Interfacial area balance equation in a two-phase mixture - Local approach vs particle approach

The interfacial area balance equation in a two-phase mixture looks quite di fferent depending whether the area per unit volume is defined as: i) the su m of ail the al-ras contained in the unit volume or ii) the slim of the are as of all the particles with their centers in this unit volume. We prove he re the complete compatibility between the two balance equations mid show th eir respective merits. (C) 2000 Academie des sciences/Editions scientifique s et medicales Elsevier SAS.