Research On The Effects Of Noise Control Of Power Plant Cooling Tower On Its Thermal Performance

The natural draft counter-flow wet cooling tower is one of the main heat exchange equipment in the cold end system of power plant,which is widely used for its high cooling efficiency and reliable operation.Due to the huge noise generated during the operation of the cooling tower,it is generally arranged around the plant boundary,but with the social development and the expansion of the city scale,the power plant boundary gradually gathers the population,and the noise of the cooling tower may affect the normal life of the nearby residents.Therefore,the power plant needs to take noise control measures to meet the relevant noise emission standards.However,it should also be noted that the noise reduction equipment attached around the cooling tower may have an impact on the performance of the cooling tower,thus affecting the economic benefits of the power plant unit,and even the operation safety.Based on the noise control project of cooling tower in a power plant in China,the mathematical model of array muffler and three-dimensional numerical model of natural draft counter-flow wet cooling tower are established with array muffler and natural draft counterflow wet cooling tower as the research object;Based on the performance test data of the array muffler,the resistance characteristics and noise reduction performance of the array muffler are calculated,and the relationship between the performance of the array muffler and its structural parameters is analyzed.Based on the numerical calculation software FLUENT,the flow field inside the cooling tower and the heat and mass transfer process of air-water two-phase are simulated.The effects of the resistance characteristics and layout of the array muffler on the thermal performance of the cooling tower and the temperature of the circulating water is analyzed.Finally,the optimization of the noise control scheme of the cooling tower is discussed.The specific work contents are as follows:In view of the noise characteristics of the cooling tower in the target power plant,the frequency spectrum characteristics of the cooling tower noise at the air inlet and at the boundary of the power plant are obtained by field test.The test results show that the noise frequency of cooling tower in power plant is wide,the noise intensity is large,more than 80 d B(A),and the noise is not easy to attenuate.The characteristics of cooling tower noise determine that effective noise reduction means must be adopted for noise control,that is,large cooling tower muffler.In view of the problem of resistance and silencing performance of the array muffler,this paper uses the performance test data of the array muffler to obtain the change characteristics of each performance under different structural parameters,and then combines the theoretical model of resistance and silencing performance of the array muffler to obtain the relationship between the performance and structure of the array muffler.The results show that the resistance characteristics of the array muffler are positively correlated with the silencing performance,that is to say,the greater the silencing quantity is,the greater the resistance coefficient is.In view of the effects of array muffler on the performance of cooling tower in power plant,based on the three-dimensional numerical model of cooling tower and the resistance characteristics of muffler,this paper calculates the changes of water temperature,ventilation,evaporation,heat emission and other indexes of cooling tower by changing the angle of array muffler surrounding the air inlet of cooling tower and the resistance coefficient of muffler.In addition,the effects of array muffler on the temperature of circulating water in cold end system of unit is calculated.The calculation results show that the noise reduction scheme adopted by the target power plant(muffler around the edge of collecting basin 180°)will make the temperature of tower water rise by 0.18 °C.If the muffler is around 360°,the outlet water temperature will rise by 0.36 °C.With the increase of the resistance coefficient or the surrounding angle of the muffler,the air flow field and the water temperature distribution in the rain area of the cooling tower deviate obviously,and the performance indexes of the cooling tower decrease,but the air flow at the air inlet of the side not surrounding the muffler will increase,resulting in the phenomenon of "compensation".The reason is that the muffler increases the density difference of wet air inside and outside the tower,and the suction force of the cooling tower increases.Finally,this paper attempts to optimize the noise control scheme of the cooling tower from the point of view of the arrangement of array muffler,and has achieved some results.