Evaporation aided improvement for cooling performance of large scale natural draft dry cooling system

The cooling performance of natural draft dry cooling system gets deteriorated at high ambient temperature. In this work, the water spray cooling is proposed to chill the inlet air of air-cooled heat exchanger to improve the cooling performance of natural draft dry cooling system in hot summer days. Based on a typical 600 MW power generating unit, a numerical model coupled the water spray with dry cooling system is developed to evaluate the cooling performance of natural draft dry cooling system with evaporation aided cooling under windless and windy conditions. The results show that the cooling performance gets improved due to water spray evaporation although the total air flow rate decreases. The heat rejection for the leeward sector increases a lot for the conspicuous inlet air temperature drop, but decreases for the windward sectors. The complete evaporation is easier to be achieved near the windward sector, but the evaporation ratio is unfavorable at the wind speed of 8 m/s. The unit back pressure gradually decreases with increasing the spraying flow rate and has an average drop of 3 kPa with a relatively high evaporation ratio at the spraying flow rate of 0.25 kg/s.