Effects of diffuser orifice plate on the performance of air-cooled steam condenser

Ambient wind has adverse impacts on the thermal-flow performances of ACSC. In this paper, a new measure to improve ACSC performance is proposed by installing diffuser orifice plate under the ACSC platform. As ambient wind flowing through diffuser hole in the plate, the velocity head converts to the pressure head, which contributes to shrink the negative pressure region under the ACSC platform and further improve ACSC performance. The numerical model of Column 4 section in a 600 MW ACSC is investigated, and the results show that under windy conditions, the diffuser orifice plate not only increases the volume flows across almost all fans due to the shrinkage of the negative pressure zone, but decreases fans' inlet air temperatures, especially for upstream fans. At a wind speed of 9 m/s, the volumetric effectiveness of windward Fan(1,4) is increased by 19.9%, and the temperature drop at windward Fan(1,4) inlet is 1.1K, as considering diffuser orifice plate. Moreover, a more uniform flow field distribution such as pressure, temperature as well as air flow rate can form via diffuser orifice plate, which may also improve heat transfer of condenser cell. At a wind speed of 9 m/s, the heat transfer effectiveness is increased by 6.6 percent points. The numerical results indicate that diffuser orifice plate is an effective way to restrain the adverse impacts of ambient wind, and it can be beneficial to operation improvement of the direct dry cooling systems in power plants.