  NJL-type effective models represent a low-energy realization of QCD and
incorporate pertinent aspects such as chiral symmetry and its spontaneous
breaking, the center symmetry in the heavy-quark limit as well as the axial
anomaly. One such model, the Polyakov-quark-meson model for three light quark
flavors, is introduced in order to study the phase structure of
strongly-interacting matter. With recent high-statistics lattice QCD
simulations of the finite-temperature equation of state, a detailed comparison
with model results becomes accessible. Such comparisons allow to estimate
volume and truncation effects of quantities, obtained on the lattice and
provide possible lattice extrapolation procedures to finite chemical potential
which are important to locate a critical endpoint in the QCD phase diagram.
