Mathematical models for simultaneous reaction and mass transfer occurring in the manufacture of high-viscosity condensation polymers are considered. Particle tracking experiments are used to estimate convective flow rates and mixing volumes in a disc-ring reactor configuration. These results are incorporated directly into a mixing-cell model without resorting to the use of restrictive assumptions regarding the convective mixing. Both a penetration theory model and a flash evaporation model are used to simulate the transport at the liquid-vapor interface. Although widely used in previous studies, the penetration theory model is ultimately rejected because it underpredicts the overall reactivity. Model results predict interactions between agitation rate, residence time, and the overall reaction rate for commercial-scale systems producing poly(ethylene terephthalate). The model is partially verified by comparison with degassing data.