Research On Freezing Characteristics Of Single Row Tubes And Traffic Control For A Direct Air-cooled System

Direct air-cooled technology has been widely used in our country where coal wealthy and water shortage due to its excellent water saving performance.Direct air-cooled system condenserdirectly working in the environment, and its finned tube bundle are prone to freezein cold winter.if it isfrozen seriously,it will leads to damage of finned tube bundle, and even lead to shut down the air cooling unit, seriously affecting the safe and economic operation of air cooling units. Therefore, it is of great significance to study the anti freezing of air cooled condenserand put forward countermeasures.Based on the analysis ofrunning situation and structureof the direct air cooling system and air cooling condenser and air cooling system, this paper in-depth analysis of the cause of the finned tube bundle freezing air cooling system.Thenthe outside air flow and heat transfer model of single row finned tube structure is established. Using FLUENT fluid calculation software for outside fin tube air flow field in numerical simulation. This paper analyzes the stages of steam condensation and condensate super-cooling heat exchanger under different air temperature, and getsthe change rulesof heat transfer coefficient and flow resistance with the environmental temperature and wall temperature of thefinned tube.The results show that the coefficient of heat transfer and flow resistance of the steam condensation phase and condensate super-cooling phase of wave-fin flat tube mainly affected by head on wind speed,and Has nothing to do with the wall surface temperature ofthe finned tube and environmental temperaturein 0.2-2m/s wind speed range. Theheat transfer coefficient and flow resistance increase a parabolic curve as the greater the head-on wind speed. The heat transfer coefficient on the condensate super-cooling phasesignificantly lower thanits on the steam condensation phase.Using the operating parameters of a 330MW power plant in0.2-2 m/s wind speed condition for example, obtained the steam condenses characteristics curves under different wall surface temperature. The curves showed that with the wind speed increases the decreasing trend of condensation length leveling off. The larger wind speed the smaller affection on condensation length changed by wind speed increasing. The lower the ambient temperature is. the smaller change rate of freeze position under different unit load is. The optimal range of steam flow control in single row tube is put forward under the premise of ensuring safety and economy, which provides theoretical reference for the operation of the direct air cooling power plant in north China.