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OP-I-25COMPARISON OF BUBBLE COALESCENCE MODELS WITH DATAFROM DIRECT COMPUTER SIMULATION AND EXPERIMENTBoshenyatov B., Semyanistij A.Russian Academy of Sciences, Institute of Applied Mechanics of RAS,Moscow, Russia, bosbosh@mail.ruBubble column reactors are widely used in industry, but questions about theirdesign and scale up remain. Modeling bubble coalescence is one of the most difficultproblems, because the laws of coalescence are not studied sufficiently. The evolutionof bubble size distributions at different heights of the column reactor are usuallycalculated on the basis of a one-dimensional population balance equation. Thebubble coalescence and break-up mechanism is described by the introduction of twomathematical functions, which have two or more unknown parameters. The values ofthese parameters as recommended by various authors may differ from each other byseveral times [1].The main objective of this paper is to improve our understanding of thefundamental mechanism of bubble coalescence.For this purpose, a direct computer simulation program was developed forcalculating the movement and coalescence of bubbles in a gas-liquid column reactor.The program allows to simulate the conditions for the generation of bubbles at thebottom of the column. Additionally, the initial distribution of bubble sizes may bespecified. The three-dimensional trajectory of each bubble (straight or spirallingmotion) and its speed are taken from the analysis of numerous experimental data.The program calculates the gas volume fraction and bubble size distribution indiscrete time steps. The result of each collision of bubbles is determined on the basisof the chosen model of coalescence.Thus the program allows one to compare a known model of coalescence withexperimental data for various parameters of bubble environments to determine theirvalidity and applicability.In order to analyse the degree of adequacy of the chosen model of coalescenceto actual physical phenomena, the results of direct computer simulation werecompared with experimental data. The experimental conditions should be such thatcoalescence plays the dominant role when the bubbles are floating up, while the84