Advances in Water Treatment and Enviromental Management

MEASUREMENTS OF MASS TRANSFER IN A BUBBLE COLUMN 145gas from the interface into the bulk of liquid by characteristic turbulent scales. Theproblem consists in the measurement of these scales in the two phase flow [6], [10].For the quantitative and qualitative determination of the volumetric interfacial areaa as a function of flow and material characteristics two sorts of measurementmethods [6], [3], [19] are commonly used:– chemical methods leading to a direct determination,– physical methods analysing bubble characteristics such as local phasedistribution, spatial bubble diameter distribution (e.g. Sauter diameter)These methods necessitate a substantial disturbance of the system or are nowunder development.2.3 ApproachTable 1: Mass-Transfer ModelsFor these investigations a bubble column was chosen because of the simpleregulation of the flow rate, the flow characteristics and the air input in this system.The relative importance of turbulence in influencing oxygen transfer from bubblesto water is discussed. It is not intended to specify design parameters in this paper,but rather to emphasize the importance of this parameter. Therefore the problem isreconsidered in a much simpler situation, namely of a uniform mean flow withapproximately isotropic turbulence characteristics [5]. However hypothetic suchflows might seem from a practical point of view, their study is believed to be anessential first step towards the more elaborate investigation of other more realistictwo-phase flows.