Dynamic modeling and operation optimization for the cold end system of thermal power plants during transient processes

This paper focuses on the dynamic modeling of the cold end system of a thermal power plant and its operation optimization during cycling load processes. A revised logarithm mean temperature difference is recommended to calculate the heat transfer quantity between exhaust steam and condenser tubes. With this method, a condenser model is developed with a maximum relative error limited within 3%. Coupled with a turbo-generator, a condenser, water pumps, and a cooling tower, a closed cooling system model is established. The total power supply (TPS) during cycling load is calculated and analyzed to optimize the operation during transient processes. A method for obtaining the maximum value of TPS is provided and used to calculate the optimal operating load rate points for switching pumps (OPSP). OPSP increases with the cycling load rate (Ve) during loading up processes decreases with Ve during loading down processes. When Ve is identical, OPSP declines with the ambient temperature for the loading up and down processes. TPS during transient processes is relevant with the switching pump load rate. The maximum value of difference in TPS with different switching pump periods is 691.4 (kW h) for switching pump numbers from 3 to 2 during loading down processes.