On the effect of a tangential intake on the performance of natural dry draft cooling towers in crosswind conditions

Crosswind has a negative effect on the performance of natural draft dry cooling towers, NDDCTs, serving thermal power plants. This, in turn, lowers the efficiency of the thermal power plant as less heat can be rejected to the ambient air through the tower. This occurs due to interaction of cross wind and cooling tower structure. This phenomenon leads to generation of primary and secondary vortices inside the tower which located in leeward side (downwind side) and windward side (upwind side) of the tower, respectively. In an innovative interpretation of the challenge, this paper aims at directing the crosswind flow through the tower shell above the heat exchangers to assist the buoyancy-induced plume. In particular, the intake of the crosswind through the tower is utilized as a tangentially-induced swirl source to help the upward draft, and its penetration in the ambient air, enhancing the tower performance which otherwise would have been significantly deteriorated. Two independent approaches are presented to assess the proposed design quantitatively. CFD simulation of a small scale tower model has revealed significant performance improvement (in terms of natural draft blockage and outlet flow velocity) when the crosswind is allowed to penetrate the tower shell, through an opening on the tower side-wall, above the heat exchangers. Results of the simulations have been validated against the experimental data collected using the tests ran on an identical model, with and without the side opening, in a wind tunnel.