A mathematical model for a continuous direct esterification reactor has been developed. The solid-liquid equilibrium of terephthalic acid (TPA) was considered in our modeling, and the characteristic dissolution time, an adjustable parameter, was introduced to account for the mass-transfer effect in the dissolution of TPA. The effects of the characteristic dissolution time, monomer feed ratio, temperature, and pressure on the reactor performance at different residence times were investigated through simulation. It was observed that the behavior of the first reactor strongly depends on whether the solid TPA is completely dissolved in the reaction mixtures. From the dynamic simulations, it was found that a sudden change in the operating conditions affects the ethylene glycol (EG) vapor flow rate instantly. For the esterification process having two reactors in series, the strategy for time distribution and recycling of EG is also discussed.