[en] A statistical formulation is used to describe gas-liquid two phase flows. It is shown that this kind of flows cannot be considered a dilute system as is currently done. A correction factor, the pair correlation function, is introduced to account for dense effects. Integrating the transport equation of the bubble volume distribution function over all possible volumes, a number density transport equation is obtained, which explicitly accounts for bubble breakup and coalescence phenomena. A complete model is constructed in conjunction with the mass and momentum conservation equations. Its predictions were contrasted against experimental results on bubble columns. Excellent agreement was found. (author)