| Due to the low winter temperatures in northern China and the uneven heat transfer in the cooling tower,it is easy to freeze below the packing of the cooling tower,air inlet and base torus,affecting the normal operation of the unit.In order to prevent the freezing phenomenon of the cooling tower,the method of manually hanging the wind deflector is usually adopted.However,in actual operation,the windshield is often hung excessively because the quantity of the wind deflector can not be adjusted in time,according to the change of the ambient temperature,so that the temperature of the circulating water is higher than the economic temperature,causing the unit Reduced vacuum and crew economy.Therefore,study different windshields,and then to find the best wind-shielding area that can prevent icing within the tower under different ambient temperatures.This reduces the cost of power generation and increases the economic benefits,at the same time,it provides a theoretical basis for the optimization of the wind deflector.The paper builds the 3D model of the cooling tower by GAMBIT software,Which analyzes the regularity of the air flow field in the tower when the natural draft counter flow wet cooling tower is not hung windshield device with ambient temperature and wind speed by numerical simulation of FLUENT software.As well as the trend of the lowest drop temperature of the three characteristic surfaces(The filler zone,the air inlet and the base torus of cooling tower).The change of the lowest drop temperature in the tower after installing different layers of wind deflector was simulated and analyzed.The optimal number of wind deflector layers to prevent icing in the tower was obtained.At the same time,two other new types of antifreezing measures were proposed,which are horizontal windshield cloth and transverse windshield boards.The specific numerical simulation results show that:(1)Without the antifreeze measures,the flow field in the cooling tower is symmetrical in the radial direction.When the wind speed increases from 0 to 4 m/s,the air flow field in the tower no longer exists axisymmetric distribution.From the center to the leeward side.As the lateral wind speed increases,the high-temperature air begins to move toward the windward side.When the wind speed is 1.5m/s,4 m/s,6.5 m/s and 8 m/s respectively,the lowest drop temperature of the circulating water in the cooling tower first and then decreases.Numerical simulation shows that when the wind speed is 4 m/s,the lowest drop temperature of the three characteristic surfaces is the highest.Under the condition of constant wind speed,through the three-dimensional numerical simulation analysis of the cooling tower,the lowest drop temperature of circulating water in the tower also decreases with the decrease of ambient temperature.(2)At the ambient temperature of 266.15 K,261.15 K and 255.15 K respectively,the air inlet of the cooling tower is rebuilt after the delaminated suspension windshield boards,hanging a layer of windshield board while can avoid icing in the tower,but because of windshield boards on each floor are large,which can cause a high water temperature of the cooling tower,which is detrimental to the unit's energy savings.Therefore,it is necessary to redesign and optimize the layout of the cooling tower windshield boards to find the optimal windshield area just to anti-freezing in the tower,and at the same time the temperature of the water in the tower will not be too high.(3)The design of the wind deflector plays a crucial role in the normal operation of the cooling tower.Through the three-dimensional numerical simulation of the windshield boards layout in cooling tower,they are longitudinal interval installation of windshield boards,transverse windshield cloths and transverse rotation windshield boards.By simulating the air flow field in the tower and the lowest drop temperature of the circulating water on each characteristic surface,it is concluded that the transverse rotating wind deflector is the best wind-blocking device among the three. |
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