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For relatively simple components, where the flow paths are reasonably well defined, a flow path approach may be adequate to calculate flow velocities, as illustrated in Fig. 2-1. In the flow path analysis approach, characteristic flow paths (i.e., through the tube bundle, between the tube bundle and shell, etc.) between regions of common pressures are identified. Flow impedances (i.e., pressure drop coefficients) are estimated. The flows within each path are then calculated. The resulting flow velocity distributions are then used to estimate vibration excitation mechanisms and predict vibration response.

Fig. 2-1 Flow‐Path Approach.

All typical operating conditions must be considered including the following: 1) as‐designed operating conditions, from zero to 100% flow, 2) operating conditions with fouling of the tubes or crudding of the tube supports, and 3) other possible operating conditions (e.g., after chemical cleaning, system testing, etc.).

Fig. 2-2 Thermalhydraulic Analysis: Axial Grid Layout for a Typical Steam Generator with Preheater (Distances in Metres).