| Abstract: | The first part of this contribution [1] presents the population balances, i.e., balance equations for the numerical density of the bubbles in the individual bubble fractions. They are solved approximately by an analytical approach. There results a straightforward balance equation for the average bubble volume. This equation can be solved analytically for simple fields of flow. For complex fields of flow it has to be solved by a numerical approach. The result obtained is the bubble volume at any time and place averaged from the size distribution of the bubbles. This permits calculation of the local size distribution of the bubbles with the aid of the approximate analytical solution. In the second part of this contribution [2], this balance equation is extended to cover large gas volumes. Large bubbles and gas plugs then occur. These possess a very small interfacial area relative to their volume. They have high rise velocities and thus short residence times in the flow. They therefore participate to only a slight extent in mass and energy transfer and have to be considered, for example, in calculation of the conversion on a chemical reaction or the mode of action of an evaporator. The calculations are performed for pure liquids and compared with the authors' own and other experimental results. The liquids used industrially are generally mixtures of substances. In such liquids the coalescence behavior deviates significantly from that in pure liquids. The influence on coalescence and thus on the interfacial area is examined in the present paper. |
