Research On The Anti-freezing Operation Of Natural Draft Dry Cooling System

The ambient temperature can reach-40? during winter in high latitude area,leading a raise of the cooling capacity of air.However,the cooling system cannot make full use of the advantage,but facing a freezing risk.Heat exchange bundles are broken and the efficiency of power plant is decreased.Adjustments of louvers and mass flow rate of circling water are proposed by researchers to improve the safety and efficiency of cooling systems during winter.Some unexpected problems occur when the two kinds of methods are put into reality.The relative low mass flow rate for lateral sector is adopted to save pump cost,then the waterside re-distribution results some bundles freezing easily.In the view of airside adjustments,the baffles of a louver are rotated simultaneously,thus the louver will go wrong inevitably.Two kinds of improvement measures are proposed in this paper,air pre-heating and rolling-type windbreakers.A practical 660 MW power plant is taken to evaluate the methods by numerical investigations for different ambient temperature and wind speeds,the water outlet temperature of each heat exchange bundle is monitored.Moreover,the needed mass flow rate of flue gas to pre-heat air and the opening degree of the new type of louver for different ambient temperature and wind speeds are obtained to provide help for operations.As for adopting the rolling-type windbreakers,at the ambient temperature of-5??the freezing can hardly happen at small wind speeds.When the wind speed arrives at 8 m/s and 12 m/s,the rolling-type windbreakers should be regulated for the sectors No.1-2,and the opening degree decreases with increasing the wind speed.For other sectors,the rolling-type windbreakers keep fully open at various wind speeds.When the ambient temperature decreases to-10? and-15?.not only the windward sectors No.1-2?but also the lateral and leeward sectors No.3-5 face freezing risks.What's more,the opening degrees for all sectors basically decrease as the ambient temperature drops.In the view of flue gas pre-heating?when the ambient temperature is-5? and ambient wind speed is over 8 m/s,flue gas is only needed to spraying for the middle and frontal sectors.With lower ambient temperature,flue gas is needed for all sectors of cooling systems.