Investigation of the dynamics of power plants requires detailed models (Maffezzoni, 1992), with representation of plant components; such models are generally used to build plant simulators, where control strategies and controllers' set-up may be assessed (Groppelli, et al., 1992). Large-scale models are generally based on first-principle equations (mass, momentum and energy balances), combined with phenomenological correlations (e.g., heat transfer correlations), and may be considered as knowledge models, i.e. models through which process dynamics can be thoroughly ascertained and understood. Knowledge models are the only reliable way, beside experimentation, to become acquainted with power-plant dynamics, and in particular with the many interactions among process variables and of their actual relevance.