Hot air extraction to improve aerodynamic and heat transfer performances of natural draft dry cooling system

A large amount of hot air in dry cooling tower of natural draft dry cooling system can be recovered for many applications, such as the boiler air supply and feed water preheating in power plants. However, the hot air extraction will definitely affect the aerodynamic characteristics of dry cooling tower and heat transfer performance of air-cooled heat exchanger. In this work, the impacts of hot air recovery on the thermo-flow performances of natural draft dry cooling system under crosswind conditions are investigated. The variable fields are presented and the outlet water temperature of air-cooled heat exchanger is calculated with the wind speed, the mass flow rate of recovered hot air and the height of hot air extractions considered. Finally, the turbine backpressure and power consumption of induced fans are compared to evaluate the overall cooling effect of dry cooling system with hot air extractions. The results show that hot air extraction is favorable for the cooling performance of natural draft dry cooling system, and the higher mass flow rate of recovered hot air leads to a stronger cooling capability. The hot air extractions are proposed to set near the tower inlet with the turbine backpressure most reduced by 9.28%, which can contribute to the design and operation of natural draft dry cooling system in need of energy conservation. (C) 2020 Elsevier Ltd. All rights reserved.