of 5, 10, and 20% were studied. The material was subjected to rheological measurements using a concentric cylinder viscometer in the shear rate range of 16.2 to 1326s−1. A lot of food products are either in the form of emulsions or suspensions whose rheological and interfacial properties are important to achieve stability of the products. The rheology and structure analysis is very important from the point of view of flow, friction factors and Reynolds number for non-Newtonian fluids and food production processes. To characterize emulsions and suspensions, first the particle size distributions were made. The experiments presented have shown that the rheological characteristics of composite systems (emulsions and suspensions) depend on concentration and properties of dispersed phase. Concentration of dispersed phase has an effect on the character of the fluid. The fluid can have Newtonian character at low concentrations of dispersed phase. Above certain concentrations the nature of non-Newtonian fluid will appear. Emulsions have a polydisperse character. Emulsions with ϕ up to 0.4 show approximately linear increase of emulsion viscosity on the oil concentration. Silica represents suspension with aggregates, agglomerates or network formed. The increase in shear rate causes gradual destruction of the structure. The rheological behaviors confirm these processes. The paprika and coffee suspensions have non-Newtonian rheological properties. The suspensions have more and more non-Newtonian characteristics increasing particles concentration. The solid particles do not form structures. The correlation equation for rheological properties of systems studied has been shown. The results may be used for example to verify numerical models or comparisons with respect to similar fluids.

Characterization of sprays for thermo-stabilized pneumatic nebulizer

The research presents the nebulizer spray chamber temperature controller responsible for controlling temperature of aerosol produced as a result of nebulizing process. The motivation to make an attempt to improve modern pneumatic devices was the shortage of this kind of apparatuses on the market allowing the production of thermos aerosol. A designed temperature controlling system for pneumatic nebulizers aims at increasing and stabilizing temperature of produced aerosols and increasing aerosol therapy safety. The system is intended for producing aerosol in the process of pneumatic nebulization with the temperature similar to that of the human body. Experiments that were carried out confirmed good performance of the device. It was proved that with the increase of temperature the amount of big droplets fall and the entire spectrum of the droplet diameter moves towards smaller droplet diameter values. Reduction of liquid viscosity related to the increase of temperature leads to the reduction of droplet diameter and, as a result, the reduction of the Sauter mean diameter value.

Atomization performance of effervescent atomizers with gas-liquid internal mixing

Atomization performance of effervescent atomizers with gas-liquid internal mixing The paper contains the results of experimental studies on water atomization process in effervescent nozzle in one-phase and two-phase systems. The gas phase flow rate causes the changes in characteristic parameters of atomization. The gas flow rate has certain effect on the Sauter Mean Diameter SMD values. SMD for airliquid systems investigated is decreasing with increase of gas volume rate. It is observed that SMD values are increasing with increase of liquid volume rate. The larger SMD values for one-phase flow in comparison with two-phase flow have also been observed. The increase of SMD value has been observed with a decrease of an outlet diameter of an effervescent nozzle.

Enhancement of mass transfer coefficients in spiral films

The wetted columns both with tangential nozzles and turbulence promoters are of great interest. The spiral motion of a liquid film gives a good stability and a great turbulence to the film. It results in the increase of the rate of transfer processes compared with those both in smooth and rough wall columns. The liquid phase mass transfer coefficients for the absorption of carbon dioxide into water have been measured on three types of threaded surfaces. The enhancement film mass transfer criteria have been proposed. The positive effect of surface ribbing in a helix in comparison with similar form incisions perpendicular to apparatus axis has been shown.

Właściwości reologiczne warstwy powierzchniowej cieczy wybranych piw komercyjnych

S t r e s z c z e n i e W pracy przedstawiono wyniki badan reologicznych warstw powierzchniowych piw: Debowe Mocne, Tyskie Gronie, Żywiec oraz Warka Strong w przeplywie oscylacyjnym. Uzyskane zalezności miedzyfazowego modulu zachowawczego Gs’ i miedzyfazowego modulu stratności Gs” w funkcji czasu mialy przebieg charakterystyczny dla rozcienczonych wodnych roztworow bialek. We wszystkich uzytych w badaniach piwach wartości obu modulow wzrastaly, a po pewnym charakterystycznym dla danego rodzaju piwa czasie dochodzilo do ich przeciecia na wykresie. Wyniki pomiarow oscylacyjnych świadczą o tym, ze w warstwach powierzchniowych piw dochodzilo do uformowania sie struktury sieciowej. Bardzo dlugi czas formowania sie tej struktury jest dowodem, ze w jej tworzeniu wazną role odgrywaly zawarte w piwach bialka. Zaobserwowano takze, ze najbardziej stabilna piana wystepowala na powierzchni piwa Żywiec. Zmierzone wartości miedzyfazowych modulow Gs’ i Gs” tego piwa byly najwyzsze. Wyniki te wskazują, ze istnieje związek miedzy wlaściwościami reologicznymi warstwy powierzchniowej piwa a stabilnością piany. Slowa kluczowe: piwo, wlaściwości reologiczne, powierzchnia miedzyfazowa, warstwa powierzchniowa, piana