The anti-freezing operation parameters of indirect air-cooled finned bundle are insufficient at present.To solve this problem

this research firstly concludes the anti-freezing model of finned tube bundle

including the thermal equilibration equations

water side and air side transport equations

as well as anti-freezing constrains.Secondly

based on the co-current and counter-current air-cooled finned tube bundles

the critical anti-freezing characteristics and margin are analyzed. Then

the critical values are discovered for finned tube bundles with middle inlet

left inlet and side inlet patterns. The research shows that

as the ambient temperature or inlet water temperature reduces

as well as the ambient wind increases

the critical anti-freezing water flow rate ascends.Besides

when the inlet water temperature decreases

the wind effects get intensified. The anti-freezing performance of counter-current finned tube bundle is inferior to that of the co-current type

meanwhile the difference becomes expanded if the wind increases or water inlet temperature decreases. The effects of inlet water temperature elevation on anti-freezing margin can be classified into three levels

which are termed as obvious range(0 ℃

10 ℃]

slow range(10 ℃

20 ℃]

and stable range(20 ℃

40 ℃]. Therefore

power plants should not always increase the water flow rate for anti-freezing operation. The air-cooled finned tube bundle with middle inlet pattern has better anti-freezing performance than others

so it's suggested preferentially for coal-fired or nuclear power plants. This research may provide guidelines of anti-freezing operation for dry-cooling power stations in China.