Thermal optimization of steam air cooled condensers for power plants

Abstract

Cooling is a significant part of any power generation cycle. An ACC (Air Cooled Condenser) is used to condense steam vapors from the steam turbine, lower heat rejection temperature and increase the power generation efficiency. Traditional evaporative cooling towers, evaporate a fraction of the recirculating water to take away its latent heat of evaporation, thereby cooling the rest of the volume of water. Even if only a small fraction of the recirculating water is evaporated, a large amount of make-up water is required. This imposes a huge requirement of water which adds to the global water crises. Further, many projects become unfeasible due to water shortages. On the other hand ACCs are dry cooling towers that do not require any water for cooling as they dissipate the waste heat directly into the ambient air. On the contrary, ACCs have a lower thermal performance than water based cooling towers and their performance is adversely affected by local weather fluctuations. Further ACCs are known for poor performance during the peak summer months which increases the turbine back pressure, thereby decreasing the overall power output of the turbine. This leaves the designers with a very narrow margin for performance optimization with respect to their capital and running costs. In this thesis the heat transfer characteristics of ACCs are evaluated based on computer simulations and theoretical formulations. For a given set of operating conditions and parameters, it is possible to design ACCs in different types and configurations. A comprehensive thermal design software package, Aspen EDR from Aspen Technologies has been used to simulate specific property methods and models to obtain the most effective design. Further design optimization has been carried out by varying the tube and fin diameters, their numbers, number of bays and fan diameters. The knowledge and results from the thesis will help design thermally optimized ACCs. The research has be done for a cooling tower manufacturing company, North Street Cooling Towers P Ltd which is based in India, that currently does not manufacture ACCs but would like to start manufacturing them in the near future. The knowledge and results from the research will help the company to design thermally optimized ACCs which will have performance advantages over what is currently available in the mainstream market.