Improving the performance of heat sink systems can generate considerable gains of plant output by increasing the overall plant efficiency. For natural draft counter-flow cooling towers, such improvement can be achieved by enhancing the aero-dynamics of air inlets. Many operating cooling towers have an air inlet with a sharp-edged concrete shell, support columns, or basin edge. The air flow entering the tower passes these zones and easily becomes turbulent and restricts the free air inlet area and reduces the overall air inflow. Improving these inflow conditions allows an increase in the overall air intake of the tower and thereby improves its cooling capability. Two European nuclear power plants, NPP Leibstadt and NPP Goesgen, developed a method to improve cooling tower efficiency by adding aerodynamic spoilers to the tower shell and if necessary, to the support columns. In case of NPP Leibstadt, additional earthworks were made to smooth the ground profile up to the edge of the water basin. The spoiler installation on the cooling tower shell helped both plants to increase the air inflow, resulting in an average temperature reduction of 0.5°C (0.9°F) of the cold water temperature. The additional groundworks of NPP Leibstadt lead to an additional average temperature reduction of 0.4°C (0.7°F). The resulting average increase in power output was 2.5 MWel for NPP Goesgen and 4.5 MWel for NPP Leibstadt. Considering the economic boundary conditions of the Swiss market, the corresponding return on investment periods of the improvements was in the range of 10 - 18 months. A natural draft cooling tower air flow optimization is currently being developed by Framatome with a major US nuclear utility. Preliminary investigations estimate a potential temperature reduction of approx. 0.7°C (1.4 F) of the cold circulating water leaving the cooling tower. Following the preliminary analysis using cooling tower design information, measurements of the air flow profile inside the tower are recorded and analysis of the tower performance is performed.
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