Transient Analyses for the Hydraulic Design of a Once Flow Through Cooling Water System at a Power Plant

Transient analyses of pressure surges due to tripping of pumps in a cooling water system (CWS) are presented in this paper. The proposed CWS would consist of four circulating water pumps, a once-flow-through condenser, two closed cooling water heat exchangers, and an outfall. The numerical model was calibrated by adjusting head loss coefficients to match the four-pump normal operating condition. Model simulations indicated that the simultaneous tripping of four pumps would result in very large negative and positive pressures throughout the system. However, significantly higher pressures were generated downstream of the condenser by the tripping of two pumps during a four-pump operating scenario. To limit the development of excessive pressures and avoid column separations, combination air inlet and outlet valves were installed at the discharge header of the pumps and at the outlet water boxes of the condenser. With these valves installed, the computed extreme pressures were close to the operating steady state pressures.