| For further reducing the cost of thermal power units, it is very necessary to analyzing performance for the cold end of thermal power system and studying the optimal operational mode. Counter flow with a large natural draft cooling tower condensing steam turbine as the research object, in this paper, condenser, circulating water system and cooling tower system were put together as a whole to analyze, mathCAD and mablab and other computer software were used to model the cold end system and then determine the optimal target of running the cold end.In this paper, firstly, the model of the subsystems of cold end and the models of cooling water inlet temperature, cooling water temperature rise, and the conderser pressure, condenser terminal temperature difference were built up, and then, using matlab software to fit the exhaust unit provided by the manufacturer of pressure on the unit output of exhaust pressure curve and the impact on the heat curve method to determine the turbine characteristics. Both the circulating pump operating point of a single pump and double pump in parallel are analyzed, and the condenser performance curve method is analyzed, too.Hyperbolic cooling towers of natural ventilation are analyzed, and the computer program of the present method based on enthalpy difference theory is performed to calculate the 600MW unit cooling tower. Result shows the various factors affects on efficiency and outlet temperature of the cooling towers.Calculation of variable conditions of condenser has been carried out based on the methods of determining the best vacuum, cold end optimization theory and practical data of power plants. Influence curves of cooling water quantity, inlet temperature of cooling water and load on condensing vacuum are obtained. Therefore, optimal operation modes of circulating water pump can be identified at different load and inlet temperature of cooling water. It is shown that the present model is much more efficient and precise. |
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