Dynamic flow phenomena in a foam application unit

If, during the operation of a foam application unit, a change in the foam production is introduced, the change in the flow becomes noticeable at the point of application onlyafter a certain response delay time. During the operation of the unit it is necessary to take this response delay into consideration. By varying the flow of foam in the application unit, the mass content of foam in the unit is changed as a result of the changed pressure inside the unit. The response delay has been mathematically derived for the flow of agiven type of foam through pipes, as well as through a foam printing unit as a whole. A deviation in the yield of foam on the substrate can be avoided by considering the respons delay caused by a change in the foam production process

The flow properties of foam

The rheological behaviour of foam, prepared from an aqueous solution with lauryl sulphate as surfactant, has been measured with a viscometer as a function of the blow ratio, bubble diameter distribution and concentration of the thickener used. The influence of wall slip and of hysteresis effects on the rheological behaviour have been determined. Calculations and measurements pertaining to the pressure drop in pipes have been performed, in which the foam was considered as a compressible pseudoplastic whose rheology depended on blow ratio. The distribution of the foam passing through a closed distribution unit has been studied. This distribution unit consisted of a pipe and a cross-head distribution slit. Complementary measurements of the flow of foam through narrow slits have been made. The design of a closed foam distribution unit is discussed. The consequences of the choice of several design parameters are examined

Foam generation in a rotor—stator mixer = Schaumerzeugung in einem rotor—stator mischer

The foaming process of an aqueous liquid system with surface active agents and thickeners in a rotor-stator mixer has been studied.\ud \ud The foaming capacity of a rotor—stator mixer may be represented by a so-called mixing characteristic. The foamabilities of several liquid systems have been measured as a function of the mixer geometry and the rotational speed.\ud \ud The hydrodynamics in a rotor-stator mixer is characterized by a Newton—Reynolds relationship. The mechanism of foaming and the dependence of several mixing parameters are different for the turbulent and laminar flow regions. The mixing process is evaluated in both regimes. In the transition region from turbulent to laminar the foaming is very poor in comparison with that in the turbulent and laminar flow regimes.\u

Foam Generation in Rotor-Stator Mixers

One of the unit operations in foam technology is foam generation in a liquid/gas mixer. The foaming process of an aqueous liquid system with a surface-active agent in a rotor-stator mixer has been studied, and it was found that it could be represented by a mixing characteristic relating the liquid flow rate to the maximum gas flow rate needed to produce a foam without 'blow-by'. Too high a gas flow rate resulted in a short-circuiting flow of gas via the rotor shaft to the outlet. The influence of the number of rotor-stator blades, equipment size and operating pressure on the behaviour of the foam mixer has been investigated

Foam Generation in Rotor-Stator Mixers

One of the unit operations in foam technology is foam generation in a liquid/gas mixer. The foaming process of an aqueous liquid system with a surface-active agent in a rotor-stator mixer has been studied, and it was found that it could be represented by a mixing characteristic relating the liquid flow rate to the maximum gas flow rate needed to produce a foam without 'blow-by'. Too high a gas flow rate resulted in a short-circuiting flow of gas via the rotor shaft to the outlet. The influence of the number of rotor-stator blades, equipment size and operating pressure on the behaviour of the foam mixer has been investigated