In allusion to high back pressure of a 300MW direct air cooling unit in summer

the wetdry joint cooling system was established and its calculation model was built.The influence of ambient temperature on back pressure and net power of both air cooling system and wet-dry joint cooling system under THA load and 75%load in sliding pressure condition was investigated and compared.The results indicated that

the wet-dry joint cooling system was less sensitive to the ambient temperature

and it showed better economy and stability.For this 300MW unit

when the main steam flow was 700t/h and the ambient dry bulb temperature was higher than 10 ℃

the wet-dry joint cooling system was suitable

while the when the main steam flow was 900t/h and the ambient dry bulb temperature was lower than 5 ℃

it was economic to shut down the wet cooling system.