Condensing Turbine Exhaust Steam in a Steam Surface Condenser Using Multiple Sources of Cooling Water

Scarcity and restrictions in the use of cooling water has prompted power plant developers to explore multiple sources of cooling mediums to condense turbine exhaust steam in a steam surface condenser. The cooling mediums can have different chemistries dictating selection of different tube and tubesheet materials. The flowrate, inlet temperature and temperature rise for the cooling mediums can be different. Some cooling mediums may not be available during certain times of the year. The resulting steam surface condenser will include multiple smaller tube bundles of various sizes operating with different flowrates and temperatures. The challenges in designing a condenser that employs multiple sources of cooling medium with different chemistries, flowrates and inlet temperatures are enormous. To ensure reliable operation a number of thermal, hydraulic and mechanical design issues must be carefully evaluated. Determining performance of the entire condenser at off-design conditions with variations in flowrates and inlet temperatures of one or more cooling water streams (or absence thereof) can be complicated. This paper highlights the major concepts that need to be addressed while designing a steam surface condenser that employs multiple sources of cooling medium to condense the turbine exhaust steam. Critical thermal, hydraulic and mechanical design issues that can impact the performance and reliability of the overall condenser are addressed.