Numerical investigation of fan performance in a forced draft air-cooled steam condenser

Inlet air flow distortions in a large air-cooled steam condenser (ACSC), caused by structures, wind and other fans may result in a significant reduction in fan performance, or volumetric effectiveness, as well as fan blade vibration. This phenomenon has an adverse effect on the heat rejection capacity of an ACSC due to a decrease in air mass flow rate. In this study the effect of inlet flow distortions on the flow rate through the fans in an ACSC is numerically investigated by modelling the flow field in a section of such a system using the computational fluid dynamics code, FLUENT. The effect of platform height on the volumetric effectiveness of two different types of axial flow fans is considered. The two fans have the same diameter, number of blades and rotational speed, but feature different blade designs, and hub-tip-ratios of respectively 0.153 and 0.4. Numerical simulations show all-round superior performance in terms of volume flow rate for the fan with a hub-tip-ratio of 0.4. It is furthermore confirmed that the addition of a walkway can significantly increase the flow rate through the fans located near the edge of the fan platform.