Numerical investigation of crosswind effects on small scale natural draft dry cooling tower with swirling enhancement

Abstract: Crosswind can significantly reduce the performance of natural draft dry cooling towers (NDDCTs) by causing cold air to intrude into the top of the tower, which reduces the net draft pressure (Terzis, Kazakos et al., 2012). The effects of swirling flow on thermal plumes rising from lab-scale NDDCTs are investigated using numerical simulations. The results indicate that the negative impact of crosswind can be mitigated at lower wind velocities, allowing the tower's capacity to recover. The flow structures in thermal plumes change significantly, shifting from a counter-rotating vortex pair to a dominant swirling vortex at higher swirl ratios. Numerical simulations are conducted using k-w SST turbulence modeling. The findings show that the cooling capacity of NDDCTs can return to normal operating levels under varying crosswind conditions. Interestingly, at certain wind velocities, the heat capacity can even exceed standard levels, as the wind directly enhances heat rejection from the heat exchanger bundles. Similar to the transverse swirl jet problem, counter-rotating vortices are observed in the deflected plume at lower swirl numbers, while at higher swirl numbers, the vortices are positioned at different heights with varying intensities. Keywords: Natural draft cooling tower, numerical simulation, swirling plume