In indirect air-cooling systems

at extremely low ambient temperatures and with low heat flux operation conditions

the water temperature can reach freezing point near the end of the tubes

resulting in deformation and cracking of the heat transfer tubes

which affects the safety operation of the unit.Thus

taking the vertical indirect air-cooling tower in 2×350MW units as the example

this paper numerically simulate the heat transfer performance of the towers at low temperatures in winter

by computational fluid dynamics(CFD)method.Through adjusting the opening degree of the louvers

different flow fields and temperature fields inside the indirect air-cooling tower can be obtained.Then

the influence of louvers opening degree on cooling capacity of the air cooling tower is investigated.The results show that

the air-cooling system can avoid freezing phenomenon by regulating the opening degree of the louvers into a proper value when the wind leakage rate of the closed louver is below the limit value.However

only reducing opening degree of the louvers at windward and leeward side will aggravate the harsh operation environments of other sector radiators

causing high risk in heat transfer tube cracking and deformation.Therefore

it is recommended that all the louvers should be adjusted simultaneously during anti-freezing operation at low heat flux condition with extremely low ambient temperature.