Thermal performance improvement of the three aligned natural draft dry cooling towers by wind breaking walls and flue gas injection under different crosswind conditions

Abstract

Abstract The substantial objective of using circulating cooling water in a typical power plant is to remove the heat effectively from the vapor cycle and to expel it to the environment. One of the most popular cooling systems for this purpose is the natural draft dry cooling tower (NDDCT) which is widely used in regions with the shortage of water, such as Iran. Environmental conditions affect the Heller cooling tower s performance strictly. Temperature, density, and the mass flow rate of sucked air into the cooling towers will all influence their operation. To improve the cooling tower s performance and air suction capability, it is proposed to inject the steam generators flue gas into the tower. In this study, a single natural draft dry cooling tower incorporating the flue gas duct is modeled to study the effect of flue gas injection on the sucked air flow rate and the radiator heat transfer. Considering the buoyancy effect term, for a 3-D incompressible flow, the Navier Stokes equations, as well as the energy equation, are solved by computational fluid dynamic method (CFD) to obtain the airflow pattern inside and outside the tower as well as the heat transfer from the radiators. The tower is assumed to be equipped with windbreak walls in one case and without it in another case so that the effect of crosswind could be investigated. Having compared the thermal performance of the towers, the results show that the thermal deficiency is more pronounced for the towers in crosswind without any flue gas injection. It is also shown that the injection of the hot flue gas (with temperature of 130\u202f°C) will increase air intake and the thermal performance of the towers which, in turn, results in the reduction of the outlet water temperature. The modeling is then extended to three aligned NDDCTs to determine the effect of flue gas injection in the presence of windbreak walls under crosswind condition. Consequently, a notable promotion had been observed in all three towers thermal performance but with different ratios.