A Comparative Analysis of the Energy Performance Characteristics of Turbine Condenser Evacuation Devices

Efficient operation of turbine condensers is an important prerequisite for economically efficient and reliable operation of the turbine units at thermal- and nuclear power plants. Noncondensable gases entering the condenser shell space significantly affect the heat transfer intensity and, hence, the pressure at the end of the steam expansion process in the turbine. Therefore, it is important to take measures for constantly removing these gases with the minimal energy expenditures. The article considers the operation principles and operational and design characteristics of air evacuation devices used in the condensers of thermal- and nuclear power plant turbine condensers, such as water jet and steam jet ejectors, and liquid-packed ring pumps. Comparison of these devices in terms of their energy performance criteria is carried out. Conditions for ensuring adequate energy performance of water jet ejectors are shown. Based on the results obtained from the tests of water jet ejectors and liquid-packed ring pumps, it is shown that liquid-packed ring pumps do not have any essential advantages in using them as devices for evacuating noncondensable gases from steam turbine condensers. The characteristics of steam jet ejectors used at Russian thermal and nuclear power plants are given. The notion of a steam jet ejector energy efficiency is introduced. The reserves for improving the energy performance of steam jet ejectors are shown. It can be seen from the numerical analysis results that the use of steam jet ejectors is more energy efficient for the power units of nuclear power plants constructed on the basis of the AES-2006 and VVER-TOI conceptual designs than the use of liquid-packed ring pumps. In addition, liquid-packed ring pumps are essentially more costly and complex in operation. In view of a long-standing positive experience of using water jet and steam jet ejectors at thermal and nuclear power plants and their good performance, it is recommended to consider them as air evacuation devices for advanced nuclear power plant turbine units.