(109b) Challenges in Fundamental Valve Tray Efficiency Modeling in the Mixed-Froth Regime

The froth regime is the most likely flow regime on an industrial distillation tray (Kister 1992). It has been the flow regime of interest for most tray efficiency models. The froth regime is classified into two sub-regimes (Hofhuis and Zuiderweg 1979, Lockett 1986) ? bubbling-froth and mixed-froth. The two-phase hydraulics and mass-transfer characteristics of the bubbling-froth are well understood and have been implemented in several tray efficiency models. The mixed-froth, however, is relatively less understood and has only been modeled on sieve trays. The recent advances in fundamental modeling of sieve tray efficiency (Garcia and Fair 2000, Syeda et al. 2007) can be attributed to improved mixed-froth modeling. Current mixed-froth models, however, have several empirical aspects that limit generalization. In this paper, the challenges in the fundamental modeling of the mixed-froth are discussed. Empirical and theoretical aspects of the current mixed-froth models and their applicability to valve trays are evaluated. This work is part of the ongoing work at OSU to identify the similarities, differences, and the gaps in sieve and valve tray efficiency models.