Abstract: In the low-temperature environment of winter, the radiators of direct air-cooled units participating in deep peak shaving are highly susceptible to freezing risks, seriously endangering the safe and efficient operation of the units. In response to the risk of freezing, a method has been proposed to preheat the cold air entering the air cooling unit by utilizing the residual heat in the flue gas at the tail of the boiler, in order to prevent the radiator from freezing. Firstly, a mathematical model of a direct air cooling system for spraying hot flue gas was established. Numerical simulation was used to analyze the outlet water temperature of each radiator under different environmental temperatures and wind speeds, with a focus on the difference in outlet water temperature between the left and right radiators of the same air cooling unit; Then, the influence of different flue gas injection velocities on the outlet water temperature of the radiator was analyzed, and a reasonable flue gas injection strategy was proposed. The results indicate that when the ambient temperature is below 253.15 K, there is a risk of the radiator freezing, and the higher the wind speed, the greater the risk; The outlet water temperature of the radiator on the leeward side of the air cooling unit is lower than that on the windward side, making it more prone to freezing; When the ambient wind speed is 4 m/s and the ambient temperature drops to 248.15 K, the risk of freezing can only be eliminated when the velocity of the smoke sprayed on the right side is greater than 7m/s and the velocity of the smoke sprayed on the left side is greater than 2 m/s. This method can effectively improve the safety of direct air-cooled islands operating in extremely cold winter weather.