| In winter,the temperature in northern China is low and the wind speed is high.The hyperbolic wet cooling towers used in most power plants are susceptible to the attack of cold wind,which leads to the ice hanging phenomenon at the air inlet at the bottom of the tower,the packing layer and the base torus,which indirectly affects the increase of the water temperature of the outgoing tower and worsens the effect of heat and mass transfer in the tower.At present,it is generally adopted to install a windscreen at the bottom of the tower.When the temperature warms up,the windscreen needs to be removed in time.This method not only consumes manpower,but also easily causes personal injury accidents.In addition,The cooling tower will also be adversely affected by environmental crosswind,which always damages the air flow field in the tower,and then affects the heat transfer between air and water in the tower,thus reducing the overall heat transfer effect of the cooling tower.Therefore,this paper comprehensively considers anti-freezing and crosswind problems to carry out an integrated study,and proposes an air inlet device installed outside the cooling tower.This device can not only prevent freezing at the bottom of the tower in winter,but also effectively improve the crosswind problem in other seasons,and improve the heat transfer performance of the cooling tower.The main research contents and conclusions of this paper are as follows:(1)The heat and mass transfer model of the cooling tower is established.When there is no crosswind and the windscreen is not opened,the flow field in the tower presents an axisymmetric distribution.When the temperature is constant and the transverse wind speed gradually increases from 0m/s to 2m/s,the optimal heat and mass transfer effect of the axisymmetric type(operating in no wind condition)in the tower is broken,and the high temperature zone of the tower air appears on the lee side.When the wind speed continues to rise to 6.5m/s,the high temperature zone inside the tower shifts from the leeward to the windward side,and the lowest water drop temperature on the characteristic surface has a trend of increasing first and then decreasing.When the temperature reaches the maximum,the transverse wind speed is 4m/s.If the air baffle is not opened,the characteristic surfaces in the tower will not be frozen,so the wind speed of 4m/s is set as the critical wind speed.(2)Numerical simulation technology is used to analyze the influence of different layers of windshields installed on the characteristic surface of cooling towers.By analyzing the optimal number of layers of windshields to prevent icing at the bottom of towers under different working conditions,conclusions are drawn: When the wind speed is 1.5m/s and the ambient temperature is 266.15 K,261.15 K,and 258.15 K,the number of layers of air baffle must be hung is 1,4,and 5,respectively.(3)Rotate the winter antifreeze device into a slanting upward deflector,so that the crosswise wind forms a deflector under the action of the deflector and improves heat transfer.Through the simulation analysis of the influence of diversion wind on the water temperature of outlet tower under different working conditions in other seasons,it is concluded that when the ambient crosswind V=4 m/s,the temperature drop of outlet tower water reaches the maximum 0.81 K.When the ambient temperature T=11℃,the temperature drop reaches the maximum 0.8K.The inlet air regulating device can not only prevent the bottom of the tower from freezing in winter,but also adjust the windscreen into a diversion structure with diversion effect in other seasons to prevent the occurrence of crosswind problems and reduce the temperature of the cooling tower out of the tower,so as to achieve an integrated study. |
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