Neue Aspekte zum Einfluß des Blasenwakes auf die Hydrodynamik und den Stoffaustausch in einer Blasensäule

New aspects of the influence of the wake of bubbles on fluid dynamics and mass transfer in bubble columns. Wake-phenomena behind solid and fluid particles moving in a continuous liquid are an important fluid-dynamic effect which has a pronounced influence on heat- and mass transfer in two-phase dispersions. In this paper results reported in the literature are used to analyse the influence of wakes behind bubbles on the hydrodynamics of bubble columns. A new class of model is introduced to describe the flow and mixing of the liquid phase, taking into account major hydrodynamic effects.     

TSD-Untersuchungen zum Einfluß von Wasser auf die molekularen Beweglichkeiten in Polyamid-6

Molecular motions in nylon 6 are studied by thermally stimulated discharge (TSD) techniques. The effect of absorbed water on the relaxation behaviour of nylon 6 is discussed. The γ relaxation process at ?145°C is attributed to local segmental motions in the amorphous phase. The intensity of the γ relaxation is reduced and broadened by absorbed water. The molecular origin of the β relaxation process in the temperature range between ?80 and ?60°C is associated with localized reorientational motions of chain segments involving nonchain-bonded or weakly bonded amide groups. It is quite likely that also rotational rate processes of water molecules bonded to CO-groups contribute to the β process. The intensity increases are due to added water, since associated water molecules are involved with those molecular motions. The α relaxation process at 70°C is associated with large-scale segmental motions at the glass transition. The chain mobility is increased by added water and gives rise to an α peak near 50°C. The α′ relaxation process in the temperature range between 100 and 110°C may either be associated with reorientational motion of stretched chain segments or with the beginning of a crystalline transformation of the γ phase into the monoclinic α form. The temperatures of TSD-peaks correspond to alternating current loss data at a frequency of 5·10^?2 Hz.     

Untersuchungen zum Einfluß der Polymermatrix auf die thermische Rückreaktion von photochromen 2,4-Dinitrobenzylpyridinen

The Influence of the Polymer Matrix on the Thermal Back Reaction of Photochromic 2,4-Dinitrobenzyl Pyridines In solid solution with polymers (polymethylmethacrylate, polyethyl acrylate and polystyrene) below T_g the thermal back reaction of the coloured forms of photochromic 2-(2′,4′-dinitrobenzyl)pyridines 1–3 can be described by second-order kinetics whereas above T_g (in polyethyl acrylate) the reaction is first order. The life time of coloured form depends on polymer structure and is longest in polar polymers of high molar mass. These results as well as the Δ^≠ and ΔH^≠ values are discussed applying the concept of reaction cavity to the solid solutions.     

Der Einfluß von Bodenpflegemitteln auf die Gleitsicherheit

Influence of Floor-Polishes on Slip-Safety The influence of usual floor-polishes with self-brightness and/or cleaning-effect was tested on slip-safety. The results of investigations are: 1. Surface-brightness shows no essential correlation with slip-safety after treating the floors. 2. Strong stickiness of floor-polishes ist not useful for a good slip-safety. 3. The slip-resistance of floors raises as a rule by dry conditions. 4. The most floor-polishes have essentially more reduced slip-resistance by wet conditions in comparison to not treated wet floors. For prevention of accidents this conclusion is very interesting.